A new rice (Oryza sativa L.) linkage map of DNA markers was developed using 119 restriction fragment length polymorphism (RFLP) markers in 202 F2 progeny derived from a cross between a Korean variety, Milyang 23, and a Japanese variety, Akihikari which belonged to cv.gr.Indica and cv.gr.Japonica, respectively. The F2 linkage map covered a total distance of 1335 cM on the 12 rice chromosomes. Non-polymorphic markers were recognized continuously on the distal region of the short arm of chromosome 5 at a length of 30 cM, which was not covered by RFLP analysis. The orientation, chromosome number of these 12 linkage groups and positions of centromere were determined and assigned to their respective chromosomes, as described by Harushima et at.(1998). In the F2 population, segregation distortions were detected in a total of 16 chromosome regions except for chromosomes 1 and 4. Among them, ten and four chromosome regions showed an increased number of progeny with genotypes of Indica and Japonica homozygotic alleles, respectively. Two other regions showed an increase in Indica/Japonica heterozygotes. Skew in favor of Indica alleles was recognized on chromosomes 2 and 3 (two regions); 5, 6, 9 and 11 (two regions); and 12 (two regions), and that of Japonica on chromosomes 7, 8 and 10 (two regions). An increase of heterozygote was detected on chromosomes 2 and 9. Such segregation distortions may be due to reproductive barriers, i.e., hybrid sterility, gametophyte genes and hybrid weakness. Such information on segregation distortions is valuable for in wide hybridization breeding between Indica and Japonica varieties. The F2 population, RFLP segregation data and the linkage map including the information of distortion should be useful for genetic analysis of agricultural traits related to the yield component and for planning breeding programs considering the segregation distortions. This study will be a starting point for the QTL analysis for agronomic traits and molecular breeding for high yield using DNA markers.
A set of 6×6 diallel crosses was made using the inbred lines from the Miyashige group of Japanese radish varieties. The root shape contours were delineated by elliptic Fourier descriptors, and information contained in the coefficients of the descriptors was summarized as the score of principal component analysis. The coefficients related to symmetrical (group A) and asymmetrical variations (group B) were handled separately. It was shown that the 1st and 2nd components of group A were associated with the aspect ratio and bluntness of the distal part of the root, respectively. The 1st component of group B was related to the degree of curvature of the root. The 1st and 2nd components of group A showed high broad and narrow sense heritabilities, and incomplete dominance. The 1st component of group B was also heritable, and showed incomplete dominance. Correlation between the proportion of dominant alleles of the parents (Vr+Wr) and the parental values showed that most alleles of the genes related either to thin shape or to straight shape were dominant. The size of the roots as expressed by their projection area was analyzed in a similar fashion. The size showed a high broad sense heritability but a low narrow sense heritability, and overdominance. The alleles producing larger root sizes were mostly dominant. Thus, symmetrical and asymmetrical variations and, also, shape and size showed different modes of inheritance.
Flavonoid compounds accumulating in the epidermal cell layers of plant tissues are considered to be among the most effective protectants against the ultraviolet-B (UV-B) radiation. To identify a transcription factor involved in the activation of the genes, such as chalcone synthase genes (CHS), in the pathway of flavonoid biosynthesis, a pair of degenerate primers was designed to amplify the most conservative region of MYB from soybean by polymerase chain reaction (PCR) or reverse transcriptase (RT)-PCR. Both of these amplification products were found to contain molecules of dozens of independent MYB-like sequences. The bacterial clones harboring a partial library of the RT-PCR products were differentially hybridized with the amplified cDNA fragments derived from total RNA of UV-B treat seedling (rMYB/UV-B+) and those from control RNA (rMYB/UV-B-). One clone designated as MYB29 showed a significantly stronger signal with rMYB/UV-B+ hybridization than with rMYB/UV-B-. Starting from the sequence information of MYB29 fragment, an entire sequence containing the complete gene designated as GmMYB29A1 was obtained by nested PCR of the flanking regions. In the course of this PCR cloning, we identified several independent products closely related to GmMYB29A1. In order to amplify the entire protein coding region of the closely related genes, two sets of primers were designed, two upstream primers containing the ATG start codon and the other two downstream primers containing the TGA stop codon. By sequencing those cDNAs amplified with RTPCR, a total of at least four members were found to comprise the subfamily, designated as GmMYB29. UV-B- responsive expression of the members of GmMYB29 was found to reach its peak within 2 hours after the onset of light exposure while in those of soybean (Gm)CHS it continued to rise for 6 hours. This finding suggested that these MYB transcription factors may activate genes for flavonoid biosynthesis including GmCHS in response to UV-B exposure.
