Novel species of Calonectria associated with Eucalyptus leaf blight in Southeast China

Diversity of Calonectria species from leaves and soils in diseased southern China Eucalyptus plantation

Calonectria leaf blight (CLB) is one of the best-known diseases of Eucalyptus spp., particularly in Asia and South America. Recently, typical symptoms of leaf and shoot blight caused by Calonectria spp. Were observed in a Eucalyptus plantation in the YunNan Province of southwestern China. Isolations were made from diseased leaves and top soil collected below the diseased trees to determine the causal agent of the disease and to consider the distribution characteristics of the Calonectria species. This resulted in 417 isolates, of which 228 were from leaves and 189 were from soil. Based on comparisons of DNA sequences for the act (actin), cmdA (calmodulin), his3 (histone H3), rpb2 (the second largest subunit of RNA polymerase), tef1 (translation elongation factor 1-alpha) and tub2 (β-tubulin) gene regions, as well as morphological characteristics, 11 Calonectria species were identified. These included Calonectria aciculata (0.7 %), Ca. colhounii (1.2 %), Ca. eucalypti (10.6 %) and Ca. honghensis (43.2 %) in the Ca. colhounii species complex, and Ca. aconidialis (15.3 %), Ca. asiatica (9.8 %), Ca. hongkongensis (1.0 %), Ca. ilicicola (6.0 %), Ca. kyotensis (0.5 %), and Ca. yunnanensis (11.3 %) in the Ca. kyotensis species complex. In addition, a novel species, accounting for 0.5 % of the isolates, was discovered and is described here as Ca. dianii sp. nov. in the Ca colhounii species complex. Most (99.1 %) of the isolates collected from the leaves resided in the Ca. colhounii species complex and a majority (95.8 %) of those from the soils were in Ca. kyotensis species complex. These results suggest that Calonectria spp. in the Ca. colhounii species complex infecting leaves might be adapted to that niche and that those in the Ca. kyotensis species complex are better adapted to a soil habitat.

Wide Distribution of Teratosphaeria epicoccoides and T. destructans Associated with Diseased Eucalyptus Leaves in Plantations in Southern China

Species of Mycosphaerellaceae and Teratosphaeriaceae represent over 40% of the fungi identified on eucalypt leaves worldwide. These include some important pathogens that mainly cause leaf blight and spot, and result in increasingly negative impacts on global commercial eucalypt industries. Eucalyptus plantations are commonly cultivated in southern China for solid wood and pulp products. However, the species diversity and geographic distribution of Mycosphaerellaceae and Teratosphaeriaceae, associated with diseased plantation Eucalyptus leaves in China, have not been clarified. In this study, we conducted the first systematic surveys and sample collections of Mycosphaerellaceae- and Teratosphaeriaceae-like fungi from diseased plantation Eucalyptus leaves in southern China. In total, 558 isolates were obtained from 59 sampled sites in five provinces. One isolate was isolated from each tree. According to the disease symptoms, conidia morphological characteristics, and DNA sequence comparisons of ITS, tef1 and tub2 gene regions. The 558 isolates were identified as Teratosphaeria epicoccoides (312 isolates; 55.9%) and T. destructans (246 isolates, 44.1%). Both species were widely distributed in the sampled regions in southern China. The genotypes of T. epicoccoides and T. destructans were determined based on ITS, tef1, and tub2 sequences. The results showed that multiple genotypes of each species of T. epicoccoides and T. destructans exist in China. Additionally, isolates with multiple genotypes were obtained in all five sampled provinces. These results suggest that both T. epicoccoides and T. destructans are not clonal. This study proved that both T. epicoccoides and T. destructans are dominant species and widely distributed on diseased Eucalyptus leaves in southern China. The wide geographic distribution and potential high genetic diversity pose challenges for the disease management of Teratosphaeria leaf blight and leaf spot in China.

Calonectria populi sp. nov., causing leaf blight of Populus deltoides in India

Populus deltoides is one of the most favored cash crops in northern India. Thus, accurate identification of pathogens affecting P. deltoides is a critical step in finding or developing effective control measures. In June 2020, symptoms of a leaf blight disease were observed on P. deltoides trees planted at Forest Research Institute, Dehradun, India. Calonectria-like fungal isolates were consistently isolated from the infected leaf samples. Morphological features coupled with phylogenetic analysis of combined partial actin (act), calmodulin (cmdA), histone (his3), translation elongation factor 1-alpha (tef1) and β-tubulin (tub2) gene regions of two fungal isolates confirmed a novel species, which is described and illustrated here as Calonectria populi sp. nov. Symptoms similar to those observed in natural conditions were caused by both the isolates on P. deltoides clone AM109 in detached leaf assays and glasshouse inoculation experiments. Finally, Koch's postulates were established by re-isolation and re-identification of the pathogen from the inoculated leaves. This work is the first to confirm a new leaf blight disease of P. deltoides caused by C. populi sp. nov. in India and worldwide.

Phylogeny, Morphology, Distribution, and Pathogenicity of Seven Calonectria Species from Leaf-Blighted Eucalyptus in HaiNan Island, China

Leaf blight caused by Calonectria species constrains Eucalyptus trees in China. Calonectria leaf disease on Eucalyptus in China was first reported in HaiNan Island in 1985. No systematic investigation of Calonectria species associated with diseased Eucalyptus in HaiNan has been performed. To understand the species diversity, distribution, and pathogenicity of these Calonectria, 400 Calonectria isolates were obtained from 278 diseased Eucalyptus planted in 17 sites in five regions. All 400 isolates were identified by DNA sequences of translation elongation factor 1-alpha, β-tubulin, calmodulin, and histone H3 gene regions and on morphology. Seven species, C. acaciicola (198 isolates), C. pseudoreteaudii (161 isolates), C. reteaudii (29 isolates), C. hawksworthii (6 isolates), C. hongkongensis (4 isolates), C. auriculiformis (1 isolate), and C. chinensis (1 isolate), were identified. This is the first report of C. acaciicola in China. C. acaciicola, C. pseudoreteaudii, and C. reteaudii belong to the C. reteaudii species complex and accounted for 97% of all isolates. The three species overlapped in vesicle shape, macroconidia size, and macroconidia septa number. Region significantly influenced C. acaciicola and C. pseudoreteaudii distribution. Representative isolates of C. acaciicola, C. pseudoreteaudii, C. reteaudii, and C. hawksworthii producing abundant macroconidia were used in conidial suspension inoculation on Eucalyptus seedlings; all were highly pathogenic to the two tested genotypes. The tolerances of two Eucalyptus genotypes were significantly different. This first systematic investigation of Calonectria species associated with Eucalyptus leaf blight in HaiNan will aid selection of disease-resistant genotypes for managing Eucalyptus leaf blight caused by Calonectria species in China.

