In an attempt to stabilize the pollen fertility of indicajaponica hybrids of rice by the incorporation of segregation-distortion-neutral alleles, a locus causing distorted segregation of male gamete in indica-japonica hybrids was identified with an isozyme marker gene Pgi1 on chromosome 3. In seven F2 populations of indica-japonica crosses and 25 F3 lines from IR 36/Kamairazu, the japonica-type allele Pgi1-2 was transmitted via male gamete with a ratio of 0.29 to 0.38 instead of the normal one of 0.5 due to the presence of a gametophyte gene ga14. The recombination value between the locus ga14 and the marker gene Pgi1 was estimated to be 0.29 by using 57 F3 lines of IR 36/Kamairazu. The male gamete transmission rate(k) of ga14-j was estimated to be 0.13∼0.22 against the ga14-i instead of the normal one of 0.5 based on the data from the F2 and F3 lines. The locus ga14 which reduced the frequency of male gametes harboring ga14-j in some indica-japonica hybrids was located in the order of Pgi1∼ga14∼bc1 on chromosome 3.
Most of the barley RFLP linkage maps have been constructed using doubled haploid(DH) lines as mapping materials and little information is available on barley RFLP linkage map using an F2 population. In the present study, we constructed an RFLP linkage map using 120 F2 plants derived from a cross between a Japanese two-rowed malting barley cultivar Ko A and a Chinese six-rowed barley landrace Mokusekko 3. A total of 222 loci were mapped using 177 RFLP probes, one isozyme marker and one morphological marker. The total map length was 1, 389 cM and the average marker-to-marker distance was 6.5cM. We compared the Ko A × Mokusekko 3 map with the Steptoe × Morex map, one of the most representative barley RFLP linkage maps, which is based on Hordeum bulbosum(Hb)-derived DH lines that represent a recombination in female gametes. The linear orders of 60 common RFLP markers were identical and no major chromosomal rearrangements were observed between both RFLP linkage maps. A significant difference in recombination frequency was detected at six intervals flanked by the adjacent common RFLP markers. A reduced map length was detected at four intervals in the F2 map and at two intervals in the Hb-derived DH map. Three out of the six intervals were located around the centromeric regions of chromosomes 5H and 6H. On the other hand, the ratio of total length between the F2 map and Hb-derived DH map within common markers was 0.98. Remarkable similarities were present at the whole-genome level between both RFLP linkage maps. The implication of these findings for the analysis of recombination frequency was also discussed.
From one BC1F1-44-15 plant(Takashina et al. 1998), which has a high capacity to regenerate shoots from root explants of L.chilense PI128644 and is self-compatible, we obtained the BC1F2 plants. They were analyzed for their capacity to regenerate adventitious shoots from root explants in vitro. The BC1F2 plants showed a bimodal distribution with two groups based on their shoot regeneration rates. Plants with a high shoot regeneration capacity and low shoot regeneration capacity segregated at a 3/1 ratio. This suggests that the shoot regeneration capacity derived from L.chilense PI128644 is controlled by a major dominant gene, which was designated as Rg-2. About 60 random amplified polymorphic DNA (RAPD) bands specific to the wild species used as a parent were generated in the BC1F1-44-15 plant using 140 ranom primers. Ten of the 60 RAPD markers, were linked to the gene for high shoot regeneration capacity by a modified bulked segregant analysis using BC2F1 plants. The segregation of 12 markers(an RFLP marker TG102 mapped on chromosome 3, a marker of the acid invertase gene invchi and 10 RAPD markers) was examined by using a BC1F2 generation. A linkage map of the molecular markers was constructed around the gene Rg-2 for the high shoot regeneration capacity. The gene Rg-2 was located at 3.2 cM from a cluster including seven RAPD markers, as well as the gene invchi.
Random amplified polymorphic DNA(RAPD) techniques were employed to estimate the genetic diversity within 13 varieties of Chinese, 26 varieties of Japanese and 11 varieties of Korean, European and Canadian B.napus. A similarity matrix was calculated from 181 polymorphic bands that were amplified with 21 strictly selected PCR primers. Based on the matrix, a phenogram was drawn using the neighbor-joining method, and principal component analysis(PCA) was also carried out with the data of the polymorphic bands. These two analyses enabled to identify a correlation among the varieties and 43 out of 50 varieties were clustered into three major groups. Most of the Japanese and four out of the 13 Chinese cultivars were clustered into one of the three major groups whereas most of the Chinese varieties were not included in the three major groups. European spring and winter types were clustered into two different groups and some of the Asian varieties were included in the groups. Our results also indicate that most of the Chinese and Japanese B.napus varieties in this study showed a unique genetic background that separated them from European varieties.
Two genetic systems are involved in the control of the plant height in wheat : Rht genes which exert a major effect, and many other genes which usually exert only minor effects on plant height. The purpose of the present study was to identify RFLP markers linked with quantitative trait loci(QTLs) with minor effects on plant height. To remove the strong effect of Rht genes, a population of recombinant inbred lines(RILs) from a cross between hexaploid wheat, T.aestivum cv. Chinese Spring and T.spelta, was used, where neither parents harbor the Rht alleles. Seven RFLP markers on chromosomes 1A, 1D, 2B, 2D, and 4B were linked with plant height. In addition, QTLs associated with morphological characters related to plant height could be identified.