Allohexaplods were bred from crosses involving Brassica carinata and two species of Sinapis;S.arvensis and S.turgida followed by colchicine treatment in order to study the interaction of the genome of the two genera in the expression of allyl-glucosinolate and p-hydrooxybenzyl-glucosinolate under combined conditions (B and S genomes). The allohexaploids of B.carinata×S.arvensis (CaSar-strains) and B.carinata×S.turgida (C-and T-strains) were studied for their stabilization process of seed fertility and fatty acid composition as internal components during F2-F4 generations. Plants with a high seed fertility were selected in all the generations and were advanced through self-and sib-cross-pollination. In the F2 generation, the seed fertility increased in all the strains through self-and sib-cross-pollination, while in F3 generation, seed fertility decreased due to diseases. In the F4 generation, the seed fertility increased again in all the strains through self-pollination. Fatty acid composition of B.carinata, S.arvensis, S.turgida and their allohexaploids (F2-F4 generations) was analyzed by gas chromatography. B.carinata, S.arvensis, S.turgida and all the strains in the F2-F4 generations contained all of the six fatty acid components; palmitic, oleic, linoleic, linolenic, eicosenoic and erucic acid. A significantly higher amount of linoleic acid and a lower amount of linolenic acid were found for all the allohexaploids in all the generations. The variation among the strains for oleic acid and linolenic acid was high. However, variation in the erucic acid composition decreased with the advance of generations in the T-strains. The parents S.arvensis, S.turgida and all the strains in the all generations showed a high variability in both biosynthetic pathways. It only the T-strains were stable in both fatty acid biosynthetic pathways in the F4 generation. However, since the variation in fertility traits and fatty acid composition remained large, considerable improvement may occur in later generations.
To examine the effects of protein subunit compositions on tofu gel formation, we prepared soymilk from a low-β-conglycinin soybean line lacking two β-conglycinin subunits and from a low-glycinin soybean line lacking three glycinin subunit groups, the proportion of glycinin to β-conglycinin (11S/7S ratio) of which was 3.76 and 0.12, respectively. The two kinds of soymilk were mixed to give various 11S/7S ratio, and heated at 80°C with 0.4% glucono-δ-lactone (GDL) in a water bath to make tofu gel or in a cell for measuring dynamic viscoelasticity. The breaking stress of the GDL-induced tofu gel made from the low-β-conglycinin soymilk was nearly four times higher than that made from the low-glycinin soymilk. The tofu breaking stress and the soymilk storage modulus both increased with increase of 11S/7S ratio. The storage modulus correlated well with the tofu gel breaking stress (r=0.932**). The decrease of glycinin content by lacking the subunit(s) resulted in decrease of 11S/7S ratio. The heated soymilk made from soybean seeds having different glycinin subunit compositions showed a close association between 11S/7S ratio and storage modulus (r=0.946**). Therefore, 11S/7S ratio is considered to have an important effect on the physical properties of tofu gel. The soymilk from low-β-conglycinin soybean and low-glycinin soybean showed a similar pH change after the addition of MgCl2. Soymilk from the low-β-conglycinin soybean coagulated immediately after addition of 0.3% MgCl2 was added. Soymilk from the low-glycinin soybean, in contrast, remained liquid even at 1°C. These results suggest that soymilk gelation properties can be improved by using soybeans with modified protein subunit compositions.
Flowering time is one of the most important traits in soybean breeding. To analyze the quantitative trait loci (QTLs) related to flowering time in soybean, we constructed a soybean linkage map using an F2 population derived from a cross between two varieties, Misuzudaizu and Moshidou Gong 503. This linkage map consists of 247 RFLP loci, including 92 markers designed in this study using soybean green leaf-derived cDNA clones together with 4 phenotypic loce, covering a total of 33 linkage groups. Based on the number of days from sowing to first flowering of each F2 plant, we identified three QTLs, FT1, FT2 and FT3, for flowering time. The Moshidou Gong 503 alleles of FT1 and FT3, and the Misuzudaizu FT2 allele reduced the flowering time. These QTLs were remarkably effective and accounted for approximately 88% of the total phenotypic variation in this population, based on the multiple-QTL model. The most effective QTL, FT1, accounted for approximately 70% of the total variation and appeared to correspond to the E1, the locus for flowering time and maturity of the classical genetic map.