Wide Distribution and Intraspecies Diversity in the Pathogenicity of Calonectria in Soil from Eucalyptus Plantations in Southern Guangxi of China

Eucalyptus spp. are extensively cultivated in southern China because of their adaptability and versatile timber production. Calonectria leaf blight caused by Calonectria species is considered a major threat to Eucalyptus trees planted in China. The GuangXi Zhuang Autonomous Region is the provincial region with the largest distribution of Eucalyptus plantations in China. The present study aimed to expound the species diversity and pathogenicity of Calonectria isolates obtained from the soil of Eucalyptus plantations in GuangXi. A total of 188 Calonectria isolates were recovered from the soil located close to Eucalyptus trees, and the isolates were identified based on the DNA sequence comparisons of the four partial regions of the translation elongation factor 1-alpha (tef1), β-tubulin (tub2), calmodulin (cmdA), and histone H3 (his3) genes. The isolates were identified as Calonectria aconidialis (74.5%), C. hongkongensis (21.3%), C. pseudoreteaudii (2.1%), C. kyotensis (1.6%), and C. chinensis (0.5%). The inoculation results indicated that 40 isolates representing five Calonectria species were pathogenic to the three Eucalyptus genotypes. Two inoculated experiments consistently showed that the longest lesions were produced by the isolates of C. aconidialis. Some isolates of C. aconidialis, C. hongkongensis, and C. kyotensis produced significantly longer lesions than the positive controls, but not the isolates of C. pseudoreteaudii or C. chinensis. These results indicated that Calonectria isolated from the soil may pose a threat to Eucalyptus plantations. Some Calonectria isolates of the same species differed significantly in their virulence in the tested Eucalyptus genotypes. The resistance of different Eucalyptus genotypes to Calonectria isolates within the same species was inconsistent. The inoculation results in this study suggested that many Calonectria isolates in each species had different levels of pathogenicity, and many Eucalyptus genotypes need to be tested to select disease-resistant Eucalyptus genetic materials in the future. The results of the present study enhance our knowledge of species diversity and the potential damage caused by Calonectria in the soil of Eucalyptus plantations. Our results also provide new insights into the breeding of disease-resistant Eucalyptus genotypes for controlling Calonectria leaf blight in China in the future.

Calonectria queenslandica: Causal Agent of Eucalyptus Leaf Blight in Southern China

Calonectria leaf blight caused by Calonectria spp. is among the most serious diseases affecting the health and sustainability of Eucalyptus plantations in southern China. Recent outbreaks of this disease in GuangDong Province prompted a need to identify the species involved. Typical symptoms of Calonectria leaf blight were observed on 2-year-old Eucalyptus urophylla × E. grandis trees in a plantation in the ZhaoQing region. In total, 38 Calonectria isolates were collected from 32 diseased trees. All isolates were identified using DNA sequence analyses of the translation elongation factor 1-α (tef1), β-tubulin (tub2), calmodulin (cmdA), and histone H3 (his3) gene regions. Phylogenetic analyses revealed that Calonectria queenslandica was the dominant species, accounting for 81.6% of the isolates collected. Other species isolated included C. pseudoreteaudii (10.5%), C. reteaudii (5.3%), and C. aconidialis (2.6%). This is the first report of C. queenslandica in China and all isolates had identical sequences in all four gene regions. PCR amplification using primers targeting the MAT1-1-1 and MAT1-2-1 genes in all C. queenslandica isolates revealed that only the MAT1-2 idiomorph was present. The results suggest that C. queenslandica was introduced into the sampled area with very limited genetic diversity. Pathogenicity tests were conducted on two Eucalyptus genotypes widely planted in the GuangDong Province using isolates representing all species collected. The results showed that these species could all cause disease but the predominance of C. queenslandica on infected trees suggests that it is the major driver of the disease problem studied. Different Eucalyptus genotypes used in the pathogenicity tests differed in susceptibility to infection by the Calonectria spp. tested, providing opportunities to avoid leaf blight by deploying disease-tolerant planting stock.

Diversity and Distribution of Calonectria Species in Soils from Eucalyptus urophylla × E. grandis, Pinus massoniana, and Cunninghamia lanceolata Plantations in Four Provinces in Southern China

The species of Calonectria include many notorious plant pathogens and are widely distributed around the world. Leaf blight caused by Calonectria species is considered one of the most prominent diseases in Eucalyptus plantations in China. Some Calonectria species isolated from soils in Eucalyptus plantations are highly pathogenic to inoculated Eucalyptus genotypes. In southern China, the plantation trees Cunninghamia lanceolata, Eucalyptus spp., and Pinus massoniana are always adjacently planted, especially in FuJian, GuangDong, GuangXi, and YunNan Provinces. The aim of this study was to understand the diversity and distribution of Calonectria in soils from plantations of different tree species in different geographic regions. Soil samples were collected from 12 sampling sites in Eucalyptus urophylla × E. grandis, P. massoniana, and C. lanceolata plantations in FuJian, GuangDong, GuangXi, and YunNan Provinces. Approximately 250 soil samples were collected from each sampling site, and a total of 2991 soil samples were obtained. A total of 1270 Calonectria isolates were obtained from 1270 soil samples. The 1270 isolates were identified based on DNA sequence comparisons of the partial gene regions of act, cmdA, his3, rpb2, tef1, and tub2. These isolates were identified as 11 Calonectria species: Calonectria aconidialis (69.50%), C. kyotensis (13.10%), C. hongkongensis (10.80%), C. ilicicola (2.50%), C. asiatica (2.36%), C. curvispora (0.31%), C. chinensis (0.24%), C. pacifica (0.24%), C. yunnanensis (0.16%), and C. canadiana (0.08%) in the C. kyotensis species complex and C. eucalypti (0.71%) in the C. colhounii species complex. The three dominant species, C. aconidialis, C. kyotensis, and C. hongkongensis, were widely distributed. The richness of Calonectria (percentage of soil samples that yielded Calonectria) in soils in the eastern regions (relatively humid regions) was higher than that in the western regions. The Calonectria richness of E. urophylla × E. grandis, P. massoniana, and C. lanceolata plantations decreased gradually. For each of the three dominant species, its richness in the eastern regions was generally higher than that in the western regions; the species richness was highest in E. urophylla × E. grandis plantations for C. aconidialis, while for each of C. kyotensis and C. hongkongensis, its species richness was highest in P. massoniana plantations. The genetic variation in C. aconidialis, C. kyotensis, and C. hongkongensis was more greatly affected by geographic region than by plantation tree species. This study expanded our understanding of the richness, species diversity, and distribution characteristics of Calonectria in soils from the plantations of different tree species in different geographic regions in southern China. Results in this study enhanced our understanding of the influencing characteristics of geographic region and tree species on the species and genetic diversity of soilborne fungi.

Comparison of Hyphal Fragments and Spores to Evaluate the Pathogenicity of the Eucalyptus Leaf and Shoot Pathogen Calonectria pseudoreteaudii

The genus Calonectria includes many aggressive plant-pathogenic species with a worldwide distribution. Calonectria leaf blight is one of the most prominent diseases of Eucalyptus trees in Southeast Asian and South American plantations. Inoculation trials to evaluate pathogenicity of Calonectria spp. typically use conidial suspensions but this is not possible for species that do not sporulate sufficiently in culture. Calonectria pseudoreteaudii is one of the species that is most aggressive to Eucalyptus in China but most isolates fail to produce conidia in culture, requiring an alternative procedure for artificial inoculation. This study compared inoculations utilizing conidial and hyphal fragment suspensions. Two Eucalyptus genotypes were used, and these were inoculated with different concentrations of hyphal fragments or conidia of three C. pseudoreteaudii isolates. Three days after inoculation, the treated Eucalyptus plants displayed similar disease symptoms, regardless of whether they had been inoculated with conidia or hyphal fragments. This was consistent for all C. pseudoreteaudii isolates and also the different Eucalyptus genotypes. The results demonstrate that hyphal fragment suspensions can be used to provide a reliable indication of C. pseudoreteaudii isolate pathogenicity when conidia are not available for inoculation studies.

