Inheritance and Allelic Relationship Among Downy Mildew Resistance Genes in Pearl Millet.
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Pearl millet downy mildew (DM), caused by Sclerospora graminicola is of serious economic concern to pearl millet farmers in the major crop growing areas of the world. To study the inheritance and allelic relationship among genes governing resistance to this disease, three DM resistant pearl millet lines (834B, IP 18294-P1 and IP 18298-P1) and one susceptible line (81B) were selected on the basis of disease reaction under greenhouse conditions against two isolates of S. graminicola (Sg 526-1 and Sg 542-1). Three resistant parents were crossed with the susceptible parent to generate F1s, F2s and backcrosses BC1P1 (susceptible parent × F1) and BC1P2 (resistant parent × F1) for inheritance study. To carry out test for allelism, the three resistant parents were crossed with each other to generate F1s and F2s. The different generations of these crosses were screened for disease reaction against two isolates Sg 526-1 and Sg 542-1 by artificial inoculation under greenhouse conditions. The segregation pattern of resistance in the F2s, and corresponding backcross generations revealed that resistance to DM is controlled by a single dominant gene in 834B and IP 18294-P1, and by two dominant genes in IP 18298-P1. Test for allelism inferred that single dominant gene for resistance in 834B is non-allelic to that governs resistance in IP 18294-1; whereas one of the two dominant genes for DM resistance in IP 18298-P1 against the test isolates is allelic to gene for DM resistance in 834B and second gene is allelic to the resistance gene present in IP 18294-P1
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