Pathogenic and morphological variability of Exserohilum turcicum isolates causing leaf blight in sorghum (Sorghum bicolor)

Abstract

Pathogenic and morphological variability among 8 isolates of sorghum leaf blight pathogen Exserohilum turcicum (Pass.) Leonard and Suggs from Rajasthan, Gujarat, Maharashtra and Andhra Pradesh was studied during 2004–05. Pathogenic variability was studied in pot-grown plants by inoculating them of on a set of 14 differential lines comprising 12 sorghum (Sorghum bicolor L. Moench) germplasm accessions and 2 maize (Zea mays L.) cultivars. The isolates exhibited variations in cultural and morphological characteristics. The isolates also showed significant variations in symptoms in the natural conditions and in latent period and disease severity on the pot-grown plants of 14 test-lines. The differences in the latent period and mean disease score were statistically significant (P = 0.05) for the host lines, isolates and also for the host line×isolates interactions. Based on the disease severity and disease reaction the 8 isolates were distinguished into 5 pathotypes. Four isolates from Rajasthan were grouped into 3 different pathotyps and 2 from Maharashtra into 2 separate pathotypes, while the others from Gujarat, Maharashtra and Andhra Pradesh into a single pathotype. The isolate from Andhra Pradesh was the most virulent, followed by that in Rajasthan.