An investigation to estimate genetic parameters in CSIRO's table grape breeding program. 2. Quality characteristics

Genetic parameters for table grape quality characteristics, including ripening date, berry size (weight, width and length) and uniformity, seediness, ^°Brix, acidity and the ratio of ^°Brix and acidity, were estimated based on two seasons' evaluations. Data were collected from a total of 5039 vines in 1999 and 1848 vines in 2000 and individual vine mixed models using the restricted maximum likelihood approach were used to account for all pedigree information. The results showed that quality characteristics were generally under strong additive genetic control; narrow-sense heritability estimates were 0.35 for ripening date, 0.63 for berry weight, 0.69 for berry width, 0.68 for berry length, 0.58 for seediness, 0.48 for ^°Brix, 0.36 for acidity and 0.10 for the ratio of ^°Brix and acidity. Berry size components (berry weight, width and length) were correlated strongly and positively with each other (r _g = 0.88 ∼ 0.96), and correlated negatively with ^°Brix and acidity (–0.19 ∼ –0.62), but positively with the ratio of ^°Brix: acidity (0.05 ∼ 0.33). ^°Brix was also favourably associated with acidity (0.41). Vine vigour was associated with ^°Brix (–0.05) and acidity (0.30) without an unfavourable impact on berry size. Thus, low vigour vines may potentially produce high quality table grapes. Ripening date was generally independent of most quality characteristics. Heritability estimates derived from seedless and seeded populations were similar to each other and mirrored the estimates for the combined population. The implications of these estimates for table grape breeding are discussed. This revised version was published online in August 2006 with corrections to the Cover Date.     

温宿红葡萄生物学特性及果实性状多样性研究

摘要：【研究目的】温宿红是新疆温宿县地方优异葡萄品种,当地长期栽培中形成了丰富的葡萄种质资源多样性,本文通过对温宿红葡萄果实与形态性状多样性的研究,以期为筛选出适合当地条件的温宿红葡萄系列新品种（系）提供材料基础。【方法】通过田间观察,以果实特性为主要指标,植株形态特征为辅,研究温宿红葡萄品种多样性。【结果】温宿红葡萄植株生长势强,晚熟、丰产,果穗松紧适中、穗梗粗壮,果粒圆、大小一致,果肉硬脆,味甜,果皮红色鲜丽,符合人们的消费习惯, 有一定的耐贮运性,是较为理想的鲜食品种。温宿红自然群体中存在诸多变异类型,初步筛选出的7个形态与果实性状多样性植株在果穗、果粒形态,果实耐压力、耐拉力、可溶性固形物含量和种子数等方面均存在显著性差异。【结论】温宿红葡萄自然群体中存在变异类型,对该品种的深入研究及初选的多样性植株具有一定育种及利用价值。     

Multi-trait selection in a diallel crossing scheme of cocoa

Cocoa breeding seeks to increase the yield by area unit. In this context, one must consider the resistance to Phytophthora disease, the most serious one in cocoa culture. Thus, herein two traits were used: yield, i.e. number of healthy pods obtained in 7 years and Phytophthora resistance, estimated by pod rot rate. A combined individual‐family selection is proposed on the basis of the total genetic value in order to spread clonal material. This selection method was applied in a 6 × 6 diallel scheme in Cameroon. The heritability of Phytophthora resistance (near 0.2) was higher than for yield (0.13). A selection index was constructed to obtain good genetic gains on each of the two traits (yield and Phytophthora resistance). To improve prediction of genetic values, a third trait, potential yield, was used. With the chosen weight, the expected genetic gain was about 35% for resistance at 1% level of selection. This selection was applied and a confirmation trial is being established with the selected trees.     

