Nutrition Determines Cultural Variability in Magnaporthe Isolates Originating From Rice and Finger Millet

Magnaporthe sp. infecting many members of poaceae and other economically important plants is a destructive pathogen. The pathogen has worldwide distribution, and cross infectivity among the isolates infecting different hosts is reported. The isolates infecting different hosts are difficult to distinguish on the basis of cultural and morphological variation. But, they differ on their differential ability to infect respective hosts, it may be due to their differential nutritional requirements. Therefore, a study was conducted to observe the cultural variation among the isolates of Magnaporthe originating from rice and finger millet on semi-synthetic (Oat Meal Agar) and synthetic media (Richard's Agar). It was observed that semi-synthetic media supports more luxuriant mycelial growth compared to synthetic media. On OMA isolate originating from rice (VII 730) showed maximum mycelial growth (37 mm) and growth rate (4.62 mm/day) while on RA isolate originating from finger millet (IX 487) showed maximum mycelial growth (39.17 mm) and growth rate (4.89 mm/day). It was observed that OMA supports more pigmentation and conidia formation in the mycelium. The results suggest that the isolates of Magnaporthe, originating from different hosts are difficult to distinguish on the basis of cultural variation and semi-synthetic media supports more luxuriant growth and sporulation of the isolates compared to synthetic media.