The role of Trichoderma koningii and Trichoderma harzianum in mitigating the combined stresses motivated by Sclerotiniasclerotiorum and salinity in common bean (Phaseolusvulgaris)

Abstract

Under natural conditions, crops typically suffer from severe challenges due to the increasing of abiotic and biotic stresses which severely affect plant growth and reduc crop yield. The present study investigated the single and combined impacts of Sclerotinia sclerotiorum and salinity stress on common bean (Phaseolus vulgaris L.) seedling which is scarcely studied. The study evaluated the in vitro and in vivo influence of two salinity tolerant Trichoderma isolates, T. koningii and T. harzianum against S. sclerotiorum under salinity stress. The results showed the ability of T. koningii and T. harzianum to grow and sporulate at high levels of salinity, 80 mM NaCl, without significantly impacting their ability to produce cell wall degrading enzymes, cellulase and chitinase. Amylase and proteinase (Prb1) genes were detected in T. harzianum. The in vitro assay revealed that both isolates could inhibit the growth of S. sclerotiorum under high salinity concentrations. In a greenhouse experiment, both Trichoderma isolates ameliorated the damaging impacts of S. sclerotiorum under salinity stress on common bean seedlings' germination and growth characteristics compared to their untreated control. Both bioagents significantly attenuated the damping-off and collar/stem rot percentages of infected common bean under salinity stress. Salinity stress intensified the effect of S. sclerotiorum on photosynthetic pigments, induced oxidative and nitrative stress, hampered ionic homeostasis, and deactivated antioxidants and defense-related molecules. On the other hand, Trichoderma isolates restrained the reduction of chlorophylls and carotenoids, ascorbate, reduced glutathione, flavonoids, phenolics, and various antioxidant enzymes, especially for single stresses and T. harzianum. All these upregulations reflected in keeping the cell membranes of common beans seedling more stable where the levels of lipid peroxidation and methylglyoxal due to the reduction of reactive oxygen species and upregulation of nitric oxide, which expressed better growth under pathogen attack or/and saline. The tested isolates, T. koningii and T. harzianum could be used as effective biological control against S. sclerotiorum on common beans in saline soils or areas irrigated with saline water.