Shoot Morphology of Eleven Alfalfa Populations

Alfalfa (Medicago sativa L.) is a major component of feed for dairy and beef cattle and one of the most productive forage species in North America. Alfalfa has been planted on millions of acres. More than 100 varieties have been developed in North America over the past 100 years. However, historically, alfalfa persistence under grazing in semiarid rangeland has generally been poor. Recently, it was discovered that naturally-selected populations of predominantly yellow-flowered alfalfa have been proven to be adapted to rangelands of western South Dakota and adjacent areas. A study was initiated in May 2006 to evaluate persistence and vigor of eleven alfalfa populations (conventional-hay type, pasture type, pure falcata, and predominately falcata) by transplanting seedlings into native and tame grasslands in South Dakota. The objective of this experiment was to investigate shoot morphology of eleven alfalfa populations in tame grasslands. The experiment was a randomized complete block design with three replications of five plants in 1.2 m long single-row plots. For each population, aboveground biomass of all plants was harvested and ten stems were randomly selected on July 25, 2008. For each stem, the morphological characteristics measured included: a) length & basal diameter, b) number of nodes, branches, pods, c) ratios of leaf to stem, branch to stem, reproductive to vegetative biomass. The results showed that pure falcata cultivar Don had the shortest and thinnest stem, the highest proportion of total stem weight in leaves and reproductive to vegetative biomass ratio, but the lowest stem total biomass. Naturally-selected predominately falcata population from Wind River Seed Co. had the longest, thickest, heaviest, most branched and pods produced stem compared to the other populations