Smut Resistance and Grain Yield of Pearl Millet Hybrids Near Isogenic at the Tr Locus

Abstract

Trichomeless pearl millet [Pennisetum glaucum (L.) R. Br.], homozygous for the tr allele, expresses resistance to smut caused by Moesziomyces penicillariae (Bref.) Vanky. These studies examined the hypotheses that smut resistance is the result of the tr allele rather than a closely linked gene, and that the tr allele has no effect on grain yield in the absence of smut. Trichomed inbreds Tilt 90DBE and Tift 8677 and trichomeless derivatives were crossed to produce eight hybrids differing for female parent and genotype at the tr locus. Hybrids were assessed for smut resistance and grain yield. Smut severity of inoculated panicles was reduced by about 13% when a Tift 90DBE genotype was used as the female parent, compared with hybrids produced with a Tift 8677 genotype as the female parent. Smut severity was reduced by about 50% in the trichomeless phenotype compared with the trichomed phenotypes. Homozygous and heterozygous trichomed hybrids did not differ in smut severity. The recessive smut resistance is most likely a pleiotropic effect of the tr allele and not the result of another closely linked gene. Although trichomelessness can be used as a marker to select for smut resistance, both parental inbreds must be trichomeless to produce smut‐resistant hybrids. Trichomeless hybrids tended to yield more than trichomed hybrids, but yield was primarily reduced in heterozygous trichomed hybrids compared to the homozygous TrTr genotype. From these results, we conclude that the tr allele can be incorporated into smut‐resistant hybrids with no detrimental effect on grain yield.