Inheritance and Allelic Relationship Among Downy Mildew Resistance Genes in Pearl Millet
Raj, Chandramani | Sharma, Rajan | Pushpavathi, B. | Gupta, S. K. | Radhika, K.
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 F₁, F₂, and backcross BC₁P₁ (susceptible parent × F₁) and BC₁P₂ (resistant parent × F₁) generations for inheritance study. To carry out a test for allelism, the three resistant parents were crossed with each other to generate F₁ and F₂ generations. 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 F₂ 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. A test for allelism inferred that a single dominant gene for resistance in 834B is nonallelic to that which 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 the gene for DM resistance in 834B and a second gene is allelic to the resistance gene present in IP 18294-P1.
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