Improvement for Agronomic Traits of Partial Waxy Wheat by Combination of Backcrossing with a PCR-based DNA Marker

To improve agronomic traits of partial waxy wheat, crossing between Chinese Baihuomai and wheat cultivars PH85-16, Jinan 17, and Yannong 15 was performed. The progeny plants were further backcrossed to these cultivars as recurrent parents for five generations. To get homozygous plants with the null allele at the Wx-D1 locus, self-pollination was carried out in the BC5F1 generation. Through another three generations, 6 partial waxy wheat lines were obtained, which had similar agronomic performance as their recurrent parents and carried the null allele at the Wx-D1 locus. In each generation, the Wx-D1 locus was identified by a PCR-based DNA marker and the agronomic traits were examined in progeny plants. The results from this study indicate that the use of backcrossing with a PCR-based DNA marker was useful in waxy wheat breeding. These partial waxy wheat lines can be used in field production.

Identification for Heat Tolerance in Backcross Recombinant Lines and Screening of Backcross Introgression Lines with Heat Tolerance at Milky Stage in Rice

The present study aimed at breeding new rice germplasms with similar genome but significantly differed in heat tolerance during the grain filling stage.A total of 791 BC1F8 backcross recombinant lines,derived from the cross of Xieqingzao B /N22 //Xieqingzao B,were used as materials.Each rice line was separated evenly into two groups,and the heat tolerance of all rice lines were evaluated at natural high temperature in fields.The rice lines with heat tolerant index higher than 90% or lower than 40% were selected to compare the phenotypic characters and further identify heat tolerance at the early milky stage in a phytotron.Rice lines with similar phenotypic characters but significantly differed in heat tolerance at the milky stage were analyzed by 887 simple sequence repeat markers that were evenly distributed on the 12 rice chromosomes.In the result,12(6 pairs) rice lines with similar phenotypic characters but significantly differed in heat tolerance at the milky stage were obtained.Molecular marker analysis indicated that the genomic polymorphism between 703T and 704S was the smallest in the 6 pairs of rice lines,with only 16 polymorphic sites,including 22 different alleles.The application of these two backcross introgression rice lines for future study on the mechanisms of heat tolerance in rice at the milky stage will be theoretically beneficial in reducing the interference caused by genetic differences from experimental materials.

Core Collection Based Backcrossing: An Eff icient Approach for Breeding, Germplasm Enhacement and Gene Discovery

Plant germplasm underpins much of crop development. Millions of germplasm accessions have been collected and conserved ex situ, and the major challenge is now how to exploit and utilize this abundant resource.

Identification and QTL mapping of Z550, a rice backcrossed inbred line with increased grains per panicle

An elite backcrossed inbred line Z550 with increased grains per panicle was identified from advanced backcrosses between Nipponbare and Xihui 18 by simple sequence repeat(SSR) marker-assisted selection(MAS). Z550 carries 13 substitution segments distributed on chromosomes 1, 6, 7, 8, 9, 10, and 12, with an average substitution length of 1.68 Mb. Compared with the Nipponbare parental line, plant height, panicle length, spikelets per panicle, grains per panicle, and grain weight for Z550 were significantly increased. While the grain width of Z550 was significantly narrower, and the seed setting ratio(81.43%) was significantly lower than that of Nipponbare, it is still sufficient for breeding purposes. Quantitative trait loci(QTLs) mapping for important agronomic traits was conducted with the F_2 population derived from Nipponbare crossed with Z550 using the restricted maximum likelihood(REML) method. A total of 16, including 12 previously unreported QTLs were detected, with contribution rates ranging from 1.46 to 10.49%. Grains per panicle was controlled by 8 QTLs, 5 of which increased number of grains whereas 3 decreased it. qGPP-1, with the largest contribution(10.49%), was estimated to increase grains per panicle by 30.67, while q GPP-9, with the minimum contribution rate(2.47%), had an effect of increasing grains per panicle by 15.79. These results will be useful for further development of single segment substitution lines with major QTLs, and for research of their molecular functions via QTL cloning.

