Heritability and correlations among traits in four-way soybean crosses

Recurrent selection programs can use several crossing arrangements to synthesize basic populations for breeding purposes. This study evaluated heritability and correlations among traits in forty-five populations of F_2[4] and F_2:3[4] generations obtained throughout four-way crosses [4] between two dialells among ten semi-late and ten late maturity soybean (Glycine max L. Merrill) genotypes. The generation advance was made by the TSHD (Thinned Single Hill Descent) method and all individual plants were evaluated for the following traits: number of days to flowering (NDF) and maturity (NDM), plant height at flowering (PHF) and maturity (PHM), agronomic value (AV) and seed yield (YLD). Four-way crosses associated with TSHD method provided high genetic variability in the populations with little or no reduction from F_2[4] to F_2:3[4]. The ‘narrow sense’ heritability estimated using correlations between F_2[4] and F_2:3[4] plants was lower than but closely related to broad-sense estimates. The populations 21(IAC-4 × IAC-9) × (GO79-1039 × Paranagoiana) and 23 (IAC-4 × Santa Rosa) × (GO79-1039 × Tropical) were the most productive with high variability in F_2[4] and/or F_2:3[4] generations. Genotypic correlations measured were generally high, positive and consistent for the two generations except for those related to AV and YLD. These results indicate that the use of four-way crosses can be an efficient method to increase the genetic base of populations for recurrent selection or cultivar development. Significant AV × YLD correlations indicated visual selection can be used as additional selection criteria for improving populations. This revised version was published online in August 2006 with corrections to the Cover Date.     

陆地棉产量相关性状的QTL定位

中棉所28和湘杂棉2号分别是以中棉所12×4133和中棉所12×8891配制而成的两个陆地棉强优势杂交种。以其F₂为作图群体,筛选6000多对SSR引物,利用两群体间27个共有多态位点,通过JoinMap 3.0软件整合了一张包含245个多态位点、全长1847.81 cM的遗传图谱。利用Win QTLCart 2.5复合区间作图法分别对两群体8个产量相关性状在F₂和F_2:3中进行QTL定位,在中棉所28群体多环境平均值的联合分析中检测到16个QTL,三环境分离分析中检测到43个QTL;在湘杂棉2号群体分别检测到20个和66个QTL。在A3、D8、D9等染色体上有QTL成簇分布现象,同时在两个群体中发现一些不受环境影响且稳定遗传的QTL。对考察的8个性状在两个群体中发现12对共有QTL,控制果枝数、衣分和籽指的QTL增效基因位点均来源于共同亲本中棉所12。综合分析推测中棉所12的育种价值主要是通过提高后代的结铃性来实现的。研究结果为棉花产量性状的分子设计育种提供了有用的信息。     

Comparison of two crossing and four selection schemes for yield, yield traits, and slow rusting resistance to leaf rust in wheat

The most important breeding objectives in crop improvement are improving grain yield, grain quality, and resistances to various biotic and abiotic stresses. The objectives of our study were to compare two crossing and four selection schemes for grain yield, yield traits, and slow rusting resistance to leaf rust (Puccinia recondita) based on additive genes in wheat (Triticum aestivum), and to identify the most efficient crossing and selection methodologies in terms of genetic gains and cost efficiency. Segregating populations were derived from 18 simple crosses and the same number of top (three-way) crosses. Half of the crosses were derived from Yecora 70 and the other half from Veery #10 as the common leaf rust susceptible parents. The four selection schemes were: pedigree, modified bulk (F₂ and F₁-top as pedigree, selected lines in F₃, F₄, F₂-top, F₃-top as bulk; and pedigree in F₅ and F₄-top populations), selected bulk (selected plants in F₂, F₃, F₄, F₁-top, F₂-top and F₃-top as bulk; and pedigree in F₅ and F₄-top populations), and nonselected bulk (bulk in F₂, F₃, F₄, F₁-top, F₂-top and F₃-top; and pedigree in F₅ and F₄-top populations). A total of 320 progeny lines, parents and checks were tested for grain yield, other agronomic traits and leaf rust resistance during the 1992/93 and 1993/94 seasons in Ciudad Obregon (Sonora State, Mexico) which represents a typical high yielding irrigated site. The influence of the type of cross and the selection scheme on the mean grain yield and other traits of the progenies was minimal. The selection of parents was the most important feature in imparting yield potential and other favourable agronomic traits. Moreover, the highest yielding lines were distributed equally. Progeny lines derived from Veery #10 crosses had significantly higher mean grain yield compared to those derived from the Yecora 70 crosses. Furthermore, a large proportion of the highest yielding lines also originated from Veery #10 crosses. Mean leaf rust severity of the top cross progenies was lower than that of the simple cross progenies possibly because two parents contributed resistance to top cross progenies. Mean leaf rust severity of the nonselected bulk derivatives was twice that of lines derived from the other three schemes. Selected bulk appears to be the most attractive selection scheme in terms of genetic gains and cost efficiency. This revised version was published online in August 2006 with corrections to the Cover Date.     

