Molecular mapping and inheritance of restoration of fertility (<Emphasis Type="Italic">Rf</Emphasis>) in A4 hybrid system in pigeonpea (<Emphasis Type="Italic">Cajanus cajan</Emphasis> (L.) Millsp.)

Key message

We report molecular mapping and inheritance of restoration of fertility (Rf) in A4 hybrid system in pigeonpea. We have also developed PCR-based markers amenable to low-cost genotyping to identify fertility restorer lines.

Abstract

Commercial hybrids in pigeonpea are based on A4 cytoplasmic male sterility (CMS) system, and their fertility restoration is one of the key prerequisites for breeding. In this context, an effort has been made to understand the genetics and identify quantitative trait loci (QTL) associated with restoration of fertility (Rf). One F₂ population was developed by crossing CMS line (ICPA 2039) with fertility restorer line (ICPL 87119). Genetic analysis has shown involvement of two dominant genes in regulation of restoration of fertility. In parallel, the genotyping-by-sequencing (GBS) approach has generated ~?33 Gb data on the F₂ population. GBS data have provided 2457 single nucleotide polymorphism (SNPs) segregating across the mapping population. Based on these genotyping data, a genetic map has been developed with 306 SNPs covering a total length 981.9 cM. Further QTL analysis has provided the region flanked by S8_7664779 and S8_6474381 on CcLG08 harboured major QTL explained up to 28.5% phenotypic variation. Subsequently, sequence information within the major QTLs was compared between the maintainer and the restorer lines. From this sequence information, we have developed two PCR-based markers for identification of restorer lines from non-restorer lines and validated them on parental lines of hybrids as well as on another F₂ mapping population. The results obtained in this study are expected to enhance the efficiency of selection for the identification of restorer lines in hybrid breeding and may reduce traditional time-consuming phenotyping activities.

     

水稻红莲型CMS育性恢复QTL分析

红莲型CMS是在我国杂交水稻生产中被广泛利用的雄性不育细胞质之一。为了同时定位红莲型CMS育性恢复主效和微效QTL,利用红莲型CMS不育系粤泰A(YTA)与“Lemont／特青”RIL群体测交,结合1张含有198个DNA分子标记的高密度遗传图谱,对测交F1群体的小穗育性和花粉育性进行复合区间作图。在对YTA的育性恢复性方面,该。RIL群体的2个亲本之间具有明显差异,特青的恢复性较强,其测交F1的小穗育性和花粉育性分别为72％和51％;而Lemont测交F1的小穗育性和花粉育性分别为32％和9％。复合区间作图定位到4个育性恢复QTL,分别位于水稻第1、2和10号染色体上,单个QTL的贡献率在5％～24％之间。其中,除1个QTL的增效基因来源于Lemont外,其余3个QTL的增效基因均来源于特青。效应最大的QTL为qRF-10-1,该QTL位于10号染色体RM258-C16标记区间,对小穗育性表型变异的贡献率为24％,对花粉育性的贡献率为17％,且该QTL被检测到的LOD值显著较高,因此是1个主效QTL,其增效基因来源于特青。除了主效QTLqRF-10-1外,其它3个QTL对性状的贡献率均在10％以下(5％～8％)。由此表明,该RIL群体对红莲型CMS的育性恢复由1个主效QTL控制,并受其它几个微效QTL的影响。该QTL定位结果与小穗育性在测交F1群体中呈连续的双峰分布的结果相一致。与主效QTL qRF-10-1紧密连锁的SSR标记为RM258,该主效QTL可作为分子标记辅助育种的操作目标之一,用于杂交稻分子育种中培育红莲型CMS的强恢复系。     