中国大菱鲆引进群体三代选育之后的收获体重遗传进展评估

评估了大菱鲆3个世代选育后（G0、G1、G2和G3）收获体重的遗传参数及遗传进展,分析数据来自于4个世代构建的总共590个家系的12980尾个体。G0、G1、G2和G3的收获体重性状估计遗传力分别为0.19±0.08、0.18±0.09、0.51±0.09和0.29±0.16,跨世代的遗传力为0.16±0.03。根据每一世代所有个体和留作亲鱼个体的平均估计育种值计算了选择差,在G0中为45.6 g,在G1中为13.1 g,而在G2代是 -27.9 g,每代平均10.3 g。遗传进展分别为10.2、37.4、0.3 g,分别相当于2.06%、8.76%、0.04%。经过3个世代选育后的收获体重性状的累积遗传进展为10.86%,平均每代3.56%,表明大菱鲆体重性状的选育工作总体上是成功的。     

A cassava clonal evaluation trial based on a new cassava breeding scheme

Cassava (Manihot esculenta) breeding at the earlier stages so far has been mainly based on a mass phenotypic recurrent selection, as little data is taken. This has resulted in a long breeding cycle and lack of organised information on the breeding values of parental lines used in the breeding programmes. The International Institute of Tropical Agriculture (CIAT) recently initiated a scheme to try and correct this, by introduction of replication and blocking in the clonal evaluation trial (CET) and collection of data on all genotypes at early stages of breeding. The aim of the study was to evaluate a CET using the new breeding scheme. Replicating and blocking of clones improved the accuracy of the data obtained. High broad-sense heritability values, comparable to those at advanced selection stages, were obtained, as environmental effects were minimised. The highest was for harvest index (HI) (0.80), followed by cassava frogskin disease (CFSD) (0.79), dry matter content (DMC) (0.75) fresh and dry root yields (DRY) (0.73), root weight (RtWt) (0.61), number of commercial roots (0.60) and roots per plant (RtPlt) (0.43). DMC, HI and RtWt were identified as important variables in selection and determination of economic yield at early stages of selection.     

Heritability of oil content and the onset of flowering in a population of Dimorphotheca pluvialis

To develop efficient breeding strategies for the improvement of oil content and onset of flowering in Dimorphotheca pluvialis, narrow-sense heritabilities of these characters were estimated. Forty plant progenies were tested in 2 years and heritabilities were estimated from parent-offspring regression as well as from half-sib family variance components analyses. For oil content, the heritabilities estimated by means of parent-offspring regression were 0.36 and 0.33 for 1993 and 1994, respectively. The heritabilities obtained from the variance components analyses were 0.41 and 0.23 for the two years. Heritability estimates for onset of flowering showed more variation. From parent-offspring regression, the heritabilities were 0.72 and 0.37, and from variance component analysis the estimates were 0.53 and 0.19 for 1993 and 1994, respectively. The obtained heritability values and realized responses suggest that particularly in early selection generations, even with mass selection, considerable progress can be expected. Since correlation studies revealed neither phenotypic nor genotypic correlation between oil content and onset of flowering, selection for both characters can be undertaken independently.     

Estimates of genetic variability and heritability for vegetative and reproductive characters of kiwifruit (Actinidia deliciosa)

The results of this study indicated a great deal of genetic variation in a number of characters of horticultural interest in kiwifruit seedling populations, and therefore, a potential to improve kiwifruit by vine selection. High narrow sense heritability was shown for pedicel length(0.62) and flowering duration (0.50) in male vines, and pedicel length (0.67),floral shoot percentage (0.54), leaf length-width ratio (0.64), fruit elongation (0.64) and fruit weight (0.52) in female vines. For these traits, selection of superior seedlings should lead to rapid genetic improvement in these populations. This revised version was published online in August 2006 with corrections to the Cover Date.     

Genetic variance models for the evaluation of resistance to powdery scab (Spongospora subterranea f. sp. subterranea) from long-term potato breeding trials

Breeding for resistance to soil-borne powdery scab in potato is an important component of the integrated management of this disease. Different genetic variance models within a mixed model framework were applied to data from long-term potato breeding trials, for the genetic evaluation of breeding lines. The multi-environment trial (MET) data came from 12 growing seasons (“years”, synonymous with environments) of New Zealand field trials screening for resistance to powdery scab on potato tubers. Pedigree information on a total of 1,031 genotypes was available. Additive components of the genetic effects were important with narrow-sense heritability estimates (and 95 % confidence intervals) from single-year analyses ranging from 0.26 (0.20, 0.44) to 0.57 (0.53, 0.85). Spatial components estimated from the residual plot effects were not important for most years and even when they were significant, estimates were small. In MET analyses, different variance structures for the genetic effects were tested; a homogeneous correlation model (CORH) gave a better fit to the data than a factor analytic FAk model of order (k), 1 and 2. The year-to-year genetic correlation estimate from CORH was 0.81 and compared with a range of 0.59–0.95 estimated from the FA1 model. There was no strong evidence of non-additive genetic effects with zero or boundary estimates for most years. Models which included the pedigree provided a better fit to the data than models that did not include this relationship information. There was no evidence for genetic improvement in resistance for powdery scab on tubers in the breeding population studied. This suggests that selection pressure for resistance in the past has been weak and greater consideration should be given to selecting parents on empirical breeding values to genetically improve breeding populations for resistance to powdery scab.     

