Endophytic Beauveria bassiana increases galling of ‘Rutgers’ tomato roots with Meloidogyne incognita

Beauveria bassiana is endophytic in many plant species and has been shown to protect host plants against insect pests and plant pathogens. However, less is known about its activity against plant-parasitic nematodes. In vitro and plant assays were conducted to determine the effect of B. bassiana 11-98 (Bb) on Meloidogyne incognita (root-knot nematode; RKN). Beauveria bassiana was confirmed as an endophyte in ‘Rutgers’ tomato and colonization patterns of Bb in ‘Rutgers’ (highly susceptible to RKN) were compared with those in ‘Mountain Spring’ (less susceptible to RKN). In greenhouse tests with ‘Rutgers’ at 30 and 60 days after treatment (DAT) with RKN and Bb, there were few differences in plant growth variables among treatments in repeated trials. However, RKN root galling and egg count/root system were enhanced in plants treated with Bb at 60 DAT. In an in vitro assay with egg masses from greenhouse tests, the percentages of hatched eggs, and mobile and immobile nematodes did not differ significantly for RKN and RKN+Bb treatments. The presence of viable Bb from roots was confirmed by collecting egg suspensions from root galls and plating them on selective medium. Colonies of Bb were verified on agar medium, but no parasitism of RKN eggs was observed. Research is needed to investigate factors responsible for increased galling by RKN in the presence of endophytic Bb in ‘Rutgers’ tomato

ENDOPHYTIC BEAUVERIA BASSIANA: A TOOL FOR COMPREHENSIVE PLANT PROTECTION

Beneficial microbial endophytes live inside plants and establish a mutualistic relationship with the host plant, obtaining nutrition and shelter, and providing protection to the host against biotic and abiotic stresses. Beneficial endophytes have emerged as alternatives to chemical pesticides for control of plant pests and diseases. The insect pathogenic fungus, Beauveria bassiana (Bb), is endophytic in some plant species. Remarkably, endophytic Bb can protect host plants against both insect pests and plant pathogens. However, less is known about the effectiveness of Bb against phytopathogens, especially plant-parasitic nematodes. Therefore, to better understand the body of published research on endophytic Bb, three separate meta-analyses were performed to determine: 1) the rate of colonization of various plant species by endophytic Bb; 2) the efficacy of endophytic Bb against insect pests, and 3) the suppression of plant pathogens by endophytic Bb. Furthermore, efficacy of Bb against root knot nematodes was tested with an in vitro bioassay. Meta-analysis revealed that Bb most effectively colonizes eudicots, angiosperms, the family Brassicaceae, and the edible crop, faba bean. Colonization was most effective in leaves and plants with fibrous roots, and when Bb was applied to foliage of whole plants. Meta-analysis of endophytic Bb efficacy against insects revealed that Bb was most effective against the insect order Hemiptera, family Aphididae, especially cotton aphids. Meta-analysis on phytopathogens indicated that endophytic Bb could significantly suppress plant disease, especially aphid-borne potyvirus. In nematode assays, Bb inhibited Meloidogyne incognita egg hatch, and hatch was indirectly proportional to the ratio of Bb conidia to nematode eggs. In summary, endophytic Bb has activity against insect pests and plant pathogens, including plant-parasitic nematodes. Meta-analyses provided a comprehensive view of the current knowledge on endophytic Bb research. These findings provide a valuable tool in further development of Bb as a sustainable plant disease management strategy