利用分子标记定位水稻野败型核质互作雄性不育恢复基因

以籼稻恢复系圭６３０与粳型广亲和品种０２４２８的Ｆ１代花药培养,获得８１个双单倍体（ＤＨ）,构建了有２３３个ＲＦＬＰ标记的分子图谱。用籼稻野败型不育系珍汕９７Ａ测定各ＤＨ系的恢复性,并将恢复性作为数量性状进行ＱＴＬ的区间作图分析,鉴别出８个基因座位,其中有２个基因座位,Ｒｆｉ－３和尾Ｒｆｉ－４,单个ＱＴＬ的基因贡献值分别是４９．６％和３５．４％,对育性恢复起主要作用,定为主效基因座位,位于第三和四染色体上,其它６个基因座位对育性恢复亦有一定的影响。表明野败型雄性不育恢复性是受主效基因和微效基因共同控制的性状。     

Genetic architecture of male fertility restoration of <Emphasis Type="Italic">Triticum timopheevii</Emphasis> cytoplasm and fine-mapping of the major restorer locus <Emphasis Type="Italic">Rf3</Emphasis> on chromosome 1B

Key message

Restoration of fertility in the cytoplasmic male sterility-inducing Triticum timopheevii cytoplasm can be achieved with the major restorer locus Rf3 located on chromosome 1B, but is also dependent on modifier loci.

Abstract

Hybrid breeding relies on a hybrid mechanism enabling a cost-efficient hybrid seed production. In wheat and triticale, cytoplasmic male sterility based on the T. timopheevii cytoplasm is commonly used, and the aim of this study was to dissect the genetic architecture underlying fertility restoration. Our study was based on two segregating F₂ triticale populations with 313 and 188 individuals that share a common female parent and have two different lines with high fertility restoration ability as male parents. The plants were cloned to enable replicated assessments of their phenotype and fertility restoration was evaluated based on seed set or staining for pollen fertility. The traits showed high heritabilities but their distributions differed between the two populations. In one population, a quarter of the lines were sterile, conforming to a 3:1 segregation ratio. QTL mapping identified two and three QTL in these populations, with the major QTL being detected on chromosome 1B. This QTL was collinear in both populations and likely corresponds to Rf3. We found that Rf3 explained approximately 30 and 50% of the genotypic variance, has a dominant mode of inheritance, and that the female parent lacks this locus, probably due to a 1B.1R translocation. Taken together, Rf3 is a major restorer locus that enables fertility restoration of the T. timopheevii cytoplasm, but additional modifier loci are needed for full restoration of male fertility. Consequently, Rf3 holds great potential for hybrid wheat and triticale breeding, but other loci must also be considered, either through marker-assisted or phenotypic selection.

     

Both epistatic and additive effects of QTLs are involved in polygenic induced resistance to disease: a case study,the interaction pepper — Phytophthora capsici Leonian

To study the resistance of pepper to Phytophthora capsici, we analyzed 94 doubled-haploid (DH) lines derived from the intraspecific F₁ hybrid obtained from a cross between Perennial, an Indian pungent resistant line, and Yolo Wonder, an American bell-pepper susceptible line, with 119 DNA markers. Four different criteria were used to evaluate the resistance, corresponding to different steps or mechanisms of the host-pathogen interaction: root-rot index, receptivity, inducibility and stability. Three distinct ANOVA models between DNA marker genotypes and the four disease criteria identified 13 genomic regions, distributed across several linkage groups or unlinked markers, affecting the resistance of pepper to P. capsici. Some QTLs were criterion specific, whereas others affect several criteria, so that the four resistance criteria were controlled by different combinations of QTLs. The QTLs were very different in their quantitative effect (R² values), including major QTLs which explained 41–55% of the phenotypic variance, intermediate QTLs with additive or/and epistatic action (17–28% of the variance explained) and minor QTLs. Favourable alleles of some minor QTLs were carried in the susceptible parent. The total phenotypic variation accounted for by QTLs reached up to 90% for receptivity, with an important part due to epistasis effects between QTLs (with or without additive effects). The relative impact of resistance QTLs in disease response is discussed.     

