Performance and combining ability in cotton (<Emphasis Type="Italic">Gossypium hirsutum</Emphasis> L.) populations with diverse parents

Improving fiber quality properties of cotton is important for increasing the efficiency of manufacturing textiles, including enhancing yarn quality and spinning performance. This study was conducted to determine if we could identify valuable cotton cultivars to use as parents in breeding programs with the goal of improving fiber properties. Seven parents were combined in a diallel design and selfed to obtain 21 F₂ populations. Positive general and specific combining ability effects were observed for all traits. General combining ability tended to be larger than specific combining ability, indicating these traits are controlled primarily by additive genetic effects. Correlations among traits were generally positive except for lint yield correlations with fiber strength and length. For improving the fiber quality measures of strength and length, line 7235 shows excellent general combining ability effects. SG125 would provide elite germplasm to increase agronomic measures of lint yield and lint percent. The MD51 genotype has the highest potential among the genotypes tested here to provide germplasm combining both improved yield and fiber strength. These parents, or their selected progeny, should be useful in a breeding program to generate variability from which selection can be used to identify lines with improved fiber and/or agronomic properties.     

Comparative yield component analysis in <Emphasis Type="Italic">Gossypium hirsutum</Emphasis> parents using fibre quality grouping

The usual practice of estimating association and direct and indirect effects among various traits in Gossypium hirsutum is with ungrouped genetic material based on staple length and strength. During 2003–2004 and 2004–2005 genotypic and phenotypic association among ten characters were estimated in G. hirsutum genotypes: (i) set-1: 10 genotypes of low fibre strength (≤196.2 mN/tex) and medium staple length (≤25.0 mm), (ii) set-2: 10 genotypes of high fibre strength (≥235.44 mN/tex) and long staple length (≥28 mm) and (iii) set-3: 20 genotypes of set-1 and 2. The differences in the estimates of associations, direct and indirect effects for different characters in fibre quality groups were examined. The complete analysis of variance for the characters under study viz; days to 50% flowering, plant height (cm), number of monopodial and sympodial branches per plant, seed cotton yield per plant (g), boll weight (g), total number of bolls per plant, lint %, 2.5% span length (mm) and fibre strength (mN/tex) indicated highly significant genotypic differences for genotypes, years and genotype × years interaction. Variation within medium staple length and low strength (set-1), high staple length and high strength genotypes (set-2) and their interaction with year were also significant. Medium staple length and low strength (set-1) versus high staple length and high strength component (set-2) was significant for all the traits indicating significant variability between the sets. A true relationship and direct selection were observed for days to 50% flowering, number of monopodial and sympodial branches per plant with seed cotton yield in the three sets suggesting that separation of genetic material based on staple length and fibre strength for improvement of seed cotton yield through these traits is not required. Magnitude and direction of direct effect and association with yield of the other traits; plant height, number of total bolls per plant, boll weight, lint %, staple length and fibre strength differed between the sets. This study concluded that more successful planning of a breeding programme can be made through path coefficient analysis if the genetic material is grouped based on staple length and fibre strength. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Genetic effects of nine <Emphasis Type="Italic">Gossypium barbadense</Emphasis> L. chromosome substitution lines in top crosses with five elite Upland cotton <Emphasis Type="Italic">G. hirsutum</Emphasis> L. cultivars

