Drought resistance is a complex quantitative trait, involving interactions of many metabolic pathways related to stress-resistant genes. Identification of a standard evaluation assay has been the most pressing problem for selection of drought-resistant genotypes and ultimately for elucidating the internal genetic mechanisms. A field phenotypic investigation was performed on more than 20 morphological traits and grain yield and its components for 201 Chinese common inbred maize (Zea mays L.) lines under water deficit in seven environments. An integrated selection criterion for drought resistance was proposed and used to identify drought-resistant maize genotypes. In it, six traits including grain yield, ear number per plant, kernel number per ear, plant height, anthesis–silking interval and degree of leaf curling were chosen as the most relevant factors related to drought resistance, as determined by statistical analysis. The integrated selection criterion was highly correlated with grain yield under both well-watered and water-stressed regimes, and was also highly correlated with other commonly used selection criteria. Moreover, for 128 (63.7%) inbred lines the evaluation result with this criterion was consistent across more than three environments thus avoiding the effect of genotype–environment interaction, though stress level between the different environments largely fluctuated. There were 43 inbred lines evaluated for drought-resistance and most were bred during 1990–2000. The criterion will be useful to identify excellent drought-resistant genotypes in future maize molecular breeding programs.

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The history of chestnut utilization in Japan is very long. Many cultivars have been preserved without being sufficiently organized and studied with respect to genetic variation. We developed 12 new SSR (simple sequence repeat) markers from Japanese chestnut (Castanea crenata) by using SSR-enriched genomic libraries. All 12 primer pairs selected for SSR analysis successfully amplified fragments in 6 Castanea species. The genetic diversity and relationships among 216 chestnut accessions were assessed by SSR markers, including 142 Japanese chestnuts, 38 Chinese chestnuts (C. mollissima), 2 European chestnuts (C. sativa), 9 American chestnuts (C. dentata), and 23 Japanese–Chinese hybrids. Among the 216 accessions, we identified 21 synonym groups (including 1 bud sport group), and 189 different genotypes. The mean values of observed heterozygosity (H_O) and the expected heterozygosity (H_E) in the Japanese chestnuts were 0.65 and 0.65, respectively. A phenogram of the 189 genotypes revealed 3 major groups, corresponding to Japanese, Chinese and American chestnuts. Japanese–Chinese hybrid cultivars were mainly included in the Chinese chestnut group. In the present study, genetic backgrounds could be identified for native and cultivated Japanese chestnuts and Japanese–Chinese hybrid cultivars, and many synonyms showing identical SSR genotypes were found. Genetic and geographical relationships of unique characteristics such as “Shidareguri” (weeping) and “Togenashi” (spineless) were also discussed. These results will improve the efficiency of cultivar identification and of chestnut breeding programs.

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The WRKY transcription factors belong to a large protein family characterized by the conserved WRKY domain. These factors have been identified to play biological functions in various plant developmental processes. WRKY proteins are also known to be involved in regulating plant responses to pathogen attack and stress-related hormones. In this study, we report the isolation and characterization of the gene (TaWRKY45) for the wheat WRKY45 transcription factor. Amino acid sequence alignment and phylogenetic analyses demonstrated that the TaWRKY45 protein is orthologous to rice OsWRKY45. Our analysis of its expression in wheat indicated that TaWRKY45 was constitutively expressed in various organs and throughout the lifetime of the plant. We observed that TaWRKY45 was upregulated in response to benzothiadiazole (BTH), a plant immune system strengthner, and Fusarium graminearum, which is a causal fungus for Fusarium head blight (FHB). The constitutive overexpression of the TaWRKY45 transgene conferred an enhanced resistance against F. graminearum to transgenic wheat plants grown under greenhouse conditions. These results indicate that TaWRKY45 is involved in the defense systems for the biotic stressors in wheat and that it may be potentially utilized to improve the disease resistance of wheat.

