Validation of <Emphasis Type="Italic">DGAT1</Emphasis>-<Emphasis Type="Italic">2</Emphasis> polymorphisms associated with oil content and development of functional markers for molecular breeding of high-oil maize

The gene encoding acyl-CoA:diacylglycerol acyltransferase (DGAT1-2) is a key quantitative trait locus that controls oil content and oleic acid composition in maize kernels. Here we re-sequenced the DGAT1-2 region responsible for oil variation in a maize landrace set and in 155 inbred lines (35 high-oil and 120 normal lines). The high-oil DGAT1-2 allele was present in most Northern Flint and Southern Dent populations but was absent in five of eight Corn Belt Dent open-pollinated populations and in most of the earlier inbred lines. Loss of the high-oil DGAT1-2 allele possibly resulted from genetic drift in the early twentieth century when a few Corn Belt Dent populations were selected for the development of high-grain-yield inbred lines. Association analysis detected significant effects of two PCR-based functional markers (HO06 and DGAT04; developed based on DGAT1-2 polymorphisms) on kernel oil content and oleic acid composition using the 155 inbred lines. Zheng58 and Chang7-2, the parent inbred lines of elite hybrid Zhengdan958, were used to transfer the favorable allele from the high-oil line By804 using marker-assisted backcrossing with the two functional markers. In BC5F2:3 populations, oil content of the three genotypes (−/−, +/−, and +/+) was, respectively, 3.37, 4.20, and 4.61% (Zheng58 recipient line) and 4.14, 4.67, and 5.25% (Chang7-2 recipient line). Oil content of homozygous kernels containing the high-oil DGAT1-2 allele increased by 27–37% compared with recurrent parents. Hence, these functional markers can be used to re-introduce the high-oil DGAT1-2 allele into modern inbred lines for increased oil content through marker-assisted backcrossing.     

Differential effect of the nitrogen form on the leaf gas exchange,amino acid composition,and antioxidant response of sweet pepper at elevated CO<Subscript>2</Subscript>

Cell wall invertases play an important role in plant growth and development, especially in the grain filling of crop plants. However, their potential in high yield crop breeding has not been investigated. In this study, the main hybrid maize cultivar Zheng Dan 958 (ZD958) was used as a basic variety to assess whether ZmGIF1, a cell wall invertase from maize, can be used to breed new cultivars with higher grain yields. ZmGIF1 expression, cell wall invertase activity, and sugar content in different parental inbred cultivars were compared with those in Zheng 58 and Chang 7-2, the parental inbred cultivars of ZD958. Parental cultivars which showed higher ZmGIF1 expression and invertase activity were selected and intercrossed to improve the expression of ZmGIF1. Compared with the basic cultivar ZD958, higher ZmGIF1 expression and cell wall invertase activity were observed in most hybrid F1 lines, leading to increased grain yield in them. All these results suggest that the expression of ZmGIF1 can be manipulated using different parental cultivars to increase the grain yield of their hybrid F1 progenies.     

8个合成群体改良玉米杂交种郑单958的育种潜力分析

玉米群体含有有利等位基因, 可作为改良杂交种的优异种质。针对持续改良我国主要玉米杂交种郑单958产量性状和商品品质的需求, 文章以8个合成群体为供体, 郑单958亲本自交系为受体, 组配16个测交组合。2009和2010年分别在北京顺义和河南新乡测量产量和籽粒容重。4个遗传参数评价显示, 合成群体可以作为新的有利等位基因供体改良杂交种性状, 其中WBMC-4和陕综3号两个群体具有同时改良杂交种产量和籽粒容重的潜力, 可分别用于改良亲本自交系郑58和昌7-2, 以及拓宽我国主要玉米类群PA和四平头的种质基础。     

Study on diversity of endophytic bacterial communities in seeds of hybrid maize and their parental lines