Crosses between Gossypium barbadense L and Gossypium hirsutum L. (Upland cotton) have produced limited success in introgressing fiber quality genes into the latter. Chromosome substitution lines (CSBL) have complete chromosomes or chromosome arms from G. barbadense, line 3-79, substituted for the corresponding chromosome or arms in G. hirsutum in a near isogenic background of TM-1. We top crossed nine CSBL and their parents (TM-1 and 3-79) with five cultivars. Parental lines and their F₂ populations were evaluated in four environments for agronomic and fiber quality traits. The CSBL and their F₂ hybrids showed wide ranges for both agronomic and fiber traits of economic importance. Genetic analysis showed that additive variances were larger than dominance variances for lint percentage, boll weight, lint yield, fiber length, strength, elongation, micronaire, and yellowness; whereas, dominance variances were larger than additive variances only for uniformity of fiber length and equal for fiber reflectance. For all traits, except boll weight and lint yield, significant additive effects of one or more chromosomes from 3-79 in TM-1 background were greater than the corresponding TM-1 chromosome. In addition, we identified specific chromosomes from G. barbadense (3-79) that carry alleles for improvements in specific fiber quality traits in Upland cotton. Favorable additive effects of individual chromosomes or chromosome segments from 3-79 relative to corresponding chromosomes or chromosomes segments from TM-1 were identified in this study as follows: Lint percentage, chromosome/arms 10, 16-15; longer fibers, chromosome/arms 01, 11sh, 26Lo; more uniform fibers, chromosomes/arms 01, 11sh, 10, 17-11; stronger fibers, chromosome/arms 01, 11sh, 12sh, 26Lo, 17-11; fiber elongation, chromosomes/arms 01, 11sh, 26Lo, 10, 17-11; reduced fiber micronaire, chromosome/arms 01, 12sh, 4-15, 16-15, 17-11; fibers with more reflectance, chromosome/arms 10, 4-15, 16-15, 17-11; fiber with less yellowness, chromosome arms 4-15, 17-11. Based on the present study, we concluded that by using CSBL, favorable fiber quality alleles can be introgressed into Upland cotton, thus greatly improving the breeder’s ability for improvement of Upland cotton for a variety of traits. These data should provide useful genetic information to the cotton breeding industry at large.     

Quantitative analysis and QTL mapping for agronomic and fiber traits in an RI population of upland cotton

Genetic mapping is an essential tool for cotton (Gossypium hirsutum L.) molecular breeding and application of DNA markers for cotton improvement. In this present study, we evaluated an RI population including 188 RI lines developed from 94 F₂-derived families and their two parental lines, ‘HS 46’ and ‘MARCABUCAG8US-1-88’, at Mississippi State, MS, for two years. Fourteen agronomic and fiber traits were measured. One hundred forty one (141) polymorphic SSR markers were screened for this population and 125 markers were used to construct a linkage map. Twenty six linkage groups were constructed, covering 125 SSR loci and 965 cM of overall map distance. Twenty four linkage groups (115 SSR loci) were assigned to specific chromosomes. Quantitative genetic analysis showed that the genotypic effects accounted for more than 20% of the phenotypic variation for all traits except fiber perimeter (18%). Fifty six QTLs (LOD > 3.0) associated with 14 agronomic and fiber traits were located on 17 chromosomes. One QTL associated with fiber elongation was located on linkage group LGU01. Nine chromosomes in sub-A genome harbored 27 QTLs with 10 associated with agronomic traits and 17 with fiber traits. Eight chromosomes in D sub-genome harbored 29 QTLs with 13 associated with agronomic traits and 16 with fiber traits. Chromosomes 3, 5, 12, 13, 14, 16, 20, and 26 harbor important QTLs for both yield and fiber quality compared to other chromosomes. Since this RI population was developed from an intraspecific cross within upland cotton, these QTLs should be useful for marker assisted selection for improving breeding efficiency in cotton line development. Paper number J1116 of the Mississippi Agricultural and Forestry Experiment Station, Mississippi State University, Mississippi State, MS 39762. Mention of trademark, proprietary product, or vendor does not constitute a guarantee or warranty of the product by USDA, ARS and does not imply its approval to the exclusion of other products or vendors that may also be suitable.     