Reciprocal recurrent selection applied to Coffea canephora Pierre

Summary Genetic parameters were estimated in trials planted in connection with a reciprocal recurrent selection programme applied to Coffea canephora in Côte d'Ivoire. Narrow sense heritability values, estimated from a breakdown of the analysis of variance, were high for architectural characters (0.22 to 0.78) and medium for tree vigour (0.13 to 0.40) and for bean weight (0.15 to 0.28). Calculated heritability values for the first two harvests were high (h²>0.7), but much lower for the following harvests (less than 0.2). Heritability estimates by parent-offspring regressions gave variable results, though they were often similar to those obtained by variance analysis, especially for bean weight. Phenotypic and genetic correlations between tree vigour traits and productivity were high. Bean weight was not correlated with vigour or production. Canopy diameter of 4 year-old trees was closely correlated with cumulated productivity from 2 to 5 years in the absence of development competition between trees, but the correlation was low if trees were in competition with each other. The consequences of the results for the choice of characters to be selected among intergroup hybrids or the parents of both populations are discussed.     

Investigation of long-term field experiments on response of breeding lines to common scab in a potato breeding program

Common scab, caused by Streptomyces scabies, is a disease that produces scab-like surface lesions on potato tubers. Testing for susceptibility/resistance of breeding lines at the Potato Research Centre of Agriculture & Agri-Food Canada (AFC) is carried out in a scab nursery maintained at AFC for the annual scab evaluation field trials. A replicated field trial routinely consists of breeding lines from previous testing season(s) plus newly selected lines. Data of scab scores generated from long-term experiments thus formulate an incomplete 2-way table over combinations of breeding lines (genotypes) and trials (years). This requires an advanced statistical method to estimate genetic parameters for evaluation purposes. A data base with 1,435 scab index scores from 344 breeding lines were extracted from 5 years (1995–1999) of field experiments in the scab nursery maintained at AFC. The statistical method Residual Maximum Likelihood (REML) was employed to estimate variance components of the breeding population and Best Linear Unbiased Predictor (BLUP) was used to predict genetic merit of breeding lines. High heritability was obtained from variance components estimated by REML. The BLUP scores of breeding lines provided reliable evaluation of their responses to common scab. Two data base sub-sets were separately formulated from the original data base for those parents and grandparents of the breeding lines having pedigree records available. They were again subjected to REML and BLUP analyses to compare the responses to common scab and identify sources of resistance at the parental and grandparental levels. Two random data sets with equal sized samples of breeding lines were also generated from the over-all data base. The two sets of BLUP scores between corresponding breeding lines and parents showed high association which provides an assessment of the validity of the evaluation process.     

Selection for Yield and its Components in a Winter Wheat Population under Different Environmental Conditions in Albania

Wheat breeding programmes in Albania depend upon the use of diverse genetic material of local origin and on special environmental conditions; the present study being conducted under drought stress conditions. Grain yield, yield components, plant height and test weight were estimated in an F₅ generation of a winter wheat population at Kamez in 1989—90 and 1990—91 and at Lushnje in 1989—90. The highest values of heritability were observed for plant height, kernel weight and spike length. Due to drought stress the heritability of kernels per spike was low. None of the correlated responses was higher than the direct response for yield. Maximum genetic gain was expected when yield, plant height, spike length, kernels/spike and kernel weight were included in the index.     

Variability of Yield Characters and Selection in Solanum ladniatum Ait.

