Allelic variation at the <Emphasis Type="Italic">Glu-1</Emphasis> and <Emphasis Type="Italic">Glu-3</Emphasis> loci,presence of the 1B.1R translocation,and their effects on mixographic properties in Chinese bread wheats

Allelic variations at the Glu-1 and Glu-3 loci play an important role in determining dough properties and bread-making quality. Two hundred and fifty-one cultivars and advanced lines from four major Chinese wheat-producing zones in the autumn-sown wheat regions were used to investigate the high-molecular-weight glutenin subunits (HMW GS) and low-molecular-weight glutenin subunit (LMW GS) composition controlled by the Glu-1 and Glu-3 loci, respectively, as well as the presence of the 1B.1R translocation, and to determine the association of storage protein composition with protein content, SDS sedimentation value, and dough-mixing properties measured by mixograph. Three, nine, and four allelic variations were present at Glu-A1, Glu-B1, and Glu-D1, respectively. Subunits 1, N, 7+8, 7+9, and 2+12 are the dominant HMW GS, with frequencies of 51.3, 39.4, 38.2, 45.0, and 59.8%, respectively. Five and eight allelic variations were present at the Glu-A3 and Glu-B3 loci (data of Glu-D3 were not available), Glu-A3a, Glu-A3d, Glu-B3j (presence of the 1B.1R translocation), and Glu-B3d are the dominant LMW GS, with frequencies of 37.1, 31.7, 44.6, and 20.3%, respectively. The frequencies of allelic variation at Glu-1 and Glu-3 differ greatly in different regions. The effects of HMW GS and LMW GS on SDS sedimentation value, mixing time, and mixing tolerance were significant at P = 0.01, with Glu-D1 and Glu-B3 showing the largest contributions to mixing time and mixing tolerance. Averaged data from two locations showed that the quality effects of glutenin loci could be ranked as Glu-B3 > Glu-B1 > Glu-A1 > Glu-D1 > Glu-A3 for SDS sedimentation value, Glu-D1 > Glu-B3 > Glu-A1 = Glu-B1 = Glu-A3 for mixing time, and Glu-D1 > Glu-B3 = Glu-B1 > Glu-A3 > Glu-A1 for mixing tolerance, respectively. The significant and negative effect of the 1B.1R translocation on dough properties was confirmed. It was concluded that the high frequency of undesirable HMW GS and LMW GS and the presence of the 1B.1R translocation are responsible for the weak gluten property of Chinese germplasm; hence, reducing the frequency of the 1B.1R translocation and integration of desirable subunits at Glu-1 and Glu-3 such as 1, 7+8, 14+15, 5+10, Glu-A3d, and Glu-B3d, could lead to the improvement of gluten quality in Chinese wheats.     

Additive and epistatic effects of allelic variation at the high molecular weight glutenin subunit loci in determining the bread-making quality of breeding lines of wheat

Summary The relation has been studied between the high molecular weight glutenin (HMWg) subunit alleles and the bread-making quality of 226 lines of winter wheat (T. aestivum L.), grown in The Netherlands. The lines represented a wide range of genetic backgrounds, and had not been selected for quality, in contrast to the established varieties used by other authors.The variation in HMWg subunit genotypes accounted for about 20% of the total variation in loaf volume among the lines. Most important was the allelic variation at the Glu-D1 locus. The Glu-D1 allele encoding the subunits 5+10 was superior to its allelic counterpart, encoding 2+12. The difference in average of loaf volume between groups of lines containing 5+10 or 2+12 was negatively related with protein content of the flours. When protein content was below 9.2%, no effect of allelic variation at the Glu-D1 locus was present. Epistatic effects between the Glu-I loci also contributed to the variation in loaf volume of the lines: i.e. the effect of allelic variation at Glu-A1 and Glu-B1 depended on the allele present at the Glu-D1. The contribution of the epistatic effects was about half the contribution of the additive effects, and should therefore be included in predictive models for bread-making quality.     

