Non-Synergistic Effect of Trichoderma harzianum and Glomus spp. in Reducing Infection of Fusarium Wilt in Banana

Microbial-Based Biofungicides Mitigate the Damage Caused by Fusarium oxysporum f. sp. cubense Race 1 and Improve the Physiological Performance in Banana

Fusarium wilt of banana (FWB) is the most limiting disease in this crop. The phytosanitary emergency caused by FWB since 2019 in Colombia has required the development of ecofriendly control methods. The aim of this study was to test the effectiveness of microbial-based biofungicides against FWB caused by Fusarium oxysporum f. sp. cubense race 1 (Foc R1) and correlate such effect with plant physiological parameters. Five Trichoderma (T1 to T4 and T9) and four Bacillus (T5 to T8)-based biofungicides were evaluated in pot experiments. In vitro, dual confrontation tests were also carried out to test whether the in vitro effects on Foc growth were consistent with the in vivo effects. While Trichoderma-based T3, T4, and T9, and Bacillus-based T8, significantly reduced the growth of Foc R1 in vitro, Trichoderma-based T1, T3, T4, and T9 temporarily reduced the Foc population in the soil. However, the incidence progress of FWB was significantly reduced by Bacterial-based T7 (74% efficacy) and Trichoderma-based T2 (50% efficacy). The molecular analysis showed that T7 prevented the inner tissue colonization by Foc R1 in 80% of inoculated plants. The T2, T4, T7, and T9 treatments mitigated the negative effects caused by Foc R1 on plant physiology and growth. Our data allowed us to identify three promising treatments to control FWB, reducing the progress of the disease, delaying the colonization of inner tissue, and mitigating physiological damages. Further studies should be addressed to determine the modes of action of the biocontrol agents against Foc and validate the utilization in the field.

Whole Genome Sequencing Reveals Novel Insights about the Biocontrol Potential of Burkholderia ambifaria CF3 on Atractylodes lancea

Root rot caused by Fusarium spp. is the most destructive disease on Atractylodes lancea, one of the large bulks and most common traditional herbal plants in China. In this study, we isolated a bacterial strain, CF3, from the rhizosphere soil of A. lancea and determined its inhibitory effects on F. oxysporum in both in vitro and in vivo conditions. To deeply explore the biocontrol potential of CF3, we sequenced the whole genome and investigated the key pathways for the biosynthesis of many antibiotic compounds. The results revealed that CF3 is a member of Burkholderia ambifaria, harboring two chromosomes and one plasmid as other strains in this species. Five antibiotic compounds were found that could be synthesized due to the existence of the bio-synthesis pathways in the genome. Furthermore, the synthesis of antibiotic compounds should be confirmed by in vitro experiments and novel compounds should be purified and characterized in further studies.

Recent advances in the use of Trichoderma-containing multicomponent microbial inoculants for pathogen control and plant growth promotion

Chemical pesticides and fertilizers are used in agricultural production worldwide to prevent damage from plant pathogenic microorganisms, insects, and nematodes, to minimize crop losses and to preserve crop quality. However, the use of chemical pesticides and fertilizers can severely pollute soil, water, and air, posing risks to the environment and human health. Consequently, developing new, alternative, environment-friendly microbial soil treatment interventions for plant protection and crop yield increase has become indispensable. Members of the filamentous fungal genus Trichoderma (Ascomycota, Sordariomycetes, Hypocreales) have long been known as efficient antagonists of plant pathogenic microorganisms based on various beneficial traits and abilities of these fungi. This minireview aims to discuss the advances in the field of Trichoderma-containing multicomponent microbiological inoculants based on recent experimental updates. Trichoderma strains can be combined with each other, with other fungi and/or with beneficial bacteria. The development and field performance of such inoculants will be addressed, focusing on the complementarity, synergy, and compatibility of their microbial components.

Isolation and Identification of Talaromyces sp. Strain Q2 and Its Biocontrol Mechanisms Involved in the Control of Fusarium Wilt

Fusarium wilt is an important disease of many food crops and often causes serious damages to yield and food quality. Consequently, numerous studies mainly focused on exploring the control strategy for Fusarium oxysporum as well as the mechanism of interaction between the F. oxysporum and other beneficial soil microorganisms. In this study, we have screened and identified an efficient biocontrol strain from the soil with infection of F. oxysporum f. sp. momordica (referred to as Fom), Talaromyces purpurogenus Q2 (referred to as TpQ2), which could be effective to reduce relative abundance of the rhizospheric Fom, leading to a significant decrease of Fusarium wilt disease incidence in bitter gourd during the greenhouse and field trails. TpQ2 can reduce the relative abundance of rhizospheric Fom through inhibition of growth and development of Fom. During the co-cultivation of TpQ2 and Fom, we confirmed that TpQ2 could significantly suppress the growth and development of Fom through disturbing the normal hyphae shape and function of the cell walls of Fom via secreting cell wall–degrading enzymes and suppression of the expression of cell wall biosynthesis genes, such as FomCFEM. In the meantime, TpQ2 showed a strong negative correlation with F. oxysporum in soil and positive correlation with beneficial indigenous microorganisms that had significant negative correlation with Fusarium populations, such as Streptomycetes, Lysobacter, and Sphingobium. To summarize, TpQ2 has a good biocontrol efficacy on Fusarium wilt of bitter gourd. The biocontrol mechanisms of TpQ2 on Fusarium wilt are complex and diverse.

