Genetic divergence across the cutting management in Alfalfa (Medicago sativa L.)

Abstract

Alfalfa (Medicago sativa L.), a forage legume, commonly known as Lucerne is a member of family Leguminosae, tribe Trigonelleae, sub- family Papilionaceae. The species by and large is tetraploid (2n=4x=32) and insect pollinated in nature. This is multicut perennial forage legume. Alfalfa is the third important forage crop in India after Sorghum (Sorghum bicolor L.) and Berseem (Trifolium alexandrinum L.). It produces more protein per ha than grain or oilseed crops. The average protein yield of alfalfa is more than twice to that of soybean (Tyagi, 1997; Barnes et al., 1988). The variability accomplished with significant genetic distance among different accessions of a species is known as genetic diversity or genetic divergence. Genetic diversity plays an important role in plant breeding because hybrids between lines of diverse origin generally display a greater heterosis than those between closely related accessions (Ram and Panwar, 1970). The maximum heterosis generally, however, occurs at an optimal or intermediate level of diversity. The D2 technique (Mahalanobis, 1936) has been used in assessing the variability present in crops, like maize, sorghum, pearl millet, wheat, linseed, cotton, tobacco, alfalfa and brassica (Moll and Stuber, 1974). In addition to it in the selection of divergent parents for hybridization, D2 statistics measures the degree of diversification and relative proportion of each component character to the total divergence. The present investigation was carried out to ascertain magnitude of genetic divergence present in the alfalfa accessions with the objectives to develop high fodder yielding materials.