Genetic variation of wheat glutenin subunits between landraces and varieties and their contributions to wheat quality improvement in China

Glutenin, one of major factors effecting bread-making quality, is comprised of a mixture of polymers, viz. high-molecular-weight glutenin subunits (HMW-GSs) and low-molecular-weight glutenin subunits (LMW-GSs). Understanding variation among these glutenin subunits can help breeders determine allelic effects on specific quality traits and to use them as genetic markers. The HMW-GS and LMW-GS compositions of 390 landraces and 225 released varieties were analyzed by SDS–PAGE, and some quality traits, including Zeleny sedimentation volume, dough development time, stability time and strengths, were evaluated. The results indicated that 17 and 13 HMW-GSs were present in landraces and released varieties, respectively. For LMW-GS (Glu-A3 and Glu-B3 loci), 12 alleles were found in both landraces and released varieties. Total allelic richness at glutenin loci in landraces was higher, but the genetic dispersion index was lower than in released varieties. Two new subunit combinations 6 + 16 and 7 + 22, and some rare subunits 6 + 9*, 23 + 22, 6* + 8, 7 and 8, were identified in landraces and released varieties. The Glu-D1 and Glu-B3 loci had significantly positive effects. Based on the comparison of the effect of each subunit on quality, it was concluded that subunits 1 at Glu-A1, 13 + 16, 17 + 18 and 6 + 16 at Glu-B1, 5 + 10 at Glu-D1, Glu-A3b at Glu-A3 and Glu-B3d at Glu-B3 contributed larger positive effects on bread-making quality than alternative alleles. From this study, genetic materials with strong gluten and good quality were identified in landraces that did not carry the 1BL.1RS translocation.     

Deficiency of individual high molecular weight glutenin subunits affords flexibility in breeding strategies for bread-making quality in wheat Triticum aestivum L.

High-molecular-weight (HMW) glutenin subunits in wheat Triticumaestivum L., allelic variation for which affects bread-making quality, areencoded by Glu-1 homoeoloci located on the homoeologous group1 chromosomes. Many alleles at Glu-B1 and Glu-D1 producetwo subunits, an x-type of low electrophoretic mobility in polyacrylamidegels, and a y-type of high mobility. In the current study, a combination ofnear isogenic lines of cultivar `Sicco' has been used to characterise theeffect upon quality of the absence of individual subunits 7 (Glu-B1x-type), 12 (Glu-D1 y-type) and, assuming an additive model ofsubunit action, 2 (Glu-D1 x-type). Absence of subunit 7 gave amoderate reduction in SDS-sedimentation volume, indicating its associationwith lower gluten strength (confirmed by Farinogram and Extensogramstudies), yet, from a full mixing input bake, a moderate increase in loafvolume and a considerable improvement in loaf score (an overall evaluationof loaf quality). Absence of subunit 12 gave a slightly larger reduction inSDS-volume, yet no change in loaf volume or score. Absence of bothsubunits 2+12 gave a larger reduction again in SDS-volume, a moderatereduction in loaf volume and a large reduction in loaf score. Absence ofsubunit 2 alone is therefore predicted to reduce SDS-volume, loaf volumeand score such that loss of this x-type subunit would lead to larger changesin quality parameters than loss of y-type subunit 12. A general conclusionof the study is that, while deficiency for HMW glutenin subunits generallyleads to reduced gluten strength and viscoelasticity, the resultantintermediate gluten strength may on occasions lead to improvements in loafperformance in situations where the base gluten strength is high. Theremay, then, be contexts in breeding programmes where selection fordeficiency would be a possible strategy for improving bread-making quality,adding to the flexibility available to the breeder. Somewhat unexpectedly,additional analysis found that, in the genetic background of cultivar `Sicco'used in this study, subunits 7+8 at Glu-B1 were indistinguishablefrom their allelic counterparts subunits 7+9 for virtually all characters, andthat subunits 2+12 at Glu-D1, while inferior in performance formixing properties compared to subunits 5+10, were associated with goodloaf characteristics.     

Introduction to bread wheat (Triticum aestivum L.) and assessment for bread-making quality of alleles from T. boeoticum Boiss. ssp. thaoudar at Glu-A1 encoding two high-molecular-weight subunits of glutenin

Two alleles, Glu-A1r encoding high-molecular-weight (HMW) glutenin subunits 39+40 and Glu-A1s encoding HMW glutenin subunits 41+42, were introgressed to bread wheat (Triticum aestivum L.) cv. Sicco from two accessions of T. boeoticum Boiss. ssp. thaoudar (A genome species, 2n=2x=14). Alleles at Glu-A1 in current commercial bread wheats encode zero or one subunit, and alleles at the homoeoloci Glu-B1 and Glu-D1 encode a maximum of two subunits; hence the maximum number of subunits found in commercial wheats is five, whereas the lines incorporating Glu-A1r and Glu-A1s carry six. Using near-isogenic lines, the current results demonstrated that the introduction of Glu-A1r resulted in diminished dough stickiness and improved stability during mixing compared with Glu-A1a encoding subunit 1, and a small improvement in gluten strength as shown by the SDS- sedimentation test. The introduction of Glu-A1a also resulted in a small improvement in gluten strength predicted by the SDS-sedimentation test. Thus the alleles are of potential value in breeding programmes designed to improve bread-making quality.     