Genetic dissection of embryo sac fertility, pollen fertility, and their contributions to spikelet fertility of intersubspecific hybrids in rice

The partial sterility of hybrids has been a major barrier for utilization of the strong heterosis expressed in hybrids between Oryza sativa ssp. indica and O. sativa ssp. japonica. Wide-compatibility varieties, comprising a special class of germplasm, are able to produce fertile hybrids when crossed to both indica and japonica varieties. However, all the work on wide compatibility and majority of studies on indica/japonica hybrid sterility reported so far were based only on spikelet fertility; thus, it is not known to what extent male and female gamete abortions influence hybrid sterility. In this study, we investigated pollen fertility, embryo sac fertility, and spikelet fertility in an F₁ population of 202 true hybrid plants derived from a three-way cross (02428/Nanjing 11//Balilla). A partial regression analysis showed that the pollen and embryo sac fertility contributed almost equally to spikelet fertility. QTL analysis based on a linkage map of 191 polymorphic marker loci identified two QTLs for pollen fertility, one QTL for embryo sac fertility, and three QTLs for spikelet fertility. The S5 locus, previously identified as a locus for wide compatibility by spikelet fertility analysis, is a major locus for embryo sac fertility, and a QTL on chromosome 5 had a major effect on pollen fertility. These two loci coincided with the two major QTLs for spikelet fertility. The study also detected a QTL on chromosome 8, showing a large effect on spikelet fertility but no effect on either pollen or embryo sac fertility. Very little interaction among the QTLs was detected. The implications of the findings in rice breeding programs are discussed.     

Phenotypic and molecular evaluation of a recurrent selection program for a polygenic resistance to<Emphasis Type="Italic"> Phytophthora capsici</Emphasis> in pepper

Criollo de Morelos 334 (CM334) is one of the most promising sources of resistance to Phytophthora capsici in pepper. This Mexican accession is distantly related to bell pepper and its resistance displays a complex inheritance. The QTLs involved in resistance to P. capsici were previously mapped. In order to transfer the resistance factors from CM334 into a bell pepper genetic background, a modified, recurrent breeding scheme was initiated. The breeding population was divided into three sub-populations which were screened by distinct phenotypic tests of increasing severity. The plants from the first sub-population were screened with low-severity tests and backcrossed to the susceptible bell pepper; the plants from the second and third sub-populations were screened by more severe resistance tests and crossed with the plants from the first and second sub-populations, respectively. In this study, the phenotypic data for the three sub-populations during five screening/intermating cycles were analysed. In parallel, the changes in allelic frequencies at molecular markers linked to the resistance QTLs were reported. The resistance phenotype and allelic frequencies strongly depended on the sub-population and screening severity. Regarding allelic frequency changes across the selection cycles, a loss of resistant QTL alleles was observed in the first sub-population, particularly for the low-effect QTLs, whereas a better conservation of the resistant QTL alleles was observed in the two other sub-populations. The same trend was observed in the phenotypic data with an increasing resistance level from the first to the third sub-populations. The changes in the allelic frequencies of loci not linked to resistance QTLs and for horticultural traits across the breeding process indicated that the recovery of the recipient parent genome was not significantly affected by the selection for resistance.Communicated by D.A. Hoisington     

水稻CMS-DA育性恢复基因定位及其互作分析

在由210个测交组合组成的青早A／（协青早B／密阳46）F6群体中,构建了由129个RFLP、SSLP组成的连锁遗传图普。应用QTL分析方法,对水矮败型质雄性不育恢复基因进行了定位。检测到一个主效基因和3个效应较小的QTL（qRf－1、qRf－1、qRf－5）,这些基因这宰存在复杂的相互作用。     

