Pathogenicity, Characterisation and Racial Distribution of <i>Fusarium udum</i> Isolates in India Causing Wilt Disease of Pigeonpea ( <i>Cajanus cajan</i> )

ABSTRACT Wilt caused by Fusarium udum is one of the most important yield‐limiting factors of pigeonpea in India, causing enormous economic loss every year. For effective management, it is essential to distinguish variability among F. udum isolates in pigeonpea across India. A total of 500 plant samples from 14 pigeonpea‐growing states of the country were used for pathogenicity and identification of pathogenic F. udum races. On the basis of virulence and geographical locations, 55 virulent isolates representing different zones were selected for further grouping into races using a set of six pigeonpea genotypes as differentials (Bahar, C 11, ICP 8863, BDN 1, KPL 44 and ICP 9174). Based on pathogenic reactions of differential genotypes, these 55 isolates were grouped into five races: 15 isolates were grouped into race 1, 25 isolates into race 2, eight isolates into race 3, seven isolates into race 4 and five isolates into race 5. All 55 isolates of F. udum were molecularly characterised using histone 3 ( H3 ) and translation elongation factor ( TEF ) genes. The findings established that there exists a great diversity among F. udum isolates representing different parts of the country. We advocate that the racial characterisation in F. udum would be helpful not only for the development of race‐specific resistance in pigeonpea cultivars but also for the deployment of multiracial resistance in pigeonpea breeding programmes.