Improvement of three popular Indian groundnut varieties for foliar disease resistance and high oleic acid using SSR markers and SNP array in marker-assisted backcrossing

Foliar fungal diseases(rust and late leaf spot)incur large yield losses,in addition to the deterioration of fodder quality in groundnut worldwide.High oleic acid has emerged as a key market trait in groundnut,as it increases the shelf life of the produce/products in addition to providing health benefits to consumers.Marker-assisted backcrossing(MABC)is the most successful approach to introgressing or pyramiding one or more traits using traitlinked markers.We used MABC to improve three popular Indian cultivars(GJG 9,GG 20,and GJGHPS 1)for foliar disease resistance(FDR)and high oleic acid content.A total of 22 BC3F4 and 30 BC2F4 introgression lines(ILs)for FDR and 46 BC3F4 and 41 BC2F4 ILs for high oleic acid were developed.Recurrent parent genome analysis using the 58 K Axiom_Arachis array identified several lines showing upto 94%of genome recovery among second and third backcross progenies.Phenotyping of these ILs revealed FDR scores comparable to the resistant parent,GPBD 4,and ILs with high(~80%)oleic acid in addition to high genome recovery.These ILs provide further opportunities for pyramiding FDR and high oleic acid in all three genetic backgrounds as well as for conducting multi-location yield trials for further evaluation and release for cultivation in target regions of India.

QTL and genetic analysis controlling fiber quality traits using paternal backcross population in upland cotton

Background:Genetic improvement in fiber quality is one of the main challenges for cotton breeders.Quantitative trait loci(QTL)mapping provides a powerful approach to dissect the molecular mechanism in fiber quality traits.In present study,F14 recombinant inbred line(RIL)population was backcrossed to paternal parent for a paternal backcross(BC/P)population,deriving from one upland cotton hybrid.Three repetitive BC/P field trials and one maternal backcross(BC/M)field trial were performed including both two BC populations and the original RIL population.Results:In total,24 novel QTLs are detected for fiber quality traits and among which 13 QTLs validated previous results.Thirty-five QTLs in BC/P populations explain 5.01%–22.09%of phenotype variation(PV).Among the 35 QTLs,23 QTLs are detected in BC/P population alone.Present study provides novel alleles of male parent for fiber quality traits with positive genetic effects.Particularly,qFS-Chr3–1 explains 22.09%of PV in BC/P population,which increaseds 0.48 cN·tex−1 for fiber strength.A total of 7,2,8,2 and 6 QTLs explain over 10.00%of PV for fiber length,fiber uniformity,fiber strength,fiber elongation and fiber micronaire,respectively.In RIL population,six common QTLs are detected in more than one environment:qFL-Chr1–2,qFS-Chr5–1,qFS-Chr9–1,qFS-Chr21–1,qFM-Chr9–1 and qFM-Chr9–2.Two common QTLs of qFE-Chr2–2(TMB2386-SWU12343)and qFM-Chr9–1(NAU2873-CGR6771)explain 22.42%and 21.91%of PV.The region between NAU4034 and TMB1296 harbor 30 genes(379 kb)in A05 and 42 genes(49 kb)in D05 for fiber length along the QTL qFL-Chr5–1 in BC/P population,respectively.In addition,a total of 142 and 46 epistatic QTLs and QTL×environments(E-QTLs and QQEs)are identified in recombinant inbred lines in paternal backcross(RIL-P)and paternal backcross(BC/P)populations,respectively.Conclusions:The present studies provide informative basis for improving cotton fiber quality in different populations.

Development of New Submergence Tolerant Rice Variety for Bangladesh Using Marker-Assisted Backcrossing

Submergence tolerant high yielding rice variety was developed using BR11 as a recipient parent applying foreground, phenotypic and background selection approaches. Recombinant selection was found essential to minimize linkage drag by BC2F2 generation. Without recombinant selection, the introgression size in the backcross recombinant lines （BRLs） was approximately 15 Mb on the carrier chromosome. The BRLs were found submergence tolerance compared to the check varieties under complete submergence for two weeks at Bangladesh Rice Research Institute, and produced higher yield compared to the isogenic Subl-line under controlled submerged condition. The BRL IR85260-66-654-Gaz2 was released as BRRI dhan52 in 2010, which was the first high yielding submergence tolerant variety in Bangladesh. BRRI dhan52 produced grain yield ranging from 4.2 to 5.2 t/hm2 under different flash flood prone areas of Bangladesh in three consecutive seasons. The study demonstrated the efficiency of recombinant selection and better adaptability of the newly released submergence tolerant high yielding variety in flash flood prone different areas of the country with respect to submergence tolerance and yield potential.

