Comparison of intra- and inter-pool crosses in faba beans (Vicia faba L.). II. Genetic effects estimated from generation means in Mediterranean and German environments

Genetic diversity between parents is important for hybrid breeding and for maximum usefulness of a cross in pure line breeding. However, wide crosses may suffer from poor adaptation in the target environments and recombination losses owing to disruption of favourable epistatic gene combinations. In this study we investigated the importance of various gene effects for different traits in the parents and generations F¹ to F⁵ derived from 99 intra- and inter-pool crosses among 20 lines of the Minor, Major, and Mediterranean germplasm pools of faba bean in Mediterranean and German environments. Yield performance of parental inbreds and progenies of crosses in different selfing generations was high in the region of adaptation of the respective germplasm pool. Heterosis for yield was greatest in interpool crosses of Minor × Mediterranean germplasm, amounting to 106% in Mediterranean and 72% in German environments. Interpool crosses exhibited significantly greater heterosis compared with intrapool crosses in both mega-environments. Generation means analysis revealed the importance of additive gene effects and dominance × dominance epistasis in Mediterranean and German environments. Dominance effects and additive × additive epistasis for yield were negligible in most crossing groups. Since intrapool crosses of Mediterranean germplasm in Mediterranean environments and crosses of Minor and Major germplasm in the German environments were most promising, we suggest crosses among adapted germplasm for hybrid breeding and for establishing new base material in line breeding in faba bean.     

Triple test cross analysis for some morphological traits in mungbean (Vigna radiata (L.) Wilczek)

Thirty progenies of mungbean were produced by crossing 10 true-breeding genotypes with three testers (NM 92, 6601, and their F₁) in a Triple Test cross (TTC) fashion and evaluated with parents in the kharif (July-October) and spring/summer (March-June) seasons. The data on parents and F₁s were analysed for pod clusters on main stem, pod clusters on branches, node of the first peduncle, nodes on main stem and average internode length to detect epistasis and estimate additive and dominance components of genetic variation. Epistasis was observed for node of the first peduncle and nodes on main stem in the kharif season. Partitioning of total epistasis revealed that both additive × additive (i type), and additive × dominance, and dominance × dominance (j and l types) interactions were significant with prevalent influence of i type interactions on these traits. Both additive and dominance components of genetic variation were significant for all those traits not significantly influenced by epistasis in either or both seasons. The additive component was predominant for pod clusters on main stem, pod clusters on branches and average internode length in the kharif season, and for the node of the first peduncle and nodes on main stem in spring/summer season whereas dominance component was important for pod clusters on main stem, pod clusters on branches, and average internode length in spring/summer season. These results suggested that particular generation of segregating population and specific breeding method for selection might be adopted in each season for the improvement of these traits in mungbean. This revised version was published online in August 2006 with corrections to the Cover Date.     

Detection of epistasis in chickpea

Summary Triple test cross-analysis was used to detect epistasis in chickpea. None of the characters investigated exhibited epistasis. In the absence of epistasis, additive and dominance effects were estimated. The results indicated the importance of additive genetic variance for seed yield, biological yield, number of primary branches, number of secondary branches, 100-seed weight, days to flower, and number of seeds per pod; dominance genetic variance for days to mature; and both additive and dominance genetic variances for plant height. Selection methods, such as pedigree and bulk, are suggested for the improvement of most characters.Joint contribution from ICARDA, P.O. Box 5466, Aleppo, Syria and ICRISAT (International Crops Research Institute for the Semi-Arid Tropics), Patancheru P.O. 502 324, A.P., India.     

The Inheritance of Earliness and Fruit Weight in Crosses between Cultivated Tomatoes and two Wild Species of Lycopersicon

The inheritance of earliness and fruit Weight in tomato was studied in tour interspecific crosses. Two cultivated varieties, i.e.‘HS 101’ and “HS 102′, were hybridized with two wild species. L. birsutum f. glabratum‘B 6013’ and L. pimpinellifolium‘A 1921′. Six generations of these crosses were evaluated for these traits and the estimates of gene effects were derived from the generation mean using an epistatic (six parameters) model. There were very wide differences between cultivated and wild species for earliness and fruit weight and in the segregating populations, plants with delayed maturity and smaller fruit size were recorded with high frequency. It was found that the inheritance pattern was mainly governed by additive gene action. Epistatic effects also contributed towards the inheritance of both traits.     

