Effect of cytoplasm on downy mildew vulnerability in pearl millet [Pennisetum glaucum (L.) R. Br.]

Abstract

Effect of cytoplasm on downy mildew vulnerability in pearl millet was studied in 144 hybrids developed by crossing six A- and six B- lines with 12 R- lines in a line x tester mating design. The six A- lines 81A1 and 8A1 (A1), Pb 313 (A2), Pb 402A (A3), 81A4 and 81A5 and their corresponding B- lines represented five different systems of cytoplasmicgenic male sterility. Three A- lines and eleven R- lines were resistant to downy mildew, the other three A- lines and one R- line were susceptible to downy mildew. The 24 parents and 144 crosses were grown separately in contiguous blocks in 2 R x 2.5 m x 0.45 m plots in randomized block design with two replications in four treatment environments (early sown non-ratooned crop, ratoon crop, late sown non-ratooned, multiple disease sick plot) during kharif 2000 and kharif 2001. The downy mildew incidence was recorded on all plants in the plot under natural as well as sick plot after 30 and 60 days of sowing. The analysis of variance showed that genotypes, parents, lines (A, B), testers, A x R, B x R hybrids differed significantly in all environments individually and on pooled basis. Differences due to A vs. B, A x R vs. B x R, (A x R vs. B x R) x E crosses contrasts were not significant in an individual environment and on pooled basis except for Avs. B-lines at 30 days in late sown non-ratooned crop during kharif 2000. The comparison of downy mildew incidence means of A-lines with corresponding B-lines and array means of A x R crosses with that of B x R crosses also showed non-significant variation. This showed that cytoplasmic effects were not responsible for downy mildew susceptibility.