Questions and avenues for lucerne improvement

Abstract

Six crucial questions for lucerne breeders are set up and discussed in relation to the available information. (i) Which width of adaptation? Genotype נlocation interaction is region-specific and may be wide enough to justify breeding for specific adaptation. Genotype נexploitation interaction requires contrasting plant types for mowing and intensive grazing. (ii) Can we breed very drought-tolerant varieties? One drought-tolerant landrace exhibited a drought-avoidance, water-conservation strategy based on limited root development, while large root featured material adapted to favourable environments and/or frequent mowing. (iii) Which selection scheme and variety type? Many schemes were proposed for synthetic varieties, but empirical or theoretical comparisons were limited in number and inference space. Non-additive genetic variation may be exploited by free hybrids (semi-hybrids) through procedures varying in complexity, possibly assisted by marker evaluation. Previous selection of exotic germplasm for adaptation is essential. (iv) How to improve the forage quality? Selection for modified stem morphology (increased internode number, decreased internode length) proved effective. Combined selection for forage yield and leaf/stem ratio seems also feasible. (v) Which opportunities for marker-assisted selection? Linkage maps for lucerne are available but useful markers for forage yield may be site-specific. Bulk segregant analysis is promising in breeding for stress tolerance. (vi) How to exploit genomic information from M. truncatula? This model species can help in developing markers and locating genes which control metabolic pathways, such as saponin content and composition. Information from M. truncatula on marker-trait association for forage yield or tolerance to abiotic stresses may be little exploitable.