Resynthesis of Brassies napus L. through Interspecific Hybridization between B. alboglabra Bailey and B. campestris L. with Special Emphasis on Seed Colour

Brassica napus L. was resynthesized through interspecific hybridization between B. alboglabra Bailey and B campestris L. with the objective or developing yellow-seeded forms of this species. For hybridization, one black-seeded form and one light brown-seeded form of B. alboglabra (a subordinate of B. oleracea) and one brown and ten yellow-seeded forms of B. campestris were chosen as parents. Crosses with B. alboglabra as the female parent were more successful than crushes with B. campestris as female. The use of the embryo rescue culture technique greatly increased the number of surviving hybrid embryos. Colchicine treatment was required for doubling the chromosome number of the amphihaploid hybrid plants. In the newly-resynthesized rape forms, the white petal of B. alboglabra was partially epistatic over the yellow petal of B. campestris. The self compatibility of B. alboglabra was hypostatic to the self incompatibility of B. campestris. The black-seeded character of B. alboglabra and the brown-seeded character of B. campestris were completely eptstatic over the yellow-seeded character of B. campestris and the light brown-seeded character of B. alboglabra. Implications of the results from this study in breeding yellow-seeded B. napus are discussed.     

Inheritance of β-carotene concentration in durum wheat (Triticum turgidum L. ssp. durum)

Despite being one of the important characteristics in determining pasta quality in durum wheat (Triticum turgidum ssp. durum), there is no direct report on inheritance of β-carotene concentration. The objectives of this study were to determine the inheritance of β-carotene concentration and the number of genes involved in six crosses of durum. For the cross PDW-233 (P₁) × Bhalegaon-4 (P₂), F₁, F₂, BCP₁ and BCP₂ populations were developed. For all other crosses, only the F₁ and F₂ populations were developed. β-carotene concentration was determined for all populations and parents of each cross grown at Hol, Maharastra, India. The cross PDW-233 × Bhalegaon-4 was also evaluated at Dharwad, Karnataka, India. Low β-carotene concentration was partially dominant in most of the crosses. Broad sense heritability was 67 and 91% at Dharwad and Hol, respectively, for the cross PDW-233 × Bhalegaon-4 and varied from 74 to 93% for the other five crosses indicating the presence of additive gene effects. The frequency distributions of the trait in the F₂ populations were not normal and were skewed towards the lower parent. Segregation of β-carotene concentration in the six F₂ populations indicated that at least two major genes and two or three minor genes with modifying effects govern the trait. Analysis of variance indicated that environment had comparatively little influence on the trait and this should allow for easy selection. The joint scaling test revealed additive × additive, additive × dominance and dominance × dominance epistatic interactions in the cross PDW-233 × Bhalegaon-4. These authors contributed equally.     

Mapping of quantitative trait loci (QTLs) for rice protein and fat content using doubled haploid lines

