Archivio Journal of Plant Pathology

Abstract:

Downy mildew caused by Sclerospora graminicola (Sacc.) Shroet. is a major biotic constraint to pearl millet production in the semi-arid tropics. The pathogen is heterothallic and frequent recombination leads to genotypic diversity and evolution of new virulent populations. Identification of resistance to new virulent populations is a prerequisite for resistance breeding. Of 123 pearl millet germplasm accessions from 15 countries that were identified as resistant (=10% incidence) at ICRISAT, Patancheru during 1990-93, only 21 remained resistant during 2006 under field screening indicating a temporal virulence change in Patancheru field population of S. graminicola. These resistant accessions when evaluated in the greenhouse against 12 diverse pathotypes, no accession showed resistance to all the 12 pathotypes. However, three accessions (IP 18295, P 1449-2 and YL 18) were resistant to 11 pathotypes, two (IP 18298 and IP 8289) to 10 pathotypes, three (IP 22396, YG 2 and YG 8) to 9 pathotypes and one (YM 16) to 8 pathotypes. Host resistance index (HRI), calculated from downy mildew incidence and latent period identified six accessions (IP 18295, -8289, P 1449-2, YG 2, -8 and YL 18) as best available resistance sources against multiple pathotypes of S. graminicola. The study showed temporal virulence change in S. graminicola population at Patancheru, emphasizing the need for closely monitoring both pathogen virulence and host resistance for effectively managing the disease through resistance breeding.