Assessing the in vitro efficacy of biocontrol agents and oil cakes against basal rot of onion incited by Fusarium oxysporum f.sp. cepae

Abstract

Onions are an important vegetable crop, which is infected by many soils and foliar pathogens. Among them, Fusarium Basal Rot (FBR) causes yield losses of up to 50 per cent in the field and 30 to 40 per cent during post-harvest storage of bulbs. For management of basal rot of onion, the efficacy of native antagonists such as six different Trichoderma sp. (T1-T6), five different Bacillus sp. (B1-B5) and five different oil cakes was assessed against the Fusarium oxysporum f.sp. cepae under in vitro condition. Among them, T3 collected from Kulithalai recorded maximum virulence as well as dark green sporulation with conidia length of 2.68–3.25 and breadth of 2.54-3.46µ. Among the tested isolates, In the case of Bacillus sp., isolate B4 recorded the maximum inhibition zone (66.16%), followed by B. subtilis (B5), which recorded a (59.03%) inhibition on the mycelial growth. Among the five different oil cakes, the filtrates of neem cake showed a maximum inhibition zone against F. oxysporum f.sp. cepae of 1.29 cm @ 15% concentration, followed by groundnut cake at 1.36 cm @ 30% concentration. Hence the different control measures, Trichoderma sp. showed critically acclaimed performance under in vitro than others. The combined application of Trichoderma sp, Bacillus sp and neem oilcake significantly inhibited the growth of basal rot of onion due to the presence of the antimicrobial property.