Development of Root‐branching in Three Alfalfa Cultivars¹

A study of rooting habit of three winter‐hardy alfalfa, Medicago sativa L., cultivars was conducted at the Univ. of Illinois Agronomy South Farm. The objectives were to study the rooting habit of three high‐yieldlng, winterhardy alfalfa cultivars during their first growing season in order to determine if any differences in root branching exist among the cultivars and to estimate phenotypic correlations between the branching‐root habit and other agronomic characters. ‘Saranac,’ ‘Victorian’ and ‘Iroquois’ alfalfa plants were sampled eight times during the first growing season. Root and top growth of the alfalfas were measured and rooting habit was evaluated on a scale where l=tap‐rooted and 5=branching‐rooted. The majority of the plants in all three cultivars were predominantly tap‐rooted, although there was a considerable amount of variation for rooting habit within cultlvars. Nine percent of the plants were classified as branching‐rooted by the last harvest. The mean root branching scores, which fluctuated during the growing season, ranged from 1.9 to 2.5. The branching.root habit in all three cultivars was positively correlated with top (r=0.27 to 0.53, significant at the 0.01 level) and root (r=0.36 to 0.57, significant at the 0.01 level) dry weights. The results indicated that these cultivars could be used as germplasm sources in developing high‐yielding, branching‐rooted alfalfa.