春白萝卜新品种雪单3 号的选育

雪单3 号是利用双单倍体育种技术选育的春白萝卜新品种。母本ED0108A 是以梅花春萝卜× 白玉春萝卜进行花药培
养获得的DH 系为轮回父本，与不育系进行多次回交，转育成的雄性不育系。父本ED3128 是由迟花春萝卜× 天鸿春萝卜进行
花药培养获得的DH 系。该品种生育期60 d（天），植株开展度45 cm，裂叶，小叶11 对，叶片数20，叶簇平展，叶色深绿；
肉质根长圆柱形，白皮白肉，根长36 cm，横径7.1 cm，单根质量1.1 kg，高抗黑腐病、芜菁花叶病毒病、黄瓜花叶病毒病和花
椰菜花叶病毒病，抗霜霉病，群体整齐度高。每667 m² 产量4 000～5 000 kg。适宜在湖北、湖南、河南、山东等地区早春栽培。     

茄子新品种海丰长茄1 号的选育

海丰长茄1 号是以双单倍体（DH）株系02-QP-19 为母本，优良自交系A-40 为父本配制而成的长茄一代杂种。平
均始花节位为第9 节，植株生长势强，叶片绿色，叶脉、叶柄和主茎的颜色为紫色，植株半开张类型。果实平均纵径31.5
cm，横径4.5 cm，果皮紫黑色，有光泽，果实顶部尖，平均单果质量220 g，VC 和VP 的含量分别为23.2 mg·kg^-1 和0.035%。
一般每667 m² 产量5 000 kg 左右。适宜北京、吉林和黑龙江等地区露地种植。     

甘蓝型油菜DH群体抗倒伏相关性状遗传分析

为明确油菜抗倒伏性的遗传规律，本文利用抗倒伏性差异显著的2个甘蓝型油菜品系配制杂交组合，构建含280个株系的DH群体，采用作物茎秆强度抗倒测量仪等考种工具对该群体进行连续两年的抗倒伏性鉴定，并利用植物数量性状的主基因 + 多基因混合遗传模型及偏度和峰度分析对抗倒伏性进行遗传分析。结果表明，茎秆抗折力和茎秆抗折强度都受到0对主基因 + 9对微效多基因控制，茎秆抗折力和单株生物量的基因间无互作，茎秆抗折强度的基因间有互补作用，茎秆抗折力和茎秆抗折强度两年的平均遗传率在50%左右，而茎秆直径两年的平均遗传率为69.338 %，单株生物量两年的遗传率分别为52.198%和69.284%，遗传率都较低，性状受环境影响都较大，因此对于茎秆抗折力、茎秆抗折强度、茎秆直径和单株生物量，在育种选择的早期阶段都不宜太严格。同时茎秆抗折强度相比茎秆抗折力更能说明作物的抗倒伏能力，因而在抗倒伏选择育种时应更加关注。     

A data transfer method for improving seed identification of maize (Zea mays) haploid breeding based on genetic similarity

Maize haploid breeding technology is able to identify haploid seeds non‐destructively, rapidly and at low cost with the help of Near‐infrared (NIR) spectral analysis. However, due to the hybridization of numerous parents and the low production rate of haploid, the haploid data collection becomes a burden for engineering this technology. Biologically, there are considerable similarities between the progeny of the same female parent and different male parents. Based on this advantage, similar spectral data can be transferred when the NIR technology is employed. A revised method of Transfer adaptive boost (TrAdaBoost) is proposed to improve identifying for the backpropagation neural network (BPNN) classifier. To avoid the negative transfer, a screening thresh is used to select out similar data, and the amount of these data are limited to join current training. The results show that the identification performances are improved significantly when the data amount is small. This method shows a high ability to make the seed identification more convenient for engineering maize haploid breeding.     

Factors affecting oat haploid production following oat × maize hybridization

Doubled haploids (DHs) are becoming increasingly important in crop breeding programmes but methods for producing oat DHs remain inefficient. In this study haploid and DH oat plants were produced using the oat × maize hybridization method. Factors influencing the rate of caryopsis and haploid embryo production including genotype, post‐pollination plant growth regulator application and temperature were investigated. The four growth regulators tested showed significant differences in their capacity to induce caryopsis formation with dicamba producing the highest numbers of caryopses, followed by picloram, 2,4‐dichlorophenoxyacetic acid (2,4‐D) and gibberellic acid (GA₃). No significant differences were observed between these growth regulators for their effect on embryo production. The concentration of dicamba was also important and was found to influence caryopsis but not embryo production, with 50 and 100 mg/l dicamba producing significantly more caryopses than 25 or 5 mg/l. Temperature had a significant impact on both caryopsis and embryo production with the magnitude and direction of response depending on genotype. Rates of haploid embryo production observed were between 0.8% and 6.7% of the pollinated florets. The proportion of haploids, which survived and were successfully doubled with colchicine following transfer to soil was between 72% and 81%.     