The matK DNA was sequenced in each of the 15 Japanese Rosa taxa, 17 other Asian taxa, and two American taxa to analyse their phylogenetic relationships. All the 14 tested taxa in the section Synstylae, associated with the section Indicae, formed one clade. It was confirmed that sections Synstylae and Indicae, with the common styles exserting from the hypanthium, are closely related to each other. Furthermore, R.brunonii and R.moschata in the section Synstylae formed an inner clade which is consistent with their common morphological traits. Two clones of R.acicularis formed one single clade which was separated from the remaining species of the section Rosa. This finding suggests that R.acicularis might be a distinctive species in the section Rosa. The remaining species of the section Rosa formed one clade which was further subdivided into two inner clades : R.rugosa and R.marreitii formed one clade, while R.acicularis var. nipponensis and R.willmottiae formed another clade. The distinctive relationship with R.acicularis implies that diploid R.acicularis var.nipponensis, traditionally treated as one variety of polyploid R.acicularis by some authors, is a primitive taxon and that it should be reassigned to its original specific rank as R.nipponensis.
Male sterility was induced in sugar beet plants by cooling treatment at the early bud stage. The percentage of male sterile flowers was higher the longer the cooling treatment and lower the temperature from 5°C to 3°C. Complete male sterility was induced by the treatment at 3°C for 50 days or 5°C for 70 days. Microscopic observations confirmed that the microspores and tapetum cells were more sensitive to cool temperature than somatic cells within a sugar beet anther. Female organs in the male sterile plants under cooling were not fatally injured and they could produce hybrid seeds by crossing with normal pollen. These results indicated that cooling treatment, which induced male sterility in sugar beet plants, was applicable as a method of castration in the breeding system.
The brown planthopper(BPH), Nilaparvata lugens Stal, is a serious pest of rice(Oryza sativa L.) in Asia. The rice ovicidal response to BPH is characterized by the formation of watery lesions which result in the death of the eggs. It is one of the factors affecting the suppression of the multiplication of BPH. To detect quantitative trait loci(QTLs) for this ovicidal response, a set of 71 rice recombinant inbred lines(F11) derived from a cross between a Japonica variety Asominori with ovicidal response and an Indica variety IR24 without ovicidal response were phenotyped for grade of watery lesions(GWL) and egg mortality(EM) of BPH. GWL and EM showed a significant positive correlation(P<0.001) and transgressive segregation was observed for EM. In composite interval mapping for GWL and EM with 293 RFLP marker loci, two QTLs each on the long arm of chromosome 1(1L) and the short arm of chromosome 6(6S) were detected for both GWL and EM. The 6S QTL explained 72.1% and 85.1% of the phenotypic variantions for GWL and EM, respectively. The QTL on 1L explained 19.8% and 17.8% of the phenotypic variations for GWL and EM, respectively. Both alleles from Asominori increased GWL and EM. The Asominori allele at the 6S QTL was essential for the ovicidal response to BPH and the Asominori allele at 1L QTL could increase the EM of BPH in the presence of the Asominori allele at the 6S QTL. It is concluded that two RFLP loci, R1954 linked to 6S QTL and C112 linked to 1L QTL can be used for marker-assisted selection.
Hybrid lethality is one of the expressions of cross-incompatibility, limiting the scope of wide hybridization. The immature embryos of the cross Nicotiana suaveolens × N.sylvestris did not grow and could not be rescued by conventional ovule culture. We observed that culture of the ovules at high temperatures(30, 32, 34°C) enabled to suppress this obstacle temporarily. Although many plantlets were obtained through ovule culture at high temperatures, the plants did not grow to maturity. On the other hand, ovule culture with a high concentration of cytokinin was effective in overcoming the obstacle. In ovule culture on 1/2 MS + BAP(10mg/l), many hybrid plantlets of the cross N.suaveolens × N.sylvestris developed and formed vigorous multiple shoots. The hybrid plants obtained from multiple shoots grew vigorously and matured in a greenhouse. Because the characteristics of the obstacle were similar to those of hybrid lethality exhibited by the seedlings of the cross between N.suaveolens and N.tabacum, we suggested that the obstacle was due to hybrid lethality that developed just after fertilization. Furthermore, we were able to obtain many mature hybrid plantlets in the cross N.suaveolens × N.sylvestris by ovule culture on a medium containing cytokinin. This is the first report on the production of mature interspecific hybrids that did not develop any lethal symptoms in this cross combination.
The effects of high molecular weight glutenin(HMWG) subunits on bread-making quality were investigated by using eight kinds of near-isogenic lines(NILs) and recurrent parent Harunoakebono. No significant difference was found in flour yield from milling and flour protein content among NILs. There was no significant difference in bread-making quality between HMWG subunits 1 and 2* at the Glu-A1 allele. A comparison of subunits 17 + 18 with subunits 7 + 8 and 7 + 9 at the GluB1 allele showed no significant difference in SDS-sedimentation volume and dough strength. However, the specific loaf volume of the former was higher than that of the latter. Subunit 20 revealed the weakest physical property of dough at the Glu-B1 allele and indicated that the physical property values of the dough were close to those of subunits 2 + 12, 4 + 12, and 2.2 + 12 at the Glu-D1 allele in spite of having subunits 5 + 10 at Glu-D1. However, subunits 20 showed a higher specific loaf volume than subunits 2 + 12, 4 + 12, and 2.2 + 12. HMWG subunits 2 + 12, 4 + 12, and 2.2 + 12, which are shared by most Japanese wheat cultivars, indicated much poorer bread-making quality than subunits 5 + 10. It is assumed that subunits 2.2 + 12 have the most negative effect on breadmaking quality among all HMWG subunits except for null alleles, although subunits 2.2 + 12 were not significantly different from subunits 2 + 12 or 4 + 12 on physical dough properties.