Molecular identification, race differentiation and host differential analysis of Fusarium oxysporum f. sp. ciceri associated with chickpea wilt

Abstract:

Fusarium wilt, caused by Fusarium oxysporum f. sp. ciceri (FOC), is one of the most destructive diseases of chickpea, causing severe yield losses worldwide. The present investigation was undertaken to assess the pathogenic, molecular, and racial diversity of FOC isolates collected from major chickpea-growing regions of India. A total of 118 diseased chickpea samples were collected from diverse agro-ecological regions, of which 82 isolates of F. oxysporum f. sp. ciceri were successfully isolated and purified. Pathogenicity of all isolates was evaluated on the susceptible chickpea cultivar JG-62 under controlled conditions. Wilt incidence ranged from 0 to 100%, indicating considerable pathogenic variability among the isolates. Based on virulence, the isolates were classified into non-pathogenic, weakly pathogenic, moderately pathogenic, strongly pathogenic, and highly pathogenic categories. Forty highly virulent isolates exhibiting 80-100% wilt incidence were selected for detailed molecular characterization. Molecular identification using universal ITS1 and ITS4 primers consistently amplified a single DNA fragment of approximately 550 bp, confirming the identity of all selected isolates as F. oxysporum f. sp. ciceri. Further race differentiation using race-specific FDP molecular markers identified four races, namely Race 1, Race 2, Race 3, and Race 4, with Race 1 being the predominant race among the collected isolates. Host differential analysis using ten international chickpea differential cultivars further confirmed the racial identity and pathogenic variability of the isolates. The susceptible cultivar JG-62 was susceptible to all races, whereas WR-315 exhibited resistance against all tested isolates, demonstrating its broad-spectrum resistance. The study revealed substantial pathogenic and molecular diversity within the Indian FOC population and highlighted the widespread occurrence of highly virulent isolates across different agro-ecological regions. The integration of pathogenicity testing, molecular identification, race differentiation, and host differential analysis provides valuable information for understanding pathogen diversity and supports the development of durable Fusarium wilt-resistant chickpea cultivars and effective disease management strategies.