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

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International audienceGenetic variation in seed yield and its components was investigated in alfalfa (Medicago sativa L.) in two experiments established in a spaced plant design. The first experiment evaluated the among-population genetic variation in a set of 45 cultivated populations. It showed a significant population effect for all the characters evaluated with a different behavior among the Mediterranean and the Nordic materials while the population $\times$ year interaction was only significant for the seed yield per plant. A second experiment evaluated the genetic variation among and within-populations in a set of 11 populations. The among- and within-population effects were significant for almost all the components. The among-population variance accounted for 5 to 31% of the total genetic variance for seed yield components, while the within-population variance explained 69 to 95% . In both experiments, the broad-sense heritabilities of characters varied from 0.27 to 0.43. The number of inflorescences, seed number per plant and seed weight per inflorescence showed high phenotypic and genetic correlations with seed yield per plant. The possibility of using the seed weight per inflorescence as a selection criterion is discussed.Variabilité génétique intra- et inter-population pour le rendement grainier et ses composantes chez la luzerne. Deux essais ont été implantés, en plantes isolées, pour évaluer la variabilité génétique pour le rendement grainier et ses composantes chez la luzerne (Medicago sativa L.). Le premier essai a mis en évidence une variabilité génétique inter-population au sein d'un ensemble de 45 populations cultivées pour toutes les composantes évaluées avec un comportement différent des types nordiques et des types méditerranéens. L'interaction année $\times$ population n'est significative que pour le rendement et le nombre de graines par plante. Le deuxième essai a évalué la variabilité génétique inter- et intra-population dans un ensemble de 11 populations. Les effets inter- et intra-population ont été significatifs pour toutes les composantes. La variance inter-population représente de 5 à 31 % de la variance génétique totale, et la variance intra-population de 69 à 95 % pour les différentes composantes. Les héritabilités au sens large des composantes ont varié de 0,27 à 0,43. Le nombre d'inflorescences et le nombre de graines par plante et le poids de graines par inflorescence sont fortement corrélés phénotypiquement et génétiquement avec le rendement grainier par plante dans un dispositif en plantes isolées. La possibilité d'utiliser certaines composantes relatives à l'inflorescence comme critère de sélection pour le rendement grainier est discutée

Alfalfa seed yield also depends to a great extent upon environmental conditions and agronomic practices. Abu-Seed yield of alfalfa (Medicago sativa L.) is important in determin- Shakra et al. (1977) showed that seed yield was signifiing the effective distribution of new cultivars to farmers. Many genetic cantly affected by the number of forage harvests prior and environmental factors affect seed yield. This study was conducted to seed production, and this effect was mainly associated to explain seed yield variation induced by either environmental conditions or cultivars. We analyzed seed yield, aboveground phytomass, with variation in the number of fertile stems per plant harvest index, and seed yield components for a set of 12 cultivars at and pods per raceme. Abu-Shakra et al. (1969) and four locations across France in each of three years. Each location ϫ Askarian et al. (1995) reported similar effects as a conseyear combination was considered an environment. Seed weight, numquence of different row spacings. In dry environments, ber of pods per inflorescence, number of seeds per pod, and mean Abu-Shakra et al. (1969) and Taylor and Marble (1986) seed weight were measured. Mean seed yield was 801 kg ha Ϫ1 . Large have shown that frequent irrigation was beneficial to variation in seed yield was found among cultivars and environments.seed yield, as it resulted in more pods per inflorescence.The cultivar ϫ environment interaction was significant. Among envi- However, Hutmacher et al. (1991) pointed out that an ronments, seed yield was highly correlated with aboveground phytoexcessive water supply may lead to excessive vegetative mass at harvest (r ϭ 0.94) as the lowest seed yields were obtained in growth and therefore be detrimental to seed production, the seeding year. The cultivars most adapted to grazing showed the possibly through a reduction in the degree of tripping lowest seed yields. Seed yield was genetically correlated with lodging (Goldman and Dovrat, 1980). Steiner et al. (1992b) esresistance (r ϭ Ϫ0.89) and harvest index (r ϭ 0.99). The mean harvest tablished that water replacement of 70% of accumulated index was 12.7%. The seed weight per inflorescence showed a high evapotranspiration was optimal for seed production. Inbroad-sense heritability (0.58) and a high genetic correlation with seed yield (r ϭ 0.91) and with harvest index (r ϭ 0.96). Variation in creasing amounts of water increased the number of raseed weight per inflorescence was associated with variation in the cemes, but decreased the number of pods per raceme. number of seeds per pod and number of pods per inflorescence. Seed Boçsa and Buglos (1983) suggested that a high numweight per inflorescence appears to have a strong genetic association ber of seeds per pod combined with high self-compatibilwith seed yield in alfalfa. Environments with high aboveground phytoity were the most important selection criteria for high mass potential also have high seed yield potential. seed yield. Hacquet (1990) found a positive correlation between see...

