Genetic components of pod shattering in soybean

Half diallel crosses among ten pure breeding lines of soybean were made in 1997 and 1998 to study the inheritance of pod shattering in soybean. Evaluation for pod shattering among F₂ segregating populations was carried out in an oven set at 80 ^°C for 12 hours. Diallel analysis was carried out to estimate genetic parameters and detect presence of non allelic interaction of genes affecting pod shattering. Hayman's diallel analysis indicated significant variation of Wr + Vr and Wr – Vr over arrays, suggesting epistatic gene action. Similarly results from a joint regression coefficient over replications were significantly (p < 0.05) different from unity and zero, suggesting presence of non allelic interaction of genes. The intercept was positive, suggesting partial dominance for the shattering trait. Both general combining ability (GCA) and specific combining ability (SCA) effects were significant (p < 0.05). This revised version was published online in July 2006 with corrections to the Cover Date.     

Investigations into the breeding system of cauliflower

In experiments to study the effect of inbreeding, I₁ progenies of summer cauliflower showed a trend towards increase in plant weight over their non-inbred commercial parents. Curd quality, however, showed no significant improvement.As summer cauliflower varieties tended to behave as pure lines, studies were made on F₁'s from crosses between five commercial varieties. The main results of hybridisation were an increase in earliness, and a slight, though significant increase in curd size over the parental varieties. It is suggested that summer cauliflowers have attained a state of homozygous balance, which could be emulated in the autumm and winter types, by selection of self-compatible individuals.     

Conformation of cauliflower curds

Cauliflower curds are composed of numerous small identical whorls. In the autumn cauliflower variety Meroni Ugo these form small pyramidal replicas of the whole curd while they are less pronounced in early summer and most other autumn cauliflower varieties. By halving the curd and its primary and secondary whorls it was possible to draw and measure the angle formed by the sides. There was good correlation between the angles of the primary and secondary whorls but less between these and the whole curd.Measurements were made of curd angles of parents and F₂ progenies from the cross Meroni Ugo × No. 35, the extremes for pyramidal and smooth curds respectively. The F₂ progenies showed a range of angles between those of the parent varieties with a slight excess of curds in the smoother or shallower angle type. It was considered that factors affecting curd conformation were polygenically inherited and that there was slight dominance of the polygenes giving smooth curds.     

大麦蛋白质含量的遗传研究

由六个亲本组成的双列杂交试验,采用三倍体遗传模型分析蛋白质含量的遗传,经二年试验,结果表明:1.大麦蛋白质的 Wr/Vr 分析指出,F_2世代籽粒蛋白质含量符合加性-显性模型,不存在上位性效应。蛋白质含量高为隐性,Hiproly 具有最多的隐性基因;蛋白质含量低为显性,Ris(?)1508具有最多的显性基因。2.控制蛋白质含量的基因作用方式     

Study of heritable variation and genetics of earliness in mungbean (<Emphasis Type="Italic">Vigna radiata</Emphasis> L. Wilczek)

Fifty-five mungbean lines were evaluated for days to maturity and grain yield per plant. This material showed considerable range of variability for the target traits. Eight genetically diverse parents were selected and used for a full diallel set of crosses to study the mode of inheritance for earliness related parameters (days to flowering, days to maturity and length of reproductive phase) during summer 2005. The F₁ generation of these crosses was sown during the spring of 2006 and the selfed seeds were used to raise the F₂ generation during kharif season. The data recorded from two generations were subjected to genetic analysis. The formal ANOVA showed the significance of both additive and dominance effects for all the traits in both generations. Significance of D, H₁ and H₂ components also confirmed the contribution of both additive and dominance effects in controlling the inheritance of these traits. The estimates of narrow sense heritability were low to moderate except higher estimates for days to maturity in F₂ generation, while the broad sense heritability estimates were relatively higher. Seasonal and environmental effects were also found to be significant. In view of the complex nature of gene action for earliness, it is suggested that breeders should look for transgressive recombinants of earliness and other desirable attributes in later segregating generations to gain higher genetic advance. The variety NM92 was found to be the best source of earliness in mungbean breeding.     

