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.
