INHERITANCE OF PARTIAL RUST RESISTANCE IN PEARL-MILLET

Quantitative disease resistance should be exploited to complement the use of genes for qualitative or hypersensitive resistance. The express ion and inheritance of partial rust resistance of pearl millet inbreds 700481-21-8 and 'ICMP 501' crossed to moderately susceptible 'Tift 38 3' were evaluated in seedling assays in the greenhouse and in generati on mean and single-seed descent populations in the field. Uredinium si zes on seedling leaves of hybrids were generally intermediate to those of the parental inbreds and consistent differences could be discerned in uredinium lengths. Area under the disease progress curves (AUDPCs) of individual plants of the parents, F-1, F-2, and backcross F(1)s to each parent were determined from field trials. Broad-sense heritabili ty estimates for both crosses were 43%. In generation mean analyses, a dditive genetic effects were significant in the cross of 700481-21-8 x 'Tift 383', whereas additive, dominance, and dominance x dominance ep istatic effects were significant for 'ICMP 501' x 'Tift 383'. The numb er of genes conferring partial resistance was estimated to be two for 700481-21-8 and 2.5 for 'ICMP 501'. A hierarchical single-seed descent analysis revealed significant differences in AUDPC among F-3-derived F-4 progenies in the F-6 generation. Selection for progenies with grea ter resistance should be possible among F-4 families. Higher levels of resistance were observed in progeny derived from 'ICMP 501'. Because segregation of resistance differed among progeny derived from 700481-2 1-8 and 'ICMP 501', the genetic basis for resistance probably differs between the two inbreds.