03413nam a2200169 a 450000100080000000500110000800800410001902200140006010000160007424500800009026000650017052029090023565000250314465000290316970000230319870000220322110344532021-07-06       2007    bl uuuu     u01u1 u    #d  a1510-78091 aREBUFFO, M.  aBreeding temperate legumesbadvances and challenges.h[electronic resource]  aLotus Newsletter, 2007, Volume 37, Issue 3, pages 105.c2007  aAbstract: Conventional breeding is an efficient tool with factors with low environmental effect, where the phenotype expression is closer to the genotype. On the other hand, selection for abiotic stresses involves complex characteristics restricting progress of conventional breeding  programs. The study of the responses of several perennial legumes to selection for water and saline stress, Al tolerance and P availability is developed in the frame of the Projects LOTASSA (FP6-2003-INCO-DEV2 PL-517617) and LESIS (FTG-787/2005). Their  approach involves the characterization and selection of naturalized populations for the identification of superior germplasm, as well as their metabolic and molecular analysis in order to develop strategies that could spead conventional breeding in the future. The  presentation describes the approach and first results. The physiological responses of the main cultivated species to Al, saline and water stress are evaluated. Divergent selection is carried out in Lotus corniculatus (Lc) and diploid L. uliginosus (=L. pedunculatus) (Lu) for  tolerance to water stress and Al tolerance, and the development of contrasting populations for root characteristics (root branching and density), the characterization of natural populations of L. glaber (=L. tenuis), Trifolium repens (Tr) and T. pratense (Tp) for water stress, L. glaber for saline stress. Chilean and Uruguayan naturalized populations of Lc, Tr and Tp are evaluated for water stress and prevailing diseases. Results show that there is genetic variability within the Lc, Lu and Lg germplasm for Al tolerance, water and saline stress, respectively, to be used in the selection process. Lc ultivar San Gabriel (Uruguay) was more sensitive to Al toxicity than Brasilian germplasm; the membrane potential in root cortex cells remains unchanged between pH 4.4 and 6 for the most tolerant Brasilian selections. Although saline stress stunted foliar and root growth, the evaluation at young stages (40 days) showed Lg entries collected in saline soils of Buenos Aires Province (Argentine) that produced 50% more forage than less adapted germplasm. There are differential responses of Chilean Lg accessions to water stress in leaf rate appearance, stem elongation and stem dry weight. Water stress (40% field capacity) was imposed for six months to Lc cultivar San Gabriel and INIA Draco. Contrasting phenotypes were identified through regrowth production (2.15 and 4.13 g/plant of fresh weight for sensitive and tolerant selections, respectively). Differences between sensitive and tolerant selections were larger for Lu (2.96 and 7.72 g FW/plant). Proline is one of the metabolite that shows high consistency with the response to water stress in several species of Lotus as well as in Tp. The  isotopic discrimination (?13C/12C) has a good correlation with water use efficiency for the cultivated Lotus species.  aLEGUMINOSA FORRAJERA  aMEJORAMIENTO DE PASTURAS1 aCONSORTIUM LOTASSA1 aCONSORTIUM LESIS.