CULTURAL AND MOLECULAR CHARACTERIZATION OF Fusarium ISOLATES CAUSING WILT DISEASE OF SOLANACEOUS VEGETABLES

Abstract

Fusarium spp. represent one of the noxious groups of plant pathogen causing wilt disease of many economically important crops. Due to presence of remarkable variability among its isolates, management options against this pathogen are quite difficult. Therefore, the present experiment was conducted to study the variability of different isolates of Fusarium spp. collected from major vegetable growing regions of Bangladesh. Those isolates varied morphologically with cottony white, cottony white with brownish center, cottony pinkish white, pinkish white, whitish purple, purplish and creamy colored colony where the colony shape was regular, regular with concentric ring to irregular. Margin of the colony were entire, wavy, curled, filiform and undulated with crateriform, fluffy, flat and convex colony texture. Mycelial growth rate of the isolates was between 2.00−10.32 mm day -1 where, the isolates DSAUB and JhKT exhibited the highest and the lowest growth, respectively. The isolates were also clustered into three groups based on colony diameter viz. fast growing, moderate growing and slow growing fungi. The variation of conidia production was between 2.66×10 6 −12.33 × 10 6 ml -1 suspension with sporulation time 3.33−7.33 days. Molecular identification of Fusarium spp. isolates was preformed through amplification of fungal DNA at ITS region, sequencing the DNA molecules and analyzing the sequence in “NCBI-BLAST” database and then six isolates viz. DSAUT, MMsB, MMsC, BGT, BGP and JJHB were identified as Fusarium oxysporum and another three isolates i.e. GBARIB, MeGP and PBC were identified as F. fujikuroi, F. solani and F. commune, respectively. Phylogenetic trees of the queried isolates in relation to globally reported Fusarium isolates revealed that there was a strong ancestral relationship among the native isolates and the respective globally reported isolates of Fusarium spp. Virulence level of the isolates also varied significantly. The isolates were grouped as highly virulent (HV), virulent (V), moderately virulent (MV) and avirulent (AV) pathogen based on disease incidence. The overall results demonstrated the existence of cultural, morphological, pathogenic and molecular variation of Fusarium spp. isolates in native environment.