Evaluation and Utilization of Morphological Variation in a Medicago truncatula Core Collection

Medicago truncatula is a model species for legume biology and has been used to develop tools for molecular genetics and genomics. Nested core collections representing the existing genetic diversity from the USDA germplasm collection have previously been identified using molecular markers. The practical value of nested core collections is that they allow implementation of efficient strategies to characterize phenotypic variation compared to random selection of accessions from the whole collection or using geographic stratification to select accessions for evaluation. The goals of this research were to efficiently use the M. truncatula core collections to characterize the natural existing variation associated with morphological traits. We assayed variation in pods (length, number of coils, direction of coiling, number of pods per raceme), leaves (morphology and pigmentation patterns), and roots (morphology and biomass) from accessions included in the nested core collections. A remarkable natural variation was identified for the morphological characteristics evaluated in pods, leaves and roots. Accessions with contrasting phenotypes for multiple traits are currently being used to develop mapping populations. The M. truncatula core collections are publicly available and should enable researchers to efficiently evaluate genetic variation for additional traits of interest.