The tripartite consortium of Serendipita indica, Trichoderma simmonsii, and bell pepper (Capsicum annum)

Abstract

Bell pepper (Capsicum annuum) is one of the most widely grown vegetables worldwide. Human health and environmental issues have raised the tendency to use biofertilizers⁄biopesticides as valuable tools in sustainable agriculture. The application of bioinoculants with the potential of plant growth promotion and biocontrol activity against diseases should be a promising alternative for the future of production systems. A combination of two compatible micro-organisms, Serendipita indica and Trichoderma simmonsii, were evaluated for their plant growth promotion/and biocontrol activity against Phytopthtora capsici on bell pepper. We also examined the impacts of varying inoculum concentrations of S. indica on the vegetative growth and against the pathogen at different phenologic stages of the plant. While we recorded a constant range of “percent root colonization” (55–56%) in response to varying inoculum concentrations across all the treatments, light microscopy observation showed the significant effect of the inoculum levels on the root colonization density by the fungus. Seed germination and germination earliness were not affected by individual or the consortium of the bioinoculants, however, a significant negative effect on seed germination was recorded with the increase of inoculum concentrations. Seed inoculation with lower inoculum concentrations (1–3% w/w) of S. indica brought about a significant increase in the vegetative growth of the plant in the greenhouse and field conditions. However, greater concentrations either did not significantly stimulated the plant growth or had less positive effects in comparison to lower ones. Greenhouse and field trials showed S. indica to have a greater impact on the growth parameters in comparison to T. simmonsii or combined use of the bioinoculants. Both the consortium of the fungi and S. indica brought about a significant increase of up to 67% in the bell pepper yield. In the case of bioprotection of the plant against P. capsici pre-emergence seed rot and plantlet blights, the most effective was the consortium of the bioinoculants in terms of declining the disease index. Therefore, we suggest this combination can provide a promising feature as a complement for crop nutrition and enhancing the plant tolerance to P. capsici.