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Department of Plant Pathology, ANGRAU-S.V. Agricultural College, Tirupati-517 502.
An in vitro study was conducted to evaluate the affinity and relative pathogenicity of Macrophomina phaseolina to twenty agriculturally important crop species. Five-day-old cultures of M. phaseolina grown on PDA (30 ± 1 °C) were used to pre-colonize Petri plates; surface-sterilized seeds (10 seeds/plate; 4 replicates per crop, n = 40) were placed equidistantly around the colony and incubated in darkness at 30 ± 1 °C for six days. Seed and seedling responses were scored on a 0–5 scale and a Virulence Index (VI) was computed following. Based on virulence crops were grouped into high (VI 4.6-4.9), moderate (VI 3.0-4.4) and low (VI 2.2-2.6) virulent categories. Pulses and oilseeds (e.g., sesame, groundnut, green gram, chickpea, redgram, black gram) and some cereals (maize) showed the highest susceptibility (VI 4.6- 4.9), while tobacco, rice and tomato exhibited the least susceptibility (VI 2.2–2.6). The results demonstrate the broad host range and strong affinity of M. phaseolina for pulses and oilseeds under the tested in vitro conditions and highlight the need for crop-specific management strategies.
KEYWORDS: Macrophomina phaseolina, virulence index, seed infection, host affinity, in vitro screening.