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Aegilops tauschii Coss., the D-genome progenitor of hexaploid wheat, has a wide species range in central Eurasia. Large natural variation in Ae. tauschii offers potential for improving modern varieties of common wheat. Maturation time, an important agronomic trait for wheat breeding, is tied to flowering time and grain-filling period. Here, we established 82 wheat synthetic lines derived through endoreduplication, forming triploid gametes, in interspecific hybrids obtained by crossing a tetraploid wheat cultivar, Langdon, with 69 Ae. tauschii accessions. Empirical study of the hexaploid synthetics showed abundant variation in heading, flowering, and maturation time and the grain-filling period throughout the two growth seasons examined. The wide variation observed in heading time in Ae. tauschii was maintained in the hexaploid background of the synthetic wheat lines. Significantly positive correlations were observed among heading, flowering, and maturation time in the hexaploid synthetics. On the other hand, no significant correlations were found between grain-filling period and the other traits examined. Some comparisons between two selected synthetic wheat lines having similar flowering time stably exhibited differences in their grain-filling periods. These observations suggest that two major genetic pathways independently determine wheat maturation time; one controls heading and flowering time and the other regulates grain-filling period.

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Both the heading date (HD) and the number of grains per panicle (GPP), which frequently correlate with each other, are important agronomic traits for rice. In this study, two sets of recombinant inbred lines (RILs) derived from crosses between Minghui 63 and Teqing (PMT) and Zhenshan 97 and Teqing (PZT), respectively, were used to dissect the genetic bases of the correlation between HD and GPP. GPP quantitative trait loci (QTLs) identified by conventional QTL analysis could be classified into two types, either dependent on or independent of HD regardless of the effect caused by flowering time. Conditional analysis detected only GPP QTLs independent of HD when the HD effect on GPP was eliminated. With conventional QTL analysis, eight and five GPP QTLs were detected in PZT and PMT, respectively. However, three and five QTLs were detected by conditional analysis. Five of eight were dependent on HD (type I QTLs) in PZT, and all QTLs identified in PMT were independent of HD (type II QTLs). Photoperiod response of qGPP7b near-isogenic lines confirmed that qGPP7b effects on GPP were caused by HD. The characteristics of type I and II QTLs related to their application in rice breeding are discussed.

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To identify the genes responsible for varietal differences in bolting time in Brassica rapa, we constructed a linkage map of 220 simple sequence repeat (SSR) markers of B. rapa. To construct the map, we used F₂ progeny obtained from a cross between the late-bolting parental line Nou 6 gou (PL6) and the early-bolting parental line Nou 7 gou (A9709). The linkage map covered 875.6 cM and 10 major linkage groups. To investigate the nature of the vernalization response in the B. rapa parental lines, we examined bolting characteristics under two different conditions i.e., greenhouse and open field. Five quantitative trait loci (QTLs) that controlled bolting time were detected by experiments in greenhouse and open field. Interestingly, the QTLs identified in the greenhouse and field experiments did not map to the same loci. Three of five QTLs were colocalized with the orthologs of well-known flowering genes of Arabidopsis, including FLOWERING LOCUS C (FLC) and FLOWERING LOCUS T (FT). The QTLs detected in this study may provide useful information for the selection of bolting traits in Chinese cabbage breeding.

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Brassica rapa plants are highly important as vegetables, sources of oilseeds and fodder crop. Here, we developed 450 unigene derived microsatellite (UGMS) markers in B. rapa using unigenes downloaded from the National Center for Biotechnology Information database. Of the 450 UGMS primer pairs, 428 (95.1%) produced repeatable and reliable amplifications of expected size in at least one parental line of B. rapa, and 70 UGMS markers gave 72 polymorphic loci between the two contrasting parental lines. Cross-species transferability analysis of these 70 polymorphic UGMS markers in five other cultivated Brassica species showed varying transferability rates ranging from 82.9% in B. nigra to 97.1% in B. juncea and B. napus, and overall 53 UGMS markers amplified targets in all five species. The B. rapa linkage map was constructed using the 72 UGMS polymorphic loci and 154 previously developed SSRs. The newly developed UGMS markers and linkage map in this study would help in future studies to better understand the organization and evolution of Brassica genomes with respect to unigenes, in addition to mapping, tagging and cloning of economically important trait QTL/gene(s) and marker-assisted breeding in Brassica crops.

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We aimed to elucidate the molecular nature of the seed-shattering habit of weedy rice Oryza sativa L. in Okayama Prefecture, Japan, which seems to be an “off-type” of the main rice varieties in Okayama. We performed time-course analyses of breaking tensile strength (BTS) and analyzed the histological features of pedicels; we also genotyped the seed-shattering genes qSH1 and sh4 of weedy rice accessions and rice cultivars. The BTS of weedy accessions and cultivars began to decrease simultaneously at three weeks after heading. The weedy accessions showed complete loss of BTS and grain dispersal at five weeks after heading. In contrast, the cultivars maintained a certain degree of BTS and did not exhibit grain dispersal. Pedicel structures, which affect BTS, differed between the weedy accessions and the cultivars. The weedy accessions had complete and cracked abscission layers, while the cultivars had incomplete and uncracked abscission layers; however, the qSH1 and sh4 sequences that influence the formation of the abscission layer showed no differences between the weedy accessions and cultivars. We surmise that the shattering habit of weedy rice in Okayama is caused by formation and degeneration of the abscission layer, mediated by unidentified shattering-related gene(s).