Molecular identification of Pm12-carrying introgression lines in wheat using genomic and EST-SSR markers

The traditional process of obtaining maize hybrids involves the generation of inbred lines through successive generations of selfing and subsequent testcrosses in order to identify the best combining ability by allelic complementation. A fast alternative to obtain inbred lines is to induce the formation of haploids followed by chromosome doubling. However, even with the aid of haploid-inducing genetic sources, this strategy has not been widely used in maize breeding programs, partly due to difficulties inherent to haploid generation and identification. In order to evaluate the possibility of using dihaploids to generate homozygous maize tropical lines, we used the androgenetic haploid inducer line W23 as a female parent in crosses with the tropical single-cross hybrid BRS1010. Within the progeny of these crosses, 462 seeds were phenotypically selected as putative haploids by the purple-colored endosperm and colorless embryo conditioned by the R1-nj gene. Among these, only four individuals were confirmed as being haploids using SSR markers, chromosome counting and flow cytometry, showing that the phenotypic marker was not efficient in detecting haploids in the tropical maize genotype used. All four haploids as well as some diploid plants presented reduced size, corroborating the difficulties for haploid identification by phenotypic evaluation. Genetic diversity analysis revealed by SSR markers divided the haploids in two groups represented by flint and dent maize inbred lines, which could be helpful in identifying complementary dihaploid lines. The present article demonstrates that a combination of haploid production and SSR fingerprinting is a feasible strategy for maize hybrid development in tropical germplasm.     

QTL analysis of seed dormancy in rice (Oryza sativa L.)

Effective cumulative temperature (ECT) after heading would be a more reasonable parameter for seed sampling of pre-harvest sprouting/seed dormancy (SD) tests in segregating populations than the days after flowering. SD is an important agronomic trait associated with grain yielding, eating quality and seed quality. To identify genomic regions affecting SD at different grain-filling temperatures, and to further examine the association between SD and ECT during grain-filling, 127 double haploid (DH) lines derived from a cross between ZYQ8 (indica)/JX17 (japonica) by anther culture were analyzed. The quantitative trait loci (QTLs) and their digenic epistasis for SD were identified using a molecular linkage map of this population. A total of four putative QTLs for SD (qSD-3, qSD-5, 6 and 11) were detected on chromosomes 3, 5, 6 and 11, together explaining 41.4% of the phenotypic variation. Nine pairs of digenic epistatic loci were associated with SD on all but chromosome 9, and their contributions to phenotypic variation varied from 2.87%–8.73%. The SD QTL on chromosome 3 was identical to the QTLs found in other mapping populations with different genetic backgrounds, which could be a desirable candidate for gene cloning and marker-assisted selection in rice breeding.     

Segregation distortion in doubled haploid lines of barley (Hordeum vulgare L.) detected by simple sequence repeat (SSR) markers

A total of 147 simple sequence repeat (SSR) markers (including86 barley and 61 wheat microsatellite markers) were tested for their segregation in a doubled haploid (DH) and an F₂ population of barley. The DH population consisted of 71 doubled haploid lines, developed from F₁ plants of a cross between Tadmor and WI2291using isolated microspore culture technique. A genetic linkage map consisting of 43 microsatellite markers was constructed using the DH population. Particularly on chromosome 4H microsatellite markers showed distorted segregation ratios. Segregation of DH lines based on molecular markers were compared with segregation of 92 F₂ lines from the same cross. The proportion of loci deviating from the expected monogenic segregation ratios in the DH population was significantly higher (19/43loci, 44%) than in the F₂ population (7/43 loci, 16%). The deviation was biased towards the WI2291 parent alleles. In line with this observation, WI2291 was found to perform better than Tadmor in regenerating green plantlets with the isolated microspore-culture technique. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effects of D-genome chromosomes on crossability of hexaploid triticale (X Triticosecale Wittmack) with maize

With the aim of producing polyhaploids of hexaploid triticale, 20 genotypes from a CIMMYT breeding programme and eight D-genome chromosome substitution lines of ‘Rhino’ were crossed with maize. In crosses between 20 triticale genotypes and maize, 15 lines produced embryos. Frequencies of embryo formation ranged from 0.0 to 5.4%, with an average of 1.1%. From a total of 200 pollinated spikes, 62 plants were regenerated. Most regenerated plants were polyhaploids with 21 chromosomes, and few aneuhaploids with 22 chromosomes were found. In crosses of triticale substitution lines with maize, all the lines produced embryos, while ‘Rhino’ produced no embryos at all. Higher frequencies of embryo formation were obtained in substitution lines with chromosomes 2D and 4D. These results suggest that D-genome chromosomes in a triticale genetic background have the effect of increasing the frequency of polyhaploid production in triticale x maize crosses.     

Wide mapping of a T-DNA insertion site in oilseed rape using bulk segregant analysis and comparative mapping

Doubled haploid oilseed rape lines segregating for a transgene inducing herbicide resistance (bar gene) were investigated for the wide mapping of the T-DNA insertion site. Bulk segregant analysis using presence/absence and intensity polymorphisms between the bulks, as well as comparative mapping with a linkage group deriving from another cross, led to the identification of 11 random amplified polymorphic DNA (RAPD) markers tightly or loosely linked to the bar gene. Ten RAPD loci out of 11 were located on the same side of the bar locus, strongly suggesting that the T-DNA integrated in a telomeric or subtelomeric position. The eleventh RAPD marker exhibited a strong segregation distortion, which could be the result of a heteroduplex formation. Comparison of the linkage groups obtained from the two crosses showed different recombination rates between markers, possibly reflecting differences in parental genetic backgrounds. Consequences and potential applications in transgene dispersal safety assessment studies are discussed.