Quantitative-genetic parameters of sorghum growth under striga infestation in Mali and Kenya

To estimate quantitative‐genetic parameters of sorghum for resistance to the hemi‐parasitic weed striga [Striga hermonthica (Del.) Benth.] and for agronomic traits, 36 diallel F₂ populations and their nine parental lines were evaluated under severe striga infestation at two locations each in Mali and Kenya. Location means for grain yield ranged from 132 to 254 g/m². F₂ populations outyielded lines on average by 18%. For striga emergence traits, F₂ heterosis values ranged from ‐36% to 232% among populations. Genetic and genotype x environment interaction variances of lines and F₂s were highly significant for all traits. Broad‐sense heritabilities for areas under striga severity progress curves and grain yield were 0.83 and 0.90 in lines, and 0.81 and 0.89 in F₂s, respectively. General and specific combining ability, and their interaction effects with locations were significant for most traits. F₂ superiority for grain yield under striga infestation demonstrates the potential merit of heterozygous cultivars in the target areas. Significant genotype x environment interaction entails multilocational testing to identify stable resistance. A combination of resistance with striga tolerance is recommended to breeders.     

Heritability and predicted gain from selection in components of crop duration in divergent chickpea cross populations

Genetic analysis of ten quantitative traits related to crop duration in chickpea was carried out using three F ₂ sib-populations; 272-2 × CDC Anna, 298T-9 × CDC Anna and 298T-9 × CDC Frontier. F ₃ and F ₄ families from these populations were further evaluated for traits found important in the initial study. Also, 112 recombinant inbred lines (RILs) of chickpea cross ICCV 2 × JG 62 were evaluated for days to flowering, days to maturity and reproductive period. An analysis of the F ₂ population data using the mixed model approach revealed that the additive component of variance was significant for days to flowering, days to first podding and days to first pod maturity, while dominance genetic variance was significant for morphological components of crop duration such as height to first pod and height at flowering. Comparatively high heritability estimates (39–48%) were obtained for days to flowering, days to first pod maturity, percent pod maturity at four months after planting and days to maturity based on offspring-parent (F ₄ and F ₃ generations) regression and/or analysis of variance for the RIL population. The predicted gain from selection as a percentage of the population mean was low (5% or less) for these key components of crop duration owing to the low variability detected within the populations, the exception being percent pod maturity. To maximize gain from selection in these traits, it is therefore, essential to increase genetic variability among the progenies, potentially through multi-parent crosses that may involve gene introgression from across desi and kabuli types of chickpea and from wild progenitors.     

Inheritance of drought resistance related traits in two crosses of groundnut (<Emphasis Type="Italic">Arachis hypogaea</Emphasis> L.)