Morphological and Molecular Characterization of Calonectria foliicola Associated with Leaf Blight on Rubber Tree (Hevea brasiliensis) in Thailand

Leaf blight is commonly observed in rubber trees (Hevea brasiliensis) and can be caused by several fungal species. From October to December 2021, the emergence rubber tree disease was observed in Krabi province, southern Thailand. Small brown to dark brown spots developed on the leaves of rubber trees and later expanded into most parts of the leaves. Fungal isolates were isolated from infected tissues and a total of 15 Calonectria-like isolates were recovered from 10 infected leaf samples. Pathogenicity testing using the agar plug method revealed that four isolates caused leaf blight on rubber tree, similar to the situation in natural infections. Based on morphological study and the molecular properties of internal transcribed spacer (ITS), calmodulin (cal), translation elongation factor 1-α (tef1-α), and β-tubulin 2 (tub2) sequences, the four fungal isolates were identified as Calonectria foliicola. To the best of our knowledge, this is the first report of rubber trees pas a new host for C. foliicola in Thailand and elsewhere. This study reports on an emerging disease affecting rubber trees in Thailand, and the results are of benefit for the development of an appropriate method to manage this emerging disease in Thailand.

Diversity and Distribution of Calonectria Species from Plantation and Forest Soils in Fujian Province, China

To meet the growing demand for wood and pulp products, Eucalyptus plantations have expanded rapidly during the past two decades, becoming an integral part of the southern China landscape. Leaf blight caused by various Calonectria spp., is a serious threat to these plantations. In order to explore the diversity and distribution of Calonectria spp. in Fujian Province soils, samples were collected in Eucalyptus plantations and adjacent plantings of Cunninghamia lanceolata, Phyllostachys heterocycle and Pinus massoniana as well as in natural forests. Three hundred and fifty-three Calonectria isolates were recovered from soil samples and they were identified based on a comparison of multilocus DNA sequence data for the act (actin), cmdA (calmodulin), his3 (histone H3), rpb2 (the second largest subunit of RNA polymerase), tef1 (translation elongation factor 1-alpha) and tub2 (β-tubulin) gene regions, as well as morphological characteristics. Six known taxa including Calonectria aconidialis, Ca. hongkongensis, Ca. ilicicola, Ca. kyotensis, Ca. pacifica, Ca. pseudoreteaudii and one novel species described here as Ca. minensis sp. nov. were identified. Of these, Ca. aconidialis and Ca. kyotensis were the most prevalent species, and found in eight and seven sites, and four and five forest types, respectively. Calonectria spp. were most abundant in soils from Eucalyptus stands, followed by P. heterocycle and natural forests. Relatively few species were found in the soils associated with Cunninghamia lanceolata and Pinus massoniana. The abundance of known Calonectria spp. suggests that these fungi have been relatively well sampled in Fujian. The results are also consistent with the fact that most Calonectria diseases are found on Angiosperm as opposed to Gymnosperm plants.

Identification and Characterization of Calonectria Species Associated with Plant Diseases in Southern China

Calonectria species are important plant pathogens on a wide range of hosts, causing significant losses to plant production worldwide. During our survey on phytopathogenic fungi from 2019 to 2021, diseased samples were collected from various hosts in Guangdong Province, China. In total, 16 Calonectria isolates were obtained from leaf spots, stem blights and root rots of species of Arachis, Cassia, Callistemon, Eucalyptus, Heliconia, Melaleuca and Strelitzia plants. Isolates were identified morphologically, and a multigene phylogenetic analysis of combined partial sequences of calmodulin (cmdA), translation elongation factor 1-alpha (tef1-α) and beta-tubulin (β-tubulin) was performed. These sixteen isolates were further identified as nine Calonectria species, with five new species: Ca. cassiae, Ca. guangdongensis, Ca. melaleucae, Ca. shaoguanensis and Ca. strelitziae, as well as four new records: Ca. aconidialis from Arachis hypogaea, Ca. auriculiformis from Eucalyptus sp., Ca. eucalypti from Callistemon rigidus, and Ca. hongkongensis from Eucalyptus gunnii. Moreover, we provide updated phylogenetic trees for four Calonectria species complexes viz. Ca. colhounii, Ca. cylindrospora, Ca. kyotensis and Ca. reteaudii. Our study is the first comprehensive study on Calonectria species associated with various hosts from subtropical regions in China. Results from the present study will be an addition to the biodiversity of microfungi in South China.

Impact of Calonectria Diseases on Ornamental Horticulture: Diagnosis and Control Strategies

Diseases caused by fungi in the genus Calonectria pose a significant threat to the ornamental horticulture industries in Europe and the United States. Calonectria spp. are particularly challenging pathogens to manage in ornamental production systems and the urban landscape for multiple reasons. A high level of species diversity and poorly resolved taxonomy in the genus makes proper pathogen identification and disease diagnosis a challenge, though recent molecular phylogenetic studies have made significant advances in species delimitation. From a disease management perspective, Calonectria spp. produce long-lived survival structures (microsclerotia) that contaminate nursery production systems and can survive multiple years in the absence of a susceptible plant host. Latent infection of plant material is poorly understood but likely contributes to long-distance dissemination of these fungal pathogens, including the clonal Calonectria spp. responsible for the global emergence of boxwood blight. Breeding for disease resistance represents a sustainable strategy for managing Calonectria diseases but is challenging due to the perennial nature of many ornamental plants and high levels of susceptibility in commercial cultivars. Ultimately, long-term sustainable management of Calonectria diseases will require an improved understanding of pathogen biology as well as integration of multiple disease management strategies.

Calonectria in the age of genes and genomes: Towards understanding an important but relatively unknown group of pathogens

The genus Calonectria includes many aggressive plant pathogens causing diseases on various agricultural crops as well as forestry and ornamental tree species. Some species have been accidentally introduced into new environments via international trade of putatively asymptomatic plant germplasm or contaminated soil, resulting in significant economic losses. This review provides an overview of the taxonomy, population biology, and pathology of Calonectria species, specifically emerging from contemporary studies that have relied on DNA-based technologies. The growing importance of genomics in future research is highlighted. A life cycle is proposed for Calonectria species, aimed at improving our ability to manage diseases caused by these pathogens.

