Variability in Fusarium oxysporum f.sp. ciceris causing wilt in chickpea

Fusarium wilt caused by Fusarium oxysporum f.sp. ciceris (Padwick) Matuo and K. Sato is a major constraint in successful cultivation of chickpea. Therefore, in the present study, 24 isolates of F. oxysporum f.sp. ciceris collected from different chickpea growing areas of Punjab and adjoining states were assessed for morphological variations. Among 24 isolates, the maximum (8.78 mm/days) and minimum (5.00 mm/day) growth rate were exhibited by Foc-21 and Foc-15, respectively. The isolates showed growth pattern from appressed, fluffy to less fluffy and mycelial colour varied from different shades of white to purplish white. A significant variation with respect to size of micro (8.9-16.9 x 3.1-6.3 µm) and macro (21.7-64.9 x 2.7-10.0 µm) conidia was also observed. At pathogenic level, twenty isolates were studied where Foc-3, Foc-7 and Foc-22 showed virulence pattern similar to existing races 1, 2, 3 and 4 on three standard differentials viz. JG 62, WR 315 and L 550, whereas the rest of the isolates did not match with any of the existing race reaction. Further, the six selected genotypes could differentiate the isolates into four pathotypes based on their aggressiveness and Foc-8 was found more aggressive (98.48% wilt incidence) whereas Foc-24 was found to be least aggressive (7.22% wilt incidence). At molecular level, the sequences of internal transcribed spacers (ITS) genomic regions of isolates were studied and they showed 99% similarity with Foc sequences by basic local alignment search tool (BLAST) analysis.