两个水稻骨干恢复系重要农艺性状的遗传基础研究

水稻骨干恢复系是指在杂交稻育种中广泛应用的一类恢复系。探明骨干恢复系的遗传基础,发掘其重要农艺性状基因/QTL,对分子标记辅助选择水稻恢复系育种具有重要应用价值。本研究以生产上广泛应用的三系骨干恢复系成恢727和两系骨干恢复系9311为亲本,培育了具有250个系的重组自交系群体。分别在2015年三亚和2016年合肥两个环境下进行了9个重要农艺性状表型和SSR分子标记基因型鉴定,用SAS9.2分析表型数据,用QTL Ici Mapping v4.1进行QTL定位分析。在三亚和合肥两个环境下共检测到39个QTL,三亚检测到16个,分布于第1、2、4、7、8、10、11和12染色体上;合肥检测24个,分布于第1、2、3、7、8、9、10和12染色体上。其中qPH1-1在三亚和合肥两个环境下都能检测到,加性效应分别为-1.75和-2.46。在检测到的39个QTL中,有24个QTL的增效等位基因来自恢复系成恢727,15个QTL的增效等位基因来自9311。共计有26个QTL曾被前人定位,13个属于尚未见文献报道的新QTL。另外,在RM279~RM521、RM336~RM3534、RM25~RM547、RM553~RM160、RM222~RM271区段内检测到5个多效性QTL位点。其中RM25~RM547位点与已经克隆的基因Ghd8位置相近。RM553~RM160位点是一个新的多效性位点,分别控制每穗实粒数、单株产量和结实率,而且效应和表型变异贡献率都较大。其余3个位点在前人的研究中分别有所报道,但其多效性则是在本研究中首次发现。在本研究新发掘到的QTL中,控制穗数的QTL qPN12-1,控制穗长的QTL qPL1-2和qPL10-1,控制总粒数的QTL qSNP2-1和qSNP10-1,控制结实率的QTL qSF3-1,控制千粒重QTL qTGW7-1和控制产量的QTL qGY1-1效应均比较大,解释的表型遗传变异比例也较高。本研究的结果将会为相关性状QTL的精细定位、克隆和育种应用奠定基础。     

Identification of QTLs affecting traits of agronomic importance in a recombinant inbred population derived from a subspecific rice cross

To detect QTLs controlling traits of agronomic importance in rice, two elite homozygous lines 9024 and LH422, which represent the indica and japonica subspecies of rice (Oryza sativa), were crossed. Subsequently a modified single-seed-descent procedure was employed to produce 194 recombinant inbred lines (F₈). The 194 lines were genotyped at 141 RFLP marker loci and evaluated in a field trial for 13 quantitative traits including grain yield. Transgressive segregants were observed for all traits examined. The number of significant QTLs (LOD 2.0) detected affecting each trait ranged from one to six. The percentage of phenotypic variance explained by each QTL ranged from 5.1% to 73.7%. For those traits for which two or more QTLs were detected, increases in the traits were conditioned by indica alleles at some QTLs Japonica alleles at others. No significant evidence was found for epistasis between markers associated with QTLs and all the other markers. Pleitropic effects of single QTLs on different traits are suggested by the observation of clustering of QTLs. No QTL for traits was found to map to the vicinity of major gene loci governing the same traits qualitatively. Evidence for putative orthologous QTLs across rice, maize, oat, and barley is discussed.     

Molecular genetic analysis of grain protein content and flour whiteness degree using RILs in common wheat

Grain protein content (GPC) and flour whiteness degree (FWD) are important qualitative traits in common wheat. Quantitative trait locus (QTL) mapping for GPC and FWD was conducted using a set of 131 recombinant-inbred lines derived from the cross ‘Chuan 35050 × Shannong 483’ in six environmental conditions. A total of 22 putative QTLs (nine GPC and 13 FWD) were identified on 12 chromosomes with individual QTL explaining 4.5–34.0% phenotypic variation. Nine QTLs (40.9%) were detected in two or more environments. The colocated QTLs were on chromosomes 1B and 4B. Among the QTLs identified for GPC, QGpc.sdau-4A from the parent Shannong 483 represented some important favourable QTL alleles. QGpc.sdau-2A.1 and QFwd.sdau-2A.1 had a significant association with both GPC and FWD. The markers detected on top of QTL regions could be potential targets for marker-assisted selection.     

