Recurrent selection for maysin, a compound in maize silks, antibiotic to earworm

A thorough knowledge of the inheritance of maysin, a flavone glycoside with antibiosis to corn earworm, Helicoverpa zea Boddie, in the silks of maize will assist breeders in choosing the most efficient method of incorporating this trait into elite inbreds. Two breeding populations, one having exotic origin (EPM), the other from southern inbred lines (SIM) were subjected to six cycles of recurrent selection for increased silk maysin. Ten per cent of the individuals evaluated in populations were selected for recombination as S₁ progenies in each cycle. Progress was evaluated as C0 to C6 population cycles in a randomized complete‐block experiment with five replications in 1997 and 1998. Maysin fresh weights in silks of the C0 populations were 0.54% for EPM and 0.36% for SIM. Responses of 0.19% per cycle in EPM and 0.22% per cycle in SIM resulted in an EPM (C6) population with 1.76% maysin and an SIM (C6) population with 1.69% maysin. Silk maysin concentrations above 0.2% begin to substantially reduce larval growth and prevent completion of the life cycle when husk coverage is sufficient to force the insect to feed on silks while entering the ear. Chlorogenic acid and two analogues of maysin, apimaysin and 3′‐methoxymaysin, were found in such minor quantities in silks that they could not be credited with any impact on antibiotic activity against the insect. Selection has effectively increased silk maysin concentration in both EPM and SIM. Trait responses for maysin are highly heritable and will allow the plant breeder to introgress resistance to the corn earworm into elite material easily.     

Inheritance of Maysin Content in Silks of Maize Inbreds Resistant to the Corn Earworm

Genetic information is needed on maysin, a compound in maize, Zea mays L., silks that is antibiotic to corn earworm larvae, Helicoverpa (formerly Heliothis) zea (Boddie), to assist in the process of breeding for resistance to this pest. This study was initiated to elucidate the inheritance of maysin content in the silks of a cross between two maize inbreds (GT114 and GT119) having resistance to the corn earworm. Reversed phase high performance liquid chromatography (HPLC) procedures were used to quantify the maysin concentration of silks from individual plants in the parent, F₁, F₂, and first backcross generations of the cross GT114 × GT119. A model assuming dominance at a single locus for low maysin content which is expressed only when a dominant modifier is present was proposed to explain the segregation ratios obtained in the F₂ and first back-crosses of GT114 × GT119. This model also provided a fit for maysin data previously generated from a cross between inbreds F6 and F44. Observations of selfed families in the backcross of GT114 × GT119 to the low maysin parent confirmed the two-locus model (one factor with dominance for low maysin expressed only when a modifier gene is also present) as a plausible explanation for inheritance of silk maysin in the cross. The process of selection for high maysin will be complicated somewhat by the presence of a gene which modifies the expression of dominance unless a method of easily identifying the gene, independent of maysin content, can be developed.     

Control of preharvest aflatoxin contamination in maize by pyramiding QTL involved in resistance to ear-feeding insects and invasion by Aspergillus spp.

Several resistance sources and resistance mechanisms to aflatoxin formation and corn earworm (Helicoverpa zea Boddie) damage to maize (Zea mays L.) have been identified. Based on this knowledge, experiments were initiated toward achievement of the following objectives: (1) to confirm earlier determinations on resistance traits of germplasm sources and to identify quantitative trait loci (QTL) associated with each of the traits, and (2) upon estimation of the degree of QTL effects on each trait, to generate a maize population, with chemical and physical resistance to Aspergillus spp. and ear-feeding insects, for inbred development. A 2-year field experiment to evaluate selected genotypes inoculated with A. flavus and infested with corn earworm revealed that significant variation exists among the genotypes for aflatoxin contamination and corn earworm damage. The protection of maize ears against aflatoxin contamination was primarily dependent on resistance to fungal infection and ear-feeding insects, and excellent husk coverage and tightness. A major QTL (p1) identified on chromosome 1S had effects of 54.0, 42.1, and 28.3% on the phenotypic variability for concentrations of silk maysin, 3′-methoxymaysin+apimaysin, and chlorogenic acid, respectively. Markers/QTLs for husk phenotypic traits and total aflatoxin concentrations have been determined, but more detailed mapping of these chromosomic regions will be necessary to locate precise markers/QTLs for husk traits and aflatoxin production. Realizing the complexity of the Aspergillus–aflatoxin-maize system and the factors affecting aflatoxin contamination, we are directing our program toward marker-assisted breeding to enhance or improve general genetic resistance to ear-feeding insects and invasion by Aspergillus spp.     

