TAXONOMIC STUDIES ON CULTURAL AND MORPHOLOGICAL CHARACTERS FOR RE-EVALUATION IN HELMINTHOSPORIUM SPECIES COMPLEX

Abstract

Fourty-two sporulating isolates of Drechslera, Helminthosporium, Bipolaris and Exserohilum obtained from
Indian Type Culture Collection, New Delhi were used in this study. Macroscopic and microscopic studies
revealed that, the isolates were assembled into two major groups and three sub-groups; there was a lot of
variation in the cultural characters.In group I (28 isolates) aerial mycelium was fluffy, cottony and whitish gray in
colour and there was wide variation in radial growth of the isolates [8.45 cm in D19 to 2.2 cm in D7]. In group
II (14 isolates), most of the cultures were black in colour and texture was smooth in which radial growth was
highest in E7 (8.65 cm) and lowest in D42 (6.25 cm). It was found that germination from two or more cells of
conidia separates Drechslerafrom Bipolaris and Exserohilum. Whereas, presence of strongly protuberant hilum
structure differentiates between Exserohilum and Bipolaris isolates. Thirteen of the isolates having strongly
protuberant hilum structure were grouped into the genus Exserohilum. Remaining 29 isolates were considered as
the genus Bipolaris group with no protuberant hilum.