Theor AppI Genet (1991) 81:445-460 ....... ~:~ :~• E : NET CS 9 Springer-Verlag 1991 Photosynthetic performance in wild emmer wheat, Triticum dicoccoides: ecological and genetic predictability E. Nero 1, B.E Carver z and A. Beiles 1 1 Institute of Evolution, University of Haifa, Mt. Carmel, Haifa 31999, Israel 2 Department of Agronomy, Oklahoma State University, Stillwater, OK 74078, USA Received February 5, 1990; Accepted February 23, 1990 Communicated by H. E Linskens Summary. In a twin study, we have shown that wild emmer wheat, Triticum dicoccoides, the progenitor of all cultivated wheats, harbours important genetic variation (Vg) in photosynthetic characteristics. This Vg resides within and between populations and ecogeographical re- gions in Israel, which is the center of origin and diversity of wild emmer wheat. Here we analyzed, by univariate and multivariate methods, the significant differentiation of variation in photosynthetic characteristics of 107 genotypes from 27 populations of wild emmer in Israel, distributed in three ecogeographical regions including central, xeric (northern cold and eastern warm) marginal, and mesic (western) marginal populations. The highest photosynthetic efficiency was displayed by populations of the xeric marginal region, but most variation for pho- tosynthetic capacity occurs between accessions within ecogeographical regions and populations. Genotypes and populations of T. dicoccoides having high photosyn- thetic capacity can be identified by climatic factors and isozyme markers. The identification by genetic markers, if substantiated by testcrosses, can facilitate the maxi- mization of conservation, in situ or ex situ, and utiliza- tion of these photosynthetic genetic resources for im- provement of hexaploid wheat (T. aestivum). Key words: Photosynthesis - Genetic resources Triticum dicoccoides - Allozyme polymorphisms - Natural selec- tion Introduction Genetic improvement of crops is essential in view of the general genetic homogenization of cultivars. Remark- ably, while crop yields have generally been increasing recently, due in part to improved agrotechniques (e.g., Avery 1985), the genetic base of most of the important food crops has been rapidly narrowing (Plucknett et al. 1983). This is due to the global extension of modern pure breeding practices, which increase genetic homogeneity (Frankel and Bennett 1970; Frankel and Hawkes 1975; Frankel and Soul6 1980; Harlan 1975, 1976). Amelioria- tion of this trend lies in the utilization of genetic re- sources from the wild progenitors of cultivars (e.g., Feld- man and Sears 1981). A global network of gene banks has been established to provide plant breeders with the genetic resources for crop improvement (Plucknett et al. 1983). However, the conservation of diverse germ plasm, either ex or in situ, is insufficient. To achieve more effi- cient and comprehensive utilization of the conserved gene pool, it is essential to predict, screen, and evaluate promising genetic resources in wild populations (Mar- shall and Brown 1981; Nevo 1987). The Near East Fertile Crescent is very rich in wild relatives of cultivated plants, and represents a major source of plant cultivation. Old World wild wheat, bar- ley, oats, and rye are the traditional cereal crops of the Old World belt of Mediterranean agriculture (Zohary 1983). The Near East Fertile Crescent, and Israel in par- ticular (Nevo 1986), represent the major center of origin and diversity of wheat, barley, and oats. Here, these crops built up a wealth of genetic diversity throughout their evolutionary history, as a result of selective pres- sures by parasites and environmental heterogeneity and stresses. This variation is neither random nor neutral. On the contrary, it displays at all levels adaptive genetic diversity for biochemical, morphological, and immuno- logical characteristics, which contribute to its adaptive nature to mountaintops and lowlands, mesic and xeric habitats, and different soil types (Nevo and Beiles 1989).