Genetic diversity of photosynthetic characters in native populations of Triticum dicoccoides

Wild emmer wheat (Triticum dicoccoides Korn) has shown wide genetic diversity for disease resistance and morpho-physiological traits of economic importance. Our objectives were to test for genetic variation (V_G) in photosynthetic characteristics residing within and between native populations sampled from three ecogeographical regions of Israel, and to identify potential sources of high photosynthetic efficiency for future wheat improvement. Accessions sampled in the center of wild emmer distribution (upper Jordan Valley) in a relatively narrow geographical range showed the greatest diversity in CO₂-assimilation rate per unit leaf area (A) or per unit chlorophyll (A/Chl). Genetic variation was absent for internal CO₂ concentration (Ci) and water-use efficiency (WUE) and generally lacking for stomatal conductance (gs). Leaf area, although quite variable, was not a significant cofactor in assessing genetic potential for photosynthesis. Accessions within a given population showed 10-times more variation in A and A/Chl than populations sampled from different locations in a region. Accessions with the highest photosynthetic efficiency were derived from upland steppic populations located in marginal habitats extending southward into Israel. Some accessions having high photosynthetic capacity (A=32 mol m^-2 s^-1) with no significant reduction in leaf size constitute a potentially valuable genetic resource yet untapped for genetic improvement of hexaploid (T. aestivum L.) wheat.Abbreviations LA total leaf area - V_G total genetic variance - PPFD photosynthetic photon flux density - WUE water-use efficiency