Global warming and price volatility are increasing uncertainty for the future of agriculture. Therefore, agricultural systems must be sustainable not only under average conditions, but also under extreme changes of productivity, economy, environment and social context. Here, we review four concepts: stability, robustness, vulnerability and resilience. Those concepts are commonly used but are sometimes difficult to distinguish due to the lack of clear boundaries. Here, we clarify the role of these concepts in addressing agronomic issues. Our main findings are as follows: (1) agricultural systems face different types of perturbations, from small and usual perturbations to extreme and unpredictable changes; (2) stability, robustness, vulnerability and resilience have been increasingly applied to analyze the agricultural context in order to predict the system response under changing conditions; (3) the four concepts are distinguished by the nature of the system components and by the type of perturbation studied; (4) assessment methods must be tested under contrasted situations; and (5) the major options allowing system adaptation under extreme and unpredictable changes are the increase of diversity and the increase of the adaptive capacity.

Legume growing has many benefits. Indeed legumes provide plant proteins for animal feed and human food. Legumes fix atmospheric N 2 and, in turn, provide cheap and green N fertilisers. Additionally, legumes are used as diversification crops in rotations based on oilseed rape and cereals. Despite those benefits, legume crops in Europe represent less than 4 % of arable lands, and European legume seeds are underused for animal and human nutrition. Nonetheless, European authorities are now fostering the development of legume crops for sustainable agriculture. Here, we analyse forage and grain legume-producing systems since 1950 in order to identify the actual constraints of legume development. We show that legumes can contribute to the agroecological transition for sustainable agriculture, food and energy and for sustainable agri-food systems. Then, we point out that high added-value niche markets are required for supporting legume production. The major research needs identified are (1) analysing the constraints of the current systems and identifying ways of moving towards systems that include more legumes, (2) identifying new and diversified uses for legumes in a sustainable food chain, (3) assessing and improving the ecosystem services provided by legumes at cropping system and territory scales and (4) promoting agroecology through and for legume crop management.

Alfalfa (Medicago sativa) is an autotetraploid, allogamous and heterozygous species whose cultivars are synthetic populations. The breeders apply selection pressure for some agronomic traits within a breeding pool to increase the frequency of favorable individuals. The objective of this study was to investigate the differentiation level among seven cultivars originating from one breeding program, and between these cultivars and the breeding pool, with eight SSR markers. These highly polymorphic and codominant markers, together with recent population genetic statistics extended to autotetraploids, offer tools to analyse genetic diversity in alfalfa. The number of alleles per locus varied between 3 and 24. All loci were at a panmictic equilibrium in the cultivars, except one, probably because of null alleles. With seven SSR loci, each cultivar was at panmictic equilibrium. The mean gene diversity was high, ranging from 0.665 to 0.717 in the cultivars. The parameter F(ST) indicated a low but significant diversity among cultivars. Among 21 pairs of cultivars, 15 were significantly different. The breeding pool also had a high diversity, and was significantly different from each cultivar except the most recent one. Considering the characteristics of the breeding program and the mode of cultivar elaboration, we found that they were unable to generate a large variety differentiation. Estimation of population genetics parameters at SSR loci can be applied for assessing the differences between cultivars or populations, either for variety distinction or the management of genetic resources.

ity and forage yield (Julier and Huyghe, 1997). A wide range of variation for digestibility could be found at the Alfalfa (Medicago sativa L.) cultivars are synthetic populations individual level, as for other traits. Depending on the formed from 8 to 200 parents and thus have a broad genetic base. importance of within-cultivar variation compared with Within-cultivar variation was compared with among-cultivar variation among-cultivar variation, and on the genetic correlafor energy value traits, morphological traits, and dry matter yield. tions when including this additional source of variation, Eleven cultivars, each represented by 15 clones of 7 to 20 genotypes, were evaluated in field plots simulating a dense canopy at INRA breeding programs could include the analysis of individ-(National Institute of Agronomic Research), Lusignan in France. Six ual plant digestibility. harvests spanning 3 yr were analyzed. Neutral detergent fiber (NDF), The objective of this study was to measure withinacid detergent fiber (ADF), acid detergent lignin (ADL), enzymatic cultivar and among-cultivar variances for alfalfa traits digestibility, leaf-to-stem ratio (LSR), number of stems, stem height, related to the energy value, forage yield, and several and dry matter yield were measured. Within-cultivar variance acmorphological traits, and to assess the phenotypic and counted for 31 to 70% of the genetic variance for LSR and quality genetic correlations when including the within-cultivar traits and 57 to 100% for morphological traits and dry matter yield.variation. Large within-cultivar variation for yield-related traits could impart yield stability across environments, as a result of competition in alfalfa MATERIALS AND METHODS canopies. Phenotypic and genetic correlations were relatively low in each harvest for dry matter yield and NDF content, but high for NDF

-Crop architecture may be modified to improve the adaptation of the crops to different environments and to increase the seed yield and its stability. The