HMW-GS和LMW-GS组成对小麦加工品质的影响

高分子量麦谷蛋白亚基(HMW-GS)和低分子量麦谷蛋白亚基(LMW-GS)是决定小麦加工品质的重要因素。以小麦品种PH82-2(亚基组成1, 14+15, 2+12和Glu-A3d, Glu-B3d, Glu-D3c)和内乡188(亚基组成1, 7+9, 5+10和 Glu-A3a, Glu-B3j, Glu-D3b)的242份F₃和F₄株系(试验I)和91份产量比较试验材料(试验II)研究了贮藏蛋白组成对小麦加工品质的影响。结果表明,HMW-GS和LMW-GS等位变异对籽粒蛋白质含量的影响不大,但对加工品质均有极显著影响(P<1%)。就位点的效应而言,Glu-D1位点对加工品质的效应较大,而Glu-D3位点的效应较小。就单个亚基而言,在Glu-B1位点,14+15<7+9;在Glu-D3位点,Glu-D3c>Glu-D3b。1B/1R易位系的部分品质性状,如和面时间、曲线下降斜度和峰积分好于非1B/1R易位系。     

小麦高分子量谷蛋白亚基间的互补效应对面包加工品质的影响

利用偃展1号的10个HMW-GS近等基因系,研究了不同HMW-GS基因对面包烘烤品质的效应。两年的品质测试结果基本一致,说明所用近等基因系是评价亚基组成对加工品质影响的较理想材料。不同HMW-GS组成对面包评分影响较大,变异系数达到21.5%。相关分析表明,面包体积与形成时间(r = 0.90, P < 0.01)、沉淀值(r = 0.89, P < 0.01)、稳定时间(r = 0.67, P < 0.05)和面粉蛋白质含量(r = 0.52, P < 0.05)均达显著正相关;面包评分与面包体积(r = 0.98, P < 0.01)、沉淀值(r = 0.93, P < 0.01)、形成时间(r = 0.89, P < 0.01)也呈显著正相关。Glu-A1位点1Ax1基因的表达可以提高多数品系的面包评分;当Glu-A1位点是Null、Glu-D1位点是5’+12时,Glu-B1位点等位变异的面包加工品质效应为7+8 > 14+15 > 6+8 > 7,而当Glu-A1位点是1号亚基、Glu-D1位点是5’+12时,Glu-B1位点的等位变异的面包品质效应为6+8 > 14+15 > 7;当Glu-A1位点是Null时,14+15与5+10组合优于与5’+12组合,7+8与5’+12组合优于与5+10组合;1Dx5基因的沉默显著降低面包烘烤品质,HMW-GS对面包品质的作用似乎在X-亚基和Y-亚基之间存在一定的配合效应,任何一种基因的缺失或沉默都会造成品质的明显下降。     

Leaf margin phenotype-specific restriction-site-associated DNA-derived markers for pineapple (Ananas comosus L.)

To explore genome-wide DNA polymorphisms and identify DNA markers for leaf margin phenotypes, a restriction-site-associated DNA sequencing analysis was employed to analyze three bulked DNAs of F1 progeny from a cross between a ‘piping-leaf-type’ cultivar, ‘Yugafu’, and a ‘spiny-tip-leaf-type’ variety, ‘Yonekura’. The parents were both Ananas comosus var. comosus. From the analysis, piping-leaf and spiny-tip-leaf gene-specific restriction-site-associated DNA sequencing tags were obtained and designated as PLSTs and STLSTs, respectively. The five PLSTs and two STSLTs were successfully converted to cleaved amplified polymorphic sequence (CAPS) or simple sequence repeat (SSR) markers using the sequence differences between alleles. Based on the genotyping of the F1 with two SSR and three CAPS markers, the five PLST markers were mapped in the vicinity of the P locus, with the closest marker, PLST1_SSR, being located 1.5 cM from the P locus. The two CAPS markers from STLST1 and STLST3 perfectly assessed the ‘spiny-leaf type’ as homozygotes of the recessive s allele of the S gene. The recombination value between the S locus and STLST loci was 2.4, and STLSTs were located 2.2 cM from the S locus. SSR and CAPS markers are applicable to marker-assisted selection of leaf margin phenotypes in pineapple breeding.     

