| Screening and utilization of wild-wheat germplasm for
rust resistance H.S. DHALIWAL and K.S. GILL* Punjab Agricultural University, Regional Research Station Gurdaspur, India Wild wheats are distributed very widely in the Mideast from the Balkan Peninsula to Transcaucasia and in both arcs of the Fertile Crescent to the Persian Gulf on the east and the Dead Sea on the west (JOHNSON & DHALIWAL 1976). Triticum boeoticum extends from Transcaucasia to Greece across Anatolia. T. urartu is distributed in Transcaucasia, eastern Anatolia and the entire fertile crescent including Syrio-Palestinian area. T. dicoccoides is endemic to the western arc of the Fertile Crescent but is also distributed sporadically in Iran, Iraq and south eastern Anatolia whereas T. araraticum is restricted to eastern arc of the Fertile Crescent. Due to their wide adaptation to diverse eco-geographic regions wild wheats are expected to vary genetically with respect to cold and drought tolerance, resistant to insect-pests and diseases and in seed protein content and quality (JOHNSON & WAINES 1977). Our cultivated wheats, bread wheat (Triticum aesitivum L. em Thell, 2n=42) and durum wheat (T. durum Desf. 2n=28) combine the genetic complement of three and two diploid species, respectively. The cultivated emmer tetraploid Triticum durum was domesticated from its wild progenitor T. dicoccoides Korn Schweinf, which evolved from an amphiploid involving two diploid wheat species, T. boeoticum Boiss and T. urartu Tum. (JOHNSON & DHALIWAL 1978). Another wild tetraploid wheat T. araraticum Jakubz. ancestral to the cultivated timopheevii tetraploid wheats was also derived from the same parentage as that of T. dicoccoides. Bread wheat originated from chromosome doubling in a hybrid between the cultivated emmer tetraploid and the wild diploid Goat grass, Aegilops squarrosa L. (MCFADDEN & SEARS 1946). At each step of hybridization and chromosome doubling only one or a few accessions of the diploids or tetraploid were involved and the resultant polyploid got reproductively isolated immediately from its parent species as a result of which the tetraploids and hexaploid wheats received only a minor fraction of the gene pool existing in their wild and primitive germplasm. It is, therefore, very important to screen the wild germ for its usefulness in the improvement and enrichment of cultivated germplasm. The importance of the wild and cultivated, germplasm in the improvement and sustained production of our crop plants and the need to preserve and conserve it has been universally recognized. Several institutes throughout the world are engaged in the collection maintenance, screening and utilization of germplasm of wheat. The University of California at Riverside is maintaining a comprehensive collection of Wild wheats and Aegilops spp. and primitive wheats. JOHNSON & WAINES (1977) have reported screening of wild wheats for protein content, essential amino acids, lysine and threonine, resistance to a nematode (Pratylenchus thornei) and "take all" disease of wheat. |
| * Dean, college of Agriculture. Punjab Agricultural University, Ludhiana. |
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