The seeds of plants are carriers of a variety of beneficial bacteria and pathogens. Using the non-culture methods of building 16S rDNA libraries, we investigated the endophytic bacterial communities of seeds of four hybrid maize offspring and their respective parents. The results of this study show that the hybrid offspring Yuyu 23, Zhengdan958, Jingdan 28 and Jingyu 11 had 3, 33, 38 and 2 OTUs of bacteria, respectively. The parents Ye 478, Chang 7-2, Zheng 58, Jing 24 and Jing 89 had 12, 36, 6, 12 and 2 OTUs, respectively. In the hybrid Yuyu 23, the dominant bacterium Pantoea (73.38?%) was detected in its female parent Ye 478, and the second dominant bacterium of Sphingomonas (26.62?%) was detected in both its female (Ye 478) and male (Chang 7-2) parent. In the hybrid Zhengdan 958, the first dominant bacterium Stenotrophomonas (41.67?%) was detected in both the female (Zheng 58) and male (Chang 7-2) parent. The second dominant bacterium Acinetobacter (9.26?%) was also the second dominant bacterium of its male parent. In the hybrid Jingdan 28, the second dominant bacterium Pseudomonas (12.78?%) was also the second dominant bacterium of its female parent, and its third dominant bacterium Sphingomonas (9.90?%) was the second dominant bacterium of its male parent and detected in its female parent. In the hybrid Jingyu 11, the first dominant bacterium Leclercia (73.85?%) was the third dominant bacterium of its male parent, and the second dominant bacterium Enterobacter (26.15?%) was detected in its male parent. As far as we know, this was the first research reported in China on the diversity of the endophytic bacterial communities of the seeds of various maize hybrids with different genotypes.     

Marker-assisted selection and evaluation of high oil in vivo haploid inducers in maize

Doubled haploid technology, which is used to rapidly purify genetic resources, is one of the key technologies in modern maize breeding. In a previous study, the major quantitative trait locus qhir1, which influences in vivo haploid induction, was narrowed down to a 243-kb region, which made it feasible to use marker-assisted selection (MAS) for inducer development. Recently, a new method was developed for haploid identification using oil content (OC). The objective of this study was to develop high oil inducer lines using MAS of the qhir1 locus. We constructed an F₂ population, two backcross populations that were backcrossed to the inducer CAU5 (BC₁F₁-CAU5) and the high oil inbred line GY923 (BC₁F₁-GY923), respectively, which was derived from the cross GY923 × CAU5, and subjected continuous selfing to develop high oil inducer lines. In each cycle, three different parameters including kernel OC, marker genotype at qhir1 and haploid induction rate (HIR) were used for pedigree selection. Three candidate high oil inducer lines were developed, with an OC of approximately 8.5 %, an HIR of approximately 8 % and superior agronomic performance, which are suitable values for the application of these lines to haploid identification by OC. Our results confirm the notion that HIR selection combined with MAS for qhir1 is an effective approach to haploid inducer breeding. In addition, we determined that the accuracy of haploid identification by OC is influenced by the female germplasm resource and the high oil inducer and that appropriate critical points for OC can balance the false discovery rate and false negative rate.     

Proteomic Analysis Demonstrates that Elongation of Below-Ear Internodes in Maize is Related to Three Different Hormones

In many grain crops, the length of internodes below ears is related to lodging resistance in the field. To clarify the relationship between internode morphological differentiation and internode proteins during primary elongation stages in maize (Zea mays L.), we used proteomics analysis to explore factors regulating internodes in eight elite inbred maize lines: Zong3, Yu87-1, Xun9058, Xun928, Chang7-2, Zheng58, P2, and A50—the parents of four commercial hybrids in China (Yuyu22, Xundan20, Zhengdan958, and Jinsai6850). A total of 66 protein spots corresponding to 48 non-redundant proteins were identified in developing seventh to ninth leaf internodes. Of these spots, seven spots corresponding to six non-redundant proteins were related to the gibberellin (GA) pathway. Nineteen protein spots corresponding to 13 non-redundant proteins were related to the auxin (IAA) pathway, and 31 protein spots corresponding to 20 non-redundant proteins were associated with ethylene biosynthesis. A correlation analysis revealed that GA and IAA contents are negatively correlated with internode length, with the first hormone more strongly length-correlated than the second.     

Characterization of the quantitative trait locus OilA1 for oil content in Brassica napus