Effects of genotype and environment on seed quality traits variability in interspecific cross-derived <Emphasis Type="Italic">Brassica</Emphasis> lines

Genotype (G), environment [i.e. year (Y) and location (L)] and their interaction (GYL) play an important role in the final expression of quality attributes. A multi-environment trial in selected interspecific cross-derived Brassica lines was conducted to evaluate the magnitude of G, Y, L and GYL effects on seed quality traits of Brassica genotypes under three locations in Poland, during the 2011–2013 cropping season. The oil, protein, fiber (Acid Detergent Fiber and Neutral Detergent Fiber) as well as glucosinolate contents was determined by near-infrared reflectance spectroscopy (NIRS) and significant differences were observed between tested Brassica genotypes and across harvesting years and growing locations. Generally, all tested hybrid lines displayed wider genetic variability for studied quality traits than control genotypes. Analysis of variance indicated that the main effects of genotypes, years and locations as well as all interactions were significant for all traits of study (except year?×?location interaction for glucosinolates). However, location had the most significant effect on oil, protein and fiber content while genotype had significant impact on glucosinolates content in Brassica seeds. Moreover, the individual lines having combination of desirable traits were also identified from F₅ to F₇ generations of tested hybrids.     

AFLP marker associations with agronomic and fiber traits in cotton

DNA markers linked with major QTL contributing to traits of importance will be a useful tool for cotton (Gossypium spp.) genetics and breeding. We crossed four photoperiod-sensitive accessions of cotton, G. hirsutum L., with a cultivar, selected day-neutral plants and backcrossed four times to each of the four photoperiod-sensitive accessions, selecting day-neutral plants at each generation. The day-neutral plants from the first cross and the four backcross generations were advanced to the F₆. These 20 day-neutral lines and four cultivars were grown in two environments at Mississippi State, MS and scored for seven agronomic and fiber quality traits. They were also scored for AFLP markers using a bulk sample of leaves from each of 24 lines. More than 50 AFLP markers were associated with the seven traits with fewer markers associated with fiber than agronomic traits. However, one to four markers were associated with 22–93% of the phenotypic variability of each of the seven traits. The results suggest that selected markers could be used in marker assisted selection (MAS) in crosses designed to use alleles from exotic accessions or cultivars to develop elite breeding lines for cotton improvement.     

陆地棉重组自交系群体纤维品质及产量性状遗传变异分析

以陆地棉优质品系0-153和大面积推广的双价转基因抗虫棉品系sGK9708为亲本构建了含有196个F6:8家系的重组自交系群体。在4个环境中,纤维长度、纤维强度、麦克隆值、伸长率、整齐度指数、单株结铃数、铃重、衣分、子指、单株子棉产量及单株皮棉产量等性状均呈正态分布,且存在双向超亲分离。多环境下变异分析表明,各性状家系间及环境间存在极显著差异。除纤维伸长率外,其余各纤维品质及产量性状都具有较高的遗传力,在0.75以上。共有6个家系在纤维长度、细度和强度性状上均超过高亲,可作为优质纤维种质。相关分析显示,有些家系可能打破了纤维品质和产量性状间的负相关。通过聚类分析得出,该群体各系分在了不同的组,表明存在着一定的遗传差异。该群体是进行优异纤维品质相关基础研究的良好材料。     

棉花IF2群体构建及其在纤维品质遗传和杂种优势研究中的应用

以陆地棉重组自交系RIL为材料,采用RIL系间随机交配的方式构建了一个含有188个组合的IF₂群体。对该群体的棉花纤维品质性状表现进行了评价,并采用A、D遗传模型对其纤维品质性状的遗传效应和杂种优势进行了分析。结果表明,陆地棉IF₂群体中5个纤维品质性状均呈现良好的正态分布,且各性状的表型平均值大多与F₁杂交种相近,具有明显的杂种优势。显性与环境的互作效应是控制棉花纤维品质遗传的主要因素,其次是基因的加性效应,环境因素对于棉花纤维品质的杂种优势表现巨大的影响,两个环境中预测到的杂种优势值具有明显的差异。IF₂群体是棉花数量性状遗传和杂种优势预测的优良研究群体。     

