Breeding Diploid Alfalfa for Regeneration from Tissue Culture

Publisher Website
Google Scholar
Abstract
Plant regeneration is necessary for most agricultural applications of tissue culture. Regeneration of alfalfa (Medicago sativa L.) from tissue culture has focused primarily on tetraploid genotypes (2n = 4x = 32). The simplified genetics of the diploid (2n = 2x = 16), however, is desirable for many aspects of alfalfa biotechnology. This study reports on the development of a diploid alfalfa population, Regen‐2x, that contains a high frequency of regenerable genotypes. Genes controlling regeneration were originally identified in five tetraploid individuals and were transferred to the diploid level using haploidy and triploid bridge crosses. The frequencies of alleles controlling regeneration were then increased by two cycles of recurrent selection. The original seed‐derived plants, which had served as donors for tissue culture and were capable of regeneration, were recombined in each cycle. This breeding strategy prevented the accumulation of somaclonal variation in the population while increasing the frequency of individuals able to regenerate from tissue culture. Ten percent of the base diploid population (Cycle 0) regenerated. Recurrent selection significantly (P < 0.025) increased the frequency of regenerating individuals to 33% and then 66% in Cycle 1 and 2, respectively. These data support the results of other studies that indicate regeneration from tissue culture is controlled by relatively few genes.