Transfer of Lysozyme Gene into indica Parents of Hybrid Rice by Backcrossing

A lysozyme gene resistant to rice blast was transferred from the donor transgenic japonica rice Zhonghua 9 （D2-1-2） into a sterile line Pei＇ai 64S（PA 64S） and restorer line 9311 of the two-line hybrid rice Liangyoupeijiu, and the restorer line Minghui 63 （MH 63） of three-line hybrid rice Shanyou 63 by successive backcrossing. The PCR analysis confirmed that foreign lysozyme gene was segregated at ratio of 1 ： 1 in backcross generations of B39311, B3MH63 and B2PA64S, and at ratio of 3 ： 1 in selfed generations of B2F2 9311, B2F2 MH63 and B1F2 PA64S, indicating that the foreign gene was stably inherited over successive generations as a dominant single copy gene. The resistance against rice blast in backcross or selfed generations and corresponding testcross combinations were investigated in 2003 and 2004. The results showed that the resistance of the transgenic rice to blast had a greater improvement than that of the corresponding recurrent parents or the corresponding check hybrid combinations. The resistance of the advanced backcross and selfed generations to rice blast is much stronger than that of the early generations. The study confirmed that transferring the lysozyme gene into hybrid parents by backcrossing was a simple and effective approach to develop new hybrid rice resistant to rice blast.

Genome-wide recombination variation in biparental segregating and reciprocal backcross populations provides information for introgression breeding in Brassica napus

Variation in patterns of recombination in plant genomes provides information about species evolution,genetic diversity and crop improvement. We investigated meiotic crossovers generated in biparental segregating and reciprocal backcross populations of the allopolyploid genome of rapeseed(Brassica napus)(AACC, 2n = 38). A structured set of 1445 intercrossed lines was derived from two homozygous de novo genome-assembled parents that represented the major genetic clusters of semi-winter Chinese and winter European rapeseeds, and was used to increase QTL resolution and achieve genomic reciprocal introgression. A high-density genetic map constructed with 6161 genetic bins and anchored centromere regions was used to establish the pattern of recombination variation in each chromosome. Around 93%of the genome contained crossovers at a mean rate of 3.8 c M Mb^(-1), with the remaining 7% attributed to centromeres or low marker density. Recombination hotspots predominated in the A genome, including two-thirds of those associated with breeding introgression from B. rapa. Genetic background might affect recombination variation. Introgression of genetic diversity from European winter to Chinese semi-winter rapeseed showed an increase in crossover rate under the semi-winter environment. Evidence for an elevated recombination rate having historically contributed to selective trait improvement includes accumulation of favorable alleles for seed oil content on hotspots of chromosome A10. Conversely, strong artificial selection may affect recombination rate variation, as appears to be the case with a coldspot resulting from strong selection for glucosinolate alleles on A09. But the cold region would be promptly reactivated by crossing design indicated by the pedigree analysis. Knowledge of recombination hotspots and coldspots associated with QTL for 22 traits can guide selection strategies for introgression breeding between the two gene pools. These results and rich genomic resources broaden our understanding of recombination behavior in allopolyploids and may advance rapeseed genetic improvement.

Application of Marker Assisted Backcrossing to Introgress the Submergence Tolerance QTL <i>SUB</i>1 into the Vietnam Elite Rice Variety-AS996

