Seedling emergence,coleoptile length,and plant height relationships in crosses of dwarf and standard-height wheats

Summary Seedling emergence was closely correlated with coleoptile length and plant height among parents, F₂ and F₃, populations of crosses involving dwarf wheats Olesen Dwarf (CI 14497), Norin 10 derivative D6301, Tom Thumb derivative D6899, and the standard-height varieties Ramona 50 and Nainari 60. Genetic mechanisms that governed plant height also influenced coleoptile length, but the relative effects of genes showing dominant or epistatic effects appeared to be different. With respect to the two parents involved in each of 15 crosses, mean F₂ coleoptile lengths were consistently closer to the low parent value than were corresponding mean F₂ plant heights. A slight curvilinear relationship was also found between coleoptile length and plant height of F₃ lines. The results suggest that selection of semidwarf wheats with long coleoptiles and improved emergence properties from crosses involving the dwarf wheats of this study would be unlikely.     

Inheritance of reduced plant height in the sunflower line Dw 89

The objective of the present research was to study the inheritance of reduced plant height in the sunflower line Dw 89. Plants of the cytoplasmic male sterile version of this line, cmsDw 89 (mean plant height of 47.4 cm) were crossed with plants of the restorer line RHA 271 (mean of 120.9 cm). F₁ plants averaged 120.4 cm, which indicated dominance of standard over reduced plant height. F₂ plants followed a segregation pattern of 1 : 15 (reduced : normal height), suggesting that reduced plant height in Dw 89 is controlled by alleles at two loci, designated Dw1 and Dw2. Class assignment in the F₂ was confirmed through the evaluation of the F₃ generation. Backcrosses to Dw 89 segregated with 1 : 3 (reduced : normal height) ratios, which confirmed the digenic inheritance of the trait. The evaluation of plant height distributions in F₃ families suggested possible genetic interaction between the Dw1 and Dw2 loci.     

长胚芽鞘小麦品种耐深播出苗好

综述澳美欧亚非30多国百多家有关研究表明,胚芽鞘长、细、硬、快的小麦品种耐深播、立苗好。从细胞能性角度阐述胚轴划分并澄清小麦胚芽鞘的错位描述及地中茎的混淆定义。图示双胚苗的第二胚芽鞘自然开裂。图释深播地中拔节现象值得春化学者关注。概述胚芽鞘遗传长度、生理长度及环境长度。提到小麦脂肪优质育种问题。对国内麦学界提出3个具有理论或实践意义的建议。     

Relationships between height and yield in near-isogenic spring wheats that contrast for major reduced height genes

The effect of two major dwarfing (Rht-B1b and Rht-D1b) genes varies with environment. Near-isogenic pairs (i.e., tall and semidwarf) of six spring wheat lines, included in the International Adaptation Trial (IAT), were grown in 81 trials around the world from 2001 to 2004. Trial yields ranged from 1 to 8 t ha⁻¹ with a mean of ca. 4 t ha⁻¹. Overall, the yield advantage of the lines possessing the dwarfing gene was ca. 10% and was particularly evident in trials where the mean height of semidwarf isolines exceeded ca. 80 cm. However, the yield advantage was greater in the slightly taller and older lines (Pavon and Galvez) than in the newer lines Nesser and Kauz and the two durum lines. Sixteen pairs of semidwarf/tall near-isolines were grown in six managed drought environment trials at CIMMYT in northwestern Mexico. In these trials, height and yield differences were small and/or negligible in the most droughted environment (2.5 t ha⁻¹) and the slope of yield versus height for each isoline pair became consistently negative with increase in irrigation. In the IAT, the slope of the yield versus height was much more variable at low heights or yields, presumably due to the fact that there were many more factors driving the response. Even at the point where the slope became consistently negative (ca. between 2 and 4 t ha⁻¹), there were some trials where tall isolines equaled or exceeded the yield of semidwarf isolines, particularly in the most recent developed cultivar, Kauz. For submission to Euphytica as part of special issue “Challenges to International Wheat Breeding”. From the International Symposium on Wheat Yield Potential: Challenges to International Wheat Breeding, Days Inn, Ciudad Obregón, Sonora, Mexico, March 19–24th, 2006.     