Species Diversity and Distribution Characteristics of Calonectria in Five Soil Layers in a Eucalyptus Plantation

The genus Calonectria includes pathogens of various agricultural, horticultural, and forestry crops. Species of Calonectria are commonly collected from soils, fruits, leaves, stems, and roots. Some species of Calonectria isolated from soils are considered as important plant pathogens. Understanding the species diversity and distribution characteristics of Calonectria species in different soil layers will help us to clarify their long-term potential harm to plants and their patterns of dissemination. To our knowledge, no systematic research has been conducted concerning the species diversity and distribution characteristics of Calonectria in different soil layers. In this study, 1000 soil samples were collected from five soil layers (0-20, 20-40, 40-60, 60-80, and 80-100 cm) at 100 sampling points in one 15-year-old Eucalyptus urophylla hybrid plantation in southern China. A total of 1037 isolates of Calonectria present in all five soil layers were obtained from 93 of 100 sampling points. The 1037 isolates were identified based on DNA sequence comparisons of the translation elongation factor 1-alpha (tef1), β-tubulin (tub2), calmodulin (cmdA), and histone H3 (his3) gene regions, as well as the combination of morphological characteristics. These isolates were identified as C. hongkongensis (665 isolates; 64.1%), C. aconidialis (250 isolates; 24.1%), C. kyotensis (58 isolates; 5.6%), C. ilicicola (47 isolates; 4.5%), C. chinensis (2 isolates; 0.2%), and C. orientalis (15 isolates; 1.5%). With the exception of C. orientalis, which resides in the C. brassicae species complex, the other five species belonged to the C. kyotensis species complex. The results showed that the number of sampling points that yielded Calonectria and the number (and percentage) of Calonectria isolates obtained decreased with increasing depth of the soil. More than 84% of the isolates were obtained from the 0-20 and 20-40 cm soil layers. The deeper soil layers had comparatively lower numbers but still harbored a considerable number of Calonectria. The diversity of five species in the C. kyotensis species complex decreased with increasing soil depth. The genotypes of isolates in each Calonectria species were determined by tef1 and tub2 gene sequences. For each species in the C. kyotensis species complex, in most cases, the number of genotypes decreased with increasing soil depth. The 0-20 cm soil layer contained all of the genotypes of each species. To our knowledge, this study presents the first report of C. orientalis isolated in China. This species was isolated from the 40-60 and 60-80 cm soil layers at only one sampling point, and only one genotype was present. This study has enhanced our understanding of the species diversity and distribution characteristics of Calonectria in different soil layers.

Global Genetic Diversity and Mating Type Distribution of Calonectria pauciramosa: An Important Wide-Host-Range Plant Pathogen

The fungal pathogen, Calonectria pauciramosa, has caused serious diseases of many important plants worldwide. Understanding the genetic diversity and mating type distribution of this pathogen provides an essential step toward the development of disease control measures. In this study, we designed 15 polymorphic microsatellite markers by using genome sequences of two Ca. pauciramosa isolates having opposite mating type and from different countries. These markers were used to determine the genetic diversity of 145 isolates representing 13 different hosts (12 plant hosts residing in 12 genera, and soil) from 10 countries. In addition, mating type genes were amplified to investigate the reproduction mode of the pathogens in these populations by using mating type primers designed for Calonectria spp. Results revealed that a single dominant genotype, isolated from 11 plant genera residing in eight families, was present in seven countries across five continents. Only mating type MAT1-1 or MAT1-2 was amplified in each of the isolates, confirming that Ca. pauciramosa is heterothallic. Both mating types were detected in isolates from Eucalyptus in South Africa and Uruguay. The MAT1-2 phenotype was widely distributed in isolates from 12 different hosts (11 plant hosts and soil) collected in 10 countries. Overall, the results suggest that there has been substantial global movement of Ca. pauciramosa and that this has shaped its current population structure.

Species Diversity, Mating Strategy and Pathogenicity of Calonectria Species from Diseased Leaves and Soils in the Eucalyptus Plantation in Southern China

Many Calonectria species are causal agents of diseases on several forestry, agricultural and horticultural crops. Calonectria leaf blight is one of the most important diseases associated with Eucalyptus plantations and nurseries in Asia and South America. Recently, symptoms of leaf rot and leaf blight caused by Calonectria species were observed in a one-year-old Eucalyptus experimental plantation in GuangXi Province, southern China. To better understand the species diversity, mating strategy and pathogenicity of Calonectria species isolated from diseased tissues and soils, diseased leaves and soils under the trees from ten Eucalyptus urophylla hybrid genotypes were collected. Three hundred and sixty-eight Calonectria isolates were obtained from diseased Eucalyptus leaves and soils under these trees, and 245 representative isolates were selected based on the sampling substrates and Eucalyptus genotypes and identified by DNA sequence analyses based on the translation elongation factor 1-alpha (tef1), β-tubulin (tub2), calmodulin (cmdA) and histone H3 (his3) gene regions, as well as a combination of morphological characteristics. These isolates were identified as Calonectria hongkongensis (50.2%), C. pseudoreteaudii (47.4%), C. aconidialis (1.6%), C. reteaudii (0.4%) and C. auriculiformis (0.4%). This is the first report of C. reteaudii and C. auriculiformis occurrence in China. Calonectria pseudoreteaudii was isolated from both Eucalyptus diseased leaves and soils; the other four species were only obtained from soils. MAT1-1-1 and MAT1-2-1 gene amplification and mating type assignment results showed that C. pseudoreteaudii is heterothallic and an asexual cycle represents the primary reproductive mode, C. reteaudii and C. auriculiformis are likely to be heterothallic and C. hongkongensis and C. aconidialis are homothallic. Based on the genetic diversity comparisons for C. pseudoreteaudii isolates from diseased leaves and soils, we hypothesize that C. pseudoreteaudii in soils was spread from diseased leaves. Both the mycelia plug and conidia suspension inoculations indicated that all five Calonectria species were pathogenic to the two Eucalyptus genotypes tested and the tolerance of the two genotypes differed. It is necessary to understand the ecological niche and epidemiological characteristics of these Calonectria species and to select disease resistant Eucalyptus genotypes in southern China in the future.

Reconsideration of species boundaries and proposed DNA barcodes for Calonectria

Calonectria represents a genus of phytopathogenic ascomycetous fungi with a worldwide distribution. In recent years, there has been an increase in the number of taxonomic studies on these fungi. Currently, there are 169 described species of Calonectria based on comparisons of DNA sequence data, combined with morphological characteristics. However, for some of these species, the sequence data utilised at the time of their description were relatively limited. This has justified an urgent need to reconsider the species boundaries for Calonectria based on robust genus-wide phylogenetic analyses. In this study, we utilised 240 available isolates including the ex-types of 128 Calonectria species, and re-sequenced eight gene regions (act, cmdA, his3, ITS, LSU, rpb2, tef1 and tub2) for them. Sequences for 44 Calonectria species, for which cultures could not be obtained, were downloaded from GenBank. DNA sequence data of all the 169 Calonectria species were then used to determine their phylogenetic relationships. As a consequence, 51 species were reduced to synonymy, two new species were identified, and the name Ca. lauri was validated. This resulted in the acceptance of 120 clearly defined Calonectria spp. The overall data revealed that the genus includes 11 species complexes, distributed across the Prolate and Sphaero-Naviculate Groups known to divide Calonectria. The results also made it possible to develop a robust set of DNA barcodes for Calonectria spp. To accomplish this goal, we evaluated the outcomes of each of the eight candidate DNA barcodes for the genus, as well as for each of the 11 species complexes. No single gene region provided a clear identity for all Calonectria species. Sequences of the tef1 and tub2 genes were the most reliable markers; those for the cmdA, his3, rpb2 and act gene regions also provided a relatively effective resolution for Calonectria spp., while the ITS and LSU failed to produce useful barcodes for species discrimination. At the species complex level, results showed that the most informative barcodes were inconsistent, but that a combination of six candidate barcodes (tef1, tub2, cmdA, his3, rpb2 and act) provided stable and reliable resolution for all 11 species complexes. A six-gene combined phylogeny resolved all 120 Calonectria species, and revealed that tef1, tub2, cmdA, his3, rpb2 and act gene regions are effective DNA barcodes for Calonectria.