Groundnut (Arachis hypogaea L.) is an important oilseed crop grown in more than 100 countries across wide range of environments. Frequent occurrence of drought is one of the limiting factors adversely affecting groundnut productivity, especially in rainfed areas, and hence genotypes having high water use efficiency (WUE) under limited available water need to be developed. In groundnut, WUE is correlated with SPAD chlorophyll meter reading (SCMR) and specific leaf area (SLA). These two traits, SCMR and SLA, can be used as surrogate traits for selecting for WUE. In order to improve SCMR and SLA, and in turn WUE in groundnut, a good knowledge of the genetic system controlling the expressions of these traits is essential for the selection of the most appropriate and efficient breeding procedure. The present investigation was conducted to determine the gene action controlling the inheritance of SCMR and SLA in two crosses, ICG 7243 × ICG 9418 and ICG 6766 × Chico, and their reciprocals. Six generations of each cross (P₁, P₂, F₁, F₂, BC₁P₁, and BC₁P₂) were evaluated for SCMR and SLA at two stages of the crop growth viz., 60 and 80 days after sowing (DAS). For SCMR at 80 DAS, additive effects were important in both the crosses whereas predominance of dominance effects with duplicate epistasis was observed for SCMR at 60 DAS and SLA at both stages in both the crosses. Predominance of additive effect for SCMR at 80 DAS suggested effective selection could be practiced even in early generations whereas for SCMR at 60 DAS and SLA at both stages in both crosses, it would be better to defer selection to later generations. Further, recording of SCMR and SLA should be done between 60 and 80 DAS for screening the germplasm lines for drought tolerance.     

Generation mean analysis of phosphorus‐use efficiency in freely nodulating soybean crosses grown in low‐phosphorus soil

Freely nodulating soybean genotypes vary in their phosphorus (P) uptake and P‐use efficiency (PUE) in low‐P soils. Understanding the genetic basis of these genotypes’ performance is essential for effective breeding. To study the inheritance of PUE, we conducted crosses using two high‐PUE genotypes, two moderate‐PUE genotypes and two inefficient‐PUE genotypes, and obtained F₁, F_2, BC₁ and BC₂ populations. The inheritance of PUE was evaluated using a randomized complete block design. A generation mean analysis of phenotypic data showed that PUE was heritable, with complex inheritance patterns and the presence of additive, dominance and epistatic gene effects. Seed P, shoot P, root P, P‐incorporation efficiency and PUE were largely quantitatively inherited traits. There were dominance, additive × additive and dominance × dominance gene effects on PUE, grain yield, shoot dry weight, 100‐seed weight, root dry weight and shoot dry matter per unit P for populations grown under low‐P conditions. Dominance effects were generally greater than additive effects on PUE‐related indices. These PUE indices can be used to select P‐efficient soybean genotypes from segregating populations.     

Genetic analysis of resistance to soybean cyst nematode in PI 438489B

Soybean (Glycine max L. Merr.) plant introduction PI 438489B is a unique source that has resistance to all known populations of soybean cyst nematode (Heterodera glycines Ichinohe, SCN). This PI line also has many desirable agronomic characteristics, which makes it an attractive source of SCN resistance for use in a soybean breeding program. However, characterization of SCN resistance genes in this PI line have not been fully researched. In this study, we investigated the inheritance of resistance to populations of SCN races 1, 2, 3, 5, and 14 in PI 438489B. PI 438489B was crossed to the susceptible cultivar ‘Hamilton’ to generate F₁ hybrids. The random F₂ plants and F₃ lines were evaluated in the greenhouse for reaction to these five populations of SCN races. Resistance to SCN races 1, 3, and 5 were mostly conditioned by three genes (Rhg Rhg rhg). Resistance to race 2 was controlled by four genes (Rhg rhg rgh rgh). Three recessive genes were most likely involved in giving resistance to race 14. We further concluded that resistance to different populations of SCN races may share some common genes or pleiotropic effects may be involved. This revised version was published online in July 2006 with corrections to the Cover Date.     

Selection of snap bean recombined inbred lines by using EGT and SSD

With the objective of selecting superior recombinant lines of snap bean, four segregating F₂ populations were selected by early generation testing and advanced by single seed descent. In a randomized complete block design with two replications within sets 120 F_6:7 lines were obtained and evaluated for seven traits of agronomic interest. The mean pod yield of the F_6:7 generation was 72% higher than in generation F₂, confirming the efficiency of early selection. There was genetic variability in the F_6:7 lines within the sets. The selection of superior genotypes was possible by the high estimates of narrow-sense heritability. Highest gains in simultaneous selection of traits were expressed by the indices proposed by Mulamba & Mock for the genetic standard deviation and by Williams, based on tentatively attributed arbitrary weights. Line 3 of the F_6:7 generation, with a yield of 8,050.0000 kg ha⁻¹ and pod fiber content of 0.3650% is highly promising to be release as new cultivar.     

