Dna Marker Assisted Breeding to Develop Alfalfa Varieties for a Water-challenged Future

Large portions of the Great Plains and the western U.S. are regularly plagued by drought and diminishing water resources for irrigation. Alfalfa cultivars adapted to these regions, and that can remain productive under reduced irrigation allotments, are clearly needed. This study evaluated the potential of using DNA marker assisted selection (MAS) technology to improve alfalfa forage productivity in drought-prone and well-watered environments. This process initially involved identifying DNA markers that were associated with alfalfa forage and root biomass production during drought stress. Some of these markers were then transferred into different alfalfa cultivar backgrounds over two generations using DNA MAS. These populations were evaluated in 2011 and 2012 under limited irrigation (LI) and normal irrigation (NI) management field conditions near Las Cruces, NM. In the first-generation MAS populations, selection for high shoot and high root biomass markers, and selection against low shoot and low root biomass markers, benefited forage productivity by 3 to 23% in the LI study. These same populations, however, yielded similarly to each other in the NI study. To produce the secondgeneration MAS populations, six of the first-generation MAS populations were each mated to three alfalfa cultivars which possessed varying degrees of drought tolerance. Significant forage yield differences were detected among the six MAS hybrids within each cultivar group in both the LI and NI studies. These results suggested that marker assisted selection impacted alfalfa productivity in all three cultivar genetic backgrounds. Some second-generation MAS populations derived from two of the cultivars outperformed their original cultivar parent by 6 to 19% in the LI study, with the greatest improvement occurring in the cultivar that exhibited the greatest sensitivity to drought stress. In the NI study, some second-generation MAS populations derived from each of the three cultivars outperformed their original cultivar parent by 6 to 7%. These observations suggest that DNA marker assisted breeding approaches can be used to develop alfalfa cultivars with improved forage productivity in both drought-prone and wellwatered environments.