Calonectria pentaseptata Causes Severe Leaf Disease of Cultivated Eucalyptus on the Leizhou Peninsula of Southern China

Eucalyptus (Myrtaceae, Myrtales) trees are widely cultivated for commercial purposes worldwide. Calonectria leaf blight is one of the most prominent diseases associated with Eucalyptus trees grown in plantations in Asia and South America. Recently, symptoms of leaf blight, shoot blight, tree death, and seedling rot caused by Calonectria species have been observed in commercial Eucalyptus plantations and nurseries in Leizhou Peninsula, which is one of the most densely Eucalyptus-planted areas in southern China. Disease samples were collected from 10 Eucalyptus species and a number of Eucalyptus grandis, E. tereticornis, and E. urophylla hybrid genotypes that were planted on plantations at 13 sites and one experimental nursery. A total of 773 isolates of Calonectria were obtained from 683 plantation trees and nursery seedlings. Fifty-five representative isolates from all the surveyed sites and Eucalyptus species/genotypes were selected for molecular identification. These 55 isolates were identified by DNA sequence analyses based on the calmodulin (cmdA), histone H3 (his3), translation elongation factor 1-alpha (tef1), and β-tubulin (tub2) gene regions, as well as a combination of morphological characteristics. The results indicated that these 55 isolates present one single species, Calonectria pentaseptata. Determined by sequences of cmdA, his3, tef1, and tub2 gene regions, only two genotypes were identified among the 55 representative isolates; 54 of these isolates share the same genotype, suggesting that the genetic diversity of Ca. pentaseptata collected during this study was relatively low. A growth study indicated that Ca. pentaseptata is a high-temperature species. The mating test results suggested that Ca. pentaseptata is heterothallic or lacks the ability to recombine to produce fertile progeny. Inoculation results showed that Ca. pentaseptata causes leaf blight and stem rot, resulting in tree death of the two widely planted Eucalyptus genotypes in southern China, and that the two genotypes differ significantly in their susceptibility to infection by Ca. pentaseptata. A selection program to develop Eucalyptus planting stocks with high levels of resistance to Calonectria leaf blight in China during the long-term should be urgently initiated.[Formula: see text] Copyright © 2020 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Comparative genomic and transcriptomic analyses reveal different pathogenicity-related genes among three eucalyptus fungal pathogens

Ceratocystis fimbriata is an important plant pathogen known to cause Ceratocystis Wilt (CW), a prevalent fungal disease known to affect Eucalyptus spp. plantations in Brazil. To better understand the molecular mechanisms related to pathogenicity in eucalyptus, we generated a high-quality assembly and annotation of the Ce. fimbriata LPF1912 isolate (LPF1912) genome, as well as the first transcriptome of LPF1912 from 16 eucalyptus clones at three infection incubation periods (12, 18, and 24 h). The LPF1912 genome assembly contains 805 scaffolds, totaling 31.8 Mb, with 43% of the genome estimated to be coding sequence comprised of 7,390 protein-coding genes of which 626 (8.5%) were classified as secreted proteins, 120 ribosomal RNAs, and 532 transfer RNAs. Comparative genomic analysis among three eucalyptus fungal pathogens (Ce. fimbriata, Ce. eucalypticola, and Calonectria pseudoreteaudii), showed high similarity in the proteome (21.81%) and secretome (52.01%) of LPF1912 and Ce. eucalypticola. GO annotation of pathogenicity-related genes of LPF1912 and Ce. eucalypticola, revealed enrichment in cell wall degrading enzymes (CWDEs), and lipid/cutin metabolism for Ca. pseudoreteaudii. Additionally, a transcriptome analysis between resistant and susceptible eucalyptus clones to CW infection indicated that a majority (11) of LPF1912 differentially expressed genes had GO terms associated with enzymatic functions, such as the polygalacturonase gene family, confirming the crucial role of CWDEs for Ce. fimbriata pathogenicity. Finally, our genomic and transcriptomic analysis approach provides a better understanding of the mechanisms involved in Ce. fimbriata pathogenesis, as well as a framework for further studies.

Draft genome sequences of five Calonectria species from Eucalyptus plantations in China, Celoporthe dispersa, Sporothrix phasma and Alectoria sarmentosa

Draft genome sequences of five Calonectria species [including Calonectria aciculata, C. crousiana, C. fujianensis, C. honghensis and C. pseudoturangicola], Celoporthe dispersa, Sporothrix phasma and Alectoria sarmentosa are presented. Species of Calonectria are the causal agents of Eucalyptus leaf blight disease, threatening the growth and sustainability of Eucalyptus plantations in China. Celoporthe dispersa is the causal agent of stem canker in native Syzygium cordatum and exotic Tibouchina granulosa in South Africa. Sporothrix phasma was first discovered in the infructescences of Protea laurifolia and Protea neriifolia in South Africa. Alectoria sarmentosa is fruticose lichen belongs to the alectorioid clade of the family Parmeliaceae. The availability of these genome sequences will facilitate future studies on the systematics, population genetics, and genomics of these fungi.

Novel species of Calonectria isolated from soil near Eucalyptus plantations in southern China

Calonectria species are soil-borne and widely distributed in tropical and subtropical regions around the world. The species in this genus include many important plant pathogens that cause serious diseases to economically important crops and forest trees. Previous research results indicated that the leaf blight and cutting rot caused by Calonectria species caused big losses to the Eucalyptus industry in southern China, and large number of Calonectria species identified in China have been collected from soil in Eucalyptus plantations. In this study, Calonectria samples were isolated from soils close to Eucalyptus plantations in Guangdong Province, southern China. These isolates were identified by DNA sequence analyses based on the calmodulin (cmdA), histone H3 (his3), translation elongation factor 1-alpha (tef1), and β-tubulin (tub2) gene regions, and combined with morphological characteristics. One novel species of Calonectria was identified and described, named Calonectria xianrensis, which resides in the Prolate Group. Results in this study suggest that more species of Calonectria may be distributed in soils in China.