Genetic analyses of agronomic traits in Tartary buckwheat (Fagopyrum tataricum (L.) Gaertn.)

The consumption of products made from Tartary buckwheat (Fagopyrum tataricum (L.) Gaertn.) has increased in recent years in Japan. Increased consumer demand has led to recognition of the need for early varieties of this crop with high and stable yields. In order to accomplish this, more information is needed on the genetic mechanisms affecting earliness and yield. We conducted genetic analysis of 3 agronomic traits (days to flowering, plant height and total seed weight per plant) to segregate F₂ and F₃ populations derived from a cross between Tartary buckwheat cultivars ‘Hokuriku No. 4’ and ‘Ishisoba’. Broad-sense heritability estimates for days to flowering, plant height and total seed weight were 0.70, 0.62 and 0.75, respectively, in F₃ population. Narrow-sense heritability for total seed weight (0.51) was highest, followed by heritability for days to flowering (0.37), with heritability for plant height (0.26) lowest. Later flowering was associated with increased plant height and higher yields. From the F₄ generation, we identified twelve candidate plants with earlier maturity and reduced plant height compared to ‘Hokuriku No. 4’, but almost the same total seed weight. These results suggest that hybridization breeding using the single seed descent (SSD) method is an effective approach for improving agronomic characteristics of Tartary buckwheat.     

Irrigation and Nutrient Effects on Growth and Water–Yield Relationship of Wheat (Triticum aestivum L.) in Central India

Increasing production of wheat from a limited water supply can result from efficient irrigation and nutrient management. A 3‐year field experiment was conducted at the Indian Institute of Soil Science, Bhopal, to study the growth, yield, seasonal evapotranspiration (ET) and water use efficiency (WUE), and the water–yield relationship of wheat in a soybean–wheat cropping system on vertisols. Three levels of irrigation, viz. I₀, no post‐sowing irrigation; I₁, two irrigations [crown root initiation (CRI) and flowering stage]; and I₂, three irrigations (CRI, maximum tillering and flowering stage) and three nutrient management treatments, viz. F₀, control (without fertilizer/manure); F₁, 100 % NPK (100–21.5–24.9 kg ha^?1); and F₂, 100 % NPK + farmyard manure (FYM‐10 t ha^?1) were tested in a split‐plot design with three replication. It has been established (through anova ) that the year effect was rather negligible and the interaction effects of irrigation and nutrient management on the growth parameters, ET, yield components, yield and WUE were significant. Plant height, progressive leaf area index, dry matter accumulation and crop growth rate were higher in I₂F₂, and I₂F₁ and I₁F₂ were statistically at par. The seasonal ET increased significantly with the increase in water supply in every nutrient treatment and it was highest in I₂F₂ and lowest in I₀F₀. The highest grain yield was obtained in I₂F₂; and a similar yield was recorded in I₃F₁ and I₂F₂. This shows a strong interaction effect between irrigation and nutrients. Yield components, viz. number of ears m^?2, number of grains ear^?1 and 1000‐grain weight were significant. The higher number of ears m^?2 containing greater number of grains with relatively heavier weights appeared to have contributed to the higher yield in I₁F₂, I₂F₁ and I₂F₂. The highest WUE obtained in I₀F₂ did not correspond to the highest yield and maximum ET, but a WUE of 10.43 kg ha^?1 mm^?1 in the I₂F₂ combination corresponded with the highest yield and the seasonal ET requirement was 391.8, which was 137 % greater than the water use at maximum WUE. The ET–grain yield relationship was linear, with a lowest regression slope (i.e. marginal WUE) and elasticity of water production (E_wp) in F₀ and a considerably higher slope and E_wp in F₁ and F₂. As the E_wp is positive and close to one in 100 % NPK treatment, the scope of improving WUE and yield with only inorganic fertilizer is very little, and relatively greater scope exists in the integrated management of organic manure and inorganic fertilizer. The results suggest that integrated nutrient management (100 % NPK + FYM) in conjunction with three irrigations maximized yield of wheat with concomitant improvement in ET and WUE under limited water availability.     