Increasing seed oil content has become one of the most important breeding criteria in rapeseed (Brassica napus). However, oil content is a complex quantitative trait. QTL mapping in a double haploid population (SG population) emerging from a cross between a German (Sollux) and Chinese (Gaoyou) cultivars revealed one QTL for oil content on linkage group A1 (OilA1), which was mapped to a 17 cM genetic interval. To further validate and characterize the OilA1, we constructed a high-resolution map using B. rapa sequence resources and developed a set of near-isogenic lines (NILs) by employing a DH line SG-DH267 as donor and Chinese parent Gaoyou as recurrent background. The results showed highly conserved synteny order between B. rapa and B. napus within the linkage group A1 and revealed a possible centromere region between two markers ZAASA1-38 and NTP3 (2.5 cM). OilA1 was firstly validated by 250 BC₅F₂ plants and was confirmed in a 10.6 cM interval between the markers ZAASA1-47 and ZAASA1-77. Further substitution mapping was conducted by using two generations of QTL-NILs, 283 lines from eight BC₅F_3:4 families and 428 plants from six BC₅F₄ sub-NILs and thus narrowed the OilA1 interval to 6.9 cM and 4.3 cM (1.4 Mb), respectively. Field investigations with two replications using homozygous BC₅F_3:4 sister sub-NILs indicated that NILs, which carry a Sollux chromosome segment across the target region showed significant higher oil content (1.26 %, p < 0.001) than their sister NILs containing Gaoyou chromosome. The OilA1 locus is of particular interest for breeding purpose in China because 80 % of Chinese cultivars do not carry this desirable allele.     

Quantitative trait locus analysis of unsaturated fatty acids in a recombinant inbred population of soybean

Soybean [Glycine max (L.) Merr.] is an important oilseed crop which produces about 30 % of the world’s edible vegetable oil. The quality of soybean oil is determined by its fatty acid composition. Soybean oil high in oleic and low in linolenic fatty acids is desirable for human consumption and other uses. The objectives of this study were to identify quantitative trait loci (QTLs) for unsaturated fatty acids and to evaluate the genetic effects of single QTL and QTL combinations in soybean. A population of recombinant inbred lines derived from the cross of SD02-4-59 × A02-381100 was evaluated for fatty acid content in seven environments. In total, 516 polymorphic single nucleotide polymorphism markers, 477 polymorphic simple sequence repeat markers and three GmFAD3 genes were used to genotype the mapping population. By using the composite interval mapping and/or the interval mapping method, a total of 15 QTLs for the three unsaturated fatty acids were detected in more than two environments. Two QTLs for oleic acid on linkage groups G [chromosome (Chr) 18] (qOLE-G) and J (Chr 16) (qOLE-J), three QTLs for linoleic acid on linkage groups A1 (Chr 5) (qLLE-A1) and G (Chr 18) (qLLE-G-1 and qLLE-G-2), and five QTLs for linolenic acid on linkage groups C2 (Chr 6), D1a (Chr 1), D1b (Chr 2), F (Chr 13) and G (Chr 18) were consistently detected in at least three individual environments and the average data over all environments. Significant QTL × QTL interactions were not detected. However, significant QTL × environment interactions were detected for all the QTLs which were repeatedly detected. Some QTLs reported previously were confirmed, and seven new QTLs (two for oleic acid, two for linoleic acid and three for linolenic acid) were identified in this study. Comparisons of two-locus and three-locus combinations indicated that cumulative effects of QTLs were significant for all the three unsaturated fatty acids. QTL pyramiding by molecular marker-assisted breeding would be an appropriate strategy for the improvement of unsaturated fatty acids in soybean.     

Mapping quantitative trait loci controlling oil content,oleic acid and linoleic acid content in sunflower (<Emphasis Type="Italic">Helianthus annuus</Emphasis> L.)

Sunflower oil with high oleic acid content is in great demand due to its nutritional as well as industrial benefits. The trait is mainly controlled by dominant alleles at a major gene, Ol, with other modifiers. The objectives of this research were to map the oil content, oleic acid and linoleic acid content in sunflower seeds. An F2 mapping population from cytoplasmic male-sterile line COSF 7A (33–35 % oleic acid) and high oleic acid inbred line HO 5–13 (88–90 % oleic acid) was developed and phenotyped for oil content, oleic acid and linoleic acid content at the F2 seed level. High phenotypic and genotypic coefficients of variation were recorded for oleic acid and linoleic acid content. High heritability and high genetic advance as percent of mean was recorded for oleic acid and linoleic acid content. This indicated the presence of the additive type of gene action controlling the traits oleic acid content and linoleic acid content. The Ol gene was mapped to linkage group (LG) 14 and tightly linked to the marker HO_Fsp_b. In addition, two more quantitative trait loci (QTLs) for oleic acid content were identified in LG8 and LG9. Two QTLs for oil content and two QTLs for linoleic acid content were also identified. All these QTLs explained over 10 % of phenotypic variation. A study was conducted with 13 genotypes differing in oil quality as well as quantity over three seasons to assess the reliability of the identified QTLs over seasons. It resulted in the identification of two potential QTLs for oleic acid as well as linoleic acid content with the markers ORS 762 and HO_Fsp_b. These markers explained more than 57.6–66.6 % of phenotypic variation. Hence it can be concluded that these markers/QTLs would be useful in the marker-assisted selection breeding programme to improve oil quality. The present study also indicated the presence of at least two other genomic regions controlling oleic and linoleic acid content in sunflower.     