甜瓜柄蔓夹角主基因+多基因遗传分析

柄蔓夹角是甜瓜株型重要性状之一,通过对甜瓜柄蔓夹角的遗传特性进行研究,以期为甜瓜株型改良育种提供理论基础。本研究以柄蔓夹角小的紧凑型甜瓜材料B103和柄蔓夹角大的疏散型甜瓜材料B297为亲本,构建四世代群体(P1、P2、F1和F2),应用植物数量性状主基因+多基因混合遗传模型多世代联合分析方法,对甜瓜柄蔓夹角进行遗传分析。两年的研究结果显示,甜瓜柄蔓夹角性状表现为数量性状,不同年份柄蔓夹角的最适遗传模型均为E-1模型,即柄蔓夹角由两对加性-显性-上位性主基因+加性-显性多基因控制。2015年秋,F2分离世代主基因遗传率是72.28%,多基因遗传率是0;2016年春,F2分离世代主基因遗传率为52.06%,多基因遗传率为0。结果表明甜瓜柄蔓夹角的遗传符合两对加性-显性-上位性主基因+加性-显性多基因遗传模型(E-1),这一性状由主基因控制,同时受环境影响。     

Differential response of Vicia faba L. genotypes to 2, 3, 5-triiodobenzoic acid (TIBA)

Summary Response to application of the growth regulator 2, 3, 5-triiodobenzoic acid (TIBA) was examined in the parents and F₁ progenies of a diallel cross of six inbred lines of Vicia faba. TIBA affected the genotypes differentially but in general gave shorter internodes, reduced apical dominance, increased pod set on the lower nodes and earlier seed maturity.     

Relationship of plant height and days to maturity with resistance to spot blotch in wheat

A total of 1,407 spring wheat (T. aestivum) lines of Indian and CIMMYT (International Maize and Wheat Improvement Centre, Mexico) origin were evaluated for plant height, days to maturity and resistance to spot blotch (caused by Bipolaris sorokiniana) during the 1994–95, 1995–96 and 1996–97 crop seasons. The frequency distribution of genotypes, based on disease score ignoring the growth stages, differed from the distribution in which disease score was assessed on a similar growth stage. Two crosses each,between `tall resistant × dwarf susceptible' and `late resistant × early susceptible' genotypes, were made. The evaluation of homozygous resistant lines in the F₃, F₄ and F₅ generations of both crosses showed a wide range of plant height and days to maturity. These lines showed significant differences for plant height and days to maturity but did not show a significant difference for AUDPC values of spot blotch. The correlation coefficients for AUDPC versus plant height or days to maturity were weak, i.e., – 0.336 and 0.061, respectively. Results indicated that resistance to spot blotch severity was independent of plant height and days to maturity in progenies from these crosses.     

Genetic analysis of flowering and maturity time in high latitude spring wheat

Due to the short growing season in the high northern latitudes, the development of early maturing spring wheat (Triticum aestivum L.) cultivars is important to avoid frost damage which can lower production and quality. We investigated earliness of flowering and maturity, and some associated agronomic traits, using a set of randomly selected high northern latitude adapted spring wheat cultivars (differing in maturity) and their F₁ and F₂ crosses made in a one-way diallel mating design. The parents, and their F₁ and F₂ crosses were evaluated under field conditions over 2 years. Anthesis and maturity times were controlled by both vernalization response and earliness per se genes, mainly acting additively. Non-additive genetic effects were more important in controlling grain fill duration, grain yield and plant height. Additive × additive epistatic effects were detected for all traits studied except time to anthesis. Segregation analyses of the F₂ populations for time to anthesis indicated the presence of different vernalization response genes. Molecular genetic analyses revealed the presence of Vrn-A1 and Vrn-B1 genes in the parental cultivars. Narrow-sense heritability was medium to high (60–86%) for anthesis and maturity times but low to medium (13–55%) for grain fill duration, plant height and grain yield. Selection for early flowering/maturity in early segregating generations would be expected to result in genetic improvement towards earliness in high latitude spring wheats. Incorporation of the vernalization responsive gene Vrn-B1 in combination with vernalization non-responsive gene Vrn-A1 into spring wheats would aid in the development of early maturing cultivars with high grain yield potential for the high latitude wheat growing regions of the northern hemisphere.     

