The agronomic purpose of evaluation: Relating nurseries to field situations

Abstract

The most successful Mediterranean pasture legumes varieties were obtained from the exploitation of genetic resources collected in the Mediterranean basin. The selection programs are often based on extend ve germplasm collections followed, initially, by seed multiplication in a nursery, where preliminary evaluation of the bio-agronomic characteristics is made. This crucial phase can be effectively utilised, if the evaluation characters are chosen to test the performances of the germplasm and an initial selection is made for new varieties in the field. Emphasis has been given in the past to climatic and edaphic adaptation, but experience has shown that the successful introduction of a new variety also depends on the crop management. This is closely related to the type of farming system and the biotic competition (weeds, pests, diseases) in which it is grown. To date, an ideotype for new varieties of annual self-reseeding legumes cannot ignore the increasing requirement of a low-input oriented agriculture, that in many developed countries includes the use of these forage crops for alternative, non-forage purposes. In this paper, the ecological characteristics of the Mediterranean rangelands are taken as a model for setting up the breeding objectives and as a guideline for choosing relevant morphological and agronomic characters to be assessed at the nursery level. Examples of the agronomic purpose of germplasm evaluation are given from recent and past screenings of annual clovers and medics, and field experienced introductions of annual pasture legumes varieties in deteriorating swards of the Mediterranean basin, both for forage or other non-productive uses. An ecological analysis of germplasm collection sites, including the recent management history of the ecosystem and other relevant biotic indicators can provide useful information, that correlated with agronomic traits, assists in the selection of accessions to keep in the following phases of selection, thus improving the efficiency of the agronomic screening. In testing far varieties to be grown under strong limiting environmental conditions, the climatic and edaphic environment of the nursery should be as similar as possible to the environment where the material is to be grown. The most limiting environmental factors, temperature and soil moisture, should be accurately monitored over the biological cycle of the collected plants, for extrapolation of the data collected in the nursery (e.g. flowering dates and duration) to a wide range of field situations. The single plant or single row forage and seed yields are not sufficiently correlated to the yields at the plant community level, but observation of some key yield components that are less influenced by the management. such as seed size, hardseededness, pod morphology and winter growth can contribute to the identification of promising genotypes from nursery data.