用RFLP鉴定普通小麦—纤毛鹅观草二体附加系中外源染色体的同源转化性

用小麦族7个部分同源群的40个RFLP探针对小麦——纤毛鹅观草二体附加系进行分析,在证实了原有细胞学鉴定结果的基础上,又进一步提供了纤毛鹅观草染色体部分同源群的分子证据。即96K025,96K026中添加的一对纤毛鹅观草染色体B属于第2部分同源群;96K012, 96K013中添加的一对染色体E属于第5部分同源群。对以上株系的衍生株系     

棉花第14染色体分子标记连锁群的构建及其应用

 利用置换系CSB14Sh与TM-1产生F₂分离群体,以SSR标记构建连锁图对置换系进行分子鉴定。利用从覆盖全基因组的3800对引物筛选出的15对多态性引物对群体进行扩增,产生23个分子标记位点。其中,21个分子标记进入了同1个连锁群。通过与前人的分子图谱比较,把该连锁群定位在第14染色体上。表明TM-1与CSB14Sh在第14条染色体上有差异,而在其它染色体上没有差异。再结合染色体置换系构建的过程,可以认为CSB14Sh确实为第14条染色体短臂的置换系。     

QTL for popping characteristics in popcorn

Popping volume (PV), flake size (FS) and popping rate (PR) are three important popping characteristics in popcorn ( Zea mays L.). We developed 259 F_2:3 lines from a cross between a dent corn inbred 'Dan232' and a popcorn inbred 'N04' that were grown during spring and summer to evaluate the three popping characteristics. Fifteen quantitative trait loci (QTL) were detected on chromosomes 1, 2, 5, 6, 7 and 8 using composite interval mapping. The numbers of QTL were 6, 4 and 5 for PV, FS and PR, respectively, with phenotypic variance explained ranging from 4.9% to 15.6% for a single QTL, accounting for a total of 54.0%, 34.5% and 39.1% of the total phenotypic variance respectively. Partially dominance and overdominance effects played an important role in popping characteristics. Only 13 pairs of digenic interactions were detected. The QTL on chromosome bin 1.05–1.06 for PV and PR, and 5.07 for FS were in accordance with previous reports and could be good candidate QTL for marker-assisted selection. There was a significant correlation amongst QTL on chromosomes 1, 6 and 8 for PV and PR.     

Molecular mapping of quantitative trait loci determining resistance to septoria tritici blotch caused by Mycosphaerella graminicola in wheat

A set of 65 recombinant inbred lines of the ‘International Triticeae Mapping Initiative’ mapping population (‘W7984’בOpata 85’) was analysed for resistance to septoria tritici blotch at the seedling and adult plant stages. The mapping population was inoculated with two Argentinean isolates (IPO 92067 and IPO 93014). At the seedling stage, three loci were discovered on the short arms of chromosomes 1D, 2D and 6B. All three loci were detected with both isolates. At the adult plant stage, two isolate-specific QTL were found. The loci specific for isolates IPO 92067 and IPO 93014 were mapped on the long arms of chromosomes 3D and 7B, respectively. This revised version was published online in August 2006 with corrections to the Cover Date.     

利用相同来源F2:3和BC2S1群体定位玉米生育期QTL

以普通玉米自交系丹232和爆裂玉米自交系N04为亲本构建259个F2:3和220个BC2S1家系群体,利用SSR标记构建分子标记遗传图谱,利用复合区间作图方法对4个生育期性状进行QTL定位和效应分析。利用F2:3群体共检测到4个抽雄期QTL、6个吐丝期QTL和3个散粉期QTL。单个QTL可解释的表型变异为6.7%~18.4%,可解释的表型总变异为28.9%~50.3%,11个QTL的增效基因来自生育期较长的亲本丹232,其余2个QTL的增效基因来自生育期较短的亲本N04;BC2S1群体检测到8个与4个生育期性状相关的QTL,单个QTL可解释的表型变异为4.5%~11.6%,可解释的表型总变异为13.2%~18.5%,增效基因来自两个亲本的QTL为3个和5个。两类群体检测出QTL的数目、位置、效应和贡献率均存在较大差异,主要原因在于BC2S1群体抽样选择所引起的群体结构差异,F2:3群体显示出较高的QTL检测能力,但回交育种过程中应慎重依据F2:3群体QTL定位结果进行标记辅助选择(MAS)。     

Mapping and validation of the quantitative trait loci for leaf stay‐green‐associated parameters in maize

