Description
Alfalfa’s drought tolerance has not been a major breeding target until recently, and the extent of genetic variation for this trait and its contributing mechanisms have not been thoroughly elucidated. Eight populations, including four landraces (Alta Sierra, Aragon, APG6567, APG44669), two Australian cultivars (Venus and Genesis), and two interspecific hybrids (AF3448 and AF3347) of alfalfa were selected based on their outstanding breeding values for dry matter production and plant persistence in Mediterranean drought-prone environments. The objective of this work was to evaluate the below and above ground phenotypic expression of these drought-tolerant alfalfa accessions, in order to identify morpho- physiological mechanisms conferring to alfalfa greater agronomical performance in drought-prone environments. Individual plants of each population were established on mesocosms of PVC tubes 11 cm in diameter and 100 cm in depth. Plants were grown at two water regimes: with water deficit (WD) and well- watered (WW). Both trials were organized in a complete block design with four replicates. Plant height, stem elongation rate, shoot dry matter, chlorophyll content, stomatal conductance, canopy temperature, leaf area, specific leaf area, crown diameter, relative length density, and root dry matter at 0-30, 30-60 y 60-100 cm were determined. The water regime affected significantly the phenotypic expression of all above and belowground morpho-physiological traits evaluated (P < 0.05), which resulted in a 40% reduction in shoot dry matter and plant height in WD relative to WW. Alfalfa populations with putative drought tolerance in Mediterranean environments did not exhibit a unique phenotypic strategy for facing severe water stress. Populations APG44669 and Alta Sierra showed divergent phenotypic expression in terms of stomatal conductance, leaf traits, root architecture, and root biomass partitioning profile.
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Root and Aboveground Traits Expressed by Landraces and Interspecific Hybrid of Alfalfa (Medicago sativa. Hybr. (Alborea)) with Putative Drought Tolerance in Mediterranean Environments
Alfalfa’s drought tolerance has not been a major breeding target until recently, and the extent of genetic variation for this trait and its contributing mechanisms have not been thoroughly elucidated. Eight populations, including four landraces (Alta Sierra, Aragon, APG6567, APG44669), two Australian cultivars (Venus and Genesis), and two interspecific hybrids (AF3448 and AF3347) of alfalfa were selected based on their outstanding breeding values for dry matter production and plant persistence in Mediterranean drought-prone environments. The objective of this work was to evaluate the below and above ground phenotypic expression of these drought-tolerant alfalfa accessions, in order to identify morpho- physiological mechanisms conferring to alfalfa greater agronomical performance in drought-prone environments. Individual plants of each population were established on mesocosms of PVC tubes 11 cm in diameter and 100 cm in depth. Plants were grown at two water regimes: with water deficit (WD) and well- watered (WW). Both trials were organized in a complete block design with four replicates. Plant height, stem elongation rate, shoot dry matter, chlorophyll content, stomatal conductance, canopy temperature, leaf area, specific leaf area, crown diameter, relative length density, and root dry matter at 0-30, 30-60 y 60-100 cm were determined. The water regime affected significantly the phenotypic expression of all above and belowground morpho-physiological traits evaluated (P < 0.05), which resulted in a 40% reduction in shoot dry matter and plant height in WD relative to WW. Alfalfa populations with putative drought tolerance in Mediterranean environments did not exhibit a unique phenotypic strategy for facing severe water stress. Populations APG44669 and Alta Sierra showed divergent phenotypic expression in terms of stomatal conductance, leaf traits, root architecture, and root biomass partitioning profile.
