Genetic Mapping of Water Use Efficiency and Carbon and Nitrogen Metabolism in Drought‐Stressed Alfalfa
2019
Santantonio, Nicholas | Pierce, Chris A. | Steiner, Robert L. | Ray, Ian M.
Identifying quantitative trait loci (QTL) associated with alfalfa (Medicago sativa L.) shoot biomass (SB), water use efficiency, and C and N metabolism can resolve potential target sites for selection and provide new insight into genetic relationships that may exist between key traits in water‐limited environments. The goal of this study was to utilize a tetraploid (2n = 4x = 32) BC₁ mapping population and a genetic map based on 334 molecular markers to detect QTL associated with SB, C isotope discrimination (CID), and C and N content during drought stress. Half‐sib families derived from 96 BC₁ individuals were evaluated for the SB trait in seeded plots near Las Cruces, NM, during two water‐stressed forage regrowth cycles in each of 3 yr (2005–2007). High costs associated with CID phenotyping precluded evaluation of the entire population. Therefore, in 2006 and 2007, shoot tissue samples for CID, C content, and N content measurements were collected from a subset of 29 families that exhibited extreme SB phenotypes in 2005. Significant genotype effects were observed among these families for SB and CID in both years and C and N content in 2006. Interval mapping identified QTL for all traits. Phenotypic effects of QTL supported significant positive genetic correlations detected between SB and CID, and between C and N content. Estimated QTL positions within the M. truncatula Gaertn. genome sequence assembly encompassed multiple candidate genes affiliated with stomatal development, cuticular wax biosynthesis, C and N metabolism, and abiotic stress response.
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