夏玉米穗部性状的遗传相关与通径分析

通过对44个夏玉米杂交种穗部6个主要性状与单株粒重遗传相关与通径分析表明:穗长与穗粗在影响单株子粒产量诸因素中占据主导地位,在对穗长、穗粗重点选择的基础上,考虑对穗行数、行粒数、出子率的选择,容重可独立进行选择。穗部性状的选择必须考虑性状间的相互制约关系,综合利用某一穗部性状对单株粒重的直接效应和通过其他性状的间接效应。     

玉米主要数量性状遗传相关和通径分析

采用不完全双列杂交遗传设计对16个玉米自交系及其组配的60个杂交组合的13个主要数量性状进行了遗传相关和通径分析。相关分析得出，各农艺性状对单株粒重的遗传相关系数由大到小依次为：单株穗重、百粒重、穗粗、穗长、株高、穗三叶面积、秃尖长、穗位、出籽率、穗行数、行粒数。而通径分析得出各农艺性状与产量的相对重要性依次为：单株穗重、出籽率、穗长、穗粗、穗三叶面积、株高、穗行敷、秃尖长、百粒重、穗位、行粒数。     

玉米几个株型性状的遗传模型及其与穗粒性状的典型相关分析

以10个玉米自交系及其按4×6组配的24个杂交组合为材料, 研究了玉米5个株型性状的杂种优势, 遗传模型, 遗传相关及其与穗粒性状的简单相关和典型相关. 结果表明, 雄穗分枝数的平均杂种优势最大, 叶面积次之, 叶形系数、叶夹角、叶向值则较小. 叶形系数、叶夹角的遗传符合加性遗传模型; 叶向值、雄穗分枝数符合加性显性遗传模     

玉米杂交种农艺性状与籽粒产量的相关和通径分析

玉米杂交种主要农艺性状遗传相关与通径分析结果表明，行粒数、穗行数、百粒重、果穗长在影响籽粒产量诸因素中占主导地位。认为单株籽粒产量改良应在稳定穗数的基础上，着重提高行粒数；适当增加穗行数以利提高百粒重；协调好穗行数、行粒数、百粒重三者关系，实现单株产量的较大幅度增长。     

海滨锦葵数量性状的相关和通径分析

对海滨锦葵的16个数量性状进行了相关和通径分析。结果表明, (1) 种子产量与果实数、地径、结果枝比、结果枝数、百粒重间呈十分显著的正相关（r = 0.945、0.770、0.567、0.497、0.397）,与粗脂肪含量间呈显著的正相关（r = 0.348）;但与结果枝高度间呈十分显著的负相关（r =－0.343）;粗脂肪含量与百粒重、结果枝底径和地径间呈十分显著正相关 (r = 0.389、0.383和0.358),但与结果枝枝下高间呈显著的负相关(r =－0.397)。(2) 果实数对种子产量的直接正效应最大,其后依次是叶长、地径、结果枝长、百粒重、分枝数、结果枝角度、结果枝高度和株高;14个产量因子中有5个对产量有直接的负效应,包括叶宽、叶长宽比、结果枝数、结果枝底径和结果枝比。相关、直接作用和间接作用相结合的分析表明,对果实数、地径和百粒重的直接选择可有效增加种子产量;选择结果枝高度低的植株对种子产量改良有益;结果枝数和结果枝比的选择有助于提高种子产量,因其通过果实数和地径的间接作用较大。     

玉米理想株型经济性状的遗传相关与通径分析

利用逐步回归、遗传相关、通径分析的统计方法,研究玉米理想株型杂交种,在一定的生态和栽培条件下,雄穗分枝,果穗长、穗行数、千粒重、出籽率对单株粒重的直接和间接效应.结果表明:行粒数、千粒重的直接作用与果穗长通过行粒数的间接作用,对单株粒重的相对决定程度都较高,在影响单株粒重诸因素中占主导地位.初步认为以这三个性状作为选择指标,直接选择,并协调好千粒重与行粒数的关系,可望选出单株籽粒产量较高的杂交种.     

