| Of particular interest were studies of additional pistils transformed
from stamens with well defined stigmas and ovaries. They were somewhat smaller
in size compared to the main pistils. In additional pistils the ovules in
the ovaries were more elongated than those in the main pistils. The peculiarity
of the ovules in additional pistils was that only the inner integument was
formed while the outer one did not develop (Fig. 3).
Mother cells of the macrospores in the ovules were not differentiated and
no embryo sacs were formed. Thus, they were as sterile as ovules in the
main pistils. Sterility of the ovules in both cases in polygynous florets
must be attributed to the manifestation of specific interaction of wheat
genome with alien cytoplasm. Some authors indicate low seed set (14 to 20%)
typical of CMS hybrids having Ae. caudata cytoplasm (PORTER, KEITH,
ATKINS 1966; KIHARA, TSUNEWAKI 1964 and others). In our experiments with
controlled pollination of non-emasculated bagged florets in 1973, the percent
of seed set ranged from 8 to 28%. Evidently in this case seed set is determined
by florets with one pistil which occured approximately in the same proportion
(Table 1). As embryological studies indicate,
they had normally developed ovaries, ovules and embryo sacs. Our findings
show that pistillody clearly expressed in wheat hybrids having Ae. caudata
cytoplasm, disturbes the development of female generative sphere, sterilises
the ovaries of the main and additional pistils. This is one of the reasons
why seed set is low. Decreased fertility resulting from the disturbance of the female generative organs is the only case of the total number of CMS wheat lines studied and it reflects the specific nature of the interaction between Ae. caudata cytoplasm and wheat genomes used as a parental form for backcrossing. Literature Cited BRESLVAETS, L.P. 1936. studies of the development of the flower of changing its sex under the influence of photoperiodism (in Russian Bull. Mosk. obshchestva ispytatelei prirody. 45 (3). BRESLVAETS, L.P. 1938. X-ray-induced morphological changes in hemp. II. Microscopic studies (in Russian). Collected Papers in memory of V.P. Lyubimenko, Kiev, Ukr. SSR Acad. of Sciences Publish House. BRESLVAETS, L.P. 1946. The plant and X-rays (in Russisn). Moscow-Leningrad, USSR Acad. of Sciences Publish. House, 191 p. FUKASAWA, H. 1953. Studies on restoration and substitution of nucleus in Aegilotriticum. I. Appearance of male-sterile Triticum durum in substitution crosses. Cytologia. 18 : 167-175. KIHARA, H. 1951. Substitution of nucleus and its effects on genome manifestation. Cytologia. 16 : 177-193. KIHARA, H. and K. TSUNEWAKI 1964. Some fundamental problems underlying the program for hybrid wheat breeding. Zeiken Ziho. 1-14. KIHARA, H. 1967. Cytoplasmic male sterility and wheat breeding (in Rusian). Selskokhozyaistvennaya biologia. 2 : 214-225. LUBIMOVA, V.F. 1951. On polygynous florets in wheat-grass hybrids (Russian). Bull. glavnogo bot. sada. 9 : 16-24. LUBIMOVA, V.F. 1968. Male sterility and formation of polygynous florish in M2 perennial wheat (in Russian). Bull. glavnogo bot. sada. 70: 25-34. LVOVA, I.N. 1963. Sex in plants (in Russian). Moscow University Publ. House. 56 p. MININA, E.G. 1952. The shift of sex in plants as affected by environ mental factors. (in Russian). Moscow, USSR Acad. of Sciences Pulish. House. 199 p. PORTER, K., A. KEITH and I. ATKINS 1965. Cross-pollination of male-sterile winter wheat (Triticum aestivum L.) having Aegilops caudata and Aegilops ovata L cytoplasm. Crop. Science. 5 (2) : 161-163. TUTAYUK, V. Kh. 1969. Teratology (in Russian). Baku. 112 p. ZHUKOVSKY, P.M. 1967. Heterosis as an evolutionary phenomenon in plant world and the problem of its utilization in agriculture (in Russian). Vestnik selskokhoz.nauk. 3 : 8-11. |
| <-- Back |