Recovery resistance to downy mildew in pearl millet

The development of symptomless shoots from Pennisetum americanum plants that show typical systemic symptoms of Sclerospora graminicola is reported. This phenomenon, referred to as recovery and the trait as recovery resistance, was detected in 28 of 33 genotypes studied, representing a wide range of breeding materials and cultivars. The genotypes showed considerable variability for the frequency of plants with recovery resistance and for the extent of sexual and asexual sporulation of S. graminicola in recovered plants before recovery. The levels of recovery resistance were substantially increased in several genotypes through pedigree selection under high disease pressure in the downy mildew nursery. Injection of growing points of the symptomless shoots of recovered plants with a sporangial suspension, or clipping the stem and shoots of recovered plants growing under high disease pressure did not generally result in subsequent disease development. Lines produced from recovered plants maintained their resistance at 3 locations in India. The phenomenon was also observed in Mali and Niger. It is suggested that recovery resistance may be an effective defence mechanism that should be exploited in breeding P. americanum for durable resistance to downy milde