Multilocation evaluation and selection of stable genotypes for reaction to downy mildew in pearl millet

Twenty-five pearl millet (Pennisetum typhoides (Burm. f.) Stapf and Hub. = P. americanum (L.) K. Schum.) genotypes were evaluated for resistance to downy mildew (Sclerospora graminicola (Sacc.) Schroet.) at 10 different locations in India and Africa during 1979 and 1980. The objective of this work was to identify genotypes with stable and generalized resistance. Genotypic differences in linear regression coefficients were found and regression lines for downy mildew incidence in the various genotypes tended to converge. It was concluded from this that selection on the basis of disease severity would enable genotypes that are superior at all disease levels to be selected. Seven genotypes, namely 700516, 700651, J-1486 × 700787-2-10, P-7, EB-83-2, NC-7174 and SSC-7218, showed low disease scores, average regressions and non-significant deviations, and therefore expressed stable, generalized resistance. Genotype 700251 was particularly suitable for high-disease environments. BJ-104, an important Indian hybrid cultivar, was very unstable and susceptible to downy mildew.