Functional stay‐green is generally regarded as a desirable trait of varieties in major crops including maize. In this study, we used an F_3:4 recombinant inbred line population with 165 lines from a cross between a stay‐green inbred line (Zheng58) and a model inbred line (B73) using 211 polymorphic simple sequence repeat markers to map quantitative trait loci for three stay‐green‐associated parameters, chlorophyll content, photosystem II photochemical efficiency and stay‐green area, at maturity stage, detected a total of 23 quantitative trait loci (QTL) on nine chromosomes. Single QTL explained 3.7–13.5% of the phenotypic variance. Additionally, we validated some important stay‐green QTL using a heterogeneous inbred family approach and found that the stay‐green‐associated parameters were significantly correlated with the plant yield. This study may contribute to a better insight into the regulatory mechanism behind leaf stay‐green in maize and a novel development of elite maize varieties with delayed leaf senescence through molecular marker‐assisted selection.     

Genetic analysis of agronomic and fibre traits using four interspecific chromosome substitution lines in cotton

Backcrossed chromosome substitution lines (CS‐B) have been developed with a homologous pair of chromosomes or chromosome arms of Gossypium barbadense (3‐79) germplasm substituted for the homologous Gossypium hirsutum(TM‐1) chromosomes or chromosome segments. We report on agronomic and fibre trait performance of four backcrossed chromosome or chromosome arm substitution lines including chromosomes 01, 11sh (chromosome 11 short arm), 12 sh and 26 Lo (chromosome 26 long arm). Data for agronomic and fibre traits were collected from replicated field experiments at two different locations in 2 years, and analysed under an additive dominance genetic model. CS‐B 12sh had higher, while CS‐B 01 and CS‐B 26Lo had lower boll weight than TM‐1. The presence of significant negative additive effects for micronaire with CS‐B 01 and significant positive additive effects for elongation and fibre strength with CS‐B 11sh suggested the substituted chromosome arms of 3‐79 in these CS‐B lines were more likely carrying genes causing these effects. Results revealed that several CS‐B lines had significant homozygous and heterozygous dominance effects for different agronomic and fibre traits suggesting that specific CS‐B lines may be useful for improving agronomic and fibre traits in hybrid cottons. These CS‐B lines also provide novel genetic resources for improving upland cotton germplasm.     

玉米抗灰斑病QTL元分析及其验证

玉米灰斑病是危害玉米生产的主要病害之一,目前对抗灰斑病基因数目、位置及作用方式仍然不清楚,这严重制约着玉米抗灰斑病育种进展。本研究利用元分析方法分析并整理了14篇玉米抗灰斑病QTL文献的信息,共筛选确定了13个一致性QTL区间。利用以自交系81162为轮回亲本、自交系CN165为非轮回亲本构建的回交导入群体根据连锁不平衡原理对13个一致性QTL进行验证,在13个一致性QTL区间共获得20多个偏分离位点。第1和第4染色体上偏分离最严重,其他染色体上偏分离度较小。说明第1和第4染色体上存在着效应较大的抗病QTL。第1染色体标记umc2227、bnlg1832、umc1243、umc2025、umc1515、umc1297、umc1461处供体基因频率均在50%以上,可能存在几个连锁的抗病基因。第4染色体上基因位于标记bnlg2291和umc1194之间。研究为精细定位供体CN165中第1和第4染色体上的抗灰斑病QTL奠定了基础。     

QTL analysis for eating quality-related traits in an F2:3 population derived from waxy corn × sweet corn cross

In order to identify quantitative trait loci (QTL) for the eating quality of waxy corn and sweet corn (Zea mays L.), QTL analysis was conducted on an F₂ population derived from a cross between a waxy corn inbred line and a sweet corn inbred line. Ten QTLs for pericarp thickness (PER), amylose content (AMY), dextrose content (DEX) and sucrose content (SUC) were found in the 158 F₂ families. Among them, four QTLs, qAMY4 (10.43%), qAMY9 (19.33%), qDEX4 (21.31%) and qSUC4 (30.71%), may be considered as major QTLs. Three of these, qAMY4, qDEX4 and qSUC4, were found to be located within a region flanked by two adjacent SSR markers on chromosome 4 (umc1088 and bnlg1265), making this SSR marker pair a useful selection tool for screening the eating quality traits of AMY, DEX and SUC. The QTL for amylose content was found to be located between markers phi027 and umc1634, raising the possibility of its identity being the Wx1 gene, which encodes a granule-bound amylose synthase. The new QTLs identified by the present study could serve as useful molecular markers for selecting important eating quality traits in subsequent waxy corn breeding studies.     