低酚棉产量、纤维品质性状的遗传分析

本文以32个低酚棉品种（系）为材料,对10个产量、纤维品质性状进行的遗传分析结果表明：低酚棉多数产量构成因素与皮棉产量为正相关,提高衣指、降低籽指虽可提高衣分和单株结铃数,但不利于增加单铃重;高产、优质的矛盾主要表现在纤维长度、比强度与衣分和单株结铃数有较强的负相关。在较大群体的基础上,通过早代的正向选     

棉花纤维素累积特性的基因型差异及与纤维比强度形成的关系

以14个纤维比强度差异明显的棉花品种为材料,研究了棉纤维素累积特性的基因型差异及与纤维比强度的关系。结果表明,棉株不同果枝部位棉铃的纤维素累积均符合Logistic曲线,棉纤维素累积的5个特征值（纤维素快速累积期的起始、终止时期,最大累积速率及其出现的时期,快速累积持续期）在品种间的变异均较大,与纤维比强度的相关系数存在大小和正负的差异。其中,纤维素最大累积速率和快速累积持续期的变异最大,前者与纤维比强度呈极显著负相关,后者与纤维比强度呈极显著正相关。进一步以纤维素最大累积速率和快速累积持续期为变量,在同样欧氏距离下,基于棉株上、中、下3个果枝部位数据的聚类结果不完全一致,但总体上14个品种可分为纤维素累积快、平缓、中等3种类型,德夏棉1号、科棉1号和美棉33B分别是其中心品种。同时以纤维比强度为变量的聚类分析表明,这3个品种又分别是低强纤维、高强纤维、中等强度纤维3种类型的中心品种。总之,在棉纤维发育过程中,纤维素累积特性存在明显的基因型差异,且高强纤维的形成是以纤维素平缓累积为基础,纤维素累积过快似乎不利于纤维比强度的形成。     

陆地棉高品质纤维种质基因库的拓建

采用远缘杂交,开展了棉属野生种的高强纤维潜力基因向陆地棉品种转育研究,以构建高纤维品质的种质基因库.在适宜的自然条件和人工条件下,陆地棉分别与异常棉(Gossypium anomalum)、辣根棉(G.armourianum)、雷蒙德氏棉(G.raimondii)等杂交,克服杂交不可交配性、杂种一代的高度不育性等,通过多年的回交选择和纤维品质测定筛选,     

Fiber initiation development in Upland cotton (<Emphasis Type="Italic">Gossypium hirsutum</Emphasis> L.) cultivars varying in lint percentage

The ovules at the stage of fiber initiation from −1 to +1 days post-anthesis (dpa) were studied, using scanning electron microscopy (SEM), in five Upland cotton (Gossypium hirsutum L.) cultivars varying in lint percentage from 28.53% to 43.10%. Our results indicated that on −1 days post-anthesis (−1 dpa), fiber cell protrusions were found in all cultivars, but these protrusions varied among different materials and the differences did not correlate with ultimate lint percentage of each cultivar. At 0 days post-anthesis (dpa), a large amount of fiber cell protrusions appeared on the ovular surface of all samples, and these protrusions had been elongated significantly by +1 dpa. Interestingly, fiber density at +1 dpa of almost all samples was always significantly lower than that at 0 dpa except Simian3, the cultivar with the highest lint percentage 43.10%. This observation suggests that with the expanding of the cotton ovular volume, fiber “diluting” degree on the ovular surfaces might be related to higher or lower lint percentage. Qiannong465, the cultivar with the lowest lint percentage (28.53%), was found to exhibit the fewest fiber protrusions. Rather, many sunken, morphologically abnormal protrusions were observed on the ovular surface at 0 dpa. Correlation analysis suggested that either fiber protrusion density at 0 dpa or fiber elongation density at +1 dpa had a highest positive correlation with lint percentage, secondly with lint index. The grey relational analysis was essentially consistent with these findings. Thus we have identified two important parameters that could provide invaluable predictive information for cotton breeding.     

