Genetic Resistance to Pearl Millet Downy Mildew II. Resistance in Wild Relatives

Abstract

Genetic resistance is the most economic and feasible method for control for downy mildew (DM) (Sclerospora graminicola) of pearl millet (Pennisetum glaucum). To identify genes for DM resistance with diverse origin, we tested 539 accessions of 12 wild Pennisetum species from 17 countries, in the greenhouse and field-disease nurseries. A total of 223 accessions were found DM free in all the tests. P. violaceum was the most susceptible of all the species, both for the frequency of susceptible accessions (93% accessions with >10% DM) and for the level of susceptibility (accessions showing up to 94% DM). Freedom of most of the P. schweinfurthii accessions from DM, coupled with resistance to rust (Puccinia penniseti), is encouraging because of its cross-compatibility with pearl millet. DM resistance genes from these wild species will be useful in the control of this disease, if found different from those of pearl millet. Successful cross-inoculation of pearl millet with sporangia produced on five wild species (P. violaceum, P. mollissimum, P. purpureum, P. padicellatum, and P. polystachyon) shows that these species may be serving as collateral/alternative hosts and also helping the pathogen in creating pathogenic variability. As-these species are present in all pearl millet growing areas, a precise information on their role under farmers’ field conditions is necessary for the development of cultivars with durable DM resistance