Characterization of virulent gene locus in the genome of Fusarium spp. causing wilt disease of Psidium guajava L. in India

Wilt of Psidium guajava L., incited by Fusarium oxysporum f. sp. psidii and Fusarium solani is a serious soil borne disease of guava in India. Forty-two isolates, each of F. oxysporum f. sp. psidii (Fop) and F. solani (Fs), collected from different agro climatic zones of India showing pathogenicity were subjected to estimate their virulence factor in terms of analysis using virulent gene-related microsatellite loci. The erratic spread and occurrence of guava wilt in different areas may be due to variable aggressiveness or virulence of different pathogenic isolates in the soil. Out of 10 virulent gene locus related microsatellite markers ofFusarium spp., only six marker viz. Xyl, KHS1, PelA1, PG6/7, CHS1/2 and FMK1/MAPK1 were successfully amplified. This indicates that all the tested Fusarium sp. isolates of guava are having virulence gene in their genome. Microsatellite marker for virulence factor genes of Xyl loci was amplified in both Fop and Fs isolates. Product size of 281 bps was exactly amplified with a single banding pattern in all the isolates of Fop and Fs. It has been observed that other five microsatellite marker for virulence factor genes such as KHS1, PelA1, PG6/7, CHS1/2 and FMK1/MAPK1 were amplified with specific band pattern. PG6/7, CHS1/2 and FMK1/MAPK1 were only amplified in Fop isolates with a product size of 765 bps, 1566 bps; 1010 bps and 1244 bps. PelA1 and KHS1were amplified only in Fs isolates with the product size of 586 bps; 1359 bps, respectively. The results indicate that virulence factor genes are in response to produce wilt disease like symptoms in guava plants and also having pathogenic gene-related locus.