CHARACTERIZATION OF WHEAT-Thinopyrum PARTIAL AMPHIPLOIDS BY MEIOTIC ANALYSIS AND GENOMIC IN SITU HYBRIDIZATION

¹ Cereal Research Centre, Agriculture and Agri-Food Canada, Winnipeg, MB

² Eastern Cereal and Oilseed Research Centre, Agriculture and Agri-Food Canada, Ottawa, ON

³ Lethbridge Research Centre, Agriculture and Agri-Food Canada, P.O. Box 3000, Lethbridge, AB

Partial amphiploids are backcross progenies of hybrids between wheat and either Thinopyrum intermedium (2n=6x=42) or Th. ponticum (2n=10x=70). They have a chromosome number of 56, with 42 wheat chromosomes and 14 coming from the Thinopyrum parent. In earlier work (Chen et al. 1996) it was shown that the genomic constitution of Th. intermedium is St, J^sJ.Th. ponticum is JJJJ^sJ^s. Partial amphiploids carry many useful agronomic traits such as resistance to stem and leaf rust, BYDV, WSMV, cold tolerance, semi-perennial growth habit. Meiotic behaviour of F1 hybrids and GISH were used to establish the genomic constitution of partial amphiploids of undefined parentage. Meiotic behaviour in individual partial amphiploids was very highly regular giving high plant fertility and virtually perfect transmission of the total chromosome complement to the progeny. Meiosis in hybrids between different accessions was highly irregular especially in proportions of unpaired chromosomes, leading to highly sterile progeny, indicating that combining traits through intercrosses would not be a feasible approach. GISH analysis indicated that of 8 partial amphiploid studied, two originated from Th. intermedium and six from Th. ponticum. In all cases the alien genome consisted of different ratios of chromosomes of the St, J^s and J genomes and hence are designated as synthetic genomes. The fact that each partial amphiploid was fertile indicated that although the genomes were synthetic, they contained chromosomes from all 7 homoeologous groups. In addition, GISH revealed numerous intergenomic translocations such as Robertsonian, telomeric and interstitial. The results of meiotic and GISH in studying the genomic constitution of partial amphiploids were complementary but the latter provided greater precision in identifying constituent genomes and translocations.