Prediction of F6 line performance from F3 families in spring oilseed rape. I. Yield and other agronomic traits

Summary The reliability of a selection among crosses based on a cross prediction in early generations was investigated in spring rapeseed. The performance of the parents, the F₂ generation, and random F₃ lines from four crosses were used to predict the probability of finding superior recombinant lines. These predictions were made for two years and compared with the observed performance of F₆ lines in the second of these two years and in an additional year. Predicted and observed performances coincided reasonably for the characters plant height, standability, maturity and an index calculated from seed yield, oil content and protein content. For seed yield and flowering time, the predictions were very unreliable. In conclusion, prediction methods may be useful in rapeseed breeding, if quality traits are of major commercial interest.     

Selection potential for seed yield from intra- and inter-racial populations in common bean

Common bean populations from crosses between lines of different races are thought to be more promising for selection of high yield potential than those from intra-racial crosses. Three distinct diallel crosses were made to test this hypothesis and to determine the possibility of substituting diallel crosses for multivariate techniques that estimate genetic divergence. The crosses were between races Mesoamerica × Mesoamerica, Mesoamerica × Durango and Jalisco, and Mesoamerica × Nueva Granada. The parents and the resulting F₄ populations were evaluated at Lavras-MG, Lambari-MG and Patos de Minas-MG, Brazil. The diallel analysis of seed yield was done and the genetic divergence estimated by Mahalanobis distance. Estimates of general and specific combining ability indicated that some inter-racial populations were more promising for selection to increase seed yield than intra-racial populations. However, due to their undesirable seed color and size, and growth habit, especially in a short term breeding program, the chances of obtaining high yielding lines with an acceptable bean is reduced. Genetic divergence was not a good measure to choose the parents because usually, the most divergent groups included were not adapted lines. This revised version was published online in July 2006 with corrections to the Cover Date.     

The mechanism of genetic control for low soil nitrogen (N) tolerance in common beans (Phaseolus vulgaris L.)

The study was conducted to determine the mode of inheritance and the genetic mechanisms associated with bean nitrogen use efficiency under low soil nitrogen. Eight widely grown and well adapted low soil N tolerant lines (CAL143, CIM9314-36, and AFR708) and non-tolerant varieties (E5, E8, GLP-2, CAL96, and SCAM80-CM/15) were crossed in a half diallel mating design. The parents and their F₁ generations were evaluated under low soil N and moderate soil N conditions. Significant genetic differences were observed for basal root length, root dry weight, nodule numbers, leaf area and grain yield for both N conditions. Inheritance of the traits associated with better performance under low soil N was found to be under both additive fixable and non-fixable genetic effects. Genotypes that had well-developed basal root systems performed better than those with less developed basal roots. F₁ hybrids from crosses between low N tolerant and non-tolerant parents performed better under nitrogen stressed conditions compared with those between susceptible parents. Hybrids involving CAL143 as one of the parents showed high levels of tolerance to low soil nitrogen conditions. Among parents, CAL143 showed the best performance for basal root length, root dry weight, nodule numbers, leaf area, and grain yield. This parent had highly significant GCA effects for the traits under both N conditions, except basal root length which was significant at Kabete and non-significant leaf area at Thika. The results show that CAL143 would be a good parent to use in a low soil N bean breeding program.     

