Monday, June 18, 2007

DNA Marker Analysis of Biomass Production under Drought-Stress in Tetraploid Alfalfa (Medicago sativa L.).

Chris Meenach1, Lei E1, Chris Pierce1, H. Yuanhong2, Joseph Bouton2, Mary Sledge3, and Ian Ray1. (1) New Mexico State University, Department of Plant and Environmental Sciences, Las Cruces, NM 88003, (2) Samuel Roberts Noble Foundation, Forage Improvement Division, Ardmore, OK 73402, Albania, (3) Department of Biology, Lipscomb University, Nashville, TN 37204

The goal of this project is to identify genetic mechanisms associated with drought tolerance in tetraploid alfalfa (Medicago sativa L).  Two first generation backcross mapping populations (~100 genotypes each) were generated between a high yielding, low water use efficient parent (M. sativa subsp. sativa var. ‘Chilean’) and a low yielding, high water use efficient parent (M. sativa subsp. falcata var ‘Wisfal’).  Half-sib seed was produced from each mapping population genotype and seeded into replicated field plots at Las Cruces, NM in fall 2004.  Forage biomass was measured in two harvests each in 2005 and 2006 that received 50% of the normal irrigation rate to induce episodic drought stress.  Significant variation among families was detected in both populations, and some families performed similarly to the drought tolerant check, ‘Wilson’. Evaluation of 2005 yield data, in conjunction with 286 EST-SSR markers, identified individual alleles that accounted for up to 15% of yield variance under drought conditions. The magnitude of marker allele effects differed between harvests, but the direction of their influence was relatively consistent. The 2006 yield data verified the effect of several of these loci. Epistatic interactions for forage yield have been detected between unlinked markers. Additional single nucleotide polymorphism (SNP) markers designed to amplify drought responsive gene sequences are also being mapped and evaluated for their associations with yield under drought stress.

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