The steroid bearing medicinal plant, S. laciniatum, was bred for high solasodine yield for commercial cultivation in Thailand. Starting materials for breeding consisted of seven populations of different origin. Variability among these populations was examined using an unselected control population cultivated over three years. Additive and dominance variance were estimated from a polycross and diallel mating design. Significant genotypic variability was found for solasodine concentration, height of the plants, and total shoot length, promising successful selection for the most important yield characters. Additive variance and heritability in the narrow sense were low for all yield characters, due to previous selection of the parental plants used for the polycross and diallel mating. No dominance effects could be found for any of the characters. In conclusion, breeding S. laciniatum for quantitative yield characters by selection will be superior to hybrid breeding. As a result of selection, significant increases in the most important yield characters in the offspring of selected populations were obtained.     

BLUP for genetic evaluation of plants in non-inbred families of annual crops

Best Linear Unbiased Prediction (BLUP) has become the most widely used method for genetic assessment of animal and perennial species, and it is potentially relevant for annual crops. The objective of this study was to assess this method for selection within non-inbred families in recurrent breeding programs. The ‘animal model’ was fitted. The data were expansion volume (EV) and grain yield of plants in recombination plots of two to three selection cycles in the popcorn population Viçosa, with half- and full-sib progenies. The ASReml program was used to perform the analyses. For both EV and yield the breeding values predicted from the additive and additive-dominant models were highly correlated. Multi-generation BLUP was, in general, more accurate than single-generation analysis. These two methods resulted in highly correlated predicted breeding values. The dominance genetic values predicted from the single- and multi-generation analysis were also highly correlated. The pedigree information reduced the percentage of coincidences among the selected individuals relative to phenotypic selection mainly in the population structured in half-sib families. Based on breeding values predicted by BLUP analysis, the most efficient selection procedure was mass selection.     

Estimates of genotypic and yearly variations on fruit quality and functional traits for tetraploid table grape breeding

We estimated genetic and environmental variance components for fruit quality traits (cluster weight, berry weight, soluble solids content, total sugar content, sugar composition, free acid content, total amino acid content, amino acid composition), and a functional trait (gamma-aminobutyric acid (GABA) content) of three commercial tetraploid table grape cultivars (Kyoho, Pione, Suiho) grown in Japan over three successive years. ANOVA showed that the effect of genotype was significant (P < 0.05) for all traits except soluble solids content and total sugar content. The effect of the year was significant for all traits except amino acid composition (γ ratio) and GABA content. The variance of genotype (σ _g ²) was highest for γ ratio (63.6%), high in sugar composition (α ratio, 60.3%) and GABA content (58.8%), and negligible for soluble solids content (0.0%) and total sugar content (0.0%). The variance of among years (σ _y ²) was very high in soluble solids content (82.8%), high in total sugar content (60.2%) and negligibly small in γ ratio (8.7%) and GABA content (6.4%). Some effects of genotype × year interaction, among vines within genotypes, and vine × year interaction were statistically significant, but these components were negligibly small. Except for soluble solids content and total sugar content, significant varietal differences in the traits were recorded. Variance estimates for each trait provides useful information for optimal yearly repetition to effectively discriminate genetic differences in fruit quality and functional traits for improving future tetraploid table grape breeding programs.     

Estimates of selection parameters associated with harvest index in oat lines derived from a bulk population

Summary Harvest index of grain crops is defined as grain yield divided by total plant yield. We estimated the heritability percentages of harvest index and its components, grain yield and plant weight, the genotypic and phenotypic correlations among these three traits, and the genotypic correlations of harvest index with plant height, 100-seed weight, grain number, and heading date by using a population of 1200 F₉-derived oat lines tested in six environments. Furthermore, we examined the relative selection efficiencies of indirect selection for yield through harvest index and of index selection for yield through yield plus harvest index.Heritability percentages were computed by use of variance-component, standard-unit, and realizedheritability methods. The heritability percentages for harvest index, grain yield, and plant weight were similar, and averaged between 50 and 65 precent across environments. Standard-unit and realized heritability percentages agreed closely and generally were lower than those computed via the variance-component method. Expected heritability percentages for harvest index calculated by using grain and plant yield data agreed almost exactly with actual values. Genotypic correlations were 0.88 between grain yield and plant weight, 0.42 between harvest index and grain yield, and –0.07 between harvest index and plant weight. Genotypic and phenotipic correlations were similar in magnitude. Theoretical and actual genotypic and phenotypic correlations of harvest index with grain yield and plant weight agreed closely. Genotypic correlations, computed via parent-offspring relationships, between harvest index and plant height, 100-seed weight, grain number, and heading date averaged –0.41, 0.43, 0.00, and –0.33 respectively.Indirect selection for grain yield through harvest index was 43 percent as efficient as direct selection, and a selection index that combined harvest index and grain yield was no more efficient than direct selection for yield. Harvest index had little value as a selection criterion for grain yield improvement when unrestricted selection was used. Indirect selection for grain yield through harvest index, however, would be expected to retain lines with a more favorable combination of yield, plant height and heading date than would unrestricted direct selection for yield.Journal Paper No. J-7914 of the Iowa Agriculture and Home Economic Experiment Station, Ames, Iowa 50010, Project No. 1752.     

