Abstract
Medicago truncatula is an omni-Mediterranean species grown as an annual forage legume. In addition to its small genome size and simple genetics, M. truncatula harbors several attributes which make it an attractive model legume. In this study, we investigated morphological and photosynthetic responses to water deficit in parental genotypes of M. truncatula recombinant inbred lines. Ten parental lines were cultivated under three water regimes (100% of field capacity (FC), 50% FC and 30% FC) and were harvested at flowering time and at the end of their lifecycle. Results from ANOVA showed that variability of measured parameters was explained by the effects of line, treatment and their interaction with treatment factor recorded the highest values. Out of the 27 traits, 14 were influenced by the line x treatment interaction. High to moderate broad-sense heritability (H²) were observed for most of the traits under control treatment and drought stress. Most of the correlations between measured traits were positive under the three water regimes. The flowering time was positively correlated with aerial and root growth rate. The tolerance of lines to water deficit seems to depend, in particular, on their ability to maintain higher photosynthetic activity. In 30% FC, principal component analysis clustered lines into two groups. The Jemalong A17 line was the least affected for most phenotypic parameters. Hence, all populations of recombinant inbred lines derived from crosses between Jemalong A17 and the remaining lines were useful for the identification of the genetic determinants for tolerance to water deficit in M. truncatula. Key words: M. truncatula, parental lines, recombinant inbred lines, water deficit, morphological traits, photosynthetic parameters.
Highlights
Environmental constraints are the main factors limiting agricultural productivity and play a major role in the distribution of plant species
Lines of M. truncatula are potentially subjected to different selection pressures (Badri et al, 2007; Lazrek et al, 2009) in their natural areas of distribution variability is expected in response to water deficit in the different genotypes used in this study
Lines may have developed an adaptive response to drought that can be exploited later to identify the genetic bases of tolerance to drought
Summary
Environmental constraints are the main factors limiting agricultural productivity and play a major role in the distribution of plant species. Water deficit is considered the most important factor in limiting crop production (Harb et al, 2010). Changes in the structure of plants (Shao et al, 2008), the growth rate and gas exchange at the leaf level (Slama et al, 2007), and overproduction of compatible compounds (Nunes et al, 2008). Photosynthetic assimilation is unavoidably reduced due to decreased CO2 concentrations at the chloroplast level (Cornic, 1994). A reduced leaf area and decreased transpiration rate is often the result of drought stress (Dong and Zhang, 2000). Gas exchange characteristics and chlorophyll concentrations are reduced as stress intensity increases
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