The result of the study contributes to enhancing and sustaining future livelihoods and food security in Vietnam vis-a-vis climate change. An innovative strategy based on marker-assisted backcrossing (MABC) was used to transform popular rice variety AS996 into the one can tolerate submergence while maintaining its original characteristics preferred by farmers and consumers. The submergence tolerance QTL SUB1 counts for up to 70% of the submergence tolerant and provides a marked improvement of submergence tolerance in all genetic backgrounds and environments tested so far. Parental diversity was carried out with 460 markers. Of which, 53 polymorphic markers were used for assessment on BC1F1, BC2F1 and BC3F1 generations. The best BC1F1 plant was P422 with highest recipient allele was 87.5%, while the additional chosen plants were P412, P428, P215 and P39 (81% - 84%). All these plants were used to develop BC2F1 generation. The six BC2F1 plants were used to develop BC3F1 and BC2F2 were the plants number P422-11 and P422-14 having 93.75% recipient alleles and P422-12, P422-3, P39-17, P39-25 having 92.25% recipient alleles. Total of 445 BC3F1 plants were confirmed the introgresion of SUB1 using ART5 and SC3. After three generations of backcrossing, application of MABC resulted in the best BC3F1 individual P422-14-177 with 100% of recipient alleles based on the number of 53 markers used with only the introgression size of SUB1 was 0.3Mb between ART5 and SC3. Phenotyping was carried out on BC3F1 and BC2F2 of the selected lines. The survival ratio of these selected lines and IR64SUB1 were the same. It convinced the successfully introgress SUB1 into AS996 rice variety. The breeding line BC4F1 having 100% genetic background of donor variety is ready for develop new submergence tolerant rice variety ASS996-SUB1 to cope with climate change.

The genetic variation of the backcross modified lines developed from the maize line 08-641 selected by different directions

In this study, two donaors CN962 and 8065 were used to improve the resistance to northern leaf blight of the recurrent parent inbred line 08-641 (R08). A total of 79 lines (BC2F4) were developed by a bidirectional selection based on the similarity and dissimilarity in the shape and color of seeds to R08.The genetic variation of these lines were analyzed by 44 pairs of SSR molecular markers, the result showed that a total of 272 alleles were detected in the improved lines and R08, 123 out of them were detected in the modified lines but discarded in R08. The modified line selected based on dissimialry in the shape and corlor of seeds to R08 have lower genetic similary between R08 than that between the lines selected based on similary in the shape and color of seeds and R08, and the genetic variation of these lines were wider. It concluded that when the backcross breeding were used to improve the maize inbred lines, multidirectional selection based on phenotypic value were contribute to create and keep genetic variation.

Combined Selection in Backcross Population of Papaya(Carica papaya L.)by the Mixed Model Methodology

The selection of superior genotypes based on the simultaneous response to several characteristics of agronomic importance is a key strategy to overcome the scarcity of available varieties of papaya. This study aimed to apply the combined selection by using distinct selection indexes based on both the genetic values obtained by the REML/BLUP methodology and the real measured values to select agronomically superior genotypes of papaya within backcross progenies. The combined selection was carried out based on genetic and phenotypic values, original and standardized, multiplied by the agronomic weights. The results of the analysis of genetic parameters indicate that the evaluated progenies have expressive genetic variability for the considered traits, and that there are real possibilities of genetic progress with the selection. Among the analyzed indexes, the one based on standardized genetic value presented greater consistency in the ranking of genetic material, demonstrating the advantage of data standardization. Five progenies belonging to the BC1 generation, and five to the BC3 generation were selected using this index. A total of 27 plants ag-ronomically superior were selected within the top five progenies and recommended for generation advance, 23 being selected by combined selection and 4 using the direct selection for the four mainly characters in papaya breeding program: production, pulp and fruit firmness and soluble solids. Beyond the selection of superior genotypes for the development of future inbred lines, this study also allowed defining the best strategy to apply the combined selection in papaya using pre-dicted breeding values obtained by BLUP. This strategy may allow higher accuracy in the selection process, thus increasing the chances of success of the breeding programs.

甘蓝型油菜pol CMS恢复系621R硼高效利用的遗传改良

油菜是需硼量最大的作物之一,在生产中需要额外增施硼肥,否则易出现大幅度减产。为了提高油菜对硼元素的利用效率,本研究以携带Bna.A03NIP5;1优良等位基因的硼高效利用材料2016-XFSB为供体亲本,以621R为轮回亲本,通过回交与MAS相结合的方法,将Bna.A03NIP5;1优良等位基因导入621R中,选育出拥有621R遗传背景并携带有Bna.A03NIP5;1优良等位基因的近等基因系材料621R^(NIP5;1A3),并在此基础上与细胞核雄性不育系RG430A配制了杂交种。利用水培和不同土质土壤栽培试验对621R和621R^(NIP5;1A3)及其杂种进行相关农艺性状的鉴定。结果表明,621R^(NIP5;1A3)及其杂交种对硼的利用效率有明显提升。农艺性状考察结果表明,621R^(NIP5;1A3)及其改良杂交种在生物量、株高、角果长、每角果粒数和千粒重等性状上有显著优势。本研究结果对油菜硼高效育种具有重要参考价值。