利用WGCNA鉴定玉米株高和穗位高基因共表达模块

株高和穗位高是玉米株型的重要影响因子,与产量性状紧密相关。加权基因共表达网络分析(weightedgene co-expression network analysis, WGCNA)是探索基因网络与特定性状间关联关系的重要方法,为株高和穗位高相关基因的挖掘提供新途径。本研究利用郑58、掖478、昌7-2和黄早四及其组配的杂交种郑单958、安玉5号、郑58/黄早四和掖478/黄早四,结合其在45,000株hm^–2和67,500株hm^–2条件下的转录组数据,采用WGCNA构建了2种密度条件下的共表达网络,分别得到24个和21个共表达模块,并鉴定到与株高和穗位高显著且高度相关(相关系数的绝对值>0.50)的共表达模块15个,其中两性状相同的模块共6个。基因功能富集分析结果表明,株高和穗位高共表达模块主要参与生长发育、光合作用、响应光刺激、植物激素、碳水化合物合成/代谢等重要活动。根据模块内基因的连接度,发现乙烯响应因子EREB14、硫胺素酶TENA2、磷酸甘油酸激酶PGK、谷胱甘肽转移酶GST2和琥珀酸脱氢酶SUDH7等是模块内的核心基因。...     

Components of Visual Selection in Early Clonal Generations of a Potato Breeding Programme

In the first two clonal generations of a potato breeding programme, clones are visually selected for ‘plant appearance’. Selection for plant appearance based on unreplicated small plots is unreliable, due to significant genotype × environment interaction and high error variance. In order to improve the selection efficiency, component traits of plant appearance were identified and the effect of selection for these components was studied. Tuber yield was found to be the principal component of plant appearance while stolon length and tuber appearance contributed significantly, but to a lesser extent. Tuber yield had a higher heritability than plant appearance. Characters determining the appearance of stolons and tubers were found to have equal or lower heritabilities than plant appearance at 80 days after planting and somewhat higher heritabilities than plant appearance at 145 days after planting. Hence, since the expected and observed selection responses of the component characters have been found to be equivalent to that of plant appearance, selection for plant appearance cannot be improved upon by separately selecting for characters like tuber yield and tuber appearance.     

Variation, Heritability and Response to Selection in Natural Populations of Caper Spurge (Euphorbia lathyris L.)

Ten natural populations of caper spurge (Euphoria lathyris L.) were evaluated in two greenhouse experiments. It appeared that the ‘between population’ component of variance predominated for most characters. Heritability values Fit into the general picture of seed oil-containing wild species. From estimates of response to selection it is concluded that for developing caper its genetic- base has to be broadened.     

Comparative genetic mapping of loci affecting plant height and development in cereals

Restriction fragment length polymorphism (RFLP) mapping data for genes determining dwarfness (GA insensitive and GA sensitive), vernalisation response and photoperiodic response in wheat, rye and barley were compared and their homoeologous relationships discussed. The GA insensitive Rht genes of wheat are not related to the GA insensitive dwarfing genes of rye or barley; however, homoeology is present for two members of the GA sensitive dwarfing genes of wheat (Rht12) and rye (Ddw1), located on the translocated segments of the long arms of chromosomes 5A and 5R, respectively. The comparative mapping of the Triticeae group 5 vernalisation response genes of wheat, rye and barley, and the group 2 photoperiodic response genes of wheat and barley, show that both gene families are located in homoeologous regions of the particular chromosomes. This revised version was published online in August 2006 with corrections to the Cover Date.     

基于QTL定位和全基因组关联分析筛选甘蓝型油菜株高和一次有效分枝高度的候选基因

株高和一次有效分枝高度是与甘蓝型油菜结荚层厚度、收获指数紧密关联的重要农艺性状,有关株高的数量性状位点(quantitativetraitlocus,QTL)和全基因组关联分析(genome-wideassociationstudy,GWAS)已有很多报道,但对一次有效分枝高度的QTL和GWAS定位以及候选基因筛选的研究报道较少。本研究利用已构建的高密度遗传连锁图对2016和2017年2个环境的186个株系组成的重组自交系群体株高和一次有效分枝高度及其最佳线性无偏预测(bestlinearunbiasedprediction,BLUP)值进行QTL定位共检测到8个株高的QTL,分别位于A03、A04和A09染色体,单个QTL解释4.60%～13.29%的表型变异,其中位于A04染色体上的QTL(q-2017PH-A04-2和q-BLUP-PH-A04-2)在2017年和BLUP中均被检测到;检测到9个一次有效分枝高度QTL,分别位于A01、A02、A05、A09、C01和C05染色体上,单个QTL解释5.12%～19.10%的表型变异,其中q-2017BH-A09-1、q-BLUP-B...     

Improvement of Salt Tolerance in Maize by Selection and Breeding

Genetic variation for NaCl tolerance at the vegetative stage was assessed in nutrient solution culture in maize (Zea mays L.). Shoot growth, and plant fresh and dry weight of the two cultivars, Akbar and Sadat were severely reduced after three weeks growth in 120, 150, and ISO mol m^?3 NaCl. There was however considerable variability between seedlings. Ten-thousands seeds of cv. Akbar were therefore screened for shoot growth at 180 mol m^?3 NaCl after four weeks growth in sand culture. A selection intensity of 0.42 % was achieved. Eighteen selected plants were polycrossed for estimation of narrow-sense heritability based on female parent-progeny regression. A narrow-sense heritability estimate of 0.54 was obtained. The progeny of the salt-tolerant selection line and selfed progeny plants of the unselccted control lines of cvs Akbar and Sadat were grown for six weeks in 0, 30, 60, 90, 120, 150, and 180 mol m^?3 NaCl in sand culture. The tolerant line produced significantly greater fresh and dry biomass and had greater shoot length than the unselected cv. Akbar, but the selection line derived from cv. Akbar was equal to the salt tolerant cv. Sadat in all the growth parameters measured. These data suggest that in maize, improvement in salt tolerance could be obtained through further cycles of selection and breeding.     

