Plant Breeding Institute, Faculty of Agriculture, Hokkaido University, Sapporo, 060 Japan
In our previous work (Kinoshita and Shinbashi 1982), the effects of 21 dwarfing genes were examined laying emphasis on morphological characters such as culm, leaf, panicle, grain and seedling characters. In this report, 22 characters including grain quality and chemical composition are examined in 19 dwarf isogenic (ID) lines of Shiokari each with a single gene and the original strain grown in greenhouse and field conditions. The 19 dwarfing genes examined are d-1, d-2, d-6, d-7, d-10, d-11, d-12, d-13, d-14, d-17(t), d-18k , d-19(t), d-27, d-30, d-35, d-42(t), sd-l(d-47), d-51 and d-52 (RGN 8: p. 7-9, 20).
Characters examined as follows;
General: Culm length, panicle number, heading date, spikelet length, spikelet width, 1000 kernel weight, and spikelet length/width.
Quality: Percentages of split hull, brown, milled and broken rice, chalky endosperm, cracked, notched, green, damaged, rusty and opaque kernels.
Composition: Amylose content, protein content, gel consistency and alkali digestion value.
An interaction between environment and dwarfness was recognized in these characters except for the proportion of rusty and opaque kernels. Correlation coefficient between amylose content and heading date was rather low in the greenhouse, but was significantly negative in the paddy field. Exceptionally, ID-11 showed a low amylose content and late heading under both conditions. There was a tendency for protein content to be high in early maturing lines.
The principal component analysis of the data for 19 characters gave an about 75% cumulative contribution by the first three (greenhouse) or four (field) factors. In the greenhouse, the first component comprised size traits, milling percentage and percent green rice, and the second component had large loadings on panicle number and grain width. In the field condition, the first component comprised grain size, rate of notched kernel and amylose content, and the second component had negative loadings on panicle number, heading date and percent
Fig. 1. Scatter diagrams obtained from principal component analysis for 19
dwarf isogenic lines. The horizontal and vertical axes show the first and the
second principal components, respectively. S means 'Shiokari' and the number
means the dwarf gene number involved in ID-lines.
cracked kernel. The pleiotropic effects of dwarfing genes, if represented by principal component analysis, seem to be influenced by environmental conditions.
In the scatter diagrams given by the first and second components, the dwarfing genes were classified into four groups according to their pleiotropic effects on rice grain quality and composition, i.e. group A (including Shlokarl) with relatively small pleiotropic effects; group B with broad grain and higher rates of notched kernel; group C (ID-1 and ID-11) with small grain, low amylose and high protein contents, higher rates of green and notched kernels; and group D (ID-10, ID-14, ID-17, ID-27) with large panicle number, and narrow grain (Fig. 1). ID-lines belonging to group A and B differed when grown in greenhouse and field. In the greenhouse, ID-35 and ID-51 were close to Shiokari, but ID-12, ID-35, and ID-47 were close to Shiokari in the paddy field.
The pleiotropic effects of so-called semidwarfing genes such as d-12 (Yukara dwarf), d-35(t) (Tanginbouzu dwarf) and sd-1 (dee-geo-woo-gen dwarf) were nearly the same as those of normal genotype represented by Shiokari.
References
Kinoshita, T. and N. Shinbashi, 1982. Identification of dwarf genes and their character expression in the isogenic background. Japan. J. Breed. 32: 219-231.
Mural, M. and T. Kinoshita, 1983. Pleiotropic effects of dwarf gene for panicle and grain characters. -Genetical studies on rice plant LXXXVI-. Res. Bull. Univ. Farm, Hokkaido Univ. 23: 1- 10.