Black Scab of Jojoba (Simmondsia chinensis) in Australia Caused by a Putative New Pathotype of Elsinoë australis

Elsinoë australis Causing Spot Anthracnose on Poplar in China

Poplar plantations provide important industrial feedstock in China. Red spot symptoms were observed on leaves of Populus tomentosa and P. deltoides in southeastern China. Based on morphology and molecular phylogenetic analysis, the fungus isolated from disease spots was identified as Elsinoë australis, which has been previously recognized as a pathogen of Citrus spp. and jojoba but has not been reported in China. Pathogenicity tests found that isolates from two poplar species caused red spot symptoms on leaves from different poplar species and also led to scab formation on the fruit of one hybrid citrus but not on fruit of orange, lemon, or grapefruit. The draft genome of one E. australis isolate was generated. The genetic architecture of the MAT1-1 and MAT1-2 loci of E. australis was revealed by genome sequence and long-range PCR analyses. Single isolates carried only one of two opposite mating-types was confirmed by idiomorph-specific PCR, suggesting a heterothallic mating system. Our results not only revealed a new E. australis pathotype causing poplar spot anthracnose in China but also provided its genome and mating system information.

Genome mining of the citrus pathogen Elsinoë fawcettii; prediction and prioritisation of candidate effectors, cell wall degrading enzymes and secondary metabolite gene clusters

Elsinoë fawcettii, a necrotrophic fungal pathogen, causes citrus scab on numerous citrus varieties around the world. Known pathotypes of E. fawcettii are based on host range; additionally, cryptic pathotypes have been reported and more novel pathotypes are thought to exist. E. fawcettii produces elsinochrome, a non-host selective toxin which contributes to virulence. However, the mechanisms involved in potential pathogen-host interactions occurring prior to the production of elsinochrome are unknown, yet the host-specificity observed among pathotypes suggests a reliance upon such mechanisms. In this study we have generated a whole genome sequencing project for E. fawcettii, producing an annotated draft assembly 26.01 Mb in size, with 10,080 predicted gene models and low (0.37%) coverage of transposable elements. A small proportion of the assembly showed evidence of AT-rich regions, potentially indicating genomic regions with increased plasticity. Using a variety of computational tools, we mined the E. fawcettii genome for potential virulence genes as candidates for future investigation. A total of 1,280 secreted proteins and 276 candidate effectors were predicted and compared to those of other necrotrophic (Botrytis cinerea, Parastagonospora nodorum, Pyrenophora tritici-repentis, Sclerotinia sclerotiorum and Zymoseptoria tritici), hemibiotrophic (Leptosphaeria maculans, Magnaporthe oryzae, Rhynchosporium commune and Verticillium dahliae) and biotrophic (Ustilago maydis) plant pathogens. Genomic and proteomic features of known fungal effectors were analysed and used to guide the prioritisation of 120 candidate effectors of E. fawcettii. Additionally, 378 carbohydrate-active enzymes were predicted and analysed for likely secretion and sequence similarity with known virulence genes. Furthermore, secondary metabolite prediction indicated nine additional genes potentially involved in the elsinochrome biosynthesis gene cluster than previously described. A further 21 secondary metabolite clusters were predicted, some with similarity to known toxin producing gene clusters. The candidate virulence genes predicted in this study provide a comprehensive resource for future experimental investigation into the pathogenesis of E. fawcettii.

Pest categorisation of Elsinoë fawcettii and E. australis

The Panel on Plant Health performed a pest categorisation of Elsinoë fawcettii and E. australis, the causal agents of citrus scab diseases, for the EU. The identities of the pests are well-established and reliable methods exist for their detection/identification. The pests are listed in Annex IIAI of Directive 2000/29/EC as Elsinoë spp. and are not known to occur in the EU. Species and hybrids of citrus (Family Rutaceae) are affected by E. fawcettii and E. australis, with the latter having a more restricted host range and geographical distribution compared to the former. The status of Simmondsia chinensis (jojoba) as a host of E. australis is uncertain. The pests could potentially enter the EU on host plants for planting and fruit originating in infested Third countries. The current distribution of the pests, climate matching and the use of irrigation in the EU citrus-growing areas suggest that the pests could establish and spread in the EU citrus-growing areas. Uncertainty exists on whether cultural practices and control methods, currently applied in the EU, would prevent the establishment of the pests. In the infested areas, the pests cause scab pustules on host leaves and fruit resulting in yield/quality losses. It is expected that the introduction and spread of the pests in the EU could impact citrus production. Cultural practices and chemical control measures may reduce the inoculum sources and to some extent the disease incidence, but they cannot eliminate the pests. Phytosanitary measures are available to mitigate the risk of introduction and spread of the pests in the EU. E. fawcettii and E. australis meet all the criteria assessed by EFSA for consideration as potential Union quarantine pests. As those pests are not known to occur in the EU, this criterion to consider them as Union regulated non-quarantine pests is not met.

A review on plant importance, biotechnological aspects, and cultivation challenges of jojoba plant

Jojoba is considered a promising oil crop and is cultivated for diverse purposes in many countries. The jojoba seed produces unique high-quality oil with a wide range of applications such as medical and industrial-related products. The plant also has potential value in combatting desertification and land degradation in dry and semi-dry areas. Although the plant is known for its high-temperature and high-salinity tolerance growth ability, issues such as its male-biased ratio, relatively late flowering and seed production time hamper the cultivation of this plant. The development of efficient biotechnological platforms for better cultivation and an improved production cycle is a necessity for farmers cultivating the plant. In the last 20 years, many efforts have been made for in vitro cultivation of jojoba by applying different molecular biology techniques. However, there is a lot of work to be done in order to reach satisfactory results that help to overcome cultivation problems. This review presents a historical overview, the medical and industrial importance of the jojoba plant, agronomy aspects and nutrient requirements for the plant's cultivation, and the role of recent biotechnology and molecular biology findings in jojoba research.