Pathogenic and genetic variation among Fusarium graminearum isolates causing head scab of wheat in India

Fusarium head blight (FHB) or head scab of wheat caused by Fusarium spp., is a global concern as recent outbreaks reported in Canada, Europe, Asia, Australia and South America. Presently, FHB is a minor disease in India but can cause significant yield loss if rain occurs during mid anthesis in Himachal Pradesh, Uttarakhand, the foot hills of Punjab and hilly areas in Tamil Nadu. Among head scab infected wheat ear heads collected from Dalang Maidan, Lahaul valley of Himachal Pradesh and Wellington, Nilgiris hills, Tamil Nadu, dominance of F. graminearum was observed. Twenty-nine Fusarium isolates were identified as F. graminearum based on morphological, cultural and molecular approaches. Pathogenic variation among 29 F. graminearum isolates was observed on wheat varieties (UP 2338, PBW 343, Sonalika, HD 2967, HD 3086, HD 29, MACS 5049, HS 645, VL 1013). After 7 and 14 days of inoculation, isolates from Wellington (Fg-W10 and Fg-W24) were found highly pathogenic while isolates Fg-W7 and Fg-W26 were found least pathogenic. Out of 23 SSR markers designed using whole genome sequence of F. graminearum PH-1 strain, 21 SSRs amplified F. graminearum isolates. Cluster analysis separated the isolates into two main groups. Group A consisting two isolates one from Wellington (Fg-W27) and another from Lahaul Spiti (Fg-L2). Group B contained all other 27 isolates. This study has shown that there is considerable pathogenic and genetic variability among F. graminearum isolates obtained from infected wheat ear heads from different geographic regions of India.