Hyoji Namai

Quantitative evaluation of common buckwheat (Fagopyrum esculentum Moench) kernel shape by elliptic Fourier descriptor

Kernel shape of 27 common buckwheat cultivars was evaluated quantitatively by image analysis using elliptic Fourier descriptors and their principal components. The relationships between the quantitative information on kernel shape and several agronomic characteristics were clarified. The closed contour of each kernel projection was extracted, and 80 elliptic Fourier coefficients were calculated for each contour. The Fourier coefficients were standardized so that they were invariant of the size, rotation, shift and chain-code starting point. Then, the principal components on the standardized Fourier coefficients were evaluated. The cumulative contribution at the fifth principal component was higher than 93%. It was found that the first, second, third and fifth principal components represented the aspect ratio of the kernel, the location of the kernel centroid, the sharpness of the two kernel tips and the roundness of the base in the kernel contour, respectively. Analysis of the variance indicated that genotypic differences in these principal components were significantly large. Because these variations of the principal components were continuous, the effect of polygenes on shape was suggested. The relationships between these principal components and agronomic traits, including flowering period, yield, 1000 seed weight and volume weight, were also investigated. It was clarified that the first principal component was closely correlated with agronomic traits such as flowerig period, 1000 seed weight and volume weight. In conclusion, it was clarified that principal component scores based on elliptic Fourier descriptors yield useful quantitative parameters for evaluating kernel shape for common buckwheat breeding.

RFLP mapping of the genes controlling hybrid breakdown in rice (Oryza sativa L.)

Abstract Complementary recessive genes hwd1 and hwd2 controlling hybrid breakdown (weakness of F2 and later generations) were mapped in rice using RFLP markers. These genes produce a plant that is shorter and has fewer tillers than normal plants when the two loci have only one or no dominant allele at both loci. A cultivar with two dominant alleles at the hwd1 locus and a cultivar with two dominant alleles at the hwd2 locus were crossed with a double recessive tester line. Linkage analysis was carried out for each gene independently in two F2 populations derived from these crosses. hwd1 was mapped on the distal region of rice genetic linkage map for chromosome 10, flanked by RFLP markers C701 and R2309 at a distance of 0.9 centiMorgans (cM) and 0.6 cM, respectively. hwd2 was mapped in the central region of rice genetic linkage map for chromosome 7, tightly linked with 4 RFLP markers without detectable recombination. The usefulness of RFLP mapping and map information for the genes controlling reproductive barriers are discussed in the context of breeding using diverse rice germplasm, especially gene introduction by marker-aided selection.

Cytogenetic and morphological characteristics of new types of diploids (2n= 22, 24, 40) derived from consecutive selfing of aneuploids in brassica crops

SummaryNew types of diploids in Brassica crops were synthesized after three consecutive selfing of aneuploids derived from backcrossing of sesquidiploids (2n=29, AAC) with B. campestris (2n=20, AA). The cytogenetic and morphological characteristics of plants with 2n=22, 24 and 40 in the S3 generation were analyzed in order to establish the extent in which these addition and polyploid lines were stabilized. A high frequency of 11II (79.7%), 12II (84.6%) and 20II (100%), were observed at metaphase I of pollen mother cells in 2n=22, 24 and 40 plants, respectively. The chromosome configuration at methaphase II also indicates that a certain level of stability has been attained cytogenetically. Although pollen stainability was relatively high, the seed set percentage was still low. Variation in morphological characteristics indicate the incorporation of one or more chromosome pairs from the C genome of B. oleracea. Other diagnostic characters such as the formation of determinate inflorescence, branching from the base of the stem, and the shift from self-incompatibility to self-compatibility must have resulted from the interaction between A and C genomes. Thus plants with 2n=22, 24 and 40 have been stabilized to some extent and can be developed into new breeding lines of Brassica. It is suggested that limited pollination could be effective in increasing the seed fertility of these plants.

Stabilization of new types of diploids (2n = 22, 24) through selfing of aneuploids (2n = 21, 22) derived from crossing of sesquidiploids (2n = 29, AAC) and Brassica campestris (2n = 20 AA)

SummaryAneuploids with 2n=21 and 2n=22 derived from crossing of sesquidiploids (2n=29, AAC) and Brassica campestris (2n=20, AA) were selfed successively in order to follow the changes in chromosome number of the progenies for three consecutive generations. Progenies with 2n=22, 23 and 24 obtained after selfing of S0 generation and the succeeding S1, S2 and S3 generations were analyzed in terms of pollen stainability, % seed set as well as cytogenetically based on meiotic behaviour with the aim of determining the possibility of addition of one or more alien chromosomes into n=10 species which may lead to differentiation of single or plural disomic addition lines. The generation of aneuploids with 2n=21 progressed in such a way that most plants seem to revert to the 2n=20 chromosome number of B. campestris after selfing. From 2n=22 aneuploids, however, the succeeding progenies showed high frequency of plants with two additional chromosomes which accounted for 50.6% and 52.9% of total S3 progenies via 2n=22 and 2n=24 S2 generations, respectively. The meiotic behaviour of these progenies indicated evidence for a rule governing the frequency distribution of chromosome number among these addition lines and high possibility to breed such disomic plants with 2n=22. A method of selecting stable aneuploids was suggested in addition to the possible role of pollination biology at various processes of such breeding program.

Evidence for Non-random Seed Setting of Ovules in the Pod of the Cruciferous Plants Brassica juncea and Raphanus sativus

Darwin (1876) had advocated that the process of sexual reproduction is the most important process in the life cycle of plants. Based on Darwin’s theory of evolution, Michurin revealed the positive effects of “mixed pollination” for making distant hybrids (from “I.V.Michurin Selected Works”, 1950). So far, several studies have been done on gametophytic selection and its efficacy for producing evolutionary change in plants (Mulcahy et al., 1975, Schlichting et al., 1987, Knox et al., 1990).