Improvement of two traditional Basmati rice varieties for bacterial blight resistance and plant stature through morphological and marker-assisted selection

Bacterial blight (BB) is a major production threat to Basmati, the aromatic rice prized for its unique quality. In order to improve the BB resistance of two elite, traditional BB-susceptible Basmati varieties (Taraori Basmati and Basmati 386), we utilized the strategy of limited marker-assisted backcrossing for introgression of two major BB resistance genes, Xa21 and xa13, coupled with phenotype-based selection for improvement of their plant type and yield. Improved Samba Mahsuri, an elite high-yielding, fine-grain-type BB-resistant rice variety served as donor for BB resistance. Backcross-derived improved Basmati lines at BC1F5 possessing a single resistance gene (i.e. either Xa21 or xa13) displayed moderate resistance to BB, while lines possessing both Xa21 and xa13 showed significantly higher levels of resistance. Two-gene pyramid lines (Xa21 + xa13) possessing good grain and cooking quality similar to their respective traditional Basmati parents, short plant stature (<110 cm plant height) and higher grain yield than the recurrent parent(s) were identified and advanced. This work demonstrates the successful application of marker-assisted selection in conjunction with phenotype-based selection for targeted introgression of multiple resistance genes into traditional Basmati varieties along with improvement of their plant stature and yield.     

Fine-mapping of QTLs for individual and total isoflavone content in soybean (<Emphasis Type="Italic">Glycine max L.</Emphasis>) using a high-density genetic map

Key message

Fifteen stable QTLs were identified using a high-density soybean genetic map across multiple environments. One major QTL, qIF5-1, contributing to total isoflavone content explained phenotypic variance 49.38, 43.27, 46.59, 45.15 and 52.50%, respectively.

Abstract

Soybeans (Glycine max L.) are a major source of dietary isoflavones. To identify novel quantitative trait loci (QTL) underlying isoflavone content, and to improve the accuracy of marker-assisted breeding in soybean, a valuable mapping population comprised of 196 F_7:8–10 recombinant inbred lines (RILs, Huachun 2 × Wayao) was utilized to evaluate individual and total isoflavone content in plants grown in four different environments in Guangdong. A high-density genetic linkage map containing 3469 recombination bin markers based on 0.2 × restriction site-associated DNA tag sequencing (RAD-seq) technology was used to finely map QTLs for both individual and total isoflavone contents. Correlation analyses showed that total isoflavone content, and that of five individual isoflavone, was significantly correlated across the four environments. Based on the high-density genetic linkage map, a total of 15 stable quantitative trait loci (QTLs) associated with isoflavone content across multiple environments were mapped onto chromosomes 02, 05, 07, 09, 10, 11, 13, 16, 17, and 19. Further, one of them, qIF5-1, localized to chromosomes 05 (38,434,171–39,045,620 bp) contributed to almost all isoflavone components across all environments, and explained 6.37–59.95% of the phenotypic variance, especially explained 49.38, 43.27, 46.59, 45.15 and 52.50% for total isoflavone. The results obtained in the present study will pave the way for a better understanding of the genetics of isoflavone accumulation and reveals the scope available for improvement of isoflavone content through marker-assisted selection.

     

Isolation and characterization of the omega-6 fatty acid desaturase (FAD2) gene family in the allohexaploid oil seed crop Crambe abyssinica Hochst

