Comparison of heterosis effects of different cytoplasm types in rice.
1989
Ji Rongqian
Cytoplasm affects agronomic characters in many crops. This study attempts to draw inferences from the effects of cytoplasm on rice progeny. Several A lines developed by nucleus substitution, with identical nuclei but different cytoplasm, were hybridized with some R lines. The F populations were then planted to observe the phenotypic differences in agronomic characters and physiobiochemical properties. Cytoplasmic effects were manifested in various ways such as the number of green leaves at harvest, 1,000- grain weight, days to heading, net photosynthetic rate, and peroxidase zymograms. This indicates the potential for broad cytoplasmic effects on the phenotypes of many characters. Nucleus-cytoplasm interactions were exhibited in panicle length, filled spikelet percentage, and exudation pressure, among others. These results proved that the materials used belong to the nucleus-cytoplasm interaction type. Hence, rice heterosis should result from better combinations between the nuclei of R, B, and A lines. Divergences of different cytoplasm affect heterosis. The R line is likely to affect cytoplasm somewhat; the B line likely affects its direction of expression. To obtain high heterosis, it must consider renewing R lines and improving B lines. On the other hand, exploiting new sources of sterile cytoplasm may be important in hybrid rice breeding.
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