QTL mapping for agronomic and fibre traits using two interspecific chromosome substitution lines of Upland cotton

CS‐B14Sh and CS‐B22Sh are cotton interspecific chromosome substitution (CS)‐B lines, in which a pair of short arms of chromosome 14 and chromosome 22 were introgressed from Gossypium barbadense doubled‐haploid line 3‐79 with the background of Gossypium hirsutum line TM‐1, respectively. These two CS‐B lines were crossed with TM‐1, and segregating progenies (F₂ and F_2:3, respectively) were obtained. Phenotypic data of lint yield, yield‐related traits and fibre‐quality traits were collected from two trials. In the cross CS‐B14SH X TM‐1, QTL for boll weight (BW), lint percentage (LP), fibre upper half mean length (UHML), micronaire reading (MIC), and fibre breaking tensile strength (STR) were repeatedly detected. Alleles from 3‐79 decreased BW and MIC, but increased UHML and STR. In the cross CS‐B22Sh X TM‐1, QTL for BW, LP, UHML, MIC, STR, fibre elongation (EL),seed weight(SW), node of first fruiting branch (NFB) and fibre uniformity index (UI) were repeatedly detected, and alleles from 3‐79 decreased UHML, UI and STR, but increased NFB, SW, MIC and EL. QTL clusters were found in both populations.     

玉米须采收时期对其功能成分、可收集产量及玉米产量的影响

为研究玉米须的最佳采收时期,以黑龙江省主栽玉米品种‘京农科728’和‘德美亚3号’为试验材料,于2017年和2018年进行玉米须采收试验,比较不同采收时期对玉米须的功能成分、可收集产量及玉米产量的影响。结果表明,玉米须总黄酮含量随吐丝日数延长呈下降趋势,总多糖含量呈增加趋势,不同采收期的玉米须总黄酮含量的变幅大于多糖的变幅。以雌穗套袋方式延迟授粉能有效促进玉米须生长,但显著降低果穗结实率。‘京农科728’和‘德美亚3号’套袋6天的玉米须产量比自然授粉条件下的采收产量分别提高79.2%和65.5%,穗粒数分别下降了57.9%和88.2%;套袋12天玉米须产量分别提高107.6%和74.8%,穗粒数分别下降96.1%和96.0%;套袋3天果穗结实未受影响。不同品种玉米须生长量差异显著,玉米须产量变异范围界于0.443~1.003 g/穗之间,平均值为0.655 g/穗,变异系数24.78%。为兼顾玉米产量与玉米须品质及产量,吐丝3~5天为玉米须最佳采收期。     

Potential for effective marker-assisted selection of three quantitative trait loci conferring adult plant resistance to powdery mildew in elite wheat breeding populations

Three quantitative trait loci (QTL) associated with adult plant resistance (APR) to powdery mildew (Blumeria graminis) in wheat (Triticum aestivum) cultivar ‘Massey’ were mapped in a previous study. The three QTL were located on chromosomes 2A, 2B and 1B, and explained 50% of the total phenotypic variation. A 293 recombinant inbred line (RIL) breeding population (UJ) derived from the cross of ‘USG 3209’, a derivative of ‘Massey’, and ‘Jaypee’ was used to evaluate the potential effectiveness of marker‐assisted selection (MAS) for APR. Powdery mildew severities of the 293 UJ RILs were evaluated in 2002 (F_{5 : 6}) and 2003 (F_{6 : 7}) under natural disease pressure in the field. The 293 RILs were also evaluated for disease severity in a 2004 (F_{7 : 8}) greenhouse experiment using a composite of five different isolates of B. graminis. Selection of RILs possessing the QTL on chromosome 2A, and to a lesser extent, the one on chromosome 1B was effective in identifying powdery mildew resistance in both greenhouse and field experiments. Overall, selecting RILs with QTL on chromosomes 2A and 2B was most successful in identifying highly resistant RILs, which had mean mildew severities of 4.4% and 3.2% in 2002 and 2003 field experiments, respectively. Breeders implementing MAS programs for APR to powdery mildew via selection of RILs containing the two QTL on chromosomes 2A and 2B likely will obtain RILs having high levels of resistance in the field, however combining all three QTL may ensure greater durability.     

