| Male fertility and sterility in the hybrids, of crosses
of T. zhukovskyi, T. sphaerococcum and T. aestivum with common
wheat carrying T. timopheevi cytoplasm R. K. MIRI Division of Genetics, Indian Agricultural Research Institute, New Delhi, India Cytoplasmic male sterility in wheat was first reported by KIHARA (1951) by transferring the nucleus of hexaploid wheat into the cytoplasm of Ae. caudata L. FUKASAWA (1953, 1958) reported male sterility when T. durum had the cytoplasm of Ae. ovata L. and that T. dicoccoides var. Kotschyanum restored the pollen fertility of this male sterile durum. The possibility of hybrid wheat became apparent only when WILSON and Ross (1962) discovered another effective source of male sterility in T. timopheevi x Bison cross and soon afterwards SCHMIDT, JOHNSON and MAAN (1962) discovered fertility restoration when a T. timopheevi derivative wheat was crossed to Nebred. Studies by several workers of this cytoplasmicgenetic male sterility and fertility restoration system have revealed that two dominant genes and some modifiers are necessary for full fertility restoration of male sterile wheat. Hence, the development of fertility restorer line (R) in different wheat varieties is not as easy and as satisfactory as in Sorghum which requires only one gene for fertility restoration. The problem of the perfect fertility restoration in wheat has not been fully overcome. T. zhukovskyi, a hexaploid wheat, appears to have arisen through chromosome doubling of timopheevi-monococcum hybrid on the basis of cytological evidence and morphological resemblance of the resynthesized species (KOSTOFF 1937a, BELL, LUPTON and RILEY 1955; UPADHYA and SWAMINATHAN 1965). If this hypothesis is valid then one would also expect T. zhukovskyi to be carrying genes for fertility restoration of male sterile wheat with timopheevi cytoplasm. Therefore, to test this, in 1965-66 season, we crossed T. zhukovskyi as a pollinator with a male sterile plant selected from a population of F3 plants derived from the stock (T. timopheevi x Marquis2) F4 x Pembina3) F2 kindly supplied by Dr. A.B. CAMPBELL, Canada Department of Agriculture, Winnipeg, Manitoba. The resulting two F1 plants, grown in pots were quite fertile and were late in maturity as compared with the original stock carrying the timopheevi cytoplasm. From this, 33 F2 plants were grown. One plant was found to be completely sterile and the rest were fertile with varying degrees of fertility. There were 21 plants in the 20 to 41 seeds per ear class and 11 plants were in the 12 to 20 seeds per ear class indicating that perhaps either two dominant genes and some modifiers permit full fertility restoration or a single gene with tetrasomic inheritance and dosage effect and some modifiers are involved in fertility restoration. Further study on inheritance of fertility restoration is in progress to obtain a definite answer. The possibility of a single gene and tetrasomic inheritance of fertility restoration seems to be remote, since this will involve the presence of the fertility restoring gene in the A genome also. The emmer group having genomic constitution AABB has received its cytoplasm from BB analyzer (KIHARA 1966). Hence the B genome is the likely carrier of the genes for restoring the fertility of its own cytoplasm. |
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