麦谷蛋白亚基Clu-1和Glu-3位点基因等位变异对小麦品质特性的影响

甲单向一步SDS-PAGE方法分析表明亲本品种Suneca和Cook在麦谷蛋白亚基的5个位点(Glu-B1,Glu-D1,Glu-A3,Glu-B3和Glu-D3)均含不同等位基因。本研究重点对Suneca×Cook的F_4代群体中在麦谷蛋白亚基位点均为纯合基因的60个系的出粉率(FY),面粉蛋白质含量(FP)及和面时间(PTM)进行了分析,以研究麦谷蛋白各亚基位点等位基因变异及位点间互作对小麦品质特性的影响。结果表明,不同基因型间出粉率无显著差异,Glu-D1位点等位基因d和a对FP的效应存在显著差异,Glu-Dld基因(编码5 10亚基)的正效应显著高于Glu-Dla基因(编码2 12亚基);Glu-D1、Glu-A3和Glu-B3位点上基因的等位变异对PTM有显著和极显著影响,含Glu-Dld、Glu-A3b和Glu-B3b基因的系分别比含Glu-Dla,Glu-A3d和Glu-B3h基因的系有较长的和面时间;Glu-B1位点上等位变异i和u以及Glu-D3位点等位基因b和e分别对PTM无明显影响。在这种遗传背景下,麦谷蛋白亚基位点对PTM的效应大小依次排列为Glu-D1>Glu-B3>Glu-A3>GIu-B1=Glu-D3。Glu-1位点和Glu-3位点间对和面特性的影响存在累加效应和互作效应。     

Effects on flowering and seed yield of dominant alleles at maturity loci E2 and E3 in a Japanese cultivar,Enrei

‘Enrei’ is the second leading variety of soybean (Glycine max (L.) Merr.) in Japan. Its cultivation area is mainly restricted to the Hokuriku region. In order to expand the adaptability of ‘Enrei’, we developed two near-isogenic lines (NILs) of ‘Enrei’ for the dominant alleles controlling late flowering at the maturity loci, E2 and E3, by backcrossing with marker-assisted selection. The resultant NILs and the original variety were evaluated for flowering, maturity, seed productivity and other agronomic traits in five different locations. Expectedly, NILs with E2 or E3 alleles flowered later than the original variety in most locations. These NILs produced comparatively larger plants in all locations. Seed yields were improved by E2 and E3 in the southern location or in late-sowing conditions, whereas the NIL for E2 exhibited almost the same or lower productivity in the northern locations due to higher degrees of lodging. Seed quality-related traits, such as 100-seed weight and protein content, were not significantly different between the original variety and its NILs. These results suggest that the modification of genotypes at maturity loci provides new varieties that are adaptive to environments of different latitudes while retaining almost the same seed quality as that of the original.     

The high and low molecular weight glutenin subunits and ω-gliadin composition of bread and durum wheats commonly grown in Portugal

A collection of 63 bread wheats (Triticum aestivum L.) and 21 durum wheats (Triticum durum Desf.) commonly grown in Portugal since 1982 were characterized for the composition of wheat storage proteins (WSP), high molecular weight glutenin subunits (HMW-GS), low molecular weight glutenin subunits (LMW-GS) and ω-gliadins. The composition of HMW-GS, LMW-GS and &-gliadins, encoded at loci Glu-1, Glu-3 and Gli-1, respectively, was revealed by sodium dodecyl sulphate polyacrylamide gel electrophoresis. WSP allelic compositions of bread and durum wheat patterns were given. In the bread wheats, a total of 24, 24 and 18 patterns were observed for HMW-GS, LMW-GS and ω-gliadins, respectively. Forty-two different alleles were identified for the nine loci studied, Glu-A1 (3), Glu-B1 (7), Glu-D1 (4), Glu-A3 (5), Glu-B1 (7), Glu-D3 (2), Gli-A1 (2), Gli-B1 (8) and Gli-D1 (4). In the case of durum wheats, 19 alleles were identified: one allele at Glu-A1, two at Glu-B3, Glu-B2 and Gli-A1, three at Glu-B1, four at Glu-A3 and five at Gli-B1. For HMW-GS, LMW-GS and ω-gliadins, three, six and six different patterns were revealed, respectively. This study represents the first attempt to discriminate the bread and durum wheat varieties commonly grown in Portugal by the allelic variation of storage proteins. The database is useful for varietal identification and for plant breeders who seek to devise effective programmes aimed at improving wheat quality.     

