The Japanese Journal of Genetics

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Respiratory and photosynthetic rates of seven cytoplasm substitution lines of a common wheat were investigated. The cytoplasm substitution lines used were (umbellulata)-, (squarrosa)-, (speltoides)-, (dicoccoides)-, (cylindrica)-, (biuncialis)-, and (ovata)-CS. The investigation was conducted in four replications with each of the outdoor-and greenhouse-grown plants. In each replication, the first completely developed leaves of fifty seedlings were used for measuring respiratory and photosynthetic rates with an infra-red gas analyser. The first two leaves of other seedlings were used for an estimation of chlorophyll content. The results obtained are summarized as follows:
(1) The umbellulata and biuncialis cytoplasms depressed the leaf development; thus both respiratory and photosynthetic rates per leaf became lower, though the efficiency in respiration and photosynthesis was higher. They also caused retardation in attaining maximum photosynthetic rate.
(2) The squarrosa, speltoides, dicoccoides and cylindrica cytoplasms caused vigorous development of the first leaf. No other consistent effect was detected with them.
(3) The ovata cytoplasm depressed the first leaf development, and caused the retardation in attaining maximum photosynthetic rate in plants grown outdoors. No effect on both respiratory and photosynthetic rates was observed.
The results clearly showed that there is cytoplasmic control of respiration and photosynthesis. The present results also agreed with the classification of plasma types by Tsunewaki et al. (1976a). The phylogenetic significance of this grouping was discussed.

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The partial pollen sterility of true-breeding lines derived from a varietal hybrid of rice (Oryza sativa L.) was attributable to duplicate genes causing sporophytic sterility in certain homozygous combinations, in the same manner as set forth by Oka and Doida (1962) for seed sterility. The sporophytic pollen sterility was characterized by an instability of pollen development resulting in a large variance of pollen fertility among spikelets of the same plant. To examine the distributions of gametophytic and sporophytic sterilities in varietal hybrids, the F₁ and F₂ plants from crosses of 38 rice strains with 3 test-strains (an Indica, a Japonica, and an Asian annual strain of O. perennis) were observed for pollen fertility. The cytoplasmic male sterility did not seem to be involved in the material. The magnitude of sporophytic F₂ sterility was estimated by subtracting from the mean F₂ sterility the amount of gametophytic F₁ sterility possibly transmitted to the F₂ population. Both the gametophytic and sporophytic sterilities of hybrids were involved in the Indica-Japonica differentiation of rice varieties, but they were not correlated among individual crosses. The crosses with the test-strain of O. perennis showed little sterility in both the F₁ and F₂ generations. This suggests that the wild progenitor-the Asian form of O. perennis would have dominant genes at many of duplicated loci and recessive mutations accumulated with domestication might have resulted in the differentiation of varietal groups like the Indica and Japonica types.

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