Morphological and cultural variability in Fusarium oxysporum f.sp. lentis causing wilt of lentil

Abstract

Vascular wilt of lentil caused by Fusarium oxysporum f.sp. lentis is one of the major threats to lentil cultivation in India. Morphological and cultural variability in F. oxysporum f.sp. lentis isolates was studied from the wilted lentil plants collected from Madhya Pradesh, Chhattisgarh, Jharkhand and Rajasthan State's, in India. Total 146 F. oxysporum f.sp. lentis (Fol) isolates were obtained after confirmation of pathogenicity tests on susceptible variety L9–12. The colonies of Fol isolates were white, dull white, pinkish white, yellowish white and brownish white. The pigmentations on standard Hi-media potato dextrose agar medium were yellowish brown, dark brown, creamy and dark tan. The isolates exhibited three types of growth pattern as oppressed, partially oppressed and fluffy. The rate of mycelia growth of the Fol isolates was slow ( 7 cm/week). Based on the morphological and cultural characteristics the isolates were grouped into fifty groups. The growth rate was considered as the main criterion for grouping of the isolates. Other important parameter for grouping the Fol isolates was the size of macroconidia; size more than 15 µm was considered as large, whereas, less than that was grouped in to small. Fast growing isolates comprised fourteen groups, those having large macroconidia formed six groups, while small size conidia were in eight groups. In medium growth rate there were seventeen groups, out of these eight groups were having large macro conidia, while in nine groups macro conidia were small. In slow growth rate there were nineteen groups, those having large macro conidia were eight, while in eleven groups small macro conidia were present. The existence of variability in F. oxysporum f.sp. lentis isolates was not limited by the States boundaries, as the isolates grouped in one group were from places of the different States. The phylogenetic tree prepared involving different morphological and cultural characteristics of the isolates depict two major groups of F. oxysporum f.sp. lentis isolates.