Genome-wide indel markers shared by diverse Asian rice cultivars compared to Japanese rice cultivar ‘Koshihikari’

Insertion-deletion (indel) polymorphisms, such as simple sequence repeats, have been widely used as DNA markers to identify QTLs and genes and to facilitate rice breeding. Recently, next-generation sequencing has produced deep sequences that allow genome-wide detection of indels. These polymorphisms can potentially be used to develop high-accuracy polymerase chain reaction (PCR)-based markers. Here, re-sequencing of 5 indica, 2 aus, and 3 tropical japonica cultivars and Japanese elite cultivar ‘Koshihikari’ was performed to extract regions containing large indels (10–51 bp) shared by diverse cultivars. To design indel markers for the discrimination of genomic regions between ‘Koshihikari’ and other diverse cultivars, we subtracted the indel regions detected in ‘Koshihikari’ from those shared in other cultivars. Two sets of indel markers, KNJ8-indel (shared in eight or more cultivars, including ‘Khao Nam Jen’ as a representative tropical japonica cultivar) and C5-indel (shared in five to eight cultivars), were established, with 915 and 9,899 indel regions, respectively. Validation of the two marker sets by using 23 diverse cultivars showed a high PCR success rate (≥95%) for 83.3% of the KNJ8-indel markers and 73.9% of the C5-indel markers. The marker sets will therefore be useful for the effective breeding of Japanese rice cultivars.     

低分子量谷蛋白亚基GlU-A3和GlU-B3位点对小麦面筋强度和烘焙特性影响

低分子量谷蛋白亚基是小麦谷蛋白亚基的重要组成部分,黄淮麦区小麦低分子量谷蛋白亚基组成对品质的效应尚缺乏系统的研究。本研究采用SDS-PAGE方法,鉴定了黄淮麦区42个小麦品种的Glu-A3位点和Glu-B3位点低分子量谷蛋白亚基组成,分析了低分子量谷蛋白亚基对小麦面筋强度和烘烤品质的影响。结果表明,在Glu-A3位点,对面筋强度和面包烘焙品质正向效应为:d,b>a,e;在Glu-B3位点,对面筋强度正效应为:h,d>f>g,b,j,对面包烘焙品质正向效应为:h>f,d>g,b,j。Glu-A3d/Glu-B3h亚基组合具有较好的面筋强度和烘焙品质。就低分子量谷蛋白亚基单个变异位点对品质综合效应而言,Glu-B3位点对品质作用比较大,与Glu-B1位点相近,同时,高低分子量谷蛋白亚基之间存在着互作效应,以Glu-B1/Glu-A3和Glu-D1/Glu-B3位点的互作效应比较显著。Glu-A3和Glu-B3位点及其所编码的不同亚基种类对品质的效应差异显著,并且与高分子量谷蛋白亚基位点存在互作,对不同位点优质亚基的聚合将有助于小麦品质的遗传改良。     

HMW-GS和LMW-GS组成及1BL/1RS易位对春小麦品质性状的影响

分析了221份春小麦品种（系）的HMW-GS、LMW-GS组成和1BL/1RS易位状况,并用其中104份品种（系）研究了HMW-GS和LMW-GS等位变异及1BL/1RS易位对品质性状的影响。结果表明,1、7+9、5+10、GluA3a和GluB3j分布较广,频率分别为57.5%、45.2%、63.8%、29.0%和42.5%。1BL/1RS易位系相当普遍,西北春麦区和东北春麦区频率分别为44.3     

Identificaiton of a clubroot resistance locus conferring resistance to a Plasmodiophora brassicae classified into pathotype group 3 in Chinese cabbage (Brassica rapa L.)