不同遗传背景的转Cry1C基因玉米品系的室内抗虫性鉴定

以转Cry1C基因的转基因玉米C492为供体,通过回交转育的方式将目标基因分别导入不同遗传背景的玉米自交系,获得转基因玉米自交系C492/N-76、C492/N202、C492/S273、C492/DH1901和C492/DH1904,采用室内离体组织生测的方法研究各品系对玉米螟和草地贪夜蛾的抗虫性。结果表明:转基因玉米C492和5个不同遗传背景自交系均表现出高抗玉米螟,虽对草地贪夜蛾的抗性有一定差异,但接虫6 d后幼虫死亡率均达到80%以上。这说明转基因玉米C492和5个不同遗传背景自交系可用于抗虫转基因玉米新品种培育,具有较好的商业化应用前景。

主栽小麦品种中5+10亚基对品质改良的影响

利用生化标记和选择性回交 (5～ 6次 )的方法将 5 +10亚基转移到黑龙江省主栽小麦品种克旱 9、克丰3、龙麦 2 0和垦大 4中。同一品种的 5 +10亚基类型与 2 +12或 3+12亚基类型相比 ,蛋白质和干面筋含量没有差别 (P >0 .1) ,湿面筋与干面筋的比值低 2 .9%～ 5 .0 % (P <0 .0 1) ,Zeleny沉降值与干面筋的比值高4 .5 %～ 13.4 %(P <0 .0 5 ) ,软化度低 15～ 2 5FU(P <0 .0 1) ,最大阻力高 82～ 193EU(P <0 .0 5 )。讨论了这种方法在改造现有小麦主栽品种中的应用。

水稻品种倒伏指数QTL分析

利用由98个株系组成的Nipponbare(粳) /Kasalath(籼)∥Nipponbare回交重组自交系群体,对水稻倒伏指数与株高、茎粗及单株生物量等性状进行了相关分析,并对水稻倒伏相关性状QTL进行了分子标记定位和遗传效应分析。结果表明,株高、茎粗、单株生物量3性状与倒伏指数的相关系数均达1%显著水平。利用基于性状标记多元线性回归分析方法,检测到与水稻倒伏指数、茎粗、株高和单株生物量有关的QTL共12个,其中与株高有关的3个分别位于第1、5和6染色体,对性状的解释率为11%～2 4 % ;与单株生物量有关的2个分布于第1和8染色体,对性状的解释率为9%～14 % ;与茎粗有关的3个分布在第1、3和6染色体,对性状的解释率为11%～2 5 % ;控制倒伏指数的4个,分别位于第1、3、8和12染色体上,对表型性状变异的解释率为10 %～18%。在第1染色体R2 4 14 C86标记区间同时检测到控制倒伏指数、株高和单株生物量的QTL ,表明该染色体区域在控制水稻倒伏性状方面起着重要的作用,同时也在一定程度上解释了株高、单株生物量和倒伏指数的显著相关。在第3染色体上检测到的qLI 3表现为增强水稻的抗倒能力,抗倒加性效应来自于高秆籼稻品种Kasalath的等位基因,且与株高、单株生物量等性状QTL不存在遗传连锁关系,有望用于中、高秆抗倒育种中分子标?

不同供体及不同回交次数对玉米自交系R08的改良效应

以R08为轮回亲本,18个优良自交系为供体亲本,经过不同代的回交和自交,选育出遗传背景与R08相近、但相互之间又存在一定差异的BC1F3和BC2F2各18个R08改良系。通过抗病性鉴定、配合力及SSR分子标记分析,探讨不同供体及不同回交次数对R08的改良效果。结果表明,36个改良系中,29个抗或高抗大斑病,大部分改良系的多数产量性状一般配合力(GCA)与R08相比并无下降或有所提高;相同供体不同回交次数选系的比较显示,对大斑病抗性的改良,回交1次自交2次(BC1F3)优于回交2次自交1次(BC2F2),且改良后代选系多数产量性状GCA大体相当;相同回交次数不同供体选系的比较表明,供体对回交后代的影响较大,供体不同回交后代选系大斑病抗性及多数产量性状GCA存在较大的差异;SSR分子标记研究结果在一定程度上揭示相同供体不同回交次数所创造的遗传变异无明显差异,相同回交次数不同供体选系在分子水平上存在较大差异;供体昌7-2和川321对改良R08的大斑病抗性和产量性状GCA作用较大,属优良供体亲本;w4-1和w10-1属回交改良优良选系。因此,利用回交法改良玉米自交系,在选准供体亲本的基础上,回交1次后,在自交过程中加强目标性状的鉴定选择及配合力测定,可提高回交改良的育种效率。