Germplasm evaluation and transfer of Verticillium wilt resistance from Pima (<Emphasis Type="Italic">Gossypium barbadense</Emphasis>) to Upland cotton (<Emphasis Type="Italic">G. hirsutum</Emphasis>)

Verticillium wilt (VW, Verticillium dahliae) is a worldwide destructive soil-borne fungal disease and employment of VW resistant cultivars is the most economic and efficient method in sustainable cotton production. However, information concerning VW resistance in current commercial cotton cultivars and transfer of VW resistance from Pima (Gossypium barbadense) to Upland (Gossypium hirsutum) cotton is lacking. The objective of the current study was to report findings in evaluating commercial cotton cultivars and germplasm lines for VW resistance in field and greenhouse (GH) experiments conducted in 2003, 2006, and 2007. In the study, 267 cultivars and germplasm lines were screened in the GH, while 357 genotypes were screened in the field. The results indicated that (1) VW significantly reduced cotton yield, lint percentage, 50% span length and micronaire, but not 2.5% span length and fiber strength, when healthy and diseased plants in 23 cultivars were compared; (2) some commercial cotton cultivars developed by major cotton seed companies in the US displayed good VW resistance; (3) many Acala cotton cultivars released in the past also had good VW resistance, but not all Acala cotton germplasm are resistant; (4) Pima cotton possessed higher levels of VW resistance than Upland cotton, but the performance was reversed when the root system was wounded after inoculation; (5) VW resistance in some conventional cultivars was transferred into their transgenic version through backcrossing; and (6) some advanced backcross inbred lines developed from a cross between Upland and Pima cotton showed good VW resistance. The successful development of VW resistant transgenic cultivars and transfer of VW resistance from Pima to Upland cotton implies that VW resistance is associated with a few genes if not a major one.     

Study of genetic diversity in safflower genotypes using agro-morphological traits and RAPD markers

This research was conducted to study the genetic diversity in safflower (Carthamus tinctorius L.) using agro-morphological traits and RAPD markers. Sixteen selected lines derived from landraces growing in various agro-climatic regions of Iran along with four exotic genotypes were evaluated in a randomized complete block design with three replications under field conditions. Days to emergence, days to initial flowering, days to flowering, days to maturity, plant height, branches per plant, capitula per plant, seeds per capitulum, 1,000-seed weight, seed yield per plant, seed yield, and reaction to powdery mildew (Leveillula taurica Arnaud) were evaluated in this study. Genetic diversity of the genotypes was assessed by RAPD markers. The results indicated significant differences among genotypes for the agro-morphological traits and clustering based on these traits classified the genotypes into five groups. Analysis of the RAPD markers revealed 15 polymorphic primers out of 50 used primers. Based on RAPD data, the highest genetic similarity was observed between the cultivars of “AC Sunset,” “AC Sterling” from Canada and the lowest relatedness observed between a local breeding line “E₂₄₂₈” and genotype “GE₆₂₉₂₃” from Germany. Cluster analysis based on RAPD markers and 54% coefficient of similarity divided the genotypes into five distinct groups. Comparing the clusters based on agro-morphological traits with those from molecular markers showed slight similarities. The finding of high genetic variation for agro-morphological traits and polymorphism at DNA level reveal that agronomic traits can be improved by selection programs.     

Genotypic comparisons of chromosomes 01, 04, and 18 from three tetraploid species of <Emphasis Type="Italic">Gossypium</Emphasis> in topcrosses with five elite cultivars of <Emphasis Type="Italic">G. hirsutum</Emphasis> L.