Rice protein content (RPC) and rice fatcontent (RFC) are two important componentsof rice nutritional quality. In order toexamine the genetic basis of these traits,a doubled haploid (DH) population and anRFLP linkage map consisting of 232 markerloci were used to search QTLs for thetraits with the computer programQTLMapper1.0. This program is based onmixed linear models and allows simultaneousmapping of both main-effect and digenicepistastic QTLs in a DH population. RPC andRFC were evaluated based on a dry weightbasis of head rice by the Kjeldahl andSoxhlet methods respectively. A total offive main-effect QTLs for RPC wereresolved. The five QTLs collectivelyexplained 74% of the phenotypic variationwith LOD=15.2. Among these QTLs, the majorQTL qRPC-5 with the largest effectwas mapped in the interval of RG435-RG172aon chromosome 5. It accounted for 35% ofthe phenotypic variation with a LOD of16.7. At this locus the allele from theparent `Gui 630' increased RPC by 1.32%.The second QTL qRPC-7 was mapped inthe interval ZG34B-G20 on chromosome 7. Itexplained 23% of the phenotypic variancewith a LOD of 6.1. Its positive alleles,also from the parent `Gui 630', increasedRPC by 1.05%. As for the remaining threeQTLs, their additive effects wererelatively small and their positive alleleswere all inherited from the parent `02428'.Three QTLs for RFC were mapped onchromosome 1, 2 and 5 respectively. Theycollectively explained 44% of thephenotypic variation. Among these loci,QTLs qRFC-2 and qRFC-5 withlarger effects individually accounted for24% and 26% of the phenotypic variancerespectively. At QTL qRFC-2 thepositive allele came from the parent `Gui630', while at QTL qRFC-5 thepositive allele from the parent `02428'.The fact that both parents possess thepositive alleles at the QTLs for the twotraits provides an appropriate explanationfor the large transgressive segregationobserved in the DH lines. Furthermore, onlyone pair of epistatic loci explaining only5.1% of the phenotypic variance wasdetected for RPC, whereas seven pairs ofepistatic loci were resolved for RFC. Thetotal absolute effects of these RFCinteractions amounted to 0.97% which ismuch larger than that (0.42%) of the threemain-effect QTLs for the trait. Alongwith the observation that RPC showed a highheritability (78%), these resultsdemonstrate that RPC in the DH populationcould be mainly controlled by relativelyfew QTLs with large main-effects. As forRFC, epistatic interactions might be aneven more important component of thegenetic basis and the segregation of the DHlines could be largely explained by a fewmain-effect QTLs and many epistatic loci.In addition, a highly negative correlation(r = –0.45) between RPC and RFC inthe DH population was observed. Thiscorrelation could be largely explained bythe linkage of qRPC-5 and qRFC-5 with the directions of effectsopposite and the co-locations of the twoepistatic loci for RFC respectively withtwo different main-effect QTLs for RPC. Theinformation reported in the present papermay be useful for improving ricenutritional quality by means ofmarker-assisted selection.     

玉米八个产量相关性状的QTL鉴定

以玉米优良自交系‘农系531’和‘SIL8’为亲本构建200个F2:3家系,利用复合区间作图法对8个产量性状进行QTL鉴定。8个性状共检测到34个QTL,单个QTL的表型贡献率为5.21%～26.62%不等,累计解释各个性状的表型变异为21.33%～74.10%。分布于第1、3、4、5、6染色体上16个QTL形成6个QTL富集区,且表型贡献率最大的QTL均位于富集区内。共检测到26对上位性互作,其中QTL间互作1对,QTL与背景间互作8对,背景间互作17对,所解释的表型变异为5.98%～15.93%不等,累计解释各性状的表型变异为15.93%～61.64%。多数产量相关性状的遗传基础非常复杂,上位性在产量相关性状形成的遗传控制中具有重要的作用。QTL富集区对于数量性状的遗传分析与作物遗传改良具有重要意义。     

水稻CSSL-Z481代换片段携带的穗部性状QTL分析及次级代换系培育

【背景】粮食安全是保障国家安全的重要基础,水稻是人民赖以生存的主要粮食作物,提高其产量是重要的育种目标。水稻产量由每株有效穗数、每穗实粒数和粒重等性状构成,其中,粒重与籽粒形状、充实程度等密切相关。但这些性状都是由多基因控制,遗传基础复杂。染色体片段代换系(CSSL)可将这些复杂性状的QTL较准确地分解为单个孟得尔因子研究,且与育种工作紧密衔接,因而是理想的遗传研究和育种材料。【目的】前期以4代换片段的水稻染色体片段代换系Z481精细定位了一个易落粒基因SH6,但Z481与受体日本晴间还存在多个显著差异的穗部性状。明晰控制这些差异性状的QTL在代换片段上如何分布,并分解为单片段代换系,对目标QTL的图位克隆及应用于水稻分子设计育种有重要应用价值。【方法】利用受体亲本日本晴与Z481杂交构建的次级F₂分离群体以SAS9.3统计软件的混合线性模型(mixed linear model,MLM)法进行穗部性状QTL定位(P<0.05),然后,根据基因型和表型,从F₂选择42个单株在F₃株系利用MAS法培育单片段及双片段代...