小麦株高QTL Qph.nau-5B的效应评价

株高直接影响小麦的产量潜力,也是植株抗倒伏性的重要组成部分。目前虽有大量株高相关QTL被鉴定到,但大多QTL的遗传效应仍不清楚。本研究前期利用小麦品种群体,通过关联分析鉴定到一个小麦株高主效QTL Qph.nau-5B。为了评价该QTL的效应,通过分子标记辅助选择分别构建了以南大2419、吉春1016和郑麦9023为供体亲本,中优9507为背景的3种等位变异的近等基因系,背景回复率均高于93%。在7个独立的试验环境中,所有近等基因系的株高较轮回亲本均显著降低,平均降幅为11.1 cm(10.3%)。Qph.nau-5B不同等位变异效应强弱不同,其中来源于吉春1016和郑麦9023的等位变异平均降秆效应相似(12.4 cm),显著大于南大2419的等位变异(8.6 cm),但各等位变异相对降秆效应大小受环境影响。此外,Qph.nau-5B对单株穗数、穗长、千粒重等农艺性状无明显负效应。本研究结果表明Qph.nau-5B具有重要的育种价值,可为小麦的株型分子设计育种提供基因资源。     

Dynamic QTL mapping for plant height in Upland cotton (Gossypium hirsutum)

Plant height served as one of model traits to analyse dynamic development. The objective of this research was to investigate quantitative trait loci (QTL) and dynamic QTL for plant height trait using an intraspecific recombinant inbred line (RIL) population and a constructed genetic map in Upland cotton (Gossypium hirsutum L.). Totally, 41 QTL and 23 conditional QTL controlling plant height were detected at two experimental environments, respectively. Four stable QTL were identified simultaneously in both environments. Some QTL identified at the early stage could not be detected at the final stage at plant maturity. Conditional QTL with different genetic effects were identified at certain stages, demonstrating that the expression of QTL had temporal characteristic during plant growth. Therefore, the study of dynamic QTL could unravel temporal genetic patterns controlling complex developmental quantitative traits.     

The distribution,in European winter wheats,of genes that influence ecoclimatic adaptability whilst determining photoperiodic insensitivity and plant height

Summary The adaptability of wheat varieties to precise environmental conditions is known to be influenced to a large extent by photoperiod sensitive genes determining ear emergence time and by the gibberelic acid insensitive dwarfing genes that are regularly used to reduce plant height. A range of European winter wheat varieties were examined to establish whether breeders in different countries have selected genotypes carrying allelic variants of photoperiodic and dwarfing genes that would be expected to provide the best levels of adaptability. In most areas modern cultivars were seen to carry the genotypes predicted to promote good levels of adaptability. Varieties cultivated in Germany however are still predominately of conventional height and late flowering lacking genes that would be expected to enhance adaptability and yield.     

The reduced height genes do not affect the root penetration ability in wheat

Root penetration (RP) ability into compacted soil is an important breeding target for drought avoidance by durum (Triticum turgidum L. var. durum) and bread wheat (T. aestivum L.) in regions with compacted soils and water deficits. However, it is said generally that yield of the current cultivars introduced the reduced height gene (Rht-B1b or Rht-D1b) are more sensitive to drought stress than that of old landraces. This study investigated the effect of the Rht genes on RP ability using the seedlings of near-isogenic lines (NILs) of Rht genes of LD222 durum wheat and April Bearded bread wheat, and 110 recombinant inbred lines (RILs) of durum wheat derived from the cross between the tall landrace (Jennah Khetifa; Rht-B1a Rht-B1a) and semi-dwarf cultivar (Cham1; Rht-B1b Rht-B1b). One seedling of each genotype was grown in a pot (6 cm diameter, 15 cm height) with a disc of 3 mm thickness made from paraffin and Vaseline mixture (PV) in 10 cm depth, as a substitute for a compacted soil layer. The RP index [number of roots penetrating through the PV disc per plant (PVRN)/total number of seminal and crown roots per plant (TRN)] was measured at eight weeks after sowing and used as the indicator of RP ability of seedling. In NILs, the shoot length decreased significantly because of the introduction of either Rht-B1b or Rht-D1b dwarfing genes, but the RP index was similar to those of tall parents. In RILs, although the RP index and shoot length were higher in Jennah Khetifa than in Cham1, the relationship between RP index and shoot length was not significant (r = 0.156). Both results indicate that RP ability of wheat does not link to dwarfness regulated by Rht genes. We suppose therefore that it would be possible to develop a high yielding semi-dwarf cultivar with excellent RP ability.     