Upland cotton, Gossypium hirsutum L. is the most widely planted cultivated cotton in the United States and the world. The other cultivated tetraploid species G. barbadense L. is planted on considerable less area; however, it produces extra long, strong, and fine fibers which spins into superior yarn. The wild cotton tetraploid species G. tomentosum Nuttall ex Seemann, native to the Hawaiian Archipelago also exhibits traits, such as drought tolerance, that would also be desirable to transfer to Upland cotton. Long-term breeding efforts using whole genome crosses between Upland and these species have not been successful in transferring very many desirable alleles into Upland cotton. Our chromosome substitution lines (CSL) have one chromosome or chromosome arm from an alien species backcrossed into the Upland cotton line,TM-1, via aneuploid technology. Five Upland cultivars were crossed with CS-B01, CS-T01, CS-B04, CS-T04, CS-B18 and CS-T18 and TM-1 the recurrent parent of the CSLs. This provided an opportunity to determine the effects of chromosomes 01, 04, and 18 from the three species in crosses with the five cultivars. Predicted genotypic mean effects of the parents, F₂, and F₃ generations for eight agronomic and fiber traits of importance were compared. The predicted hybrid mean effects for the three chromosomes from each species were different for several of the traits across cultivars. There was no single chromosome or species that was superior for all traits in crosses. Parental and hybrid lines often differed in the effect of a particular chromosome among the three species. The predicted genotypic mean effects for F₂ and F₃, with a few exceptions, generally agree with our previous results for additive and dominance genetic effects of these CSL.     

Genetic mapping of quantitative trait loci for fiber quality and yield trait by RIL approach in Upland cotton

The improvement of cotton fiber quality has become more important because of changes in spinning technology. Stable quantitative trait loci (QTLs) for fiber quality will enable molecular marker-assisted selection to improve fiber quality of future cotton cultivars. A simple sequence repeat (SSR) genetic linkage map consisting of 156 loci covering 1,024.4 cM was constructed using a series of recombinant inbred lines (RIL) developed from an F₂ population of an Upland cotton (Gossypium hirsutum L.) cross 7235 × TM-1. Phenotypic data were collected at Nanjing and Guanyun County in 2002 and 2003 for 5 fiber quality and 6 yield traits. We found 25 major QTLs (LOD ≥ 3.0) and 28 putative QTLs (2.0 < LOD < 3.0) for fiber quality and yield components in two or four environments independently. Among the 25 QTLs with LOD ≥ 3, we found 4 QTLs with large effects on fiber quality and 7 QTLs with large effects on yield components. The most important chromosome D8 in the present study was densely populated with markers and QTLs, in which 36 SSR loci within a chromosomal region of 72.7 cM and 9 QTLs for 8 traits were detected.     

Genetic combining ability estimates in the F<Subscript>1</Subscript> and F<Subscript>2</Subscript> generations for yield,its component traits and alkaloid content in opium poppy (<Emphasis Type="Italic">Papaver somniferum</Emphasis> L.)

The F ₁ and F ₂ generations of a twenty parent fractional diallel cross of opium poppy (P. somniferum L.) were analyzed for combining ability for ten quantitative and five quality (alkaloids) traits. The results indicated significant differences among the parents for combining ability for all the traits. The GCA and SCA components of variances were significant for all the characters. However, the SCA component of variance (δ ²s) was predominant indicating the preponderance of non-additive gene effect for all the traits except for leaves/plant and papaverine in F₁ hybrids. The average degree of dominance (δ ²s/δ ²g) was more than unity indicating over dominance and also confirming non-additive mode of gene action. Among the parents IS-16, IS-13 and NBRI-1 for early flowering, BR226 and BR241 for branches/plant, capsule weight/plant, seed yield/plant and husk yield/plant, BR227 for leaves/plant, UO1285 for capsule size and opium yield/plant, NBRI-5 for husk yield/plant, morphine, codeine, and thebaine and ‘Papline’ for plant height and papaverine content were found good general combiners. Parent ND1001 was good combiner for codeine and narcotine content. Inclusion of good general combiners in a multiple crossing program or an intermating population involving all the possible crosses among them subjected to bi-parental mating may be expected to offer maximum promise in breeding for higher opium, seed yield and alkaloid contents.     

