Progress in development of spotted medics (Medicago arabica L. Huds.) for Mediterranean farming systems

Abstract

Spotted medics (Medicago arabica) have become naturalised in Australia, but the spiny nature of their pods has prevented commercial release of any cultivar. Fifty-eight accessions representing Medicago arabica in the Australian Medicago Genetic Resources Collection were grown as spaced plants at Turretfield, South Australia, and the variation for important agronomic traits was studied. There was large variation for traits including days to flowering, dry matter production, pod and seed yield, and pod spininess. Principal component and cluster analyses conducted for 13 traits revealed 5 clusters. One of the clusters identified comprised accessions originating from Greece and Cyprus, which were found to have high agronomic potential. The study has helped in identifying the relationship among traits, namely pod spininess, days to flowering, dry matter yield, and pod and seed yield, which would be useful to breeders for future breeding and selection programs. A sward trial at Moree, New South Wales, comprising a selected cohort of spotted medic accessions, enabled the identification of 2 early flowering and high dry matter yielding accessions; however, both exhibited spiny pods. These 2 accessions were crossed with a smooth-podded accession, and the F1 plants were confirmed using a microsatellite marker. Days to flowering showed a continuous pattern of variation in the F2, suggesting that the trait is quantitatively inherited, whereas segregation ratio revealed that a single recessive gene controlled the smooth pod trait. Early flowering, smooth-podded F2 plants were selected for cultivar development.