Distribution and pathogenic diversity in Fusarium udum Butler isolates: the causal agent of pigeonpea Fusarium wilt

Background: Fusarium wilt (Fusarium udum Butler), an important soil-borne disease of pigeonpea [Cajanus cajan (L.)], causes significant yield losses across the major pigeonpea production regions. Widespread and high diversity in F. udum hampers the breeding for pigeonpea wilt resistance. The study aimed to elucidate the pathogenic diversity and distribution of F. udum variants in major pigeonpea growing regions of India. Results: The roving survey was conducted in major pigeonpea-growing states of India to collect the F. udum isolates. Pathogenic variability of 60 F. udum isolates which are selected from diverse geographical locations and pathogenicity test were performed against 11 pigeonpea host differentials cultivars [ICP 8858, ICP 8859, ICP 8862, ICP 8863, ICP 9174, C 11, BDN 1, BDN 2, LRG 30, ICP 2376 and Bahar (ICP 7197)]. The current study indicated distribution of F. udum isolates into nine variants (0, 1, 2, 3, 4, 5, 6, 7 and 8). Variant-2 and 3 were found to be widespread and predominant in most pigeonpea producing regions. Variant-7 (Karnataka) and Variant-8 (Madhya Pradesh and Maharashtra) were found highly virulent, as most of the host differentials were susceptible to these variants. Three host differential cultivars namely ICP 9174, BDN-2 and Bahar (ICP 7197) were found resistant to most of the F. udum isolates. Conclusion: The present study generated significant information in terms of variants of F. udum which could be used further for the deployment of location-specific wilt resistant cultivars for optimized disease-management strategies. Study is also useful for development of broad-based wilt resistant cultivars to curtail the possible epidemics