Effect of some environmental factors on the asexual phase of Peronosclerospora sorghi

Abstract

Peronosclerospora sorghi, produced a maximum of 10,800 conidia/cm² of diseased sorghum leaves at 100% relative humidity but only about 3600 conidia at 85% relative humidity underin vitro conditions. The sporulation was totally inhibited at 80% relative humidity and below. Infected sorghum leaves kept in darkness after completion of the previous crop of the spores, did not sporulate in continuous darkness even at the optimum relative humidity and temperature. Optimum temperature for sporulation is 21-23°C, 31°C and 30°C are minimum and maximum respectively. At 26°C and above, conidiophores were malformed and produced only a few conidia. For conidial germination, 21-25°C were optimum while at 13°C conidial germination was as low as 52%. At 32°C, 80% germination was recorded but 35°C and above no germination occurred. After inoculation with conidial suspension, a minimum of 3 hr moisture was essential to induce systemic infection.