Morpho-cultural variability among neck blast isolates of Pyricularia oryzae from basmati rice in Punjab

Variability among 40 neck blast isolates of Pyricularia oryzae collected from different agro-ecological zones of Punjab was studied with respect to morphological and cultural traits. The isolates exhibited different colony colours and forms with distinct margins and were categorized in four groups. Blackish grey coloured colonies were produced by most of the isolates followed by whitish grey and only one isolate (NB-14) produced grey coloured colonies on oatmeal agar (OMA) medium. Isolates produced variable colony forms as circular, irregular, circular with saltation having colony margins as entire or undulate or entire with concentric rings. The conidial size ranged from 20.74–24.91μm × 7.53–10.23 μmon OMA medium and 20.85–26.33μm×6.76–8.32 μm on Paspalum grass medium, respectively. The isolates cultured on OMA medium produced higher number of conidia per ml (7.49×10⁶) than on Paspalum grass medium (6.74×10⁶). Based on colony growth rate (Kr), the isolates were categorized into two groups and were designated as medium growers (Kr = 6-8mm/24 hrs) and fast growers (Kr >8mm/24 hrs). Most of the isolates were medium growers and only three isolates viz., NB-1, NB-4 and NB-33 were observed as fast growers.