Physiological Traits Under Water Stress in Bread Wheat Genotypes.

Improving water stress tolerance is a major goal in plant breeding programs.

The objective of this study was to compare the wheat cultivar PROINTA Elite (P-Elite) with three selected lines, PEL4, PEL8 and PEL9, obtained by mutagenesis from this variety. The four genotypes were grown at a field experiment that included two levels of water conditions i) full irrigation (I) and ii) water stress imposed between end of tillering and middle of the grain filling period (D). Measurements included leaf physiological traits as carbon exchange rate (CER), stomatal conductance (SC), transpiration (LT), light adapted chlorophyll fluorescence (CF), proline content (PC) and membrane thermostability (MT). CER declined after anthesis and did not show differences among water conditions and cultivars. SC and LT decreased under water stress and reductions were lower in P-Elite than in the lines (17 vs. 30% and 11 vs. 20%, respectively). CF, a measure of the efficiency of light capture of PSII reaction center, showed a greater decline in two out three experimental cultivars. Two lines (PEL 4 and PEL9) showed higher values in PC and MT in respect to P-Elite when grown under water stress. In spite of PEL4, a suspected line bearing water stress tolerance, and P. Elite showed comparable values of CER, the former was able to reduce leaf transpiration suggesting greater water use efficiency.