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To identify the genes associated with the formation and development of the male strobilus of Cryptomeria japonica D. Don (Sugi), male strobilus-specific suppression subtractive hybridization (SSH) libraries were constructed from three different stages of male strobilus development. From these SSH libraries, 1,012 unigene sets including 314 contigs were assembled from 2,448 sequences. The profiles of the genes isolated from the SSH libraries differed strongly according to developmental stage: 49%, 13% and 29% of genes were unique to the early stage (stage E), tetrad stage (stage T), and mature stage (stage M) SSH libraries, respectively. To evaluate the reliability of the SSH libraries, we focused on the eight genes strongly concentrated in the three SSH libraries and performed RT-PCR analysis. All genes tested were expressed more strongly in the male strobilus than in the shoot. Our findings suggest that the gene profiles associated with male strobilus development differ in both number and kind of dominantly expressed genes.

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A QTL analysis was performed to determine the inheritance of flowering time in barley, using a set of recombinant inbred lines developed from a winter-type × spring-type cross. Two photoperiod responsive loci, Ppd-H1 and Ppd-H2, were detected on chromosome arms 2HS and 1HL respectively. Segregation for eam8 (mapping to the terminus of chromosome arm 1HL) and Eam5 (close to Sgh2 on chromosome arm 5HL) was also observed. These latter two genes functioned under 12 h to 24 h photoperiods. In addition, eps2S and eps7S, known to lie on chromosome arms 2HS and 7HS respectively, were detected. A new QTL for flowering time, qDHE.ak-1HS, was mapped 23 cM from the terminus of chromosome 1HS, and appears to be expressed under extremely short day lengths.

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Deficiencies of iron (Fe) and zinc (Zn) in afflict over three billion people worldwide, and deficiencies of these minerals in soil also limit crop production in one-third (Fe) and nearly half (Zn) of the world’s total cereal growing area. Screening genetic resources for improving wheat grain Fe and Zn contents and efficiency can contribute to both human health and crop production. We evaluated 47 wheat-Aegilops disomic addition lines derived from 6 Aegilops species to identify the chromosomes carrying genes for high grain Fe and Zn concentrations. Addition lines with chromosomes 1S^l and 2S^l of Ae. longissima, 1S^S and 2S^S of Ae. searsii, 2U and 6U of Ae. umbellulata, B of Ae. caudata, 4S^v of Ae. peregrina, and 5 M^g of Ae. geniculata showed increased grain Fe or Zn concentration of between 50% and 248% compared with the recipient cultivar, Chinese Spring. Most of alien chromosomes addition lines with significantly higher grain Fe and/or Zn concentrations belonged to the U and S genotypes and homoeologous groups 1 and 2 chromosomes. These lines could be used for the precise introgression of genes into elite wheat cultivars to improve wheat micronutrient concentrations.

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Quantitative trait loci (QTLs) for low cadmium concentration in brown rice were analyzed in 2008 and 2009 using 126 RIL (F₆ and F₇ plants) grown in a paddy field with high Cd concentration, which were derived from a cross between a high yielding Japanese rice cultivar ‘Fukuhibiki’ and an African upland rice cultivar ‘LAC23’ with the lowest cadmium concentration in rice grains. Totally two QTLs controlling low cadmium concentration in grains were identified in both 2008 and 2009, i.e., one on chromosome 3 (qLCdG3) and one on chromosome 11 (qLCdG11), which had opposite additive effects. In qLCdG11, ‘LAC23’ alleles had the effect of reducing cadmium concentration, but qLCdG3 had the opposite effect. The explained phenotypic variances of qLCdG11 were 9.4% in 2008 and 12.9% in 2009, and those of qLCdG3 were 13.9% in 2008 and 8.3% in 2009. Cadmium concentrations in brown rice showed positive correlations with grain length and grain weight. QTLs for grain length and grain weight were detected on chromosomes 3 and 11, but their positions differed from those for cadmium concentrations. These results suggest a possibility of successful marker-assisted selection of low cadmium trait derived from ‘LAC23’.