Genotypic association between grain yield and six agronomic traits in a cross between rice varieties of contrasting plant type

Summary Phenotypic and genotypic correlation coefficients as well as path analysis were computed to evaluate the genetic association between six agronomic traits and rice grain yield and also among the traits in a representative sample of F₇ lines in the tall Peta × semi-dwarf I-geo-tze cross maintained as an unselected bulk from F₃ through F₅. Data were taken on grain yield, duration from seeding to heading, panicle number, ratio of panicles to tillers, angle of the flag leaf, angle of the leaf below the flag leaf, and plant height on the two parents and 139 F₇ lines. The F₇ lines were divided into three groups based on plant height: tall, intermediate, and short (semi-dwarf).Differences in grain yield were highly significant among lines in the tall and short groups, and significant among the intermediate lines. Significant to highly significant differences among lines were obtained in each of the height groups for all of the agronomic traits except for the ratio of panicles to tillers in the intermediate and tall groups.Path analysis showed that among the semi-dwarf progenies, erect flag leaf angle made the largest positive contribution to grain yield, followed by high panicle number and early maturity. Among the intermediates, the erectness of the leaf below the flag contributed most to high yield and was closely followed by earliness in maturity. For the tall lines, erect leaves below the flag leaf and high panicle number contributed positively to yield, whereas tallness and late maturity had a negative effect.Phenotypic and genotypic correlation coefficients indicated that low grain yield was closely associated with tall stature, drooping leaves, and low panicle number in the tall lines. In the intermediate lines, low grain yield was associated with late maturity and drooping leaves. Among the semi-dwarf lines, high grain yield was correlated with erect flag leaves and a high ratio of panicles to tillers. When the lines in different height groups were combined, highly significant phenotypic correlations were obtained between high yield levels and erect leaves, a short plant stature, early maturity, or a high panicle number. Erect flag leaves and high yield levels were associated at a significant level. The genotypic correlation coefficients of the above paired traits were identical in sign and generally greater in value than the corresponding phenotypic correlation coefficients.Mail address: P. O. Box 583, Manila, Philippines.     

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.     

Investigations on the inheritance and responses to selection of riceyness in early summer cauliflower

F₁'s grown from crosses between cauliflower plants with perfect and very ricey curds showed a continuous distribution in the degree of riceyness (classified into four grades) with slight dominance of the most ricey grades. The effect of environment upon the expression of riceyness was shown, by X² tests on F₁'s, F₂'s and selfed parents grown in more than one year, to be limited.Selections made consistently over three generations for grade 1 curds resulted in marked increases in the proportion of curds in that grade, but selection for grade 2 and 3 curds over two generations was less successful. When disruptive selection was practised, i.e., the selection of plants showing a different grade from that for which the parent was selected, the progenies of these plants generally showed an increase in the proportion of the newly selected grade.From these results it was concluded that the inheritance of riceyness appeared to be under polygenic control and that plants were still heterozygous for polygenes at the F₃ generation.     

Combining ability for seed yield traits of Chenopodium quinoa breeding lines

For a better understanding of the inheritance of seed yield traits in Quinoa (Chenopodium quinoa) Willd., a half-diallelic crossing experiment with six diverse but uniform breeding lines was conducted. True hybrid plants were detected by means of differences in panicle colour in 14 out of the 15 crosses performed. The agronomic performance of 14 F₂ populations and six parental lines was evaluated in field trials on fertile clay soil. General and specific combining ability of the lines (GCA and SCA) were estimated. Highly significant differences in GCA effects were found between the lines for plant height at maturity, early flowering, early maturity, seed yield and thousand seed weight. Significant SCA effects were only found for plant height at maturity. However, SCA effects were rather small and accounted for 7% of the total variance. The finding of large GCA effects and low SCA effects suggests that best selection results could be expected from crosses between the agronomic best performing genotypes. This revised version was published online in August 2006 with corrections to the Cover Date.     