Selection response for carbon isotope discrimination in a Triticum polonicum×T. durum cross: Potential interest for improvement of water efficiency in durum wheat

This study has been conducted to evaluate the usefulness of carbon isotope discrimination (δ) in mature kernels as a criterion for the improvement of water-use efficiency and yield under drought in durum wheat. For this purpose, Triticum durum‘Om Rabi 5’ was crossed with T. polonicum pseudochrysospermum 9 (Tp9) which has been found to be more drought tolerant and to have a lower carbon isotope discrimination value of the grain. The F₂ population showed a wide segregation for carbon isotope discrimination. Further, divergent selections (selection of plants most different in carbon isotope discrimination) were made among individual F₂ plants, and for carbon isotope discrimination in F₃ progenies under field conditions. Selected F₃ and F₄ progenies were evaluated under field conditions for morphological and agronomical traits. Broad-sense heritability (h²_b), response to selection and realized heritability (h²_r) were high. The narrow-sense heritability (h²_n= 0.37 ± 0.047) indicated that additive and dominance effects were involved in the genetic control of carbon isotope discrimination. Negative correlations were noted between carbon isotope discrimination and grain yield and between carbon isotope discrimination and biomass yield within years and generations. An explanation of this result is attempted by analysing the relationships between carbon isotope discrimination and several phenological and morphological traits influencing the water-use efficiency. The divergent groups selected for low and high carbon isotope discrimination exhibited significant differences for days to heading, plant height, shape of the spike and number of spikelets per spike. Correlations were also found between carbon isotope discrimination and plant height, harvest index, shape of the spike, spike length, and number of spikes per plant. The potential use of carbon isotope discrimination as a criterion for the improvement of water-use efficiency in durum wheat is discussed by considering the genetics of this trait (variability, heritability, response to selection) and also the associations with phenological and morphological traits.     

Correlated response to recurrent selection for groat-oil content in oats

Summary One hundred random oat (Avena sativa L.) lines from a base (C₀) and each of three populations (C₁, C₂, and C₃) improved for groat (caryopsis) oil content by phenotypic recurrent selection were evaluated for correlated changes in several unselected agronomic traits. In addition, the parents of the base population and four check varieties were evaluated for the same traits. Phenotypic recurrent selection for high groat-oil content resulted in no significant correlated response in mean expression of any trait. Mean grain yield, biomass, groat yield, and harvest index of the improved populations were equal or superior to the mean of the parents and, with the exception of harvest index, equivalent to the mean of the check varieties. Mean test weight and seed weight of all populations were lower than for parents or check varieties. Selection for high groat-oil content caused a decline in genotypic variance for test weight and groat fraction, but reductions in genotypic variance for heading date and plant height may have resulted from culling for good agronomic type. Broad-sense heritability remained moderate to high for all traits except groat fraction. Phenotypic and genotypic correlation coefficients revealed negative, though mostly nonsignificant, relationships between groat-oil content and several traits, which may reflect a purported bioenergetic limitation to increasing groat-oil content in oats. Oil yield, however, was positively correlated with grain and groat yield, groat fraction, biomass, and harvest index. Results suggest that development of high-oil oat cultivars with current levels of production traits via phenotypic recurrent selection is possible.Journal Paper no. J-13038 of the Iowa Agric. and Home Econ. Exp. Stn., Ames, IA 50011. Project 2447.     