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Many rice mutants with altered storage protein composition, which relate to protein body II (PB-II), have been produced in order to obtain rice with new cooking properties or lowered protein digestibility, but the PB structures in the endosperm of such mutants remain obscure. We examined the polypeptide composition and ultrastructure of the endosperm during seed development using rice mutants with the low-glutelin-content gene (Lgc1) and/or 26 kDa globulin deficient gene (glb1). Lgc1 and glb1 have deletions of a region including glutelin structural genes and 26 kDa globulin gene, respectively. Mutants with Lgc1 accumulated prolamin polypeptides from an early stage of seed development, and numerous intact PB-I and a few, small, chipped PB-II were observed in the endosperm. The glb1 mutant showed deformed PB-II structures, which had similar electron density to wild-type PB-II. Both glutelins and globulins accumulate in PB-II, but the influence of the change in their composition on PB-II structure would be different. The unique PB-II structure in the glb1 mutant may bring about new processing properties for rice.

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A simple and rapid method for the extraction of crude glucosinolates from powder of freeze-dried radish roots was developed using a common solvent, methanol/water = 80: 20 (v/v) at room temperature. Hot methanol is not required for the extraction procedure of this new method. Both 4-methylthio-3-butenyl glucosinolate, which is a major glucosinolate in radish root, and total glucosinolates of Japanese radish cv. ‘Karami 199’ were quantified using HPLC. The amounts of glucosinolate extracted using this new method were 4–6% higher than those obtained using the conventional method with hot methanol. To compare the new method with the conventional method, the amounts of glucosinolate extracted from roots of eight cultivars in Japanese radish and five breeding lines were estimated. A high positive correlation was found between them. This simple and rapid method 1) obviates hot methanol for glucosinolate extraction and 2) requires only one-third of the extraction time of the conventional method, enabling glucosinolate extraction from about 150 samples by one person in a single day.

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Common wheat (Triticum aestivum) evolved through hybridization between cultivated tetraploid emmer wheat (T. turgidum), which has A and B genomes, and the wild diploid species, Aegilops tauschii, which has the D genome. Although the evolution of common wheat is generally understood, specific details remain unclear. For example, the phylogenetic relationships and origins of the six wheat subspecies (ssp. spelta, macha, vavilovi, aestivum, compactum, and sphaerococcum) have not yet been thoroughly resolved. To clarify the origin of ssp. sphaerococcum, we employed comparative sequence analysis of the D genome-specific sequence-tagged-site (STS) locus A1 in common wheat accessions, including sphaerococcum. Only the two known alleles, type A and type B were found among the accessions. Of the two sphaerococcum accessions, both possessed the type A allele. Four aestivum accessions also possessed the type A allele, while the remaining three accessions possessed the type B allele. Conversely, the accessions of the four remaining subspecies possessed the type B allele. Since sphaerococcum has morphological traits that differ from aestivum and which are pleiotropically regulated by a single recessive gene designated s, sphaerococcum most likely originated from aestivum, with the type A allele at the A1 locus arising through a spontaneous mutation at the s locus.

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Rice (Oryza sativa L.) genes AS2-2 and SUT1-2, which are alleles at OsAGPS2 (AS2) on chromosome 8 and OsSUT1 (SUT1) on chromosome 3, respectively, were suggested to improve grain filling in extra-heavy panicle rice cultivars. This study examined the distribution of these alleles among 315 rice cultivars. A discriminant function based on phenol reaction of hulls, apiculus hair length and KClO₃ sensitivity in seedlings was used to classify cultivars into japonica (192 cultivars) and indica (123 cultivars). Genotyping for the AS2 and SUT1 alleles were performed with In/Del and SSR markers, respectively. In japonica cultivars, the frequencies of AS2-2 and SUT1-2 were very low (3.6% and 6.3%, respectively), whereas they were more common in indica cultivars (56.1% and 74.0%, respectively). In addition, in indica cultivars the genotypes of AS2-2 SUT1-2, as well as AS2-1 SUT1-1, were more frequent than expected from independent segregation of these alleles. It was suggested that artificial and/or natural selection contributed to this non-random distribution of alleles at AS2 and SUT1. The alleles for good grain filling should, thus, be explored in indica cultivars to improve the grain filling of extra-heavy panicle types of rice in future breeding programs.

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