QTL involved in the partial restoration of male fertility of C-type cytoplasmic male sterility in maize

Partial restoration of male fertility limits the use of C-type cytoplasmic male sterility (C-CMS) for the production of hybrid seeds in maize. Nevertheless, the genetic basis of the trait is still unknown. Therefore, the aim to this study was to identify genomic regions that govern partial restoration by means of a QTL analysis carried out in an F₂ population (n = 180). This population was derived from the Corn Belt inbred lines B37C and K55. F₂BC₁ progenies were phenotyped at three locations in Switzerland. Male fertility was rated according to the quality and number of anthers as well as the anthesis-silking interval. A weak effect of environment on the expression of partial restoration was reflected by high heritabilities of all fertility-related traits. Partial restoration was inherited like an oligogenic trait. Three major QTL regions were found consistently across environments in the chromosomal bins 2.09, 3.06 and 7.03. Therefore, a marker-assisted counter-selection of partial restoration is promising. Minor QTL regions were found on chromosomes 3, 4, 5, 6 and 8. A combination of partial restorer alleles at different QTL can lead to full restoration of fertility. The maternal parent was clearly involved in the partial restoration, because the restorer alleles at QTL in bins 2.09, 6.04 and 7.03 originated from B37. The three major QTL regions collocated with other restorer genes of maize, a phenomenon, which seems to be typical for restorer genes. Therefore, a study of the clusters of restorer genes in maize could lead to a better understanding of their evolution and function. In this respect, the long arm of chromosome 2 is particularly interesting, because it harbors restorer genes for the three major CMS systems (C, T and S) of maize.     

Construction of high-density linkage map and identification of QTLs for resistance to sorghum downy mildew in maize (<Emphasis Type="Italic">Zea mays</Emphasis> L.)

Sorghum downy mildew (SDM), caused by obligate biotrophic fungi Peronosclerospora sorghi, is an economically important disease of maize. The genetics of resistance was reported to be polygenic thereby necessitating identification of QTLs for resistance to SDM to initiate effective marker-assisted selection programs. During post-rainy and winter season of 2012, 645 F_2:3 progeny families from the cross CML153 (susceptible) × CML226 (resistant) were screened for their reaction to SDM. Characterization of QTLs affecting resistance to SDM was undertaken using the genetic linkage map with 319 polymorphic SSR and SNP marker loci and the phenotypic data of F_2:3 families. Three QTLs conferring resistance to SDM were consistently identified on chromosomes 2, 3 and 6 in both seasons. The resistant parent CML226 contributed all the QTL alleles conferring resistance to SDM. The major QTL located on chromosome 2 explained 38.68% of total phenotypic variation in the combined analysis with a LOD score of 9.12. All the three QTL showed partially dominant gene effects in combined analysis. The detection of more than one QTL supports the hypothesis that quantitative genes control resistance to P. sorghi. The generation was advanced to F₆ using markers linked to major QTLs on chromosomes 2 and 3 to derive 33 SDM resistant maize inbred lines.     

Inheritance and QTL mapping of glandular trichomes type I density in <Emphasis Type="Italic">Cucumis melo</Emphasis> L.

To determine the genetic basis of the density of glandular trichomes type I in melon, a six-generation family and a recombinant inbred lines (F₇) population have been tested for the character; both genetic groups have been obtained from a cross between the Zimbabwean melon line TGR-1551 (high density of glandular trichomes) and the Spanish cultivar ‘Bola de Oro’ (low density of glandular trichomes). Classic quantitative genetic analysis indicated an oligogenic model for the inheritance of the character with an important additive component and strong epistatic relationships between loci. The quantitative trait locus (QTL) analyses revealed that the character is controlled by one major QTL, tric11, which explained between 23.8 and 58.7 % of its phenotypic variance; other minor QTLs of weaker effect and dependent of the assayed growing conditions were also found to be involved in the character expression. A codominant marker, the microsatellite ECM63, was found to be linked to the major QTL tric11. The validation of this marker in advanced backcrosses confirmed that the TGR-1551 alleles for this QTL increased glandular trichome density. The validation of the detected QTL was also done in other genetic backgrounds, which indicated that ECM63 could be effective in the selection of plants with high density of glandular trichomes type I.     