海岛棉数量性状的相关与通径分析

本文通过对海岛棉新海系列的棉花品种（系）进行相关和通径分析．相关分析表明：单株皮棉产量与单株铃数、株高、比强度呈极显著正相关;生育期与长度呈显著正相关;单株铃数与株高、果枝数呈显著正相关;果枝节位与强度、衣分呈极显著负相关;其它各性状均呈一定程度的正或负弱相关。偏相关分析表明：单株皮棉产量与单株铃数、单铃重、衣分呈极显著正相关：衣分与单株铃数、单铃重呈极显著正相关;长度、细度、强度与各品质性状呈一定程度的不显著正或负相关。通径分析表明：单株铃数对单株皮棉产量的贡献率最大．其次是单铃重和衣分的贡献率较大．其它各性状对单株皮棉产量产生的正向或负向效应都不大．但是株高、果枝数、比强度通过单株铃数产生的间接效应的正向作用较大。研究各性状的相关关系可以指导我们对育种目标性状的选择,提高育种效率。     

玉米9个农艺性状与产量的遗传相关及通径分析

本文通过对 14个杂交玉米品种 9个主要农艺性状进行遗传相关与通径分析 ,结果表明果穗长、结实长、行粒数、株高与单株籽粒产量遗传相关达极显著水平。进一步进行通径分析 ,结果表明 ,各性状对单株籽粒产量直接贡献的大小依次为 :结实长 >穗粗 >千粒重 >穗位高 >出籽率 >株高 >行粒数 >穗行数 >穗长。选育春播高产杂交种时 ,要重视选择果穗结实长、果穗粗、千粒重高的类型。     

不同产量水平玉米杂交种主要农艺性状的遗传相关与通径分析

对2006-2008年参加陕西省夏玉米区试的150个杂交种的主要农艺性状进行相关和通径分析,得出在不同产量水平下影响玉米产量的主要农艺性状,并提出了高产水平下的玉米育种应在主攻千粒重的基础上选择行粒数多的杂交种,同时注意协调好穗行数与千粒重,行粒数之间的关系.     

高粱杂交种株型性状与产量的遗传相关和通径分析

以相关分析法研究了 1 3个高粱杂交种 9个株型性状与单株子粒产量的关系 ,结果表明 :高粱杂交种高产的株型性状应是 :株高适中 ,株型紧凑 ,叶宽但叶长适宜 ,并着重对顶数三叶的长和宽进行合理选择 ,这样有利于合理安排群体密度 ,增加光合面积 ,提高产量     

冬小麦品种数量性状的典型相关分析

对41份冬小麦品种产量构成因素、植株性状、穗部性状的典型相关分析表明:产量构成因素与穗部性状间、产量构成因素与植株性状间、穗部性状与植株性状间均呈显著相关,说明通过穗部性状、植株性状间接选择产量性状是可能的.     

玉米tasselseed突变体ts12的遗传分析与分子鉴定

性别决定与玉米雄穗和雌穗发育密切相关,性别决定基因功能研究对性别决定分子机制的解析具有重要意义。利用甲基磺酸乙酯(EMS)处理B73花粉,获得了一个玉米雄穗结实突变体tasselseed12 (ts12)。用扫描电镜对ts12突变体雄穗的形态学观察,发现未成熟雄穗长13mm时,小穗呈现出明显的雌性化特征。利用图位克隆的方法,把ts12定位于分子标记LM4和RM5之间,物理距离约为290 kb,该区间共有9个注释基因,其中包括已报道的性别决定基因Tasselseed2 (Ts2)。通过克隆ts12突变体中Ts2基因编码序列,发现Ts2基因编码区第196个碱基鸟嘌呤被替换为腺嘌呤,导致该位点编码的甘氨酸被替换为精氨酸,由此推测该保守位点突变可能是tasselseed表型产生的原因。ts12和ts2等位性测验结果表明所有F1、F2代植株雄穗均可产生花丝,推测ts12是ts2基因一个新的等位突变体。以加外源茉莉酸(JA, 1 mmol L–1)处理ts12突变体,发现处理后的小穗大部分可恢复正常。Ts2基因表达分析揭示在正常植株未成熟雄穗中的表达量最高,其次是未成熟雌穗及叶片中;在ts12未成...     