Crambe (Crambe abyssinica Hochst ex. R. E. Fries) is an ideal crop for industrial oil production because of its high erucic acid content (C22:1, approx. 60 %) in its seed oil. The value of crambe oil can be improved by increasing C22:1 content or reducing polyunsaturated fatty acids (PUFA). The FAD2 gene plays a critical role in PUFA biosynthesis. To identify targets for breeding, we characterized FAD2 in crambe for copy number and expression profile. Seven copies of FAD2 were detected in allohexaploid crambe. Three genes (CaFAD2-C1, -C2 and -C3) were expressed in multiple tissues, including root, seedling, leaf, flower, bud and developing seeds. In developing seeds, the expression of these genes was upregulated with CaFAD2-C3, being expressed predominantly with a peak at 20 days after pollination. This gene is therefore a promising candidate gene for determining PUFA levels in seed oil. Four other FAD2 genes were considered to be “pseudo-genes” as they harbour internal stop codons and were not expressed. Among the six crambe varieties with consistent variation in oil composition, no nucleotide polymorphisms were found in the CaFAD2-C1, -C2 and -C3 genes. In seeds at 30 days after pollination, statistically significant expression level polymorphisms for only one gene, CaFAD2-C2, was found among the varieties. However, although significantly different, the difference in expression was small and did not explain the variation in oil composition. Given the absence of genetic variation in CaFAD2 genes in crambe breeding lines, breeding for high erucic acid content calls for a molecular breeding approach whereby mutations are chemically induced to increase the genetic variation.     

Mapping of quantitative trait loci for oil content in cottonseed kernel

Oil content in cottonseed is a major quality trait which when improved through breeding could enhance the competitiveness of cottonseed oil among other vegetable oils. Cottonseed oil content is a quantitative trait controlled by genes in the tetraploid embryo and tetraploid maternal plant genomes, and the knowledge of quantitative trait loci (QTLs) and the genetic effects related to oil content in both genomes could facilitate the improvement in its quality and quantity. However, till date, QTL mapping and genetic analysis related to this trait in cotton have only been conducted in the tetraploid embryo genome. In the current experiment, an IF₂ population of cottonseed kernels from the random crossing of 188 intraspecific recombinant inbred lines which were derived from the hybrid of two parents, HS46 and MARCABUCAG8US-1-88, were used to simultaneously locate QTLs for oil content in the embryo and maternal plant genomes. The four QTLs found to be associated with oil content in cottonseed were: qOC-18-1 on chromosome 18; qOC-LG-11 on linkage group 11; qOC-18-2 on chromosome 18; and qOC-22 on chromosome 22. At a high selection threshold of 0.05, there was strong evidence linking the QTLs above the oil content in cottonseed. Embryo additive and dominant effects from the tetraploid embryo genome, as well as maternal additive effects from the tetraploid maternal plant genome were found to be significant contributors to genetic variation in cottonseed oil content.     

Identification and fine mapping of qRBSDV-6 MH , a major QTL for resistance to rice black-streaked dwarf virus disease

Rice black streaked-dwarf virus (RBSDV) disease is recently expanding in southern China and poses a serious threat to rice crops. Few studies related to the genetics and breeding of RBSDV resistance have been reported. We have previously mapped a number of quantitative trait loci (QTLs) for RBSDV resistance by using a recombinant inbred line population of ‘Zhenshan 97’ (ZS97, susceptible)/‘Minghui 63’ (MH63, resistant) with natural infection data in two locations. In the present study, we confirmed the presence of a number of resistant QTLs on chromosomes 6, 7, and 9 from MH63 by using the same population in four different locations. We then focused on a major QTL, qRBSDV-6 ^MH , on chromosome 6 and introduced it into a highly susceptible japonica rice variety, ‘Huaidao 5’, using MH63 as the donor via marker-assisted selection, to generate seven backcross inbred lines (BILs). Natural infection and artificial inoculation-based tests revealed that all of the BILs had a significantly higher resistance to RBSDV than the recurrent parent. These results demonstrate that qRBSDV-6 ^MH is a stable major resistance QTL of high breeding value. We also constructed a set of chromosome segment substitution lines (CSSLs) specific to the qRBSDV-6 ^MH region and these used as fine mapping population. Combining the genotypes of CSSLs with the phenotypes from natural infection data in a highly RBSDV epidemic area during two different sowing seasons, we were able to precisely map qRBSDV-6 ^MH to the markers S18 and S23 at a physical distance of 627.6 kb on the Nipponbare reference genome.     

Linkage mapping and identification of QTL affecting deoxynivalenol (DON) content (Fusarium resistance) in oats (Avena sativa L.)