An efficient plant regeneration procedure using embryo axis and shoot tip explants was developed in faba bean (Vicia faba L.). Embryo axes and shoot tips were cultured on MS medium (Murashige and Skoog 1962) supplemented with benzyladenine (BA) and thidiazuron (TDZ). Differential regeneration efficiency was observed due to factors including growth regulator combinations in the medium, explants, basal media and lines used. Explants cultured on medium with TDZ in combination with BA produced a higher number of shoots compared with either cytokinin alone. The embryo axes promoted the formation of more adventitious shoots than shoot tips. The frequency of multiple shoot formation varied among the lines tested. Line 740 cultured on MS medium containing TDZ in combination with BA (2.0 mgl-1 each) gave the highest number of shoots per explant (10.2 and 7.7) from both embryo axes and shoot tips, respectively. Explants cultured on MS or MSB (MS salts+B5 vitamins) produced the highest number of shoots. The efficiency of TDZ combined with BA for multiple shoot induction was not improved when 0.25-1.00 mgl-1 of naphthaleneacetic acid (NAA) was added. Regenerated shoots were rooted on half-strength MS basal medium lacking growth regulators or supplemented with either NAA, IBA or IAA (0.25-1.0 mgl-1) prior to transfer to greenhouse conditions. We developed a rapid, reliable, high-frequency method for producing multiple shoots from faba bean shoot tip and embryo axis explants.
Soybean seed protein consists of two major groups, 7S globulin (β-conglycinin) and 11S globulin (glycinin). A mutant line, cgdef mutant, lacking three major 7S globulin subunits, α, α' and β, was developed by γ-ray irradiation. The deficiency was controlled by a single recessive allele, cgdef. This mutation is associated with cgdef syndrome, morphological abnormality, sterility and lethality. The objective of this study is to perform detailed genetic analysis of the Cgdef locus using AFLP technique. We identified two AFLP markers that cosegregated with the Cgdef using 167 segregants obtained by selfing of a plant heterozygous for cgdef. After cloning and sequencing the two AFLP framents, they were converted to sequence-characterized amplified regions (SCARs). Linkage analysis of the two AFLP-SCAR markers in 103 F2 plants derived from a cross between Mo-shi-dou Gong 503 and the plant heterozygous for cgdef showed that these markers are tightly linked to Cgdef at a distance of 1.1±0.12 cM. Furthermore, in the F2 population, all phenotypes of the cgdef syndrome including leaf abnormality, sterility and lethality were recombined with cgdef. This indicates that the cgdef syndrome is derived not from pleiotropy of the cgdef locus but from close linkage with some other unidentified gene(s). The markers might be useful for positional cloning of Cgdef.
Analysis of quantitative trait loci (QTLs) associated with a resistance to fungal invasion within plant tissues (Type II resistance) in the case of Fusarium head blight (FHB) was conducted in doubled haploid lines (DHLs) developed form the cross Fukuho-komugi (moderately susceptible)/Oligo culm (very susceptible) using random amplified polymorphic DNA (RAPD) markers. Transgressive segregants of 26 lines with R, MR and M levels of resistance and seven lines with a VS level of resistance were detected in this population of 110 DHLs, using the parental values as standards. It is suggested that the unique configuration of resistance genes is causing the skewed distribution for Type II resistance in this cross. From the results of QTL analysis using 65 RAPD markers in the DHLs, four RAPD markers, OPZ-10680 OPAG-18340 OPAF-06345 and OPW-13435 associated with Type II resistance were identified. Three RAPD markers were linked with recombination values of 6.4 and 11.8%. These RAPD markers were individually selected by t-test. Hence, it is suggested that the specific regions of the tentatively designated linkage group c of the wheat genome are associated with Type II resistance to FHB. As a result, it may be possible to detect the latent susceptible modifier of Fukuho-komugi using three of them. Finally, the relationship between the characteristics of FHB caused by Fusarium graminearum and resistance mechanisms in wheat was analyzed based on the results of this study and data from the literature for the resistance to FHB. It is suggested that breeding strategies including pyramiding of resistance genes and introgression of additive minor genes in an adapted background may enable to make rapid progress in the breeding of FHB-resistant wheat varieties.