Mapping quantitative trait loci controlling seed dormancy and heading date in rice, Oryza sativa L., using backcross inbred lines

 To detect quantitative trait loci (QTLs) controlling seed dormancy, 98 BC₁F₅ lines (backcross inbred lines) derived from a backcross of Nipponbare (japonica)/Kasalath (indica)//Nipponbare were analyzed genetically. We used 245 RFLP markers to construct a framework linkage map. Five putative QTLs affecting seed dormancy were detected on chromosomes 3, 5, 7 (two regions) and 8, respectively. Phenotypic variations explained by each QTL ranged from 6.7% to 22.5% and the five putative QTLs explained about 48% of the total phenotypic variation in the BC₁F₅ lines. Except for those of the QTLs on chromosome 8, the Nipponbare alleles increased the germination rate. Five putative QTLs controlling heading date were detected on chromosomes 2, 3, 4, 6 and 7, respectively. The phenotypic variation explained by each QTL for heading date ranged from 5.7% to 23.4% and the five putative QTLs explained about 52% of the total phenotypic variation. The Nipponbare alleles increased the number of days to heading, except for those of two QTLs on chromosomes 2 and 3. The map location of a putative QTL for heading date coincided with that of a major QTL for seed dormancy on chromosome 3, although two major heading-date QTLs did not coincide with any seed dormancy QTLs detected in this study. Received: 10 October 1997 / Accepted: 12 January 1998     

The genetic basis of postzygotic reproductive isolation between Drosophila santomea and D. yakuba due to hybrid male sterility

A major unresolved challenge of evolutionary biology is to determine the nature of the allelic variants of "speciation genes": those alleles whose interaction produces inviable or infertile interspecific hybrids but does not reduce fitness in pure species. Here we map quantitative trait loci (QTL) affecting fertility of male hybrids between D. yakuba and its recently discovered sibling species, D. santomea. We mapped three to four X chromosome QTL and two autosomal QTL with large effects on the reduced fertility of D. yakuba and D. santomea backcross males. We observed epistasis between the X-linked QTL and also between the X and autosomal QTL. The X chromosome had a disproportionately large effect on hybrid sterility in both reciprocal backcross hybrids. However, the genetics of hybrid sterility differ between D. yakuba and D. santomea backcross males, both in terms of the magnitude of main effects and in the epistatic interactions. The QTL affecting hybrid fertility did not colocalize with QTL affecting sexual isolation in this species pair, but did colocalize with QTL affecting the marked difference in pigmentation between D. yakuba and D. santomea. These results provide the basis for future high-resolution mapping and ultimately, molecular cloning, of the interacting genes that contribute to hybrid sterility.     

QTL mapping and epistatic interaction analysis of field resistance to sudden death syndrome (<Emphasis Type="Italic">Fusarium virguliforme</Emphasis>) in soybean

Key message

Two interactive quantitative trait loci (QTLs) controlled the field resistance to sudden death syndrome (SDS) in soybean. The interaction between them was confirmed.