In Chinese cabbage (Brassica rapa), the clubroot resistance (CR) genes Crr1 and Crr2 are effective against the mild Plasmodiophora brassicae isolate Ano-01 and the more virulent isolate Wakayama-01, but not against isolate No. 14, classified into pathotype group 3. ‘Akiriso’, a clubroot-resistant F₁ cultivar, showed resistance to isolate No. 14. To increase the durability of resistance, we attempted to identify the CR locus in ‘Akiriso’. CR in ‘Akiriso’ segregated as a single dominant gene and was linked to several molecular markers that were also linked to CRb, a CR locus from cultivar ‘CR Shinki’. We developed additional markers around CRb and constructed partial genetic maps of this region in ‘Akiriso’ and ‘CR Shinki’. The positions and order of markers in the genetic maps of the two cultivars were very similar. The segregation ratios for resistance to isolate No. 14 in F₂ populations derived from each of the two cultivars were also very similar. These results suggest that the CR locus in ‘Akiriso’ is CRb or a tightly linked locus. The newly developed markers in this study were more closely linked to CRb than previously reported markers and will be useful for marker-assisted selection of CRb in Chinese cabbage breeding.     

Relationship between common wheat (Triticum aestivum L.) gluten proteins and dough rheological properties

This paper reports the correlation between the rheological properties of bread wheat dough and the types and quantities of endosperm proteins in 28 common wheat cultivars. Different methods were used to analyse the allelic composition of these cultivars and the relative quantities of the different proteins contributing to the gluten structure. Neither dough strength (W) nor tenacity/extensibility (P/L) correlated with allelic composition. Different wheats with the same allelic composition (i.e., with respect to glutenins) showed different rheological properties. The glutenins were the most influential components of W and P/L, especially the high molecular weight (HMW) glutenin subunits and in particular the type x form. These proteins seem to increase W and are the main constituents of the gluten network. The gliadins and low molecular weight (LMW) glutenin subunits appear to act as a “solvent”, and thus modify the rheological properties of the dough by either interfering with the polymerisation of the HMW glutenin subunits, or by altering the relative amounts of the different types of glutenin available. Thus, the protein subunits coded for by the alleles Glu-B1x7 and Glu-D1x5 stabilised the gluten network, whereas those coded for by Glu-B1x17 and Glu-D1x2 had the opposite effect. Dough properties therefore appear to depend on the glutenin/gliadins balance, and on the ratio of the type x and type y HMW proteins. The influence of external factors seems to depend on the allelic composition of each cultivar.     

Characterization of HMW-GS and evaluation of their diversity in morphologically elite synthetic hexaploid wheats

High molecular weight glutenin subunit composition and variation in 95 Elite-1 synthetic hexaploid (SH) wheats (Triticum turgidum/Aegilops tauschii; 2n = 6× = 42; AABBDD) were determined by sodium dodecyl sulphate polyacrylamide gel electrophoresis method (SDS-PAGE). Twenty two different alleles at Glu-1 loci in SHs were observed. Forty four different patterns of HMW-GS in synthetics were found. This higher HMW glutenin composition was due to higher proportion of D-genome encoded subunits in these SHs. 8% urea/SDS-PAGE better discriminated subunit 2* than 12% gels. However 12% urea/SDS-PAGE allowed differentiated mobility of Glu-D^t1 subunits. Genetic variability at Glu-D^t1 locus was greater than Glu-A1 and Glu-B1 loci. The relative high frequency of superior alleles, Glu-B1b and Glu-D^t1d indicated the superior bread making quality attributes embedded in these synthetic hexaploid wheats. Of the 95 Elite-1 SHs 27.1% possessed superior alleles at Glu-A1 and 51% had superior alleles at Glu-B1 locus. At Glu-D^t1 frequency of inferior allele 1Dx2 + 1Dy12 was very low (5.26%) and nine different rare alleles along with the higher frequency (22.1%) of D-genome encoded subunit, 1Dx5 + 1Dy10, were observed. These superior alleles shall form the priority selective sieve for their usage in wheat improvement efforts.     

