International Crops Research Institute for the Semi-Arid Tropics
Abstract
Downy mildew (DM) caused by Sclerospora graminicola is a widespread and economically most important disease of pearl millet causing substantial annual yield losses, particularly in single-cross F1 hybrids in India. Currently, in India about 50% of the 9 million ha under pearl millet cultivation is grown with more than 70 hybrids in which DM incidence has been highly variable, with some hybrids showing more than 90% incidence in farmers' fields. With increasing area under hybrid cultivation since the 1970s the disease has become more severe due to evolution of new virulent pathotypes in response to new hybrid genotypes. At ICRISAT, breeding for DM resistance using conventional pedigree breeding and more recently marker-assisted backcross breeding has been successful, and a large number of disease resistant hybrids have been developed and deployed. This has, to a large extent, helped in arresting the occurrence of widespread DM epidemics since the 1990s. In view of the increasing severity of the disease and evolution of new more virulent pathotypes, there is a need to develop a long-term DM resistance breeding strategy in India. In this paper, we discuss various aspects of the pearl millet-DM pathosystem, factors that influence disease resistance breeding and suggest short-, medium- and long-term strategies for DM resistance breeding
