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 absorption and partitioning of N is determined by its availability and demand during the various phenological stages of the crop. In two experiments conducted in rainfed areas of the Mediterranean climate region of central Chile, legume-wheat (Triticum aestivum L.) rotations were compared to oat (Avena sativa L.)-wheat systems (with and without applications of N fertilizer). The objective was to assess the contribution of legumes to the availability of soil N and N uptake by the wheat crop following grain legumes. N mineralization and uptake, N use efficiency (NUE), and N uptake efficiency (NUpE) by wheat were evaluated at different phenological stages in 2010. Synchronization existed between accumulated soil N mineralization and N uptake by the wheat. N uptake by wheat was higher in Experiment II (Andean foothill) than in Experiment I (interior dryland). Grain yields after legumes ranged 60-110% and 72-103% of yields in the fertilized cereal rotation (oat-wheat) in Experiments I and II, respectively. There was high correlation between soil N availability vs. grain yield (R 2 = 0.84 and 0.64) and N uptake vs. grain yield (R 2 = 0.55 and 0.64) for Experiments I and II, respectively. Rotations with lupine (Lupinus spp.) and field peas (Pisum sativum L.) showed high NUE and NUpE in Experiment I, and Experiment II in pea. The lowest NUE was after oats with N fertilizers. It is concluded that wheat cultivated in both agro-ecological areas after grain legumes or green manure was more efficient in N uptake and use than cereal, especially when the latter was fertilized.

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.

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.

Despite annual legume pasture are of great importance for dryland agricultural systems in Mediterranean environments, there are few studies of N2 biological fixation (NBF) reported in Chile. In this study the NBF of four annual legume species: subterranean clover (Trifolium subterraneum L.), yellow serradella (Ornithopus compressus L.), arrow-leaf clover (T. vesiculosum L.), and crimson clover (T. incarnatum L.) (Experiment 1), as well as seven mixtures of these species (Experiment 2) were assessed. The NBF was measured by the 15 N natural abundance technique. The objective was to determine NBF in the legume species and in distinct mixtures used. The study was carried out in an Andisol of the Andean Precordillera located in the humid Mediterranean zone of Chile. Pasture was evaluated for biomass; and total N and natural abundance of 15 N were analyzed in plant material samples. In Experiment 1 (monospecific legume species pasture), N derived from fixation ranged between 43 and 147 kg N ha

Lucerne (alfalfa, Medicago sativa L.) is grown extensively worldwide owing to its high forage biomass production and nutritional value. Although this crop is characterised as being tolerant to drought, its production and persistence are affected by water stress. Selection of genotypes of high yield potential and persistence after a long period of drought is a major objective for lucerne-breeding programmes in Mediterranean environments. This selection could be enhanced and accelerated by the use of physiological and productivity traits and their estimation through remote-sensing methods. A set of nine cultivars of lucerne from Australia and the USA were assessed in four locations in Mediterranean central-south Chile. Several physiological and productivity traits were evaluated: forage yield (FY), stomatal conductance (gs), water potential (WP), leaf area index (LAI), nitrogen (N) content, and isotope composition (δ13C and δ18O) of the dry matter. Spectral-reflectance data were used to estimate the traits through spectral-reflectance indices (SRIs) and multivariate regression methods. For the SRI-based estimations, the R2 values for each assessment were &lt;0.65. However, traits such as LAI, WP, gs, and N content showed higher R2 values when data from the different assessments were combined. Regression-based estimation showed prediction power similar to or higher than the SRI-based approaches. The highest R2 value was for δ13C (0.78), but for most traits the combination of data from different assessments led to higher trait estimation, with respective R2 values for LAI, FY, WP and gs of 0.67, 0.71, 0.63 and 0.85. Among regression methods, the best estimation was achieved by using support vector machine regression. The use of spectral-reflectance data collected at field level and multivariate regression models has great potential to estimate physiological and productivity traits in lucerne under water deficit and could be useful in lucerne-breeding programmes.