QTL analysis of kernel size and shape in two hexaploid wheat mapping populations

Kernel size and shape in wheat are important because of their relationship with yield and milling quality. This paper reports QTL analyses of kernel morphology in two hexaploid wheat mapping populations, grown in NY and CA. Kernel morphology was evaluated through a new and improved method, combining measurements from two orthogonal pictures. Single marker regression showed that several genomic positions, scattered through the genome, were related to kernel size and shape, in both populations. The direction of allele effects was consistent between environments, although the LOD scores varied considerably. Composite interval mapping revealed QTLs on all seven homoeologous groups, considering both populations. For the QTLs detected through this method, the signal and magnitude of additive effects were similar between environments, indicating small QTL × environment interaction. In the population W7984 × Opata 85, the strongest signal was detected on the chromosome 5B, for kernel length. In the population AC Reed × Grandin, the most important QTLs were detected on chromosome 2D, affecting the lateral dimensions of the kernel. This study agreed with previous reports that the genetic control of kernel length and width are largely independent. Additionally, it was shown that QTLs detected on different mapping populations, with identical evaluation methods, can be very distinct.     

QTL analysis of submergence tolerance at tillering stage in rice

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QTL analysis of submergence tolerance at tillering stage in rice

A double haploid(DH) population derived from a cross between an indica variety Zaiyeqing 8(ZYQ 8) and a japonica variety Jingxi 17(JX 17), and their parents were completely submerged for 5 d at tillering stage to evaluate their submergence tolerance.     

QTL IciMapping:Integrated software for genetic linkage map construction and quantitative trait locus mapping in biparental populations

QTL Ici Mapping is freely available public software capable of building high-density linkage maps and mapping quantitative trait loci(QTL) in biparental populations. Eight functionalities are integrated in this software package:(1) BIN: binning of redundant markers;(2) MAP: construction of linkage maps in biparental populations;(3) CMP: consensus map construction from multiple linkage maps sharing common markers;(4) SDL: mapping of segregation distortion loci;(5) BIP: mapping of additive, dominant, and digenic epistasis genes;(6) MET: QTL-by-environment interaction analysis;(7) CSL: mapping of additive and digenic epistasis genes with chromosome segment substitution lines; and(8) NAM: QTL mapping in NAM populations. Input files can be arranged in plain text, MS Excel 2003, or MS Excel 2007 formats. Output files have the same prefix name as the input but with different extensions. As examples, there are two output files in BIN, one for summarizing the identified bin groups and deleted markers in each bin, and the other for using the MAP functionality. Eight output files are generated by MAP, including summary of the completed linkage maps, Mendelian ratio test of individual markers, estimates of recombination frequencies, LOD scores, and genetic distances, and the input files for using the BIP, SDL,and MET functionalities. More than 30 output files are generated by BIP, including results at all scanning positions, identified QTL, permutation tests, and detection powers for up to six mapping methods. Three supplementary tools have also been developed to display completed genetic linkage maps, to estimate recombination frequency between two loci,and to perform analysis of variance for multi-environmental trials.     

PCR-based markers for identification of HMW-GS at Glu-B1x loci in common wheat

The bread wheat elasticity, which is very important for bread-making quality, is largely determined by the composition of high-molecular-weight glutenin subunits (HMW-GS). The HMW-GS encoded by Glu-B1 loci are highly polymorphic and the combinations 17+18 and 14+15 are good for bread making. Thus it is very important to identify the alleles at Glu-B1 loci for wheat quality improvement. In this study, the five common HMW-GS types encoded by Glu-B1x locus carried by 18 Chinese bread wheat cultivars (or lines) were analyzed by SDS-PAGE. Two pairs of PCR primers which could distinguish the Glu-Blx alleles of the five common HMW-GS types were designed based on the Glu-B1x gene sequences (Reddy and Appels, 1993; Genbank accession: X13927; Genbank accession:AY367771). 22 recombinant inbred lines (RILs) derived from Jing711 (contains 17 subunit on Glu-B1x) and Pm97034 (contains 14 subunit on Glu-B1x) were used to validate the accuracy of the primers, which showed that the two specific markers could be used together to distinguish alleles at Glu-B1x locus and accelerate wheat quality breeding by marker assisted selection.     