Implications of the population effect in the selection of soybean progeny

The goal of this study was to verify the influence of the population effect in the estimates of genetic and phenotypic components and to identify the best soybean progeny or lines in a commercial soybean breeding programme. We evaluated 292 populations for grain yield and absolute maturity during three agricultural years. To quantify the efficiency of the inclusion of the population's effect in the model, we estimated genetic gain with the selection, the Spearman's correlation, the coincidence index, the realized gain and correlated response of selected genotypes with and without the effect of the population. It was found that the variance components, heritability and coefficient of experimental variation were better estimated when the effect of the population was included, providing greater gain with selection for grain yield and absolute maturity. Coincidence and ranking among the selected progeny with and without the effect of the population are of greater magnitude in more advanced inbreeding generations and at higher percentage of selected progeny. The use of the population effect has greater importance in earlier generations of inbreeding.     

Heritability of morphophysiological traits and inbreeding effects in grazing-type lucerne

To estimate heritability and inbreeding in grazing‐type lucerne, 14 parent genotypes and their half‐sib and selfed progeny were grown under spaced‐plant conditions. Dry‐matter weight (four cuts), plant height, basal plant diameter, stem density, and late‐autumn vegetation were recorded on a plant basis. Genetic coefficients of variation for the three germplasm groups, and broad‐sense heritability on a plot basis for parents were computed from variance component estimates; narrow‐sense heritability was estimated from progeny‐parent regression. Genetic variation was generally greater among selfed than half‐sib progeny. Broad‐sense heritability was high, while narrow‐sense heritability was much lower for all traits except plant diameter. Inbreeding effects, assessed with comparison between parents and selfed progeny, were notable for plant weight and late‐autumn vegetation only. The high correlation coefficients computed between parents and either progeny suggested the equivalent value of self‐ and polycross‐progeny tests for selecting superior parents.     

葡萄品种资源果实重要经济性状分析

对郑州果树研究所国家葡萄种质圃内的主要葡萄栽培品种的果穗和浆果的主要经济性状进行了鉴定评价。结果表明,在葡萄果穗形状、果穗大小、果粒形状、果粒大小、果粒重量、可溶性总糖含量、总酸含量、果实颜色、果肉硬度和香味等方面均存在丰富的遗传多样性。在丰富的多样性中,具有圆锥形、圆形和短椭圆形果粒、软肉、无香味的品种最多,其它穗形、果形、硬度和特殊香味特征均是葡萄的遗传变异中人为选择的结果。     

Heritability estimates and response to selection for the pungency and single center traits in onion

Summary Heritabilities of the pungency and single center traits were estimated in onion breeding populations using selection response and half-sib family analyses. Pungency was determined indirectly by measuring enzymatically produced pyruvic acid in individual bulbs. After one generation of selection, pungency was lowered by 8.1% and 8.9% in the populations 90-61-1 and 89-69-8, respectively, and realized heritabilities of 0.21 and 0.51 were estimated.Selection had no effect in lowering the pungency of population 90–62. Heritability estimates calculated through half-sib progeny analysis were 0.53, 0.48, and 0.25 for pungency in the populations 90-61-1, 90–62 and 89-69-8, respectively. The number of single centered onions was increased by 19% and 22% in populations 90–62 and 89-69-8, respectively, after one generation of selection, and the realized heritability estimates were 0.37 and 0.34, respectively.