Screening and efficacy evaluation of antagonistic fungi against Phytophthora infestans and combination with arbuscular mycorrhizal fungi for biocontrol of late blight in potato

Abstract

Late blight caused by Phytophthora infestans is the most devastating disease of potato crops worldwide. Control practices mostly rely on synthetic fungicides or copper-based products. In recent years, biological control agents have generated significant enthusiasm as eco-friendly sustainable alternatives. Here, the filtrates of 149 filamentous fungi and yeasts were tested in vitro against P. infestans MUCL 54981. The most effective filtrates were then combined in alginate beads with the arbuscular mycorrhizal fungus (AMF) Rhizophagus irregularis MUCL 41833 and tested in vitro for their compatibility, and finally in the greenhouse for their efficacy against P. infestans. The filtrates of Penicillium aurantiogriseum MUCL 47586, Penicillium griseofulvum MUCL 29201, Trichoderma virens MUCL 18139, and Verticillium psalliotae MUCL 18310 totally suppressed conidial germination and growth of P. infestans in vitro. In whole potato plants in vitro, only the filtrate of T. virens significantly suppressed P. infestans plant infestation. With the exception of P. griseofulvum, none of the selected filtrates affected the germination, root colonization, and spore production of R. irregularis following their combined entrapment in alginate beads. According to these results, the filtrate of T. virens was selected for the greenhouse experiment with the potato variety Annabelle. The filtrate was used as leaf spray and/or as root treatment in combination with R. irregularis entrapped in alginate beads. Root treatments with AMF alone as well as with the AMF entrapped with the filtrate of T. virens significantly reduced the area under disease progress curve compared to the non-treated plants. LC-MS analyses of the filtrate showed the production of koninginin D, gliotoxin, and koningic acid, three antifungal compounds, which could have impacted P. infestans. Conversely, foliar application of the filtrate, whether the plant was colonized by the AMF or not, did not reduce symptoms of the disease, possibly because of the greenhouse growth conditions making the potato plants more susceptible to P. infestans and counterbalancing the positive effects of the antimicrobial secondary metabolites or AMF. Our results demonstrated the potential of R. irregularis MUCL 41833 combined or not with a filtrate of T. virens MUCL 18139 into alginate beads as a biological control strategy against P. infestans.

Friend or Foe? Biocontrol interactions of Pythium oligandrum within the potato cropping system

“…infestans (De Vrieze et al, 2020). Finally, in a recent study induced resistance caused by BCAs was also speculated to play a part in the reduction of late blight symptoms on potato plants cultivated in vitro (Lalaymia et al, 2022).…”

Environmental and Agronomical Factors Limiting Differences in Potato Yielding between Organic and Conventional Production System

“…In addition to the above-mentioned agrotechnical treatments limiting the development of late blight, alternative methods of controlling late blight are still being sought. Research on biological methods using the antagonistic effects of bacteria and fungi in combating late blight is being conducted all the time [92]. Positive results are most often obtained in laboratory tests.…”

Secondary Metabolites, Other Prospective Substances, and Alternative Approaches That Could Promote Resistance against Phytophthora infestans

“…The direct application of living microbes could have undesirable side effects on the plant host, the microflora, and the soil environment. This can be avoided by the application of cell-free extracts [72,73]. On the other hand, the metabolome of endophytes varies depending on their environment.…”