Molecular genetic mapping of quantitative trait loci associated with loaf volume in hexaploid wheat (Triticum aestivum)

Major efforts in wheat research are being made to improve the yield and quality of wheat. Loaf volume (Lv) is the main quality parameter deciding the bread making potential of wheat. To genetically dissect quantitative trait loci (QTLs) for Lv, a Recombinant Inbred Line (RIL) population (F₈) was developed from a cross between two Indian wheat varieties “HI 977” and “HD 2329”. A total of 914 SSR and 100 ISSR primers were used for molecular analysis and the genetic map comprising 19 chromosomes was constructed with 202 SSR markers and 2 HMW glutenin subunit loci: Glu-B1 and Glu-D1. The phenotypic data were collected from six environments including three different agro-climatic zones for 2 consecutive years. Dissection of Lv through AMMI model revealed significant G×E variance for the trait. QTL analysis was performed using composite interval mapping. A total of 30 QTLs for Lv were detected and significant QTLs were identified on 6B and 6D chromosomes; 1B, 1D, 2A, 3A, 5B and 5D also contributed genetically to Lv. Association between 6B and 6D QTLs and variable expression of gliadins on group 6 chromosomes were discussed. QTLs detected in this study were compared with other QTL analysis in wheat.     

Gibberellin-sensitive Rht alleles confer tolerance to heat and drought stresses in wheat at booting stage

The present study compared six near-isogenic lines from different backgrounds, varying in Rht (reduced height) alleles for gibberellin (GA) response, for heat and drought tolerance. Various temperature (day/night: 20/12 °C to 39/31 °C), and irrigation (100% field capacity and no irrigation) treatments were imposed at booting stage. Results depicted a 50% reduction in grain yield at 36.7 °C with irrigation and at 31.2 °C without irrigation. Number of grains per spike was severely reduced over 26 °C for water-stressed plants while irrigated plants did not show any significant reduction up to 34 °C. Ear numbers per pot and spikelets per spike were unaffected by irrigation till 33 °C. In Mercia, grain nitrogen, sulphur, and Hagberg falling number (HFN) were significantly higher for severe dwarfs (Rht-D1c and Rht-12), however, in Maris Widgeon, rht (tall) recorded higher nitrogen and sulphur concentration while Rht-B1b presented the maximum sedimentation of sodium dodecyl sulphate (SDS). The SDS was higher in Maris Widgeon while HFN were superior in Mercia. Conclusively, the present study demonstrated that heat and drought stresses severely reduced the grain yield while improved grain quality traits. The GA-insensitive semi dwarf Rht-B1b was the most promising genotype for grain yield and HFN under combined drought and heat stresses.     

QTL analysis of cold tolerance at seedling stage in rice (Oryza sativa L.) using recombination inbred lines

Cold tolerance at seedling stage of rice (Oryza sativa L.) is a favorable trait for the stable establishment in temperate and high-elevation areas. In the present study, 71 recombinant inbred lines (RIL) derived from the cross of Asominori (Japonica) and IR24 (Indica) were used to identify quantitative trait loci (QTL) affecting cold tolerance at seedling stage. The putative QTL was further confirmed using some chromosome segment substitution lines (CSSLs), in which IR24 was used as the donor parent and Asominori as the recurrent parent. The average seedling mortality was used as cold tolerance after cold treatment with 6 °C for 7 days and recovery culture with 25 °C for 4 days at three-leaf seedling stage. Three QTL affecting cold tolerance at seedling stage were detected on chromosomes 1, 5 and 6 with LOD scores ranging from 2.2 to 4.1 using composite interval mapping (CIM). Among them, qSCT-1 located in the region of XNpb87-2-C955 on chromosome 1 was a major QTL which explained 24.51% of total phenotypic variance and favorable allele came from japonica parent, Asominori. In addition, IR24 alleles at the other two loci (qSCT-5 and qSCT-6) increased cold tolerance. And these three QTL were confirmed by four lines from the IR24 CSSLs. Transferring favorable allele from japonica variety to indica background or pyramiding different QTL identified from indica is an effective way to improve cold tolerance of rice.     

南疆麦棉间作对棉花苗期风灾防范效果研究

为探究麦棉间作预防棉花苗期风灾技术在棉花生产中的应用效果,于2021年在新疆巴音郭楞蒙古自治州尉犁县兴平乡进行示范试验,以该技术的3种种植模式(麦棉同播间作垂直风向模式、麦棉同播间作同风向模式、先麦后棉错时播种间作模式)为处理,以常规种植模式为对照,对该技术防风固沙能力和减灾保产效果进行验证.结果表明,与采取补种和重播...     

Effect of allelic variation at the Glu-3/Gli-1 loci on breadmaking quality parameters in hexaploid wheat (Triticum aestivum L.)