Foliar pathogens of eucalypts

Species of eucalypts are commonly cultivated for solid wood and pulp products. The expansion of commercially managed eucalypt plantations has chiefly been driven by their rapid growth and suitability for propagation across a very wide variety of sites and climatic conditions. Infection of foliar fungal pathogens of eucalypts is resulting in increasingly negative impacts on commercial forest industries globally. To assist in evaluating this threat, the present study provides a global perspective on foliar pathogens of eucalypts. We treat 110 different genera including species associated with foliar disease symptoms of these hosts. The vast majority of these fungi have been grown in axenic culture, and subjected to DNA sequence analysis, resolving their phylogeny. During the course of this study several new genera and species were encountered, and these are described. New genera include: Lembosiniella (L. eucalyptorum on E. dunnii, Australia), Neosonderhenia (N. eucalypti on E. costata, Australia), Neothyriopsis (N. sphaerospora on E. camaldulensis, South Africa), Neotrichosphaeria (N. eucalypticola on E. deglupta, Australia), Nothotrimmatostroma (N. bifarium on E. dalrympleana, Australia), Nowamyces (incl. Nowamycetaceae fam. nov., N. globulus on E. globulus, Australia), and Walkaminomyces (W. medusae on E. alba, Australia). New species include (all from Australia): Disculoides fraxinoides on E. fraxinoides, Elsinoe piperitae on E. piperita, Fusculina regnans on E. regnans, Marthamyces johnstonii on E. dunnii, Neofusicoccum corticosae on E. corticosa, Neotrimmatostroma dalrympleanae on E. dalrympleana, Nowamyces piperitae on E. piperita, Phaeothyriolum dunnii on E. dunnii, Pseudophloeospora eucalyptigena on E. obliqua, Pseudophloeospora jollyi on Eucalyptus sp., Quambalaria tasmaniae on Eucalyptus sp., Q. rugosae on E. rugosa, Sonderhenia radiata on E. radiata, Teratosphaeria pseudonubilosa on E. globulus and Thyrinula dunnii on E. dunnii. A new name is also proposed for Heteroconium eucalypti as Thyrinula uruguayensis on E. dunnii, Uruguay. Although many of these genera and species are commonly associated with disease problems, several appear to be opportunists developing on stressed or dying tissues. For the majority of these fungi, pathogenicity remains to be determined. This represents an important goal for forest pathologists and biologists in the future. Consequently, this study will promote renewed interest in foliar pathogens of eucalypts, leading to investigations that will provide an improved understanding of the biology of these fungi.

Ten new species of Calonectria from Indonesia and Vietnam

Vietnam and Indonesia have rapidly growing and extensive plantation forestry programs, especially of Acacia spp. and Eucalyptus spp. As these plantations expand, the threat from pests and diseases also increases. Calonectria species are among those pathogens causing diseases of trees in plantations and nurseries in these countries. Extensive surveys were conducted across plantations and nurseries of Vietnam and parts of Indonesia, where a large number of Calonectria isolates were retrieved from diseased leaves and soils associated with symptomatic trees. The aim of this study was to identify and resolve the phylogenetic relationships among these isolates using DNA sequence comparisons of four gene regions as well as morphological characters. From a collection of 165 isolates, the study revealed five known and 10 undescribed species. The relatively high diversity of Calonectria species found in this study supports the view that many more species in this genus remain to be discovered in other areas of Southeast Asia.

Whole genome and transcriptome analysis reveal adaptive strategies and pathogenesis of Calonectria pseudoreteaudii to Eucalyptus

BACKGROUND

Leaf blight caused by Calonectria spp. is one of the most destructive diseases to affect Eucalyptus nurseries and plantations. These pathogens mainly attack Eucalyptus, a tree with a diversity of secondary metabolites employed as defense-related phytoalexins. To unravel the fungal adaptive mechanisms to various phytoalexins, we examined the genome of C. pseudoreteaudii, which is one of the most aggressive pathogens in southeast Asia.

RESULTS

A 63.7 Mb genome with 14,355 coding genes of C. pseudoreteaudii were assembled. Genomic comparisons identified 1785 species-specific gene families in C. pseudoreteaudii. Most of them were not annotated and those annotated genes were enriched in peptidase activity, pathogenesis, oxidoreductase activity, etc. RNA-seq showed that 4425 genes were differentially expressed on the eucalyptus(the resistant cultivar E. grandis×E.camaldulensis M1) tissue induced medium. The annotation of GO term and KEGG pathway indicated that some of the differential expression genes were involved in detoxification and transportation, such as genes encoding ABC transporters, degrading enzymes of aromatic compounds and so on.

CONCLUSIONS

Potential genomic determinants of phytoalexin detoxification were identified in C. pseudoreteaudii by comparison with 13 other fungi. This pathogen seems to employ membrane transporters and degradation enzymes to detoxify Eucalyptus phytoalexins. Remarkably, the Calonectria genome possesses a surprising number of secondary metabolism backbone enzyme genes involving toxin biosynthesis. It is also especially suited for cutin and lignin degradation. This indicates that toxin and cell wall degrading enzymes may act important roles in the establishment of Calonectria leaf blight. This study provides further understanding on the mechanism of pathogenesis in Calonectria.

Calonectria species isolated from Eucalyptus plantations and nurseries in South China

Diseases caused by species of Calonectria (Ca.) represent a serious threat to the growth and sustainability of Eucalyptus plantations in China. Symptoms caused by these fungi mainly include leaf blight on trees in plantations and rotting of stems and leaves in nurseries. Extensive surveys have recently been conducted where Calonectria species were collected in Eucalyptus plantations and nurseries in the FuJian, GuangDong, GuangXi, and YunNan Provinces of South China. Additional isolates were baited from soil samples in the Hong Kong Region. The aim of this study was to identify the 115 Calonectria isolates obtained using comparisons of DNA sequence data for the β-tubulin (tub2), calmodulin (cmdA), histone H3 (his3) and partial translation elongation factor-1α (tef1) gene regions as well as their morphological features. Seven known species were identified, including Calonectria arbusta, Ca. asiatica, Ca. chinensis, Ca. eucalypti, Ca. hongkongensis, Ca. mossambicensis and Ca. pentaseptata. In addition, six novel taxa were collected and are described here as Ca. aciculata, Ca. honghensis, Ca. lantauensis, Ca. pseudoturangicola, Ca. pseudoyunnanensis, and Ca. yunnanensis spp. nov. Overall, the results reflect a high diversity of Calonectria species in China.

Botryosphaeriaceae from Eucalyptus plantations and adjacent plants in China

The Botryosphaeriaceae is a species-rich family that includes pathogens of a wide variety of plants, including species of Eucalyptus. Recently, during disease surveys in China, diseased samples associated with species of Botryosphaeriaceae were collected from plantation Eucalyptus and other plants, including Cunninghamina lanceolata, Dimocarpus longan, Melastoma sanguineum and Phoenix hanceana, which were growing adjacent to Eucalyptus. In addition, few samples from Araucaria cunninghamii and Cedrus deodara in two gardens were also included in this study. Disease symptoms observed mainly included stem canker, shoot and twig blight. In this study, 105 isolates of Botryosphaeriaceae were collected from six provinces, of which 81 isolates were from Eucalyptus trees. These isolates were identified based on comparisons of the DNA sequences of the internal transcribed spacer regions and intervening 5.8S nrRNA gene (ITS), and partial translation elongation factor 1-alpha (tef1), β-tubulin (tub), DNA-directed RNA polymerase II subunit (rpb2) and calmodulin (cmdA) genes, the nuclear ribosomal large subunit (LSU) and the nuclear ribosomal small subunit (SSU), and combined with their morphological characteristics. Results showed that these isolates represent 12 species of Botryosphaeriaceae, including Botryosphaeria fusispora, Cophinforma atrovirens, Lasiodiplodia brasiliense, L. pseudotheobromae, L. theobromae and Neofusicoccum parvum, and six previously undescribed species of Botryosphaeria and Neofusicoccum, namely B. pseudoramosa sp. nov., B. qingyuanensis sp. nov., B. wangensis sp. nov., N. hongkongense sp. nov., N. microconidium sp. nov. and N. sinoeucalypti sp. nov. Aside from B. wangensis, C. atrovirens and N. hongkongense, the other nine Botryosphaeriaceae species were isolated from Eucalyptus trees in South China. Botryosphaeria fusispora (26 % of the isolates from Eucalyptus) is the dominant species, followed by L. pseudotheobromae (23 % of the isolates from Eucalyptus). In addition to species found on Eucalyptus trees, we also found B. pseudoramosa on M. sanguineum; B. wangensis on C. deodara; C. atrovirens on D. longan; L. theobromae on C. lanceolata, D. longan and P. hanceana; and N. hongkongense on A. cunninghamii. Pathogenicity tests showed that the 12 species of Botryosphaeriaceae are pathogenic to three Eucalyptus clones and that Lasiodiplodia species are the most aggressive. The results of our study suggest that many more species of the Botryosphaeriaceae remain to be discovered in China. This study also provides confirmation for the wide host range of Botryosphaeriaceae species on different plants.