Genetic analysis of quantitative traits across environments in linseed (Linum usitatissimum L.)

Summary Fourteen lines of linseed (Linum usitatissimum L.) were evaluated for general and specific combining ability through line × tester cross analysis using five diverse testers in two different environments. Seventy F₁'s and nineteen parental genotypes were raised in completely randomized block design with two replications with respect to yield and yield related traits. Considerable genetic variation was observed for all the traits studied. The additive as well as non-additive gene effects played significant role in the inheritance of yield and related traits with preponderance of non-additive gene effects for all the traits studied. Higher proportion of general combining ability × environment interaction variance as compared to specific combining ability × environment estimates was recorded. Additive genetic variances were more sensitive than non-additive genetic variances to the changing environment. Low estimates of heritability (narrow sense) for primary branches per plant, capsules per plant, seeds per capsule, seed yield per plant, harvest index and oil content and medium heritability for days to 50% flowering, days to maturity, plant height and 1000-seed weight was observed. Among the female parents LCK-9816, Parvati, Himalini, KL-168 were good general combiners for yield and related traits along with oil content, whereas among male parents, Surbhi and KL-224 were good general combiners for yield related traits and oil content but KL-221 was good general combiner for seed yield and related traits.     

Genetic markers and the selection of quantitative traits in forage grasses

Summary Marker assisted selection is based upon the principle that if a gene (or block of genes) is linked to an easily identifiable genetic marker it may be more efficient to select in a breeding programme for the marker than for the trait itself. The recent developments in molecular marker technology has allowed several approaches to be applied to the forage grasses. The most effective methods involve the production of detailed genetic maps which can be used for determination of the location of Quantitative Trait Loci (QTLs). Application of these methods toLolium has lead to the identification of 10 QTL's affecting mainly phenological characteristics. Up to 80% of the variation in inflorescence production in the establishment year may be accounted for by one region of the genome.     

Genetic variation and selection criterion for digestibility traits of forage maize

Summary Variations in feeding value characteristics were studied on a factorial mating design, within a multilocal network. The in vitro digestibility of dry matter (IVDDM), neutral detergent fiber (NDF), acid detergent fiber (ADF), acid detergent lignin (ADL), starch, soluble carbohydrate, protein and ash contents were evaluated on whole plant samples. The in vitro digestibility of the non-starch and non-soluble carbohydrate plant part (IVDNSC) was also computed from near infra-red reflectance spectroscopy estimations of IVDDM, starch and soluble carbohydrate contents. Variations due to general combining ability (GCA) were more important, for all traits, than variations due to specific combining ability (SCA). Variations due to the GCA × environment interaction were also sizeable and were partly explained by the earliness of the lines. IVDDM was primarily influenced by the relative proportions of cell walls and starch in the whole plant, which were particularly susceptible to the development stage of the plants, at harvest. When adjusted for earliness, there was generally no significant relation between the line per se value and GCA performance in the biochemical constituent contents of the plant. On the contrary, IVDNSC seemed to be a feeding value trait worth evaluating at the inbred line level. It was also almost independent of the ripening stage and could be easily computed from whole plant samples. IVDNSC, with a simultaneous control of starch content, might be a good selection criterion for evaluating and improving the nutritive value of forage maize.     

