The inheritance of some important agronomic traits (the node of the first peduncle, nodes on main stem, average internode length, pod clusters on main stem and pod clusters on branches) has been studied through a half diallel cross of six diverse mungbean genotypes. Additive and dominant gene actions were responsible for the inheritance of node of the first peduncle, pod clusters on main stem and pod clusters on branches, whereas only additive gene effects were responsible for nodes on main stem and average internode length. However, the additive gene effects were predominant for all these traits. For the lower node of the pod peduncle, the cultivar, NM 92 and combination, NM 92×VC 3902A were the best general and specific combiners, respectively. The combination NM 92×6601 may be used directly to select lodging-resistant mungbean genotypes. High narrow-sense heritability estimates for node of the first peduncle and average internodal length indicated the possibility of developing mungbean genotypes with pod peduncles starting from lower nodes and resistant to lodging.
To determine the diversity within hop, Humulus lupulus, species at the molecular level, the entire intergenic spacer (IGS) of 18S-26S rDNA in hop was sequenced, and phylogenetic analyses were performed using the partial external transcribed spacer (ETS). In the IGS of the European cultivars, North American wild hops and Japanese wild hops, three types of subrepeats were identified and designated as A-, B- and C-type subrepeats, respectively. Their repetition and position were found to determine the IGS length and structural differences among them. Phylogenetic analysis using partial ETS with the related species, H. japonicus, as outgroup led to the following implications. The North American wild hops with a high alpha-acid content and disease resistance, which contribute to hop breeding, are genetically different from European cultivars, and genetic variation within North American wild hops was observed. Japanese wild hops, which have never been used for new cultivar development in the world, could be distinguished from both European and North American hops, suggesting that Japanese wild hops could be used as a new gene source for breeding.
A Chinese six-rowed barley landrace, Mokusekko 3, exhibits a wide resistance spectrum to all the barley yellow mosaic virus strains in Japan (BaYMV-I, -II, -III) and in Europe (BaYMV-1, -2) as well as to barley mild mosaic virus (BaMMV). To identify the genetic basis for the resistance to BaYMV, a cross between a Japanese malting barley cultivar Ko A (susceptible) and Mokusekko 3 was made to generate F2 and F3 populations. The reaction of the F2-derived F3 lines to BaYMV was investigated in a field infected with BaYMV (-I or both -I and -II) during two growing seasons, 1996 and 1997. BaYMV disease severity of the F2 individuals was quantitatively expressed as the percentage of the susceptible seedlings within the F3 line. For the linkage analysis along the whole chromosome, a map of the barley genome consisting of 100 markers was used. The map covers 1291cM with an average density of 14cM. The interval mapping method was used to identify the quantitative trait loci (QTLs) for resistance to BaYMV. A new QTL for resistance to the BaYMV was located in the terminal region of chromosome 7HS, explaining 20-25% of the phenotypic variance, in addition to those in the terminal region of chromosome 3HL and centromeric region of chromosome 4H. The three QTLs accounted for 55-57% of the total phenotypic variance. The location of the QTLs on chromosomes 4H and 3HL corresponded well to that of rym1 and rym5 which were previously mapped for resistance to BaYMV in Mokusekko 3 using morphological and isozyme markers. Based on these results, the effect of pyramiding of these resistance factors into modern barley cultivars by marker-assisted selection is was examined.
Molecular linkage maps of disease-related genes in the Japanese pear cultivars ‘Kinchaku’ and ‘Kosui’ with RAPD markers were constructed. Using the pseudotestcross method, two separate maps were constructed from the segregation data of 82 F1 individuals. The linkage map for ‘Kinchaku’ consisted of 120 loci in 18 linkage groups spanning 768cM, while that for ‘Kosui’ contained 78 loci in 22 linkage groups extending over 508cM. The resistance allele of pear scab and the susceptibility allele of black spot were mapped in different linkage groups in ‘Kinchaku’. Compared with the reports on apple genome mapping, we estimated that these maps covered at least about a half of the total pear genome.
Genetic and nucleotide sequence studies were performed on a new variant of soybean Kunitz trypsin inhibitor (SKTI) detected in wild soybean (Glycine soja) and showing a slightly slower electrophoretic mobility than the Tia type. The segregation analysis of SKTI bands in F2 seeds from crosses of the new variant type with Tia or Tib type showed that the variant type is controlled by an allele codominant to Tia and Tib at an SKTI locus. Nucleotide sequence analysis showed that this variant has 217 amino acids composed of 181 amino acid residues of mature SKTI and extra 25 and 11 amino acids at N- and C-terminal regions, respectively. This sequence was identical to that of Tia (=KTi3), except that a G→A transitional mutation occurred at position 500 of Tia, which results in the translational change from Arg to Lys. The result of isoelectric forcusing-PAGE coincided with this change. In addition, three nucleotides GCT were inserted at the N-terminus, which leads to an Ala addition in the precursor of this SKTI protein. From these results, we propose the genetic symbol Tie for the new variant of SKTI.
To identify the chromosomal regions controlling cool-temperature tolerance (CT) at booting stage of rice (Oryza sativa L.), we performed quantitative trait locus (QTL) analysis with doubled-haploid lines (DHLs). We constructed a linkage map with 135 restriction fragment length polymorphism (RFLP) markers and 34 random amplified polymorphic DNA (RAPD) markers using 212 DHLs derived from crosses between two cultivars, Akihikari (moderately cool-temperature susceptible) and Koshihikari (cool-temperature tolerant). Both parental cultivars belong to the temperate japonica group. The degree of tolerance of each DHL was measured as the degree of sterility in the field with a running cold-water system. Three QTLs were mapped one each to chromosomes 1, 7, and 11. The QTL with the largest effect, qCT-7, was mapped to chromosome 7 and explained 22.1% of the total phenotypic variation. The other two QTLs, qCT-1 and qCT-11, explained approximately 5% each. For all of the QTLs, alleles from Koshihikari increased the degree of CT. We also mapped QTLs for heading date and culm length, which are thought to affect CT.
A wild barley, Hordeum vulgare L. ssp. spontaneum (C. Koch.) Thell. (syn. H. spontaneum C. Koch.) is considered to be the progenitor of cultivated barley (H. vulgare L. ssp. vulgare). A complete set of Triticum aestivum L. cv. ‘Shinchunaga’-H. spontaneum OUH602 whole chromosome addition lines, and 5 telosomic addition lines were developed. Chromosome constitutions of the addition lines were confirmed by C-banding and genomic in situ hybridization. Addition lines for the entire 1H chromosome and its long arm are only available as monosomic and monotelosomic additions, respectively, because of sterility. All other lines were recovered as disomic or ditelosomic additions. Self-sterile monosomic 1H and monotelosomic 1HL addition lines can be reproduced by backcrossing the plants having simultaneous addition of the long arm of barley chromosome 6H, because the plants with such chromosome constitutions recover partial female fertility. In general, the phenotypic alternations observed in each of the wheat-H. spontaneum OUH602 addition lines were similar to those previously noted in the corresponding lines of the ‘Chinese Spring’ wheat-‘Betzes’ barley addition series and the primary trisomic series of the H. spontaneum accession OUH602. Monotelosomic 1HL addition and ditelosomic 1HS addition are especialy valuable for unequivocal chromosome arm localization of barley genes and markers clustered around the centromeric region of 1H. The utility of the wheat-H. spontaneum addition lines is discussed.