Genera of phytopathogenic fungi: GOPHY 1

Genera of Phytopathogenic Fungi (GOPHY) is introduced as a new series of publications in order to provide a stable platform for the taxonomy of phytopathogenic fungi. This first paper focuses on 21 genera of phytopathogenic fungi: Bipolaris, Boeremia, Calonectria, Ceratocystis, Cladosporium, Colletotrichum, Coniella, Curvularia, Monilinia, Neofabraea, Neofusicoccum, Pilidium, Pleiochaeta, Plenodomus, Protostegia, Pseudopyricularia, Puccinia, Saccharata, Thyrostroma, Venturia and Wilsonomyces. For each genus, a morphological description and information about its pathology, distribution, hosts and disease symptoms are provided. In addition, this information is linked to primary and secondary DNA barcodes of the presently accepted species, and relevant literature. Moreover, several novelties are introduced, i.e. new genera, species and combinations, and neo-, lecto- and epitypes designated to provide a stable taxonomy. This first paper includes one new genus, 26 new species, ten new combinations, and four typifications of older names.

Transcriptomic Analysis of Calonectria pseudoreteaudii during Various Stages of Eucalyptus Infection

Eucalyptus leaf blight caused by Calonectria spp. is a serious disease in Eucalyptus seedling and plantations. However, the molecular mechanisms of the infection process and pathogenesis of Calonectria to Eucalyptus is not well-studied. In this study, we analyzed the transcriptomes of C. pseudoreteaudii at three stages of Eucalyptus leaf infection, and in mycelium grown in potato dextrose broth using Illumina RNA-Seq technology. We identified 161 differentially expressed genes between C. pseudoreteaudii from leaf and mycelium grown in potato dextrose broth. GO and KEGG enrichment analyses of these genes suggested that they were mainly involved in oxidoreductase activity, hydrolase activity, and transmembrane transporter activity. Most of the differentially expressed genes at the early infection stage were upregulated. These upregulated genes were mainly involved in cell wall hydrolysis and toxin synthesis, suggesting a role for toxin and cell wall hydrolases in the establishment of Calonectria leaf blight. Genes related to detoxification of phytoalexins were continually upregulated during infection. The candidate effectors and putative pathogenicity determinants identified in this study will help in the functional analysis of C. pseudoreteaudii virulence and pathogenicity.

The forgotten Calonectria collection: Pouring old wine into new bags

The genus Calonectria with its Cylindrocladium asexual morphs has been subject to several taxonomic revisions in the past. These have resulted in the recognition of 116 species, of which all but two species (C. hederae and C. pyrochroa) are supported by ex-type cultures and supplemented with DNA barcodes. The present study is based on a large collection of unidentified Calonectria isolates that have been collected over a period of 20 years from various substrates worldwide, which has remained unstudied in the basement of the CBS-KNAW Fungal Biodiversity Centre. Employing a polyphasic approach, the identities of these isolates were resolved and shown to represent many new phylogenetic species. Of these, 24 are newly described, while C. uniseptata is reinstated at species level. We now recognise 141 species that include some of the most important plant pathogens globally.

Fungal Planet description sheets: 371-399

Novel species of fungi described in the present study include the following from Australia: Neoseptorioides eucalypti gen. & sp. nov. from Eucalyptus radiata leaves, Phytophthora gondwanensis from soil, Diaporthe tulliensis from rotted stem ends of Theobroma cacao fruit, Diaporthe vawdreyi from fruit rot of Psidium guajava, Magnaporthiopsis agrostidis from rotted roots of Agrostis stolonifera and Semifissispora natalis from Eucalyptus leaf litter. Furthermore, Neopestalotiopsis egyptiaca is described from Mangifera indica leaves (Egypt), Roussoella mexicana from Coffea arabica leaves (Mexico), Calonectria monticola from soil (Thailand), Hygrocybe jackmanii from littoral sand dunes (Canada), Lindgomyces madisonensis from submerged decorticated wood (USA), Neofabraea brasiliensis from Malus domestica (Brazil), Geastrum diosiae from litter (Argentina), Ganoderma wiiroense on angiosperms (Ghana), Arthrinium gutiae from the gut of a grasshopper (India), Pyrenochaeta telephoni from the screen of a mobile phone (India) and Xenoleptographium phialoconidium gen. & sp. nov. on exposed xylem tissues of Gmelina arborea (Indonesia). Several novelties are introduced from Spain, namely Psathyrella complutensis on loamy soil, Chlorophyllum lusitanicum on nitrified grasslands (incl. Chlorophyllum arizonicum comb. nov.), Aspergillus citocrescens from cave sediment and Lotinia verna gen. & sp. nov. from muddy soil. Novel foliicolous taxa from South Africa include Phyllosticta carissicola from Carissa macrocarpa, Pseudopyricularia hagahagae from Cyperaceae and Zeloasperisporium searsiae from Searsia chirindensis. Furthermore, Neophaeococcomyces is introduced as a novel genus, with two new combinations, N. aloes and N. catenatus. Several foliicolous novelties are recorded from La Réunion, France, namely Ochroconis pandanicola from Pandanus utilis, Neosulcatispora agaves gen. & sp. nov. from Agave vera-cruz, Pilidium eucalyptorum from Eucalyptus robusta, Strelitziana syzygii from Syzygium jambos (incl. Strelitzianaceae fam. nov.) and Pseudobeltrania ocoteae from Ocotea obtusata (Beltraniaceae emend.). Morphological and culture characteristics along with ITS DNA barcodes are provided for all taxa.

New species, hyper-diversity and potential importance of Calonectria spp. from Eucalyptus in South China

Plantation forestry is expanding rapidly in China to meet an increasing demand for wood and pulp products globally. Fungal pathogens including species of Calonectria represent a serious threat to the growth and sustainability of this industry. Surveys were conducted in the Guangdong, Guangxi and Hainan Provinces of South China, where Eucalyptus trees in plantations or cuttings in nurseries displayed symptoms of leaf blight. Isolations from symptomatic leaves and soils collected close to infected trees resulted in a large collection of Calonectria isolates. These isolates were identified using the Consolidated Species Concept, employing morphological characters and DNA sequence comparisons for the β-tubulin, calmodulin, histone H3 and translation elongation factor 1-alpha gene regions. Twenty-one Calonectria species were identified of which 18 represented novel taxa. Of these, 12 novel taxa belonged to Sphaero-Naviculate Group and the remaining six to the Prolate Group. Southeast Asia appears to represent a centre of biodiversity for the Sphaero-Naviculate Group and this fact could be one of the important constraints to Eucalyptus forestry in China. The remarkable diversity of Calonectria species in a relatively small area of China and associated with a single tree species is surprising.

