Changing climates and associated increased variability pose risks to alfalfa (Medicago sativa L.) cultivation, with the requirement to establish, survive, and maintain production under water stress. Crop wild relatives (CWR) of alfalfa include populations that have evolved to survive in a number of different, extreme environments, but until recently have had limited use in breeding programs. Here we report on the phenotypic diversity of alfalfa crop wild relatives that were selected to represent extremes in drought tolerance (by sourcing germplasm from environments with extremes in low rainfall, high temperature, shallow soils, and winter freezing) with the aim of providing germplasm with drought tolerance and improved forage yield traits for breeding programs in both warm and cool dry temperate environments. Newly formed hybrids created between M. sativa, M. arborea L. (a woody shrub), and M. truncatula Gaertn. (an annual species from the Mediterranean region) were developed or acquired to introduce new genetic diversity from the tertiary genepool. Preliminary characterization and evaluation was used for taxonomic classification, and to identify wild accessions and pre‐bred (hybrid) lines that offer new diversity for growth habit, seed size, fall dormancy, and forage yield. The accessions and pre‐breeding lines described have been donated to the Australian Pastures Genebank for conservation and distribution.

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The phenotypic diversity and productivity of a diverse alfalfa (M. sativa subspp.) panel of cultivars, landraces and wild relatives with putative drought tolerance were evaluated in two Mediterranean environments (central Chile and Southern Australia). In Chile, 70 accessions were evaluated in rainfed conditions and in Australia 30 accessions under rainfed and irrigated conditions, during three growing seasons. Large phenotypic variation was observed among and within subspecies for NDVI, stem length, intercepted PAR and forage yield. Principal component analysis indicated that the first two principal components (PC) accounted for 84.2% of total variance; fall dormancy, taxa, and breeding status were closely related to the agronomical performance of alfalfa accessions. Forage yield varied largely among accessions across years and locations. A linear relationship was found between annual forage yield and annual water added to the experiments (R2 = 0.60, p < 0.001). The GxE analysis for forage yield allowed the detection of the highest yielding accessions for each of the two mega-environments identified. The accessions CTA002 and CTA003 showed greater forage yield in both Chile and Australia environments. It is concluded that new breeding lines derived from crosses between cultivated alfalfa (M. sativa subsp. sativa) and wild relatives belonging to the primary (M. sativa subsp. falcata) and tertiary (M. arborea) gene pool, achieve outstanding agronomical performance in drought-prone environments.

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C. Ovalle, S. Espinoza, V. Barahona, M. Gerding, A. Humphries, and A. del Pozo. 2015. Lucerne and other perennial legumes provide new options for rainfed livestock production in the Mediterranean-climate region of Chile. Cien. Inv. Agr. 42(3): 461-474. In dryland Mediterranean environments, the productivity of annual legumes is low during autumn and winter, with plant senescence typically beginning by the middle of spring because of low soil water availability. Therefore, the use of deep-rooted perennial legumes may provide an alternative to annual legumes in regions with a soil moisture deficit. We evaluated the germplasm of new perennial legumes with deep rooting systems in two field experiments in the interior drylands of central Chile. In experiment 1, sixteen genotypes of four perennial legume species, nine cultivars (cvs.) of Medicago sativa, two of Hedysarum coronarium, three of Lotus tenuis, and two of Lotus corniculatus were evaluated for three seasons (2012-2014). In experiment 2, eight additional genotypes from two perennial legume species (M. sativa and H. coronarium) were evaluated between 2013 and 2015. Additionally, sixteen cultivars and accessions of M. sativa were evaluated in raised beds, with nine from Australia, two from Spain, two from California and three of Andean origin. We evaluated plant survival, nodulation, plant height at the end of the winter period and temporal distribution of biomass production. The persistence of M. sativa cultivars was high (over 80% survival after three years), but only the lucerne produced high yields (8-11 Mg ha-1 in the third season). Significant differences for winter production were detected among the lucerne cultivars, associated with their winter activity class, but no differences were found in total biomass production. The persistence of L. tenuis, L. corniculatus and H. coronarium was poor, and the biomass production was low, most likely because rhizobia failed to persist. Based on these preliminary results on perennial legumes, lucerne has great potential as a forage crop in the interior drylands of central Chile. However, more research on rhizobial strains, nodulation, plant growth and biomass accumulation, and root distribution and water use, among other factors, is required to better understand the persistence of perennial legumes in rain fed environments.

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