| In addition to the cytological evidence (UPADHYA and SWAMINATHAN 1965)
on the origin of T. zhukovskyi, the presence of fertility restoring
factors in this species supports the view that T. timopheevi might
have been one of its putative parents and that T. zhukovskyi might
be carrying the cytoplasm of T. timopheevi. If this is true, then
the fertility restoring system of T. timopheevi should be identical
to that of T. zhukovskyi. Thus, the two gene hypothesis of fertility
restoration seems to be more plausible. It is interesting to note that T. timopheevi arose from T. dicoccoides (WAGENAAR 1966) which restores the fertility of male sterile durum and male sterile dicoccum wheats carrying Ae. ovata cytoplasm (FUKASAWA 1958) and it is quite likely that T. dicoccoides may also restore the fertility of male sterile common wheat with timopheevi cytoplasm. And T. zhukovskyi arose from T. timopheevi (UPADHYA and SWAMINATHAN 1965). T. zhukovskyi restores the fertility of male sterile T. aestivum with timopheevi cytoplasm. With the objective of finding possible new sources of fertility restoration, we corssed T. sphaerococcum as a pollinator with the same male sterile plant which was used in the cross with T. zhukovskyi. Thirty three F1 plants obtained were highly male sterile and the seed setting was poor, with a maximum of 4.3 seeds per ear. Two plants were in less than one seed per ear class, 15 plants in 1-2 seeds class, 12 plants in 2-3 seeds class and three plants were in 3-4 seeds per ear class. This suggests that T. sphaerococcum does not carry dominant gene for fertility restoration and that perhaps it contains recessive genes for sterility in homozygous condition. Sterile plants selected from the stocks (T. timopheevi x Marquis2) F4 x Pembina3) F2 and (T. timopheevi x Marquis2) F4 x Selkirk3) F2 were also crossed with the hexaploid spring wheat varieties e.g. C. 303, S. 310, S 227, C 306, NP 830, NP 875, S 308, Sonora 64, Lerma Rojo and PV 18 as male parents with a view to develop sterile lines in them. The resulting F1 plants, grown from these crosses were found to be highly sterile on the basis of seed set data and hence presumably these varieties carry recessive genes for sterility. Backcross progenies resulting from crossing F1 plants with C 303 and Sonora 64 were also highly sterile because in most of the plants less than two seeds per ear were obtained. These varieties can be made fully sterile after a few backcrosses, when their characters are fully recovered. The sterility noted in some of the intervarietal crosses was not as complete as in Sonora 64, C 303 and in the cross involving T. sphaerococcum species. The progenies of all the aforementioned crosses were grown in pots and the heads were not bagged. Data on sterility and fertility were collected by taking the average seed setting per ear of a plant. The very low seed setting observed on sterile plants might be either due to cross pollination or due to the fact that the sterility was not complete. |
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