Biocontrol potential of Trichoderma spp. isolated from tea (Camellia sinensis) plantations against key postharvest fungal pathogens of banana

Abstract

Sri Lanka is a top exporter of the global favorite fruit; banana and is home to many varieties. However, bananas are highly susceptible to many postharvest fungal diseases such as anthracnose, cigar end rot and crown rot. Colletotrichum musae, Lasiodiploidea theobromae and Colletotrichum gloeosporioides are major causal agents of these diseases. Meanwhile, tea (Camellia sinensis), another major export crop for Sri Lanka, harbors a unique microbial niche, that includes Trichoderma sp., fungus with well documented biocontrol properties through the mechanisms such as mycoparasitism, competition and antibiosis. Twelve Trichoderma spp. isolates were obtained from the microflora of tea plantations and characterized based on colony morphology and growth rate. Their inhibitory activity against the selected banana pathogens were determined, focusing on the biocontrol agent-pathogen interactions through mycelia, volatile compounds and non-volatile compounds. The seven most promising isolates from dual culture assays were further tested for pathogenicity on banana fruits. The most effective, non pathogenic, isolate was selected for detailed assessment of its effect on spore germination of the pathogens. Modes of interaction were further analyzed using light microscopy and scanning electronic microscopy, revealing features such as hyphal coiling and squeezing, typical of mycoparasites’ behavior. FTIR spectroscopy was used to detect the presence or absence of organic compounds such as peptaibols, associated with antibiosis mechanism. Out of the 12 primary isolates, one Trichoderma isolate, TYST6, showed significant inhibition (P<0.05) with 71%, 60% and 72% reduction against Colletotrichum musae, Lasiodiploidea theobromae and Colletotrichum gloeosporioides respectively, compared to undisturbed growth. It was non pathogenic. A bioagent that can control these diseases would reduce postharvest losses and food wastage.