Effects of Host Resistance, Temperature, and Duration of Wetness of Leaf Blight Development of Grain Sorghum
The effects of post-inoculation temperatures and periods of leaf wetness of leaf blight (Exserohilum turcicum (Pass.) Leonard and Suggs) development were studied in three sorghum genotypes (IS 3443C-40, ICSV 1, and 296B or Local FSRP) having varying levels of blight resistance. In two different experiments, pot-grown plants of these genotypes were spray-inoculated and subjected separately to i) six temperature regimes (10, 15, 20, 25, 30 and 35°C) for 24h with a 12h photoperiod and high relative humidity (100% RH) and ii) six periods of leaf wetness (RH-100%) of 2, 4, 6, 8, 24, and 48 h at 25°C. Leaf blight severity (percentage leaf area damaged) was maximum (55%) at 25°C at 24 h of leaf wetness period in the susceptible genotypes Local FSRP and 296B. There was no leaf blight development at 10°C and 35°C and, significnatry, only low blight development (%) upto 8 h of leaf wetness. Implication of these findings in refining leaf blight screening technique is discussed.