Wheat Information Service 41-42 p. 17 (1976)
Morphology and cytology of teratological floral organs of wheat hybrids having Aegilops caudata cytoplasm
M. I. RYABININA and O. G. SEMENOV
Laboratory of Experimental Biology, Dokuchaev Soil Institute Moscow, USSR

Cytoplasmic male sterility (CMS), as a phenomenon responsible for sterility of male reproductive organs of the flower has developed in the course of plant evolution (ZHUKOVSKY 1964). CMS in wheat was first produced experimentally by the Japanese scientists H. KIHARA (1951) and H. FUKASAWA (1953). By translocating the wheat nucleus to alien cytoplasm, they obtained plants which, although manifesting sterility, retained female fertility. This made it possible to pose the problem of utilizing heterosis in wheat breeding.

Since 1962 experiments have been made at the Laboratory of Experimental Biology of Agricultural Plants on the transfer of wheat genomes to different cytoplasms. Both male sterility and the specific effect of alien cytoplasm were found in the CMS wheat hybrids. Thus, plants having Triticum timopheevi cytoplasm possess good viability and a normal growing period. Aegilops ovata cytoplasm causes a longer vegetative period and a vigorous growth of vegetative material. Hybrids having Aegilops caudata cytoplasm are characterized by reduced female fertility. The findings of some researchers (KIHARA and TSUNEWAKI 1964, KIHARA 1967, PORTER, KEITH and ATKINS 1965) and our observations show that the development of the female organs in these hybrids is disturbed as a result of the transformation of stamens into pistils and pistillody is manifested.

Analysis of published data on the transformation of male sex into female demonstrates that it can be caused by a number of reasons, such as unfavourable ecological factors (TUTAYUK 1969) or produced experimentally (BRESLAVETS 1936, 1938, 1946, MININA 1952, LVOVA 1963) as well as during hybridization (LUBIMOVA 1951, 1968).

As mentioned above, we have come across genetically-based transformation of stamens into pistils in our studies of a CMS hybrid having Aegilops caudata cytoplasm and Triticum aestivum nucleus (var. erythrospermum, the 16th backcross). The hybrid seeds were received from Professor H. KIHARA by Academician I.E. GLUSHCHENKO who kindly offered them for our work.

During 1970-1972 this hybrid having Ae. caudata cytoplasm was crossed with spring wheat varieties including Saratovskaya 29, Moskovka, Krasnozernaya and others. It is interesting to note that under new growing conditions in Moscow crosses between this hybrid and T. aestivum varieties retained the CMS trait and also showed pistillody. This phenomenon was observed in a large number of florets. Analysis of florets in spikes of hybrid plants is given in Table 1.

Table 1. Morphology of florets in CMS wheat hybrid having
Ae. caudata (B18 S. caudata x Moskovka)

Total
number of
spikes
studies
Total
number of
florets
studied
Including
Florets
with 1 pistil
and 3 stamens
Florets
with 2 pistils
and 2 stamens
Florets
with 3 pistils
and 1 stamens
Florets
with 4 pistils
without stamens
Number
% of
total
Number
% of
total
Number
% of
total
Number
% of
total
10
200
31
14.5
60
29.5
70
30.4
42
21.6

The Table shows that 85.5% of florets were pistilloid, i.e. had 2, 3 or 4 pistils and fewer stamens, and only 14.5% had normally a single pistil and 3 stamens with sterile pollen grains in the anthers. It should be noted that degeneration of pollen grains in the anthers of pistilloid florets not affected by the transformation proceeds similarly to that in CMS hybrids. Analysis of florets along the spike shows that basal florets have generally four pistils while apical florets-one or two.