Based on the results of an analysis of yield traits in sugar beet F₁ hybrids, the beneficial effect of heterosis on the amount of root weight and sugar yield was recognized. The F₁ generation in which the common pollen parent “NK-210” was used in 15 combinations of half-diallel crosses between 5 kinds of male-sterile lines and each maintainer line, was analyzed to determine whether the effects on yield traits depended on the coefficient obtained for the relationship between parental lines (hereafter referred to as “coefficient of parentage”). Parental data were input from the breeding data in JAPAN in a total 1039 combinations. The breeding data base was constructed using Prolog (the inference type computer language) and calculated. The correlation between the coefficient of parentage and sugar yield was extremely high, namely R² = 0.92. When the coefficient of parentage increased, the sugar yield decreased. This relationship was nearly linear. The regression of sugar yield on the coefficient of parentage was y = −37.3x + 103, compared with the value in the standard variety “Monohomare”. The value of the coefficient of parentage increased by 0.1 and the sugar yield decreased by about 4% compared with the values obtained in “Monohomare”. When the value of the coefficient of parentage exceeded 0.1, the sugar yield did not exceed that of “Monohomare” in any of the lines in 15 combinations. Similarly, the relationship between the coefficient of parentage and the sugar yield in 250 three-way cross F₁s and 424 single-cross F₁s was investigated based on the yield test conducted from 1993 to 2004 in JAPAN. Among the hybrids with a sugar yield exceeding that of “Monohomare”, few showed coefficient of parentage above 0.1. In the majority of the hybrids with a high yield performance, the coefficient of parentage was below 0.1. Therefore, it is important to use the effect of heterosis efficiently by selecting the hybrid combinations in which the coefficient of parentage is lower than 0.1 for high yield performance in sugar beet.

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Diversity analyses were carried out for common wheat landraces of the Xinjiang-Uyghur Autonomous District (Xinjiang) in China, which is located close to the center of diversity of cultivated wheat. Firstly, microsatellite DNA polymorphisms were analyzed by PCR using 42 kinds of primer sets in 75 landraces, 3 improved cultivars from the Xinjiang, 61 wheat cultivars from foreign countries, including neighboring ones, at the Gene Bank of the National Institute of Agrobiological Sciences through 2003 and 2004. Based on a similarity matrix calculated from coincidence coefficients of electorophoretic zymograms, principal coordinate analyses were conducted to examine differentiations between Xinjiang landraces and foreign cultivars and among Xinjiang landraces. The results of principal coordinate analyses revealed that distinctive differentiation had appeared between Xinjiang landraces and foreign wheat cultivars and also between spring and winter type wheat among Xinjiang landraces. It is considered that Xinjiang wheat landraces were genetically differentiated from foreign cultivars and that they are more closely related to cultivars from such neighboring countries as Afghanistan, Pakistan, Turkey and Russia than to those from Japan and the other parts of China. The differentiation between the spring and the winter types of wheat among Xinjiang landraces was attributed to the founder effects of their ancestors. In order to elucidate phenotypic differentiation between the spring and the winter types of wheat, six traits of 71 Xinjiang landraces, i.e. days to heading, culm length, panicle length, number of grains per panicle, number of spikelets per panicle, and 1000-grain weight were investigated at the Institute of Crop Germplasm Resources of the Xinjiang Academy of Agriculture in 2003 and 2004. Principal component analysis was conducted based on a matrix of correlation coefficients. The analysis showed that there was distinct differentiation between the spring and the winter types of Xinjiang landraces. In conclusion, Xinjiang wheat landraces were differentiated from foreign cultivars in terms of DNA polymorphism. Among Xinjiang landraces, a distinctive differentiation was also observed between the spring and the winter types in terms of agronomic traits as well as SSR polymorphisms. These differentiations are considered to be caused not only by adaptation to diverse natural and wheat-growing conditions but also by the founder effect associated with genetic differences among ancestors of Xinjiang wheat landraces.

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Chromosome composition in interspecific somatic hybrids of Oryza species was investigated by genomic in situ hybridization (GISH). Four hybrids between Oryza sativa (AA) and γ-ray treated (0, 9.7, 19.4 and 48.6 Gy) O. punctata (BBCC) were obtained by protoplast fusion. Reduction in the chromosome number was observed in different hybrid plants treated with increasing doses of γ-rays. One of the results suggested a reduction in the number of A genomic chromosomes in one of the hybrids. When increasing doses of γ-rays were applied, the B and C genomic chromosomes were hardly distinguishable, presumably due to the formation of novel chromosome composition derived from the B and C genomes of O. punctata. We suggest that the novel chromosome chimeras were generated by γ-ray-induced chromosomal breaks, followed by rearrangements during the repair process, leading to the fusion of the genomic segments in O. punctata.

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