| I. Research Notes An analysis of induced homoeologous pairing in hybrids between ph mutant of Triticum aestivum and tetraploid wheat species T. timopheevii and T. militinae T. SHNAIDER, H. PEUSHA and O. PRIILINN Institute of Experimental Biology, Academy of Science of Estonian S.S.R., Estonia, U.S.S.R. Triticum timopheevii Zhuk. (AAGG,2n=28) is a tetraploid wheat species first found in Central Transcaucasia (Western area of Georgia, U.S.S.R.) by academician P.M. ZHUKOVSKI (1928). Triticum militinae Zhuk. et Migush. (AAGG, 2n = 28) was isolated as a spontaneous mutant from experimental plots of T. timopheevii by P.M. ZHUKOVSKI in 1950 and it differed from the latter by naked grains and black awns. Both of these species have attracted interest of wheat breeders and geneticists on account of their exceptionally high immunity to diseases. Therefore they have frequently been included as parental material in wheat breeding programs. However, a typical characteristic of these species is that their F1 hybrids with other wheat species have irregular meiosis and they are highly sterile. For a long period wheat breeders endeavoured to solve the problems of sterility in F1 hybrids, since a deeper knowledge of the basic genetical structure and function of the genetic system in T. timopheevii and T. militinae is not only of fundamental but also of practical importance. SACHS (1953) and FELDMAN (1966) assumed that poor chromosome pairing in hybrids F1 between tetraploid wheat species involving T. timopheevii was due to criptic structural differences. This conclusion was supported also by SEARS (1956) and RILEY et al. (1958). However, WAGENAAR (1961, 1963, 1966) suggested that irregular meiosis in F1 hybrids was due to genetic system with some asynaptic genes which affected chromosome pairing and chiasma formation. In our crosses we used a mutant ph1 and nulli-tetrasomic line cv. Chinese Spring for the purpose of inducing alien chromosomes of hexaploid and tetraploid wheat to pair. It is known that homoeologous pairing in wide hybrids F1 is limited by the Ph1 gene located on chromosome 5B in common wheat. The use of mutant ph1 with deletion of Ph1 locus gives a possibility to transfer genetic material from alien species to common wheat varieties (SEARS 1976, 1980). In this paper we present cytological analysis of meiosis in F1 hybrids, between hexaploid and tetraploid wheat species using mutant ph1 and nulli-tetra compensation line. |
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