Quantitative trait loci of acid detergent fiber and grain chemical composition in hulled × hull-less barley population

Cultivated barley is the major livestock feed grain in the Northern Plains and Northwestern United States due to the fact that its short growing season and limited rainfall limit the planting and production of corn. Starch and fiber content play a significant role in feedlot performance of animals raised on barley feed. To study the underlying genetic locations and mechanisms for these traits, a recombinant inbred line population was derived from a cross between the hulled barley cultivar Valier and a hull-less Swiss landrace line, PI370970. Valier has a high acid detergent fiber content (ADF) and low starch and protein while PI370970 contains low ADF and high starch and protein content. To detect associated QTLs, data were collected and analyzed from irrigated and rain-fed environments. A total of 30 main effect QTLs and four epistatic QTLs were identified which conditioned ADF, starch and protein content under rain-fed, irrigated and combined analyses. These QTLs were located on chromosomes 2H, 3H, 5H, 6H and 7H. Major ADF and starch QTL were identified on chromosome 7H near the nud locus (the locus controlling hulled vs. hull-less caryopsis). High heritability estimates for both ADF and starch content suggest that early selection for these traits during breeding would be productive. Low ADF-QTL were independently verified in a second population in a different genetic background.     

Genetic variation between Spanish and American versions of sweet corn inbred lines

Conservation of maize inbred lines in different stations causes variability among strains. The objective of this research was to determine agronomic and molecular differences in American sweet corn inbreds maintained in Spain. American and Spanish strains of five sweet corn inbred lines were characterized by using 34 RAPD primers that produced 168 consistent bands. Strains of four of these inbreds were crossed in a diallel design, and hybrids were evaluated in four environments in northwestern Spain. The RAPD characterization showed no differences between strains for two inbreds, while divergence between strains was largest for the inbred 15125. Most primers did not reveal any variability between pairs of strains, while some primers produced variations at high rates. Differences in agronomic performance among Spanish and American strains were most important for P51, followed by P39, while strains 1453 or 15125 were not significantly different. Molecular differences between strains were not related to agronomic performance. Residual heterozygosity or outcrossing cannot explain these results. Lack of adaptation could have caused stress‐induced mutagenesis. Natural selection could have eliminated unfavourable selective mutations, but neutral mutations can be found at the molecular level and favourable mutations could have been selected at the agronomic level.     

Graphical Genotype of Maize Inbred B86 Revealed by RFLPs

The objective of this study was to investigate the origin of chromosome segments of maize (Zea mays L.) inbred B86 from its parental inbreds B52 and Oh43 using RFLPS. B86 was selected to combine resistance to the first and second brood of the European corn borer with the favorable agronomic performance of Oh43. RFLP analyses of the three inbreds were performed with three restriction enzymes (EcoRI, EcoRV, HindIII) and 178 DNA probes covering all ten maize chromosomes. For two DNA probes in combination with one enzyme, B86 showed a new RFLP pattern not present in the two parents. Based on results from 119 polymorphic DNA probes, the proportion of the B86 genome contributed by B52 (51.3 %) and Oh43 (48.7 %) was almost equal.     

Dynamic quantitative trait loci underlies isoflavone accumulation in soybean seed

Most of quantitative trait loci (QTL) underlying soybean seed isoflavone contents were derived from the harvest stage of plant development, which uncover the genetic effects that were expressed in earlier seed developmental stages. The aim of this study was to detect conditional QTL associated with isoflavone accumulation during the entire seed development. A total of 112 recombinant inbred lines developed from the cross between ‘Zhongdou 27’ (higher seed isoflavone content) and ‘Jiunong 20’ (lower seed isoflavone content) were used for the conditional QTL analysis of daidzein (DZ), genistein (GT), glycitein (GC) and total isoflavone (TI) accumulations through composite interval mapping with mixed genetic model. The results indicated that the number and type of QTL and their additive effects for individual and total isoflavone accumulations were different among R3 to R8 developmental stages. Three unconditional QTL and six conditional QTL for DZ, four unconditional QTL and five conditional QTL for GT, six unconditional QTL and five conditional QTL for GC, six unconditional QTL and seven conditional QTL for TI were identified at different developmental stages, respectively. Unconditional and conditional QTL that affect individual and total isoflavone accumulations exhibited multiple expression patterns, implying that some QTL are active for long period and others are transient. Two genomic regions, Satt144‐Satt569 in linkage group F (LG F; chromosome 13, chr 13) for DZ, GC, GT and TI accumulations and Satt540‐Sat_240 in LG M (chr 07) for TI and GC accumulations, were found to significantly affect individual and total isoflavone accumulations in multiple developmental stages, suggesting that the accumulation of soybean seed isoflavones is governed by time‐dependent gene expression.     

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0.03~342.8 cM,平均长度为91.1 cM,导入片段总长为3 643.9 cM,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0.03~343.4 cM,平均长度为75.5 cM,导入片段总长为5 895.2 cM,覆盖率为79.2%。