Mycotoxins caused by Fusarium spp. is a major concern on food and feed safety in oats, although Fusarium head blight (FHB) is often less apparent than in other small grain cereals. Breeding resistant cultivars is an economic and environment-friendly way to reduce toxin content, either by the identification of resistance QTL or phenotypic evaluation. Both are little explored in oats. A recombinant-inbred line population, Hurdal × Z595-7 (HZ595, with 184 lines), was used for QTL mapping and was phenotyped for 3 years. Spawn inoculation was applied and deoxynivalenol (DON) content, FHB severity, days to heading and maturity (DH and DM), and plant height (PH) were measured. The population was genotyped with DArTs, AFLPs, SSRs and selected SNPs, and a linkage map of 1,132 cM was constructed, covering all 21 oat chromosomes. A QTL for DON on chromosome 17A/7C, tentatively designated as Qdon.umb-17A/7C, was detected in all experiments using composite interval mapping, with phenotypic effects of 12.2–26.6 %. In addition, QTL for DON were also found on chromosomes 5C, 9D, 13A, 14D and unknown_3, while a QTL for FHB was found on 11A. Several of the DON/FHB QTL coincided with those for DH, DM and/or PH. A half-sib population of HZ595, Hurdal × Z615-4 (HZ615, with 91 lines), was phenotyped in 2011 for validation of QTL found in HZ595, and Qdon.umb-17A/7C was again localized with a phenotypic effect of 12.4 %. Three SNPs closely linked to Qdon.umb-17A/7C were identified in both populations, and one each for QTL on 5C, 11A and 13A were identified in HZ595. These SNPs, together with those yet to be identified, could be useful in marker-assisted selection to pyramiding resistance QTL.     

The control of seed oil polyunsaturate content in the polyploid crop species Brassica napus

Many important plant species have polyploidy in their recent ancestry, complicating inferences about the genetic basis of trait variation. Although the principal locus controlling the proportion of polyunsaturated fatty acids (PUFAs) in seeds of Arabidopsis thaliana is known (fatty acid desaturase 2; FAD2), commercial cultivars of a related crop, oilseed rape (Brassica napus), with very low PUFA content have yet to be developed. We showed that a cultivar of oilseed rape with lower than usual PUFA content has non-functional alleles at three of the four orthologous FAD2 loci. To explore the genetic basis further, we developed an ethyl methanesulphonate mutagenised population, JBnaCAB_E, and used it to identify lines that also carried mutations in the remaining functional copy. This confirmed the hypothesised basis of variation, resulting in an allelic series of mutant lines showing a spectrum of PUFA contents of seed oil. Several lines had PUFA content of ~6 % and oleic acid content of ~84 %, achieving a long-standing industry objective: very high oleic, very low PUFA rapeseed without the use of genetic modification technology. The population contains a high rate of mutations and represents an important resource for research in B. napus.     

Identification of the quantitative trait loci (QTL) underlying water soluble protein content in soybean

Water soluble protein content (SPC) plays an important role in the functional efficacy of protein in food products. Therefore, for the identification of quantitative trait loci (QTL) associated with SPC, 212 F_2:9 lines of the recombinant inbred line (RIL) population derived from the cross of ZDD09454 × Yudou12 were grown along with the parents, in six different environments (location × year) to determine inheritance and map solubility-related genes. A linkage map comprising of 301 SSR markers covering 3,576.81 cM was constructed in the RIL population. Seed SPC was quantified with a macro-Kjeldahl procedure in samples collected over multiple years from three locations (Nantong in 2007 and 2008, Zhengzhou in 2007 and 2008, and Xinxiang in 2008 and 2009). SPC demonstrated transgressive segregation, indicating a complementary genetic structure between the parents. Eleven putative QTL were associated with SPC explaining 4.5–18.2 % of the observed phenotypic variation across the 6 year/location environments. Among these, two QTL (qsp8-4, qsp8-5) near GMENOD2B and Sat_215 showed an association with SPC in multiple environments, suggesting that they were key QTL related to protein solubility. The QTL × environment interaction demonstrated the complex genetic mechanism of SPC. These SPC-associated QTL and linked markers in soybean will provide important information that can be utilized by breeders to improve the functional quality of soybean varieties.     