Evaluation of genetic variances, heritabilities, and correlations for yield and fiber traits among cotton F2 hybrid populations

Summary F₂ hybrid cultivars continue to occupy a small portion of the cotton (Gossypium hirsutum L.) production are in the United States, but occupy a larger proportion of the production area in some other countries. Sixty-four F₂ hybrids resulting from crosses of four commercial cultivars and 16 pest-resistant germplasm lines were evaluated for five fiber and four yield traits in four environments at Mississippi State, MS. An additive-dominance genetic model was employed for these traits. The minimum norm quadratic unbiased estimation (MINQUE) method was used with a mixed model approach for estimating genetic variance and covariance components and for predicting genetic correlations. This study investigated genetic variances, heritabilities, and genetic and phenotypic correlations between agronomic and fiber traits among these 64 F₂ hybrid populations and discussed the usefulness of these populations for use as hybrids or for selections for pure lines.Dominance variance accounted for the major proportion of the phenotypic variances for lint yield, lint percentage, and boll size indicating that hybrids should have an advantage for these traits compared to pure lines. A low proportion of additive variance for fiber traits and the significant additive x environment variance components indicated a lack of substantial useful additive genetic variability for fiber traits. This suggests that selections for pure lines within these F₂ populations would have limited success in improving fiber traits. Genetic and phenotypic correlation coefficients were of comparable magnitude for most pairs of characters. Fiber strength showed a positive additive genetic correlation with boll weight. Dominance genetic correlations of fiber strength with elongation and 2.5% span length were also significant and positive; however, the additive genetic correlation of length and strength was zero.Contribution of the USDA-ARS in cooperation with the Mississippi Agric. and Forestry Exp. Stn.     

Genetic studies of seed longevity in hexaploid wheat using segregation and association mapping approaches

Xieyou9308 is the first commercial super hybrid rice released in 1996 in China. To clarify its genetic mechanism underlying high yield potential, a recombinant inbred line (RIL) population derived from the cross between the maintainer line XieqingzaoB (XQZB) and the restorer line Zhonghui9308 (ZH9308) and two derived backcross F₁ (BCF₁) populations were developed for the identification of quantitative trait loci (QTLs) related to ten important agronomic traits (tiller number (TN), heading date (HD), and grain yield per plant (GYPP), etc.). The BCF₁ performance was closely correlated with the performance of their parental RILs according to both the analysis of broad-sense heritability (h _B ²) and phenotypic correlation coefficient (PCC) in the two BCF₁ populations, but not proved by QTL analysis. A total of 21 additive-effect main QTLs (M-QTLs), 22 dominant-effect M-QTLs, and 19 dominant-effect M-QTLs were detected with the WinQTLCart 2.50 software for the ten traits in the RIL and two BCF₁ populations, respectively. Of theses, three QTLs (qHD7a, qPPP3a, and qPL10) of 21 were detected repeatedly in the RIL and one BCF₁ populations, ten QTLs underlying four traits were only detected repeatedly in two BCF₁ populations, and nine QTLs controlling more than two traits were detected repeatedly, the additive-effect QTLs and dominant-effect QTLs play an important role in the performance of agronomic traits and no epistatic QTL of additive by additive effect and dominant by dominant-effect was detected for all traits in three populations. This research is valuable for M-QTL related to important agronomic trait in future fine mapping and positional cloning.     

Selection for protein content in soybean from single F<Subscript>2</Subscript> seed by near infrared reflectance spectroscopy

Soybean seed averages about 40% protein and is a dominant source of protein in animals and human foods. Increasing protein in soybeans is a goal in soybean breeding programs. Initial selection for protein among progeny from breeding populations is often based on non-destructive Near Infrared Reflectance (NIR) spectroscopy analysis of a 5 g or more seed sample in the F₃ or later generations. NIR spectroscopy analysis for protein on single F₂ seed would allow selection at the earliest possible time and improve selection efficiency for protein content; however this practice has not been evaluated. The objective of this study was to test effectiveness of NIR spectroscopy analysis of single F₂ seeds to select for increased protein content from two populations developed from high and average protein content parents. F₂ seeds from a single F₁ plant of each population showed a normal distribution with transgressive segregation for protein concentration. In both populations, F₃ seeds produced from plants from single F₂ seeds with either low or high protein content were analyzed for protein by NIR spectroscopy. Protein means and ranges of F₃ seed selected from high protein F₂ seeds were higher in protein than F₃ seed from low protein F₂ seeds which produced low means and ranges in protein content. This shows that analysis of single F₂ seed for protein content using NIR spectroscopy was effective in selecting for increased protein in the F₃ generation. Analysis of single F₂ seeds from breeding populations will improve breeding efficiency for protein in soybean breeding programs.     

