Genetic resources of wild emmer, triticum dicoccoides, for wheat improvement in the third millennium
2001
The genetic resources and diversities of wild emmer wheat, Triticum dicoccoides, the progenitor of almost all cultivated wheats, are reviewed, primarily based on the research program at the Institute of Evolution, University of Haifa, Israel, during the period 1979-2000. Diverse genetic polymorphisms have been described across Israel in the following systems: allozymes and DNA markers at both macro- and microgeographical scales; a and b amylases; photosynthetic yield; Cab (chlorophyll a/b binding proteins) circadian rhythms; herbicide response; genetic divergence of heat production; salt tolerance; Na<SUP>22</SUP> uptake; drought and temperature resistance, storage proteins; amino acids; and disease resistances (leaf, stem, and stripe rusts; wheat soil-borne mosaic virus) and their ecological and allozyme and/or DNA marker correlates. Genetic mapping of resistance to chlorotoluron, yellow rust, and powdery mildew on chromosomes 6B, 1BS, and 5BS, respectively, was conducted as a prelude to cloning and transformation. Finally, a genome-wide map of 549 molecular markers (SSR, AFLP, RAPD) was prepared for the ongoing qualitative trait loci (QTL) analysis, including the genetic changes that occurred during domestication. These results strongly support the idea that wild emmer harbors rich genetic resource polymorphisms appropriate for wheat improvement. Cultivar release is a long-term process. Cultivars that contain T. dicoccoides genes encoding resistance to powdery mildew and yellow (= stripe) rust, as well as high protein content and improved baking quality, are expected to be commercially released in the foreseeable future. Thus T. dicoccoides will play a major role in wheat improvement in the third millenium. Finally, in situ conservation is highly recommended to safeguard the evolutionary dynamics and rich genetic resources of T. dicoccoides for future breeding.
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