Distribution of the Rht-B1b, Rht-D1b and Rht8 reduced height genes in autumn-sown Chinese wheats detected by molecular markers

Reduction of plant height has played a significant role in improving wheat production and knowledge of dwarfing genes in Chinese wheat will be very important for developing high yielding cultivars. Molecular markers were used to detect the presence of genes Rht-B1b (Rht1), Rht-D1b (Rht2) and Rht8 in 220 wheat genotypes from autumn-sown wheat regions in China. They include landmark landraces, leading cultivars and core parents involved in wheat breeding from the 1950s to the present. Results indicated that Rht-D1b and Rht8 dominate with frequencies of 45.5% and 46.8%, respectively, followed by Rht-B1b with a frequency of 24.5%. The frequencies of Rht-B1b and Rht-D1b increased, from 8.6 to 32.2% and 36.2 to 53.4%, respectively, whereas the frequency of Rht8 has remained constant over time, when compared with cultivars released before and after 1990. This indicates that both the Rht-B1b and Rht-D1b were successfully used in wheat production in Chinese environments. Our study shows that Rht-B1b and Rht-D1b can be used in the post-anthesis heat stressed environments. Rht-B1b in Chinese wheats is derived from two sources, viz., Norin 10 and the Italian introduction St2422/464 (Rht-B1b and Rht8). The identity of Rht-B1b in these two sources still needs to be confirmed. Suwon 86 carrying both Rht-B1b and Rht-D1b, and Chinese cultivars, Huixianhong and Yaobaomai, are the primary sources of Rht-D1b in Chinese wheats. It is likely that Rht-D1b in Youbaomai derives from an unknown introduction. Italian introductions such as Funo and Abbondanza, and Lovrin 10 with the 1B/1R translocation, and Chinese landraces are the three major sources of Rht8. This information will be very valuable for wheat breeding in China, and internationally.     

Interactions between different genotypic tissues in citrus graft chimeras

The heritability of tolerance of wheat F₃ lines to competition from annual ryegrass (Lolium rigidum), and its relationship to morphological traits, were determined using crosses between wheat cultivars with good and poor competitive ability. Forty F₂-derived F₃ lines from a cross between two late flowering varieties (Machete × Spear) and 40 from a cross between early flowering varieties (Wilgoyne × Gutha) were grown in the field with and without annual ryegrass. There was significant genetic variation between lines within each of the two populations in a number of aspects of plant growth and development, including yield in monoculture. The estimates of heritability for % yield loss due to competition were 0.25 and 0.57 in the two crosses respectively, indicating that selection for high tolerance to competition in the F₃ generation or later should be effective. Fairly strong relationships between height and % yield loss and between leaf length and % yield loss suggest that these may be useful auxiliary traits when selecting for low % yield loss. However, differences between crosses in the magnitude and sign of genetic and phenotypic correlation between traits indicate that competitive ability is a complex character influenced by many factors. This revised version was published online in August 2006 with corrections to the Cover Date.     

Response to selection, combining ability and heritability of coleoptile length in winter wheat

Selection of winter wheat cultivars with long coleoptiles is an important component of improving emergence, weed suppression and grain yield in low rainfall regions of the world. Seven winter wheat cultivars were hybridized in a Griffing’s half-diallel mating design, method 2 (reciprocals excluded, parents included), model 1 (fixed), and the progeny analyzed for coleoptile length in the F₁ through F₄ for response to selection, general combining ability (GCA), specific combining ability (SCA) and heritability. Highly significant differences existed for GCA among progeny in each generation. SCA was highly significant in the F₁, F₂ and F₄, although SCA estimates were inconsistent among generations in each progeny population. The SCA/GCA ratio was 0.15, 0.11, 0.06 and 0.04 in the F₁ through the F₄, respectively, indicating that additive effects increased with homozygosity. Broad-sense heritability for coleoptile length was estimated at 0.86, 0.76, 0.60 and 0.78 for the F₁ through the F₄, respectively. Realized heritabilities ranged from −0.16 to 0.85 with a mean of 0.32 in the F₃ and ranged from −0.68 to 0.68 with a mean of 0.13 in the F₄. Spearman’s rank correlation coefficients (R_S) were significant for all generation comparisons except the F₁:F₂, indicating that changes in rank for coleoptile length were insignificant. Cultivars with long coleoptiles and high GCA were the best parents for improving coleoptile length. Sustained selection over generations for coleoptile length was more effective than one generation of selection for genotypes both with and without reduced height genes.