-Morphological and agronomic characteristics were studied on 46 tetraploid populations of Medicago sativa ssp. sativa and ssp. falcata over three growing cycles in a spaced plant experimental design. The

Seed yield is of little agronomic importance in alfalfa (lucerne) but is critical in the marketing of varieties. In order to develop breeding criteria, the quantitative genetics of seed yield components must be studied. The objective of this study was (1) to evaluate combining ability for seed yield and its components and (2) to estimate the genetic control of these same characters. A 7 × 7 diallel mating design, including reciprocals, among parents from different varieties, and a 7 × 7 factorial design within the ‘Flamande’ population were evaluated. In the diallel design, where the progenies were evaluated over two growing seasons, a high genotype effect was found for seed yield and its components while genotype × year interaction was only significant for seed yield per plant. General combining ability (GCA) effects explained most of the variation due to genotype effect. Specific combining ability (SCA) and reciprocal effects were only significant for seed yield per plant. ‘Europe‐1’, ‘Rival‐5’ and ‘Medalfa‐7’ were the most promising parents, conferring the highest GCA for most of the characters evaluated, especially for seed weight per inflorescence. In the factorial design, seed weight per pod was the only character for which the year effect was not significant. Male and female effects were significant for all characters and these effects were larger than the male × female interaction variance for all the characters. These results were stable over the 2 years for most characters. Additive variance was larger than dominance variance, for all traits. This resulted in high narrow‐sense heritabilities, especially for seed yield per plant, seed weight per inflorescence and number of seeds per pod. Seed weight per inflorescence and number of seeds per inflorescence were highly correlated with seed yield per plant among the full‐sib (FS) families, in both experiments. Increase in seed yield potential in alfalfa could be achieved by the use of seed weight per inflorescence as a selection criterion.

An important objective in lucerne breeding is the improvement of feeding value. An understanding of the inheritance of digestibility and cell wall related traits would facilitate the breeding of varieties with higher feeding value. The aim of this experiment was first to determine the genetic control of dry matter digestibility and related biochemical and morphological traits, and to assess phenotypic and genetic correlations between these traits. Quantitative genetic parameters were estimated for enzymatic solubility, neutral detergent fibre (NDF), acid detergent fibre (ADF), acid detergent lignin (ADL), protein content, plant height, and leaf-to-stem ratio. A 7 × 7 diallel design with reciprocals and without selfing among parents from different populations and a 7 × 7 factorial design within the ‘Flamande’ population were studied. In the diallel study, effects due to general combining ability (GCA) were higher than those due to specific combining ability (SCA) for all characters tested. In the factorial study, the F1 progeny effect was significant for all characters. The male effect was highly significant for all traits and higher than the female effect except for plant height. The additive variance was higher than the dominance variance for all characters except for plant height. The inheritance was predominantly additive. The highest narrowsense heritabilities were found for NDF and ADF and leaf-to-stem ratio. As a consequence, NDF or ADF would be more efficient selection criteria than enzymatic solubility in a breeding program for improved feeding value. In both mating designs, NDF, ADF, and ADL were positively correlated with one another and negatively with enzymatic solubility and protein content.

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