| A perusal of the results (Table 1) shows that
Ae. ovata and Ae. caudata cyloplasms caused an increase in
ear length and number of productive tillers per plant. However, the seeds
of these sterile analogues when obtained by crossing with maintainer or
restorer lines, were highly shirvelled owing to their late maturity. This
may be due to a sudden rise in temperature and a proportional decrease in
relative humidity soon before the harvest time in late March and early April
which caused forced maturity in the late maturing types. This not only caused
the production of shrivelled seeds but also caused a drastic decrease in
grain yield per plant. A comparative performance of the first five bread
wheat cultivars and their male sterile analogues for days to flower, effective
tillers per plant and spike length in cm may be seen in Fig.
1. Triticium timopheevi cytoplasm had relatively less pronounced effects than the Aegilops cytoplasms on the characters measured. This cytoplasm also increased effective tillers per plant and spike length in some cultivars but had equal maturity period and more or less the same plant height as the normals. Thus in comparison with normal plants with T. aestivum cytoplasms, the male sterile analogues with T. timopheevi cytoplasm were agronomically superior and could give highly yields when crossed with a diverse but effective male fertility restorer line. KIHARA (1966) first reported that various cytoplasms exerted different influences on substituted genomes. However, INGOLD (1968) observed that Ae. ventricosa cytoplasm did not cause major changes in the manifestation of substituted genomes. HORI& TSUNEWAKI (1969), TAHIR (1971) and MAAN (1979) studied the effects of s-cytoplasm and reported delayed maturity due to Ae. ovata cytoplasm. There appears to be a striking similarity between the results of this investigation and that of TAHIR (1971), that the cytoplasm of Ae. ovata delayed heading and increased tiller number and spikelength in wheat. This may possibly be explained due to the common lineage between the materials studied in both the cases. He, however, did not study Ae. caudata cytoplasm which was found in the present study to transfer identical side effects as may be seen in Table 1. Considering the side effects of male sterile cytoplasms of all the three species in the genomic background of bread wheat cultivars studied in this case it was concluded that T. timopheevi offered the best results of s-cytoplasm which carried plasmagenes that in interaction with the nuclear genes of T. aestivum improved many agronomic attributes besides conferring effective and stable male sterility in the bread wheat analogues. References HORI, T. & TSUNEWAKI, K. 1969. Basic studies on hybrid wheat breeding. Effects of three alien cytoplasms on main quantitative characters of hexaploid wheats. Jap. J. Breed. 19: 425-430. INGOLD, M. 1968. Male sterility and restorer systems in wheat. Euphytica 17. Supl. 1: 69-74. KIHARA, H. 1966. Cytoplasmic male sterility in relation to hybrid wheat breeding. Zuchter 37: 86-93. MAAN, S.S. 1979. Cytoplasmic relationships among the D and M genome Aegilops species. Proceed V Int. Wheat Genet. Symp: 231-260. TAHIR, C.M. 1971. Genetic influence of male sterile cytoplasms and fertility restoring genes on performance of common wheat varieties. Jap. J. Breed. 21: 189-194. |
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