Studies in the breeding of self-pollinating cereals

Genetic analysis of a diallel series of crosses involving six varieties of winter wheat is described. Predictions on the potentialities of the parental combinations involved are made, based on the analysis of yielding capacity and its principal components (grain weight, grains per ear and ears per plant) obtained in F₁ and F₂ trials.The validity of these predictions is estimated by comparison with estimates of mean yield and variance in yielding capacity obtained from trials, in F₃ and F₄, of randomly selected F₂ plant progenies from each of the component crosses. The results obtained are discussed in relation to practical problems of crop prediction, and a system is outlined combining the analysis of diallel series of crosses in F₁ and F₂ with trials, in F₃ and F₄, of F₂ plant progenies from selected crosses.     

Generation mean analysis of spring wheat (Triticum aestivum L.) seedlings tolerant to high levels of manganese

Effective utilisation of wheat (Triticum aestivum L.) germplasm tolerant to high manganese (Mn) in a breeding program requires an understanding of the genetics of Mn tolerance. Five wheat cultivars differing in their response to high Mn were crossed in a half diallel design with no reciprocals. Seedlings of parents and progeny generations were phenotyped in high Mn nutrient solutions. Total chlorophyll concentration, which was positively correlated with leaf elongation rate during recovery from Mn stress, was used for phenotyping Mn tolerance. Means of chlorophyll concentration of P₁, P₂, F₁, F₂, BC₁, and BC₂ generations, in all crosses which showed significant variation among generations, were subjected to line crosses analysis to estimate gene effects. The continuous frequency distribution of seedlings with differential Mn tolerance, the similarity of the F₁ and F₂ means, and the high and significant levels of additive gene action indicated quantitative inheritance for Mn tolerance at seedling stage. A preponderance of additive effects indicated that selection for Mn tolerance in early generations should be effective.     

Honeycomb selection for yield in early generations of spring wheat

Summary The effectiveness of the honeycomb selection method for yield in spring wheat (Triticum aestivum L.) was evaluated using progenies from two wheat crosses, Glenlea x NB131 and Glenlea x Era. Honeycomb selection was carried out in the F₂ and F₃ generations, grown at the University of Manitoba in the summers of 1980 and 1981, respectively. In both generations, divergent selection was made for both high and low yield. Plants selected in the F₃ generation were entered in an F₄ yield test in the summer of 1982. Results of the experiment showed that honeycomb selection for yield in the F₂ and F₃ generations was effective in identifying parents of high- and low-yielding lines. F₃ plants from highyielding F₂ selections gave higher yields than those from low-yielding F₂ selections by 11.5% and 13.0% for Glenlea x NB131 and Glenlea x Era crosses, respectively. The F₄ yield test showed that high yielding selections from both crosses significantly outyielded by 8.9% low yielding selections and by 14.4% the unselected composite lines. It is concluded that the honeycomb selection method can be used for early generation selection in spring wheat.     

甘蓝型油菜发芽种子耐湿性的主基因+多基因遗传分析

油菜湿害是我国特有的自然灾害,对油菜种子发芽、出苗和幼苗生长造成严重影响,导致单产显著下降。为研究油菜种子发芽耐湿性的遗传规律,本文利用耐湿性遗传差异较大的2个甘蓝型油菜纯系中双9号和GH01的杂交后代衍生的世代家系群体构建油菜耐湿性遗传体系,并以主基因+多基因家系世代联合分析方法对油菜耐湿性的遗传规律进行分析。结果表明,中双9号×GH01组合的耐湿性的遗传受2对完全显性主基因+加性-显性多基因控制,表现为耐湿对不耐湿完全显性。该组合的第1对主基因加性效应与显性效应相等,为0.0696;第2对主基因的加性效应与显性效应相等,为0.0530。多基因加性效应为0.3275,显性效应为负值([h]= –0.2137)。主基因存在显性效应,该组合的耐湿性存在杂种优势,多基因显性效应为负,多基因显性效应使F₁代耐湿性降低。F₂家系的主基因遗传力为73.57%,表现出较高的遗传力,建议育种工作者对耐湿性在早期选择效率较高。