转基因玉米HGK60在不同遗传背景下抗虫性鉴定及农艺性状分析

为研究转基因玉米HGK60在不同遗传背景下遗传稳定性和抗虫效果,利用转Bt cry1Ah基因的转基因玉米HGK60为供体,通过回交转育的方式将cry1Ah基因分别导入玉米自交系郑58、昌7-2、lx05-4、lx03-2,获得转基因玉米自交系HGK60-郑58、HGK60-昌7-2、HGK60-lx03-2、HGK60-lx05-4,并杂交获得HGK60-郑单958（HGK60-郑58 × HGK60-昌7-2）和HGK60-鲁单9066（HGK60-lx05-4 × HGK60-lx03-2）,转化体特异性PCR证明cry1Ah基因已转入不同遗传背景玉米中,ELISA检测不同遗传背景转基因玉米叶片中Cry1Ah蛋白表达情况,结果表明在不同遗传背景玉米自交系和杂交种中Cry1Ah蛋白表达没有显著差异;田间人工接虫和室内玉米螟抗虫性鉴定结果表明,不同遗传背景的转基因玉米高抗玉米螟,室内接虫后4 d幼虫死亡率达到100%;对不同遗传背景转基因玉米HGK60进行农艺性状分析,结果显示与受体对照玉米相比,两者之间农艺性状没有显著差异,转基因玉米HGK60可用于抗虫玉米品种的选育。     

Genetic control of soybean seed oil: I. QTL and genes associated with seed oil concentration in RIL populations derived from crossing moderately high-oil parents

Soybean seed is a major source of oil for human consumption worldwide and the main renewable feedstock for biodiesel production in North America. Increasing seed oil concentration in soybean [Glycine max (L.) Merrill] with no or minimal impact on protein concentration could be accelerated by exploiting quantitative trait loci (QTL) or gene-specific markers. Oil concentration in soybean is a polygenic trait regulated by many genes with mostly small effects and which is negatively associated with protein concentration. The objectives of this study were to discover and validate oil QTL in two recombinant inbred line (RIL) populations derived from crosses between three moderately high-oil soybean cultivars, OAC Wallace, OAC Glencoe, and RCAT Angora. The RIL populations were grown across several environments over 2 years in Ontario, Canada. In a population of 203 F_3:6 RILs from a cross of OAC Wallace and OAC Glencoe, a total of 11 genomic regions on nine different chromosomes were identified as associated with oil concentration using multiple QTL mapping and single-factor ANOVA. The percentage of the phenotypic variation accounted for by each QTL ranged from 4 to 11 %. Of the five QTL that were tested in a population of 211 F_3:5 RILs from the cross RCAT Angora × OAC Wallace, a “trait-based” bidirectional selective genotyping analysis validated four QTL (80 %). In addition, a total of seven two-way epistatic interactions were identified for oil concentration in this study. The QTL and epistatic interactions identified in this study could be used in marker-assisted introgression aimed at pyramiding high-oil alleles in soybean cultivars to increase oil concentration for biodiesel as well as edible oil applications.     

Fine mapping of Co-x,an anthracnose resistance gene to a highly virulent strain of Colletotrichum lindemuthianum in common bean

Key message

The Co - x anthracnose R gene of common bean was fine-mapped into a 58 kb region at one end of chromosome 1, where no canonical NB-LRR-encoding genes are present in G19833 genome sequence.

Abstract

Anthracnose, caused by the phytopathogenic fungus Colletotrichum lindemuthianum, is one of the most damaging diseases of common bean, Phaseolus vulgaris. Various resistance (R) genes, named Co-, conferring race-specific resistance to different strains of C. lindemuthianum have been identified. The Andean cultivar JaloEEP558 was reported to carry Co-x on chromosome 1, conferring resistance to the highly virulent strain 100. To fine map Co-x, 181 recombinant inbred lines derived from the cross between JaloEEP558 and BAT93 were genotyped with polymerase chain reaction (PCR)-based markers developed using the genome sequence of the Andean genotype G19833. Analysis of RILs carrying key recombination events positioned Co-x at one end of chromosome 1 to a 58 kb region of the G19833 genome sequence. Annotation of this target region revealed eight genes: three phosphoinositide-specific phospholipases C (PI-PLC), one zinc finger protein and four kinases, suggesting that Co-x is not a classical nucleotide-binding leucine-rich encoding gene. In addition, we identified and characterized the seven members of common bean PI-PLC gene family distributed into two clusters located at the ends of chromosomes 1 and 8. Co-x is not a member of Co-1 allelic series since these two genes are separated by at least 190 kb. Comparative analysis between soybean and common bean revealed that the Co-x syntenic region, located at one end of Glycine max chromosome 18, carries Rhg1, a major QTL contributing to soybean cyst nematode resistance. The PCR-based markers generated in this study should be useful in marker-assisted selection for pyramiding Co-x with other R genes.