One hundred and three natural populations of Medicago L. were collected in Spain, mainly from roadsides, non-irrigated or grazed lands. This germplasm was evaluated at Montpellier (France) with control cultivars and Spanish landraces under completely random block design, replicated four times, and observed for 64 qualitative or quantitative characters. Differences between natural populations and cultivated controls are highly significant, but gene flow occurs between wild and cultivated compartment and hybrid populations were identified. On the basis of multivariable analysis, the accessions were grouped into four clusters depending on their proximity with the cultivated pool to facilitate their management and ex situ conservation. The relationship between environment of the site of collection and phenotypic characteristics of the natural populations was also discussed. Different policies of conservation of these genetic resources are suggested to avoid their disappearance even when they disappeared from the other regions of the western Mediterranean. Spanish wild pool of alfalfa, also called 'Mielga', appears of great interest for the breeding of alfalfa because it contains a large diversity of characteristics (prostrate habit, rhizomes) linked to tolerance to grazing or drought environment. With the need for more sustainable systems in agriculture, the erosion of natural habitats and the necessity for rehabilitation of degraded ecosystems, the importance of this wild pool is really inestimable.
production under open-field pollination. An analysis of variance of these traits revealed the superiority of cultivar Fakir for vegetative and seed production. The local varieties showed a better winter growth, a quick start in the spring and a earlier flowering time while keeping a good level of frost tolerance. This is a very interesting trait for the farming systems in these regions, because it allows grazing during the winter which is complementary to the alfalfa cultivars used. Sainfoin shows a large variability for aftermath flowering. The differences between the 2 types of growth, '1 cut' and '2 cuts', are highly significant. The '1 cut' local varieties are less productive and show a low persistency. This is the contrary of what is generally observed by farmers. This could be due to the frequency of cutting (3-4 cuts during the growing season) which is the normal rate for the 2 cuts' types. In these regions '1 cut' local vari-* Correspondance et tirés à part eties are usually grazed in spring and autumn, with a rest period during the summer. Principal component analysis was carried out to identify clusters of homogeneous behaviour. Firstly, there is a definite separation between the '1 cut' and '2 cuts' types and between the cultivars and local varieties. This confirms the originality of these local varieties. A hierarchical clustering method on the first 4 components was used to separate the different groups. A partition into 6 clusters was chosen. Each cluster was described by means of the different traits and compared with the other clusters. The genetic resources of sainfoin are very difficult to preserve, because this species is allogamous, self-incompatible, requires insect pollination, and its seeds have a low viability (5-8 years), even in a cold chamber. These clusters were used to build some 'genetic pools' to preserve the local varieties collected.
Phoma medicaginis Malbr. et Roum., agent responsable de la maladie des tiges noires de la luzerne, est présent en France. Ses dégâts, qui peuvent être importants, incitent les sélectionneurs à en tenir compte. Cependant, comme son développement est faible en pépinière, il est nécessaire de disposer, pour les familles en cours de sélection, de tests d'infection artificielle.La méthode proposée consiste à pulvériser une suspension de spores de P. medicaginis sur des plantules âgées de 28 j préalablement écimées au-dessus de la 2' feuille trifoliolée. Ces plantes sont maintenues à 21 °C, en atmosphère d'humidité saturante pendant 72 h. L'enceinte climatisée est réglée ensuite, pendant 45 j, à 18 °C avec une humidité relative minimum de 95 p. 100, sous une photopériode de 16 h (5 000 lux). Les symptômes sont notés selon une échelle de 1 à 6. Les notes de 19 familles et cultivars obtenues en conditions artificielles sont comparées à celles répertoriées antérieurement au champ ; le coefficient de corrélation est hautement significatif (r = 0,91). Trois variétés de luzerne artificiellement infectées par différents isolats de P. medicaginis en utilisant cette méthode, ont un classement constant.Pour ces 3 variétés, les descendances issues d'un cycle de sélection massale et intravariétale, comparées à leurs parents respectifs, présentent une sensible amélioration de la résistance à P. medicaginis. La méthode proposée semble être un bon outil de sélection de la luzerne pour la résistance à ce champignon.Mots clés additionnels : Sélection, classement des variétés. SUMMARYMethod of artificial inoculation for screening for resistance to spring black stem in alfalfa.Phoma medicaginis Malbr. & Roum., the causal pathogen of the black stem disease of alfalfa, occurs in France where losses may be severe. It is therefore necessary to take it into account during breeding programs. However, outbreaks of the disease arc rare in nurseries and it is important to test the susceptibility of selected families by artificial inoculation with the fungus. The following method is suggested : alfalfa seedlings (28 days old) are cut above the insertion of the second trifoliate leaf and inoculated with a spore suspension (1.5 10 6 spores ml-') of P. medicaginis ; seedlings are held at 21 °C, 100 % R.H., for 72 h and then grown for 45 days at 18 °C with a 16 h photoperiod (5 000 lux) and 95 % R.H. ; symptoms are rated according to a 1 to 6 scale.
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