ARS | Publication request: Linkage Groups Associated with Partial Rust Resistance in Pearl Millet

Submitted to: International Sorghum and Millets Newsletter
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 19, 2004
Publication Date: December 1, 2004
Citation: Wilson, J.P., Devos, K.M. 2004. Linkage groups associated with partial rust resistance in pearl millet. International Sorghum and Millets Newsletter. 45:51-52.

Interpretive Summary: Partial rust resistance or 'slow-rusting' is expressed by slower development of disease symptoms and epidemics in the field. Identifying slow-rusting can be time consuming and prone to error. Previous studies indicated that pearl millet 'ICMP 501' had 2 to 3 genes for slow-rusting resistance. The hypothesis was evaluated by segregation of components and expression of partial rust resistance with molecular markers, which are particularly valuable to provide greater precision in selecting for traits that express a high degree of variability, or greater efficiency in selecting for traits that are normally difficult to select for. Segregation of markers indicated that there were 3 linkage groups (LG) in ICMP 501 on LG 1, 3, and 7 that conferred low disease in the field. Another linkage group (LG 5) from Tift 383 also contributed to disease reduction and was apparently associated with a growth-stage related response to infection. The associations with linkage groups identified from these studies will be useful to design additional studies that will provide more effective selection by molecular markers.

Technical Abstract: Partial rust resistance has been identified in pearl millet ICMP 501, and is expressed as longer latent period, reduced uredinium size, and lower area under the disease progress curve in field epidemics. Previously conducted quantitative genetic analyses of crosses of ICMP 501 x Tift 383 estimated that area under the disease progress curve (AUDPC) was conferred by a minimum of 2.5 genes. The present studies were conducted to compare results of inheritance of resistance obtained from quantitative genetic analyses with segregation of molecular markers in a population of recombinant inbred lines (RILs) derived by single-seed descent from the cross Tift 383 x ICMP 501. The 44 probes detected 47 loci in the Tift 383 x ICMP 501 RIL population. Three chromosome regions were associated with rust resistance in the field as measured by AUDPC. Significant differences (P'0.01) in AUDPC were associated with a distally located marker on LG 1, with three markers on LG 3 and two markers on LG 7. At all loci, low AUDPCs were associated with the alleles from ICMP 501, the resistant parent. Markers on linkage group 5 derived from Tift 383 were associated with greater levels of resistance among the RILs. The alleles from ICMP 501 likely confer true resistance, while the alleles from Tift 383 most likely provide a maturity-related physiological resistance.