Location: Forage Seed and Cereal ResearchTitle: Pathotype-specific QTL for stem rust resistance in Lolium perenne Author
Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/13/2013
Publication Date: 1/30/2013
Citation: Pfender, W.F., Slabaugh, M. 2013. Pathotype-specific QTL for stem rust resistance in Lolium perenne. Theoretical and Applied Genetics. 126:1213-1225. Interpretive Summary: Finding and incorporating genetic resistance to plant diseases can be greatly facilitated by knowledge of the chromosomal location and the nearby DNA (‘genetic markers’) of the resistance genes. Such information is lacking for stem rust of perennial ryegrass, an important forage and turf grass. Further, there is no information on the location of different genes that may be involved in resistance to various strains of the pathogen. In this research we expanded our existing genetic map of perennial ryegrass, adding genetic markers that occur on several other ryegrass maps. On this genetic map we detected chromosomal locations for three genetic resistance sites in ryegrass reacting to inoculation by pure strains of the stem rust pathogen. There are individual genetic locations that respond to individual pathogen strains, and one genetic location that responds to more than one strain. By finding these genetic locations, and well-known markers that are near them, we have created a tool that can be modified for finding rust-resistant plants in a breeding program.
Technical Abstract: A genetic map populated with RAD and SSR markers was created from F1 progeny of a stem rust-susceptible and stem rust-resistant parent of perennial ryegrass (Lolium perenne). The map has markers in common with several other Lolium spp. maps including EST-SSR anchor markers from a consensus map. A QTL analysis was conducted with disease severity and infection type data obtained by controlled inoculation of the population with each of two genetically distinct, previously-characterized pathotypes of Puccinia graminis subsp. graminicola. Each pathotype activated a specific QTL on one of the linkage groups (LG): qLpPg1 on LG7 for pathotype 101, or qLpPg2 on LG1 for pathotype 106. Both pathotypes also activated a third QTL, qLpPg3, in common on LG6. Each of the three QTL was located in proximity to an anchor marker used on a consensus map. These QTL had been detected also in previous experiments in which a genetically heterogeneous inoculum of the stem rust pathogen activated all three QTL together. By aligning markers common to other published reports, it appears that two and possibly all three of the stem rust QTL are in genomic regions containing some of the L. perenne QTL activated in response to the crown rust pathogen (P. coronata).