Variability of Macrophomina phaseolina (Tassi.) Goid. the causal organism of root rot of sesame and its management

Abstract

Ten isolates of Macrophomina phaseolina (Tassi) Goid. (sclerotial stage: Rhizoctonia bataticola (Taub) Butler) collected from different major sesame growing areas of Telangana, Karnataka and Andhra Pradesh were studied for their variability on morphological, cultural and pathogenic characteristics. The hyphal cell size varied from 13.75 x 3.75 μm (Mp 9) to 31.39 x 4.5 μm (Mp 5), size of sclerotia varied from 82.41 x 58.90 μm (Mp 6) to 135.18 x 101.88 μm (Mp 8). Based on shape of sclerotia the isolates were classified in to three groups. irregular, round and ovoid groups. The number of sclerotia per microscopic field at 10x varied from 14 (Mp 2) to 42 (Mp 7). There was no significant difference in the colony growth rate recorded among the isolates of M. phaseolina which varied from 7.66 to 8.65 mm, Isolates categorized into three groups viz., partially submerged, submerged, fluffy on the basis of colony texture and colony colour varied from black, grey and light grey colour. Based on the disease incidence isolates were categorized into two categories viz., virulent (2 isolates) and highly virulent (8 isolates).