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.