Confirming a major QTL and finding additional loci responsible for field resistance to brown spot (Bipolaris oryzae) in rice

Brown spot is a devastating rice disease. Quantitative resistance has been observed in local varieties (e.g., ‘Tadukan’), but no economically useful resistant variety has been bred. Using quantitative trait locus (QTL) analysis of recombinant inbred lines (RILs) from ‘Tadukan’ (resistant) × ‘Hinohikari’ (susceptible), we previously found three QTLs (qBS2, qBS9, and qBS11) that conferred resistance in seedlings in a greenhouse. To confirm their effect, the parents and later generations of RILs were transplanted into paddy fields where brown spot severely occurred. Three new resistance QTLs (qBSfR1, qBSfR4, and qBSfR11) were detected on chromosomes 1, 4, and 11, respectively. The ‘Tadukan’ alleles at qBSfR1 and qBSfR11 and the ‘Hinohikari’ allele at qBSfR4 increased resistance. The major QTL qBSfR11 coincided with qBS11 from the previous study, whereas qBSfR1 and qBSfR4 were new but neither qBS2 nor qBS9 were detected. To verify the qBSfR1 and qBSfR11 ‘Tadukan’ resistance alleles, near-isogenic lines (NILs) with one or both QTLs in a susceptible background (‘Koshihikari’) were evaluated under field conditions. NILs with qBSfR11 acquired significant field resistance; those with qBSfR1 did not. This confirms the effectiveness of qBSfR11. Genetic markers flanking qBSfR11 will be powerful tools for marker-assisted selection to improve brown spot resistance.     

Reverted glutathione S-transferase-like genes that influence flower color intensity of carnation (Dianthus caryophyllus L.) originated from excision of a transposable element

A glutathione S-transferase-like gene, DcGSTF2, is responsible for carnation (Dianthus caryophyllus L.) flower color intensity. Two defective genes, DcGSTF2mu with a nonsense mutation and DcGSTF2-dTac1 containing a transposable element dTac1, have been characterized in detail in this report. dTac1 is an active element that produces reverted functional genes by excision of the element. A pale-pink cultivar ‘Daisy’ carries both defective genes, whereas a spontaneous deep-colored mutant ‘Daisy-VPR’ lost the element from DcGSTF2-dTac1. This finding confirmed that dTac1 is active and that the resulting reverted gene, DcGSTF2rev1, missing the element is responsible for this color change. Crosses between the pale-colored cultivar ‘06-LA’ and a deep-colored cultivar ‘Spectrum’ produced segregating progeny. Only the deep-colored progeny had DcGSTF2rev2 derived from the ‘Spectrum’ parent, whereas progeny with pale-colored flowers had defective forms from both parents, DcGSTF2mu and DcGSTF2-dTac1. Thus, DcGSTF2rev2 had functional activity and likely originated from excision of dTac1 since there was a footprint sequence at the vacated site of the dTac1 insertion. Characterizing the DcGSTF2 genes in several cultivars revealed that the two functional genes, DcGSTF2rev1 and DcGSTF2rev2, have been used for some time in carnation breeding with the latter in use for more than half a century.     

Development and validation of DNA markers linked to Sdvy-1, a common bean gene conferring resistance to the yellowing strain of Soybean dwarf virus

The yellowing strain of Soybean dwarf virus (SbDV-YS) causes yellowing and yield loss in common bean (Phaseolus vulgaris). The most effective control is achieved through breeding for resistance. An indeterminate climbing cultivar with a white seed coat, ‘Oofuku’, is resistant to SbDV-YS in inoculation tests. We crossed ‘Oofuku’ with an elite cultivar, ‘Taisho-Kintoki’, which is SbDV-YS-susceptible, determinate dwarf with a red-purple seed coat, and performed amplified-fragment-length polymorphism analysis of F₃ lines. From nucleotide sequences of the resistant-specific fragments and their flanking regions, we developed five DNA markers, of which DV86, DV386, and DV398 were closely linked to Sdvy-1, a resistance gene. Using the markers, we developed ‘Toiku-B79’ and ‘Toiku-B80’, the near-isogenic lines (NILs) incorporating Sdvy-1 in the background of ‘Taisho-Kintoki’. The NILs had similar growth habit, maturity date and seed shape to those of ‘Taisho-Kintoki’. The quality of boiled beans was also similar, except that the NILs had more seed coat cracking than ‘Taisho-Kintoki’. The NILs showed no SbDV-YS infection in inoculation tests. We suggest that Sdvy-1 is a useful source of SbDV-YS resistance in common bean.