Monday, November 13, 2006

Genetic Mapping of Fall Armyworm Resistance and Salinity Tolerance in Zoysiagrass.

R.W. Jessup1, B.L. Burson1, R. Krishnaramanujam2, M.C. Engelke3, A.D. Genovesi3, J.A. Reinert3, M.L. Binzel4, T.L. Kamps5, S. Schulze5, and A.H. Paterson5. (1) USDA-ARS, Heep Center, Texas A&M University, College Station, TX 77843-2474, (2) Texas A&M University, 2474 TAMU, College Station, TX 77843-2474, (3) Texas A&M University Research and Extension Center, Dallas, TX 75252-6599, (4) Dept. of Horticultural Sciences, Texas A&M University, College Station, TX 77843-2133, (5) University of Georgia, Athens, GA 30602

Zoysiagrass (Zoysia matrella L.) is a highly drought- and salt-tolerant grass that is grown extensively across the central and southern United States as a turf grass.  Zoysiagrass is a tetraploid (2n=4x=40), has a protogynous flowering behavior, and is highly cross-pollinated.  In recent years, breeders have developed improved cultivars, but additional breeding efforts are needed to reduce injury from biotic and abiotic stresses.  Therefore, the objective of this research was to construct a detailed linkage map of zoysiagrass to serve as a framework for marker-assisted breeding of the species.  A total of 65 AFLP primer combinations, 330 buffelgrass [Pennisetum ciliare (L.) Link syn. Cenchrus ciliaris L.] EST-SSRs, and 160 bermudagrass (Cynodon dactylon L.) EST-SSRs were surveyed for DNA polymorphism between 'Diamond' and 'Cavalier' zoysiagrass, parents of the mapping population.  Four hundred and five AFLPs, 54 buffelgrass EST-SSRs, and 29 bermudagrass EST-SSRs were mapped across 73 F1 hybrids, yielding linkage maps for the zoysiagrass cultivars 'Diamond' and 'Cavalier'.  Linkage data confirmed earlier reports that zoysiagrass is an allotetraploid with preferential chromosome pairing during meiosis.  Linkage data also indicated that the zoysiagrass genome is somewhat larger than that of maize.  Mendelian mapping identified markers linked to a fall armyworm resistance locus in Cavalier.  QTL analysis confirmed the Mendelian mapping results and identified another fall armyworm resistance locus in Diamond.  QTL analyses of six parameters related to salinity tolerance revealed four salinity tolerance QTLs in Diamond and one salinity tolerance QTL in Cavalier.  Implications of the genome maps and markers linked to fall armyworm resistance and salinity tolerance for zoysiagrass improvement programs will be discussed.