Analysis of tofu‐related traits by a bench‐scale tofu production method and their relationship with agronomic traits in European soybean

European tofu manufacturers are becoming more and more interested in locally grown soybeans. A prerequisite for the development of European tofu cultivars is to improve our understanding of how the environment and genetics affect soymilk and tofu quality, as well as how quality and agronomic traits are correlated. This study was based on 215 recombinant inbred lines derived from two populations and grown at three locations that were evaluated for tofu traits in a bench‐scale tofu laboratory. The heritabilities of most of the evaluated tofu traits were moderately high with h² > 0.6. We observed significant genotypic variance components, but an even stronger contribution of the location. The network analysis of the evaluated traits was population‐dependent; however, the tofu traits were not associated with any of the agronomic traits. Collectively, our results indicate the potential to improve tofu‐related traits in European soybean. The bench‐scale tofu production method provides a valuable tool to test soybean lines in breeding programmes; however, the method needs to be further improved and automated to minimize errors due to the laboratory staff.     

AFLP标记与棉花重要农艺性状的关联研究

 以陆地棉（Gossypium hirsutum L.）品种中棉所8号和海岛棉（Gossypium barbadense L.）品种Pima 90-53杂交产生的包含91个单株的BC₁F₂群体及其衍生BC₁F_2:3群体为材料,利用逐步多元回归分析确定分子标记与重要农艺性状的相关关系,为分子标记辅助选择提供依据。试验材料分别种植在保定市郊和沧州青县两个点,每个株行考察衣分、子指、铃重、皮棉重、子棉重5个产量性状和2.5%纤维跨距长度、马克隆值、纤维整齐度、纤维伸长率、纤维比强度5个品质性状。以20对AFLP引物组合产生的125个位点对10个重要农艺性状进行多元线性回归分析,发现其中4对引物组合产生的15个位点与10个性状有着显著相关性（P≤0.05,P≤0.01）,而后通过逐步多元回归分析获得6个位点,对9个农艺性状所解释的表型变异为6.2%～30%。结果表明,与9个农艺性状显著相关的6个AFLP位点可以用于未来的分子标记辅助育种计划。     

渐渗系IL6的遗传评价和渗入片段的鉴定

 用海岛棉3-79的6号染色体渐渗系(简称IL6)和背景亲本TM-1构建了F₂、F_2：3群体,在2年的田间重复实验中调查了18个重要农艺性状,作遗传评价。并获得F₂群体的分子数据,进行QTL定位和单标记分析。结果表明:亲本IL6中的渐渗片段,组成有3-79的6号染色体,3-79的非6号染色体和大部分的TM-1片段。IL6的产量、品质性状都优于受体亲本TM-1,遗传分析也发现产量、品质性状增效基因位点来自IL6,说明所渗入片段起着关键作用。亲本农艺性状表现和遗传分析结果表明,IL6渗入片段含有总铃数、单株铃数、衣分、果枝数、比强度、麦克隆值等性状的主基因。而QTL定位和单标记分析结果显示,IL6渗入片段含有单株铃数、衣分、果枝数、株高、子指、整齐度等性状的QTLs。     

Combining ability of soybean (Glycine max) for low phosphorus tolerance on acidic soils of Western Ethiopia

Determining the gene actions governing the inheritance of traits of interest has paramount importance in designing a breeding approach to improve the progeny populations. This study was undertaken to determine the combining ability of nine selected parental lines in the F₂/F₃ segregating populations for low P tolerance. The experiment was laid out in an alpha lattice design in two locations, that is Mettu and Assossa of Western Ethiopia that are characterized by soils with low P and pH. General combining ability (GCA) effects were highly significant for grain yield, pod length, days to maturity and plant height, while specific combining ability (SCA) effects were highly significant for grain yield, 100-seed weight, pod length and plant height. The parent Hardee-1 was identified as the best general combiner for yield, number of seeds per pod, pod length, plant height and pod number. The results suggest that additive gene action was important for several of the studied traits, implied by significant GCA effect, which might indicate selection for these traits could be effective in later segregating generations.