Since 1983 there has been no yield increase of alfalfa in the United States and even some decrease in parts of the Midwest. Alfalfa yield could be increased in two different ways. The first way would be to produce hybrid or semihybrid varieties that could outyield current cultivars due to hybrid vigor. To be able to produce hybrids, distinct alfalfa germplasm with different genetic backgrounds are crossed. The second method would be to increase regrowth ability in order to add one more harvest per year. The cultivars that are grown in the southwestern states are genetically distinct from those grown in Iowa and also are known to have the ability to regrow faster. These two features of southern alfalfa varieties make them attractive for cultivar improvement in Iowa. However, because southern cultivars do not have adequate cold resistance to be able to survive in Iowa winters, we have selected winter hardy populations from each cultivar over the past several years.