Low molecular weight glutenin subunits (LMW-GS) encoded by the Glu-3 loci are known to contribute to wheat breadmaking quality. However, the specific effect of individual Glu-3 alleles is not well understood due to their complex protein banding patterns in SDS-PAGE and tight linkage with gliadins at the Gli-1 locus. Using DNA markers and a backcross program, we developed a set of nine near isogenic lines (NILs) including different Glu-A3/Gli-A1 or Glu-B3/Gli-B1 alleles in the genetic background of the Argentine variety ProINTA Imperial. The nine NILs and the control were evaluated in three different field trials in Argentina. Significant genotype-by-environment interactions were detected for most quality parameters indicating that the effects of the Glu-3/Gli-1 alleles are modulated by environmental differences. None of the NILs showed differences in total flour protein content, but relative changes in the abundance of particular classes of proteins cannot be ruled out. On average, the Glu-A3f, Glu-B3b, Glu-B3g and Glu-B3i_Man alleles were associated with the highest values in gluten strength-related parameters, while Glu-A3e, Glu-B3a and Glu-B3i_Chu were consistently associated with weak gluten and low quality values. The value of different Glu-3/Gli-1 allele combinations to improve breadmaking quality is discussed.     

New B low Mr glutenin subunit alleles at the Glu-A3, Glu-B2 and Glu-B3 loci and their relationship with gluten strength in durum wheat

The B low M_r subunits of glutenin of the F₂ generation from three durum wheat crosses were analysed. Three new alleles were found at three different loci: Glu-A3i coding for 5+20 subunits, Glu-B2c coding for subunit 12* and Glu-B3l coding for 1+3+13*+16 subunits. The genetic distances between Glu-A3-Gli-A1, Glu-B2-Gli-B1, Glu-B3-Glu-B2 and Glu-B3-Gli-B1 were calculated. The effects of the allelic variation at the Glu-A3, Glu-B2 and Glu-B3 on protein content and gluten strength, as measured by the SDS-sedimentation test, were determined using F₄ lines from the three crosses. All the new alleles affected significantly gluten strength. The presence of Glu-A3i had a negative influence on SDSS values compared with the allele a. For Glu-B2 and Glu-B3 the data obtained enable the effects of the alleles on SDSS volume to be ranked: a=b>c for Glu-B2 and a>b>l for Glu-B3. The results also shown that the allelic variants at Glu-B3 had a much greater effect on gluten strength than the variants at Glu-A3 or Glu-B2 loci. A high percentage of variation in sedimentation volume was explained by the prolamins (52 and 70%).     

Identification and validation of QTLs for cold tolerance at the booting stage and other agronomic traits in a rice cross of a Japanese tolerant variety,Hananomai, and a NERICA parent,WAB56-104

In Africa, cold temperatures occur in the highlands of East and Southern Africa and in some areas of the Sahel region of West Africa leading to substantial rice yield losses. Cold tolerance (CT) at booting stage on basis of spikelet fertility after cold water irrigation was evaluated using F₂ population derived from a cross between temperate japonica, Hananomai, and tropical japonica, WAB56-104. Two Quantitative trait loci (QTLs) for CT were detected on chromosome 8 and 10 with enhanced effects on the trait coming from Hananomai and WAB56-104 allele, respectively. The QTLs explained 30% and 33% of phenotypic variation in spikelet fertility, respectively. CT was negatively correlated with panicle number (r = ?0.35, p < 0.01) and positively correlated with panicle weight (r = 0.61, p < 0.001). Selected BC₁F₄ and BC₁F₅ genotypes having homozygous alleles for both CT QTLs exhibited higher spikelet fertility under cold stress. The identified QTLs will be useful in the development of cold-tolerant varieties for production in high altitude areas through marker-assisted selection.     

Relationship among leaf (Puccinia recondita Roberge ex Desmaz f. sp. tritici) and yellow (Puccinia striiformis Westendorp. f. sp. tritici) rust resistance and some agro-morphologic traits in wheat hybrids at seedling stage

This research was carried out to determine if dominant morphological traits can be use instead of the rust resistance tests as marker characters for some agro-morphologic traits both leaf (Puccinia recondita Roberge ex Desmaz. f. sp. tritici.) and yellow rust (Puccinia striiformis Westendorp f. sp. tritici) disease. For this, 13 wheat parent (4 are T. durum Desf. and 9 are T. aestivum L.) were used and three main agro-morphologic traits (Namely, Leaf Colour (LC) (Dark and light green, Dg and Lg, relatively); Auricle Colour (AC) (White and Red, Wh and Re, relatively) and Leaf Waxiness (LW) (Waxy and Non waxy, Wx and Nw, relatively) were investigated at the seedling stage. They were found as dominant and concluded that investigated traits could be used as a morphological marker character for the leaf and yellow rust disease resistance tests under greenhouse conditions without doing complex and risky rust tests. And determined that, these traits may be use effectively without doing the complex rust tests in the limited populations or for the pre-selections. Doing with this, it will be bring a great accuracy, successful, correction and speed to the rust disease studies and provides important and valuable information for the plant breeders and pathologists. In addition, knowing of the resistance type (genetic mechanism etc.) in wheat facilitates it will be make to find out the suit and most appropriate breeding and selection methodology/methodologies.