The Combination of a Biocontrol Agent Trichoderma asperellum SC012 and Hymexazol Reduces the Effective Fungicide Dose to Control Fusarium Wilt in Cowpea

The use of synthetic fungicide needs to be gradually reduced because of its adverse effect on human health and the environment. An integrated approach combining fungicides with biological control agents (BCAs) can be used to reduce the fungicide doses, thereby minimizing the risks associated with chemical fungicides. In this study, the combined application of a BCA Trichoderma and a fungicide hymexazol was used to manage the cowpea wilt disease caused by Fusarium oxysporum. The Trichoderma SC012 strain, which is resistant to hymexazol, was screened out and identified as T. asperellum. T. asperellum SC012 showed hyperparasitism to F. oxysporum and could penetrate and encircle the hyphae of pathogen on a medium amended or not with hymexazol. When combined with hymexazol, the population density in the rhizosphere soil of cowpea showed no significant difference compared with the treatment Trichoderma used alone. When the concentration of T. asperellum SC012 or hymexazol was halved, their combined application could control cowpea wilt disease more effectively than their individual use. The findings showed that the combination of Trichoderma and hymexazol could reduce the use of chemical fungicide, which is eco-friendly and may be an important part of integrated control of Fusarium wilt in cowpea.

Inoculation with arbuscular mycorrhizal fungus modulates defense-related genes expression in banana seedlings susceptible to wilt disease

Banana as an important economic crop worldwide, often suffers from serious damage caused by Fusarium oxysporum f. sp. Cubense. Arbuscular mycorrhizal (AM) fungi have been considered as one of the promising plant biocontrol agents in preventing from root pathogens. This study examined the effect of AM fungal inoculation on plant growth and differential expressions of growth- and defense-related genes in banana seedlings. Tissue-cultured seedlings of Brazilian banana (Musa acuminate Cavendish cv. Brail) were inoculated with AM fungus (Rhizophagus irregularis, Ri), and developed good mycorrhizal symbiosis from 4 to 11 weeks after inoculation with an infection rate up to 71.7% of the roots system. Microbial abundance revealed that Ri abundance in banana roots was 1.85×106 copies/ml at 11 weeks after inoculaiton. Inoculation improved plant dry weights by 47.5, 124, and 129% for stem, leaf, and the whole plant, respectively, during phosphate depletion. Among a total of 1411 differentially expressed genes (DEGs) obtained from the transcriptome data analysis, genes related to plant resistance (e.g. POD, PAL, PYR, and HBP-1b) and those related to plant growth (e.g. IAA, GH3, SAUR, and ARR8) were up-regulated in AM plants. This study demonstrates that AM fungus effectively promoted the growth of banana plants and induced defense-related genes which could help suppress wilt disease. The outcomes of this study form a basis for further study on the mechanism of banana disease resistance induced by AM fungi.

Weed-Associated Fungal Endophytes as Biocontrol Agents of Fusarium oxysporum f. sp. cubense TR4 in Cavendish Banana

The antagonistic activity of fungal endophytes isolated from weeds growing in Cavendish banana farms was determined against Fusarium oxysporum f. sp. cubense TR4 (Foc TR4) causing Fusarium wilt of Cavendish banana. Forty-nine out of the total 357 fungal endophytes from the roots of weeds exhibited antagonistic activity against Foc TR4. High inhibitory activity at 79.61–99.31% based on dual culture assay was recorded in endophytes Lasiodiplodia theobromae TDC029, Trichoderma asperellum TDC075, Ceratobasidium sp. TDC037, Ceratobasidium sp. TDC241, and Ceratobasidium sp. TDC474. All five endophytes were identified through DNA sequencing with 86–100% identity. Endophyte-treated Grand Naine and GCTCV 218 plantlets showed significantly lower disease incidence (p = 0.014), significantly lower degree of leaf yellowing (p = 0.037) and rhizome discoloration (p = 0.003). In addition, the cultivar Grand Naine was consistently highly susceptible compared with the tolerant cultivar GCTCV 218.

Biological Control of Alternaria Leaf Spot Caused by Alternaria spp. in Jerusalem Artichoke (Helianthus tuberosus L.) under Two Fertilization Regimes

The objectives of this study were to evaluate the efficacy of integrating resistant genotypes of Jerusalem artichoke with Trichoderma harzianum isolate T9 to control Alternaria leaf spot caused by Alternaria spp. under two fertilization regimes and to determine whether T9 application induced chitinase and β-1,3-glucanase activity in Jerusalem artichoke leaves. Six Jerusalem artichoke varieties (resistant varieties JA15, JA86, and JA116 and susceptible varieties HEL246, HEL293, and JA109) and three disease control methods (a non-inoculated control, application of T. harzianum T9, and fungicide sprays (propiconazole at a rate of 30 mL/20 L of water, 375 ppm)) was conducted in two separate trials (different fertilization regimes) at the experimental farm of the Faculty of Agriculture, Khon Kaen University, Khon Kaen, Thailand. Resistant genotypes controlled Alternaria leaf spot effectively. Application of Trichoderma showed low efficacy to control Alternaria leaf spot, but in specific susceptible genotypes-HEL246 and HEL293-the application of Trichoderma could reduce disease severity up to 10%. The application of Trichoderma was associated with a rise in production of chitinase and β-1,3-glucanase in HEL246 seedlings. The number of Trichoderma propagules in soil, as well as the extent of colonization of roots and leaves, were monitored. The results indicated that application of Trichoderma had higher propagules than non-inoculated control. Neither varietal resistance nor the disease control methods used in this study impacted the yield or yield components of Jerusalem artichoke.