Mapping the d1 and d2 dwarfing genes and the purple foliage color locus P in pearl millet

The d(1) and d(2) dwarfing genes and the P purple foliage color gene were placed on the restriction fragment length polymorphism (RFLP)-based molecular marker linkage map of pearl millet [Pennisetum glaucum (L.) R. Br.] using a mapping population based on a cross of inbred lines IP 18293 (D-1/D-1, d(2)/d(2), P/P) and Tift 238D1 (d(1)/d(1) D-2/D-2 p/p). A skeleton genetic linkage map of 562 cM (Haldane function) was constructed using 33 RFLP markers and these three morphological markers. The D-1/d(1) plant height locus mapped to pearl millet linkage group 1, while the D-2/d(2) plant height locus and the P/p foliage color locus mapped to pearl millet linkage group 4. Loose genetic linkage was observed between the D-2/d(2) and P/p loci, with 42% repulsion-phase recombination corresponding to 92 cM (Haldane). This loose linkage of morphological marker loci detected on pearl millet LG4 can likely find use in applied pearl millet breeding programs, as host plant resistances to both downy mildew and rust have previously been identified in this genomic region. Such exploitation of these morphological markers in an applied disease resistance breeding program would require development of appropriate genetic stocks, but the relatively loose genetic linkage between d(2) and P suggests that this should not be difficult.