利用回交导入系群体发掘水稻种质资源中的有利耐盐QTL

以中等感盐籼稻IR64与粳稻Tarom Molaii培育的85个BC2F8回交导入系为材料,定位苗期在140mmolL-1NaCl胁迫下影响叶片盐害级别、幼苗存活天数、地上部和根部的K+、Na+浓度等6个耐盐相关性状的QTL。幼苗存活天数与地上部Na+浓度呈极显著负相关,与地上部K+浓度呈显著正相关,与根部K+、Na+浓度无关,表明叶片盐害是由于地上部Na+积累过多造成的。根部K+浓度与Na+浓度高度正相关,但与地上部的K+、Na+浓度均无关,表明根对K+、Na+的离子吸收与向地上部运输存在不同的机制。检测到影响6个耐盐相关性状的23个QTL,包括影响叶片盐害级别的5个、幼苗存活天数的6个、地上部K+浓度的4个、地上部Na+浓度的4个、根部K+浓度的1个和根部Na+浓度的3个。影响地上部K+、Na+浓度与影响根部K+、Na+浓度的QTL分布在不同基因组区域,进一步表明根和茎对K+、Na+的吸收存在不同的遗传机制。通过比较图谱,发现影响耐盐相关性状的23个QTL中有12个(占52.2%)与以往不同群体中影响耐盐相关性状的QTL定位在同一或相邻的染色体区域。其中在第2染色体RM240～RM112区间检测到1个影响地上部所有4个耐盐相关性状的主效QUL,其增加耐盐性的有利基因来自供体Tarom Molaii,适宜用作标记辅助选择耐盐性的遗传改良。

玉米衔接式单片段导入系群体的构建和评价

以生产上广泛种植的玉米杂交种豫玉22的亲本自交系87-1和综3为受体亲本,以糯质、抗病性较好的玉米自交系衡白522为供体亲本,采用回交和自交的方法,结合SSR分子标记辅助选择,分别构建了以87-1和综3为背景的衔接式玉米单片段导入系群体,并对其遗传背景、导入片段大小、数目和覆盖率等进行了评价。结果表明,87-1背景的导入系群体导入了40个供体片段,片段长度介于0.03～342.8cM,平均长度为91.1cM,导入片段总长为3643.9cM,覆盖率为48.9%;综3背景的导入系群体导入了78个供体片段,片段长度介于0.03～343.4cM,平均长度为75.5cM,导入片段总长为5895.2cM,覆盖率为79.2%。

导入热带种质的温带玉米自交系的利用潜力

用5个热带及亚热带玉米自交系和5个导入热带种质并经连续回交改良的温带玉米自交系,采用Griffing双列杂交方法III杂交,共配制90个杂交组合。2008年和2009年以大面积推广杂交种云瑞6号为对照,对供试自交系进行配合力、杂种优势及利用潜力研究。结果表明,导入热带种质并经连续回交改良的温带玉米自交系YML598、YML58的多数性状一般配合力效应为极显著正值,在杂交育种中具有较大的利用潜力;单株产量配合力效应值与诸多产量影响因素的配合力效应值密切相关,雌雄间隔期、秃尖与单株产量呈负相关,而其他性状与单株产量呈正相关;产量对照优势H≥10%的组合大多为热带、亚热带种质×改良温带种质,单株产量特殊配合力效应为极显著正值的组合均为热带、亚热带种质×改良温带种质,说明热带、亚热带玉米种质与经热带种质改良后的温带玉米种质之间仍具有较强的杂种优势,且导入热带种质的温带系与热带、亚热带供体系的杂种优势仍然存在,其所属的杂种优势群并未改变。以热带、亚热带玉米种质为供体,采用连续回交的方法改良温带玉米自交系是利用热带、亚热带玉米种质的有效方法。