Magnitude of inbreeding depression and genetic variation analysis of agro‐morphological traits in orchardgrass

Inbreeding depression is the reduction in the fitness of inbred offspring relative to progeny from unrelated parents. In orchardgrass (Dactylis glomerata L.), limited efforts have been made to evaluate the effects of deliberate selfing on agro‐morphological traits and to estimate the genetic variation of traits. Twenty‐five genotypes of orchardgrass, along with 25 S₁ (full‐sibs) and 25 families of half‐sibs, were created in 2012 and used to assess the consequences of the first generation of inbreeding and outcrossing for offspring fitness and to estimate heritabilities, genetic parameters and correlations of agro‐morphological traits during the period of 2013–2014 in the field. Different levels of inbreeding depression were observed for the traits, with higher values for plant height, days to inflorescence emergence and dry matter yield. The degree of inbreeding or outbreeding effects varied among the studied genotypes. This facilitates the development of inbred lines for further studies. The results showed that some of the studied genotypes were self‐fertile, thereby indicating the possibility of developing inbred lines from these genotypes. Heritabilities ranged from 0.10 for the number of stems per plant to 0.64 for spread among the studied populations. Spread had high heritability as well as high correlation with forage yield, thereby indicating that this trait could be used to improve forage yield indirectly.     

利用SSCP技术分析棉花纤维差异表达的基因

 单链构象多态性(Single strand conformation polymorphism,SSCP)技术是一种简便、灵敏的多态性检测方法,可以检测出在非变性聚丙烯酰胺凝胶电泳中因构象差异而导致的单链DNA片段迁移率的不同。本研究根据棉花基因芯片筛选的纤维发育中差异表达基因设计了162对引物,利用SSCP技术在4个陆地棉品种、4个海岛棉品种中进行多态性检测。结果表明,在162对引物中,146对引物经PCR扩增后在1.5%的琼脂糖凝胶电泳中检测出现清晰、明亮的带。经过SSCP分析,54对引物在陆地棉之间产生多态性,共出现116个多态性位点;45 对引物在海岛棉之间产生多态性,共出现111个多态性位点;79对引物在陆地棉和海岛棉之间产生多态性,共出现260个多态性位点;36对引物在陆地棉之间、海岛棉之间同时出现多态性。进一步聚类分析后表明,海岛棉和陆地棉分别聚在了一起。     

Variation in traits affecting nodulation of common bean under intercropping with maize and sole cropping

Common bean (Phaseolus vulgaris L.), an important food crop in Europe, America, Africa and Asia, is thought to fix only small amounts of atmospheric nitrogen. It contributes significantly to the sustainability of traditional cropping systems because of the predominance of small-scale farmers who cultivate beans in those areas. The objectives of this work were to evaluate bush bean varieties under common agronomic cropping systems and to evaluate breeding lines under low N-fertility sole cropping and intercropping systems. The purpose of the study was to characterize the genotype and cropping system's variability in symbiotic and plant characters and to identify the most suitable genotypes to establish an effective symbiosis with indigenous strains of Rhizobium. No significant differences among the bush bean varieties evaluated under typical fertilization practices were observed for N₂-fixation and plant traits except for seed nitrogen. Significant differences among the bean lines studied under low N-fertilization conditions were detected for plant growth,plant component and N₂-fixation traits. A significant interaction of bean genotype x cropping system was found for number of nodules per plant and nodule moisture on the bush bean varieties studied, and for days to emergence, days to flowering, end of flowering, shoot length, root dry weight and shoot nitrogen on the bean lines evaluated. Nodulation parameters were correlated positively with the yield components, shoot and root parts and duration of flowering, and correlated negatively with seed crude protein, pod and seed dimensions and seed dry weight. These observations indicate that it may be possible to increase both the symbiotic N₂-fixation and seed yield through plant breeding. This revised version was published online in August 2006 with corrections to the Cover Date.