Abstract

Sudden death syndrome (SDS), caused by Fusarium virguliforme, is a major disease of soybean [Glycine max (L.) Merr.] in the United States. Breeding for soybean resistance to SDS is the most cost-effective method to manage the disease. The objective of this study was to identify and characterize quantitative trait loci (QTLs) underlying field resistance to SDS in a recombinant inbred line population from the cross GD2422?×?LD01-5907. This population was genotyped with 1786 polymorphic single nucleotide polymorphisms (SNPs) using SoySNP6 K iSelect BeadChip and evaluated for SDS resistance in a naturally infested field. Four SDS resistance QTLs were mapped on Chromosomes 4, 8, 12 and 18. The resistant parent, LD01-5907, contributed the resistance alleles for the QTLs on Chromosomes 8 and 18 (qSDS-8 and qSDS-18), while the other parent, GD2422, provided the resistance alleles for the QTLs on Chromosomes 4 and 12 (qSDS-4 and qSDS-12). The minor QTL on Chromosome 12 (qSDS-12) is novel. The QTL on Chromosomes 8 and 18 (qSDS-8 and qSDS-18) overlapped with two soybean cyst nematode resistance-related loci, Rhg4 and Rhg1, respectively. A significant interaction between qSDS-8 and qSDS-18 was detected by disease incidence. Individual effects together with the interaction effect explained around 70% of the phenotypic variance. The epistatic interaction of qSDS-8 and qSDS-18 was confirmed by the field performance across multiple years. Furthermore, the resistance alleles at qSDS-8 and qSDS-18 were demonstrated to be recessive. The SNP markers linked to these QTLs will be useful for marker-assisted breeding to enhance the SDS resistance.

     

Genetics of intrinsic postzygotic isolation in a circumpolar plant species, Draba nivalis (Brassicaceae)

Sterility barriers, ranging from incomplete to fully developed, were recently demonstrated within taxonomic species of the genus Draba, suggesting the existence of numerous, cryptic biological species. Because these taxa are predominately selfers and of Pleistocene origin, it was concluded that hybrid sterility evolved quickly and possibly by genetic drift. Here we used genetic mapping and QTL analyses to determine the genetic basis of hybrid sterility between geographically distant populations of one of these taxonomic species, Draba nivalis. Fifty microsatellite loci were mapped, and QTL analyses identified five loci underlying seed fertility and two underlying pollen fertility. Four of five seed fertility QTLs reduced fertility in heterozygotes, an observation most consistent with drift-based fixation of underdominant sterility loci. However, several nuclear-nuclear interactions were also found, including two that acted like reciprocal translocations with lowest fitness in double heterozygotes, and two that had a pattern of fitness consistent with Bateson-Dobzhansky-Muller incompatibilities. In contrast, pollen fertility QTLs exhibited additive inheritance, with lowest fertility associated with the paternal allele, a pattern of inheritance suggestive of cytonuclear incompatibilities. The results imply that multiple genetic mechanisms underlie the rapid evolution of reproductive barriers in Draba.     

水稻品种USSR5早熟性的遗传分析

USSR5为极早熟的前苏联品种,以抽穗期近等基因系和抽穗期QTL近等基因系为测验品种,对USSR5的抽穗期基因型进行分析,表明USSR5携带了非感光基因e1、无感光功能的Se-1e基因、感光抑制基因i-Se-1和显性早熟基因Ef-1,从而使它表现极早熟的特性。此外,本研究调查了USSR5和N22的BC1F1和F2群体的抽穗期,利用WindowsQTLCartographer1.13a软件,采用复合区间作图法,在全基因组范围内,分析了南京夏季正常日照条件下2个群体的抽穗期QTL,在USSR5/N22//USSR5BC1F1群体,共检测到2个位点,分别位于第7、8染色体上,其LOD值分别是6.11和2.91,对表型总变异的解释率分别为27.38%和11.15%,2个位点上来自USSR5的等位基因均提早抽穗。在USSR5/N22F2群体,共检测到5个位点,分别位于第1、2、7、9、10染色体上。5个位点LOD值介于3.02～8.4,对表型总变异的解释率分别为4.07%和15.41%。除qHd-9外,其余控制抽穗期的4个基因位点上提早抽穗的等位基因均来源于USSR5。比较分析发现效应较大的qHd-7即是Hd4(E1),USSR5在该位点上携带非感光基因hd4(e1)。尽管本研究定位的其它抽穗期QTL和已知抽穗期基因之间尚不能一一对应,但在早熟性水稻品种选育中,USSR5将可作为良好的基因源加以利用。