Potential for Biological Control of Postharvest Fungal Rot of White Yam (Dioscorea rotundata Poir) Tubers in Storage with Trichoderma harzianum

Potential of Trichoderma harzianum for biological control of postharvest fungal rot of white yam (Dioscorea rotundata Poir) tubers in storage was studied. Pathogenicity test revealed the susceptibility of healthy looking yam tubers to Aspergillus niger, Botryodiplodia theobromae and Fusarium oxysporum f. sp. melonganae after fourteen days of inoculation. Treatments comprising A. niger, B. theobromae and F. oxysporum each paired with T. harzianum and were arranged in completely randomized design and stored for five months between December, 2015 and April, 2016 and December, 2016 and April, 2017. Results revealed that tubers treated with the pathogenic fungi alone caused mean percentage rot of between 6.67% (F. oxysporum) and 22.22% (A. niger) while the paired treatments produced only between 2.22% (T. harzianum X F. oxysporum) and 6.67% (T. harzianum X A. niger). In the second year of storage, mean percentage rots were between 13.33% (F. oxysporum) and 28.89% (A. niger) while in the paired treatment rots were only between 6.67% (F. oxysporum X T. harzianum) and 8.89% (A. niger X T. harzianum). Tubers treated with antagonist alone produced 0.00% and 2.22% in the first and second year respectively. Result revealed that there was a significant difference (P ≤ 0.05) in mean percentage rot between the first year and the second year except where B. theobromae was inoculated alone, A. niger and T. harzianum paired and B. theobromae and T. harzianum paired. The most antagonized fungus in paired treatment for both years was F. oxysporum f. sp. melonganae while the least antagonized was A. niger and B. theobromae. The study recommended the use of T. harzianum in the control of rot causing pathogens of yam tubers in storage as better alternative ways of reducing tuber rot compared with the use of chemical fungicides which are environmentally hazardous.