Diversity and potential impact of Calonectria species in Eucalyptus plantations in Brazil

Species in the genus Calonectria (Hypocreales) represent an important group of plant pathogenic fungi that cause serious losses to plant crops in tropical and subtropical climates. Calonectria leaf blight is currently one of the main impediments to Eucalyptus cultivation in Brazil, and various species of Calonectria have been associated with this disease. Since most previous identifications were solely based on morphological characters, much of the published literature needs to be re-evaluated. The aim of this study was thus to identify and determine the phylogenetic relationships among species that occur in the Eucalyptus growing regions of Brazil by using partial sequences of the β-tubulin, calmodulin, translation elongation factor 1-α and histone H3 gene regions. Based on extensive collections from soil and infected eucalypt leaf samples from plantations, phylogenetic inference revealed the Ca. pteridis complex to be the most common species complex present in Eucalyptus plantations in Brazil. By elucidating taxa in the Ca. pteridis, Ca. cylindrospora and Ca. candelabra species complexes, 20 novel Calonectria species were identified, and a new name in Calonectria provided for Cylindrocladium macrosporum as Ca. pseudopteridis.

Transcriptome and proteome analysis of Eucalyptus infected with Calonectria pseudoreteaudii

Cylindrocladium leaf blight is one of the most severe diseases in Eucalyptus plantations and nurseries. There are Eucalyptus cultivars with resistance to the disease. However, little is known about the defense mechanism of resistant cultivars. Here, we investigated the transcriptome and proteome of Eucalyptus leaves (E. urophylla×E. tereticornis M1), infected or not with Calonectria pseudoreteaudii. A total of 8585 differentially expressed genes (|log2 ratio| ≥1, FDR ≤0.001) at 12 and 24hours post-inoculation were detected using RNA-seq. Transcriptional changes for five genes were further confirmed by qRT-PCR. A total of 3680 proteins at the two time points were identified using iTRAQ technique.The combined transcriptome and proteome analysis revealed that the shikimate/phenylpropanoid pathway, terpenoid biosynthesis, signalling pathway (jasmonic acid and sugar) were activated. The data also showed that some proteins (WRKY33 and PR proteins) which have been reported to involve in plant defense response were up-regulated. However, photosynthesis, nucleic acid metabolism and protein metabolism were impaired by the infection of C. pseudoreteaudii. This work will facilitate the identification of defense related genes and provide insights into Eucalyptus defense responses to Cylindrocladium leaf blight.

BIOLOGICAL SIGNIFICANCE

In this study, a total of 130 proteins and genes involved in the shikimate/phenylpropanoid pathway, terpenoid biosynthesis, signalling pathway, cell transport, carbohydrate and energy metabolism, nucleic acid metabolism and protein metabolism in Eucalyptus leaves after infected with C. pseudoreteaudii were identified. This is the first report of a comprehensive transcriptomic and proteomic analysis of Eucalyptus in response to Calonectria sp.

Genera in Bionectriaceae, Hypocreaceae, and Nectriaceae (Hypocreales) proposed for acceptance or rejection

With the recent changes concerning pleomorphic fungi in the new InternationalCode of Nomenclature for algae, fungi, and plants (ICN), it is necessary to propose the acceptance or protection of sexual morph-typified or asexual morph-typified generic names that do not have priority, or to propose the rejection or suppression¹ of competing names. In addition, sexual morph-typified generic names, where widely used, must be proposed for rejection or suppression in favour of asexual morph-typified names that have priority, or the latter must be proposed for conservation or protection. Some pragmatic criteria used for deciding the acceptance or rejection of generic names include: the number of name changes required when one generic name is used over another, the clarity of the generic concept, their relative frequencies of use in the scientific literature, and a vote of interested mycologists. Here, twelve widely used generic names in three families of Hypocreales are proposed for acceptance, either by conservation or protection, despite their lack of priority of publication, or because they are widely used asexual morph-typified names. Each pair of generic names is evaluated, with a recommendation as to the generic name to be used, and safeguarded, either through conservation or protection. Four generic names typified by a species with a sexual morph as type that are younger than competing generic names typified by a species with an asexual morph type, are proposed for use. Eight older generic names typified by species with an asexual morph as type are proposed for use over younger competing generic names typified by a species with a sexual morph as type. Within Bionectriaceae,Clonostachys is recommended over Bionectria; in Hypocreaceae,Hypomyces is recommended over Cladobotryum, Sphaerostilbella over Gliocladium, and Trichoderma over Hypocrea; and in Nectriaceae,Actinostilbe is recommended over Lanatonectria, Cylindrocladiella over Nectricladiella, Fusarium over Gibberella, Gliocephalotrichum over Leuconectria, Gliocladiopsis over Glionectria, Nalanthamala over Rubrinectria, Nectria over Tubercularia, and Neonectria over Cylindrocarpon.

Effects of Fungicide Treatments for the Control of Epidemic and Exotic Calonectria Diseases in Italy

The efficacy of 11 fungicides was evaluated for the control of Calonectria infections on bottlebrush (Callistemon "Masotti") and feijoa (Acca sellowiana), with special emphasis on Calonectria pauciramosa and C. morganii, which are the most destructive species in Italian ornamental nurseries. Three nursery experiments were performed with the selected fungicides in order to determine their ability to prevent leaf spot caused by C. morganii on bottlebrush and leaf spot and crown and root rot caused by C. pauciramosa on bottlebrush and feijoa. All fungicides were effective in reducing disease infections, except for cyproconazole, propamocarb + fosetyl-Al, and K phosphite that were the least effective in reducing C. morganii leaf spot. In contrast, K phosphite proved more effective in reducing crown and root rot caused by C. pauciramosa. Fungicides were also evaluated in growth-cabinet experiments for their ability to reduce incidence and severity of leaf spot on bottlebrush caused by the exotic pathogens C. pseudomexicana, C. tunisiana, C. polizzii, and C. mexicana. Copper hydroxide, fosetyl-Al, prochloraz, prochloraz + cyproconazole, and tebuconazole were always effective in reducing Calonectria leaf spot on bottlebrush. However, some differences in levels of control might be attributable to Calonectria isolate. Overall, this study clearly indicates that new fungicides can be employed for chemical management of Calonectria infections in ornamental nurseries.

Calonectria spp. causing leaf spot, crown and root rot of ornamental plants in Tunisia

Calonectria spp. are important pathogens of ornamental plants in nurseries, especially in the Northern Hemisphere. They are commonly associated with a wide range of disease symptoms of roots, leaves and shoots. During a recent survey in Tunisia, a number of Calonectria spp. were isolated from tissues of ornamental plants showing symptoms of leaf spot, crown and root rot. The aim of this study was to identify these Calonectria spp. using morphological and DNA sequence comparisons. Two previously undescribed Calonectria spp., C. pseudomexicana sp. nov. and C. tunisiana sp. nov., were recognised. Calonectria mexicana and C. polizzii are newly reported for the African continent. Pathogenicity tests with all four Calonectria spp. showed that they are able to cause disease on seedlings of Callistemon spp., Dodonaea viscosa, Metrosideros spp. and Myrtus communis.