Genetic analysis of drought-adaptive traits at seedling stage in early-maturing maize inbred lines and field performance under stress conditions

Maize hybrids that are tolerant to drought at the seedling stage are needed to boost productivity in the rainforest agro-ecology of West Africa. Genetics of tolerance of maize seedling to drought stress is not well understood and is poorly documented. The objectives of this study were to screen early-maturing maize lines for seedling drought tolerance, determine the inheritance and the combining ability of selected inbred lines, and evaluate the performance of seedling drought-tolerant hybrids under field conditions. Forty-nine early maize lines were screened for drought tolerance at the seedling stage. Ten drought-tolerant and two susceptible inbred lines were selected and used in diallel crosses to generate 66 hybrids. The twelve inbred lines and their hybrids were evaluated under induced drought at seedling stage in the screen house and under marginal growing conditions on the field for two seasons. Data collected were subjected to analysis of variance using the DIALLEL-SAS program. Mean squares for both GCA and SCA were significant for most traits in all research environments, indicating that additive and non-additive gene actions are controlling seedling traits under stress conditions. However, for most traits, SCA was preponderant over GCA in all environments, indicating overdominating effect of non-additive gene action. Which in turn implied that the best improvement method for the traits is hybridization. Inbred TZEI 7 had the best GCA effect for seedling traits under screenhouse conditions and for grain yield and other agronomic traits under drought conditions in the field. Hybrids TZEI 357?×?TZEI 411 and TZEI 380?×?TZEI 410 showed superior SCA effects under screen house conditions. In conclusion, the study established wide genetic variability for drought tolerance at seedling stage among tropical early-maturing maize germplasm however, the non-additive gene action was more important for most seedling traits.     

Marker analysis for quantitative traits in sugar beet

Many economically important traits are inherited quantitatively and are analysed by breeders in replicated field trials. If dense maps are available, chromosomal regions containing quantitative trait loci (QTL) can be identified and this opens up the possibility of preselecting for quantitative traits in the laboratory. In this study, QTL analysis for yield and yield components in sugar beet is used in two different populations tested in several environments in both populations, QTL were detected for all traits investigated, and their predictive value in breeding schemes was analysed by correlating predicted with observed values. Tolerance to Rhizomania, caused by a gene on chromosome 3, was the main source of genotype‐environment interaction in one population, allowing selection on a QTL basis within macro‐environments with or without Rhizomania infestation, respectively. No clear results were found for the second population tested in environments with and with‐out Cercospora infestation. Consequences for breeding strategies are discussed.     

Genetic variation for traits relating to nitrogen content of maize stalks

Summary The objective of this research was to obtain information about expression of genes controlling N concentration in the lower stalk internodes of maize at silking stages and in two other stages during the grain filling period. The inheritance of nitrate-N concentration, total N concentration, and the nitrate-N/total N ratio in the lower stalk internodes was measured in an eight-line diallel cross experiment and in an experiment involving segregating generations. The results show that the parameters examined, particularly nitrate-N concentration, are genetically controlled and that maize plants differ in this respect. Moreover, the magnitude of the general combining ability effects in relation to the size of specific combining ability obtained from the diallel analysis and the mean squares of the analysis of variance of generation means indicated additive heritability of nitrate-N concentration and other N-related traits in maize stalks. These findings suggest to us that a cyclic selection program in maize should be effective in modifying the level of N-related traits concentration in the stalks.     

Genetic stability of quantitative characters in successive generations in maize inbred lines

Summary Genetic stability was evaluated in 11 long-time inbred lines of maize (Zea mays L.) by measuring 10 plant, ear, and seed characters in successive generations reproduced by self-pollination in ear-to-row progenies. The lines were reproduced through 10 generations, and the studies were made for generations 1, 3, 5, 7, 9, and 11. All lines had been inbred more than 10 generations before the start of the study. For 106 F-tests among generations, significant variation was observed for 40 tests (P<0.05). Major changes were observed in two inbred lines; in most other cases, the statistically significant changes were too small to be of practical importance.Joint contribution: Plant Science Research Division, Agricultural Research Service, U.S. Department of Agriculture, and Journal Paper No J-7245 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa. Project No 1897.