Inheritance of Corolla Size, Number of Stamens and Percentage of Plants with Petaloid Stamens in Evergreen Azaleas (Rhododendron Subsect. obtusa)

Research has been carried out on the inheritance of corolla size, number of stamens and percentage of plants with petaloid stamens (double flower) in evergreen azaleas (Rhododendron Subsect. obtusa). For this purpose two incomplete diallel crosses were used. The first one included seven species and one cultivar and the second diallel 13 cultivars. In both diallels for all three characters the GCA mean squares were high. Also, the positive correlation between the parental values and the GCA estimates for flower size and number of stamens indicates that the expression of these characters is mainly determined by additive gene action. A negative correlation was found between GCA estimates for die n number of stamens and the percentage of plants with petaloid stamens. When breeding azaleas with large double flowers, parents can be directly selected on the basis of these characters since additive genetic variance dominates. As no genetic correlations were found between corolla size and number of stamens (percentage of plants with petaloid stamens) the breeding will not be hampered by unfavourable linkage of genes for these characters.     

Genetic studies of selection criteria for productive and stable peas

In this study we investigated the genetic determinism of criteria suitable for breeding for seed yield and yield stability in dry pea (Pisum sativumL.) using a diallel cross involving eight genotypes. Seven criteria related to plant and seed development were evaluated including: onset of flowering, node of first flower, leaf appearance rate, rate of progression of flowering, number of podded nodes on the main stem, mean dry seed weight per podded node and number of basal branches per plant. Most of these traits measured are related to timing of seed set and are thought to be critical in determining yield stability. We combined different diallel analyses (Hayman,1954; Griffing, 1956) with a Principal Component Analysis, to divide the parental lines into groups sharing similar genetic control for the traits studied. We found that the two main groups, defined according to their genetic control of node of first flower, also differed for all the others characters and, in particular, did not reach the same levels of productivity. These results indicated that crosses within the group with the highest productivity, but between lines with differing development and architectural features, could be a good starting point for breeding high-yield pure lines. This revised version was published online in August 2006 with corrections to the Cover Date.     

Genetic analysis of flower and lateral shoot production in Gerbera

Summary An incomplete diallel cross with selfs and reciprocals was made with twelve cultivars of Gerbera jamesonii. Very significant differences occurred between GCA's of the parents for cut flower yield, earliness and number of lateral shoots. The selfs were mainly responsible for the significant SCA's.A positive genetic correlation occurs between the number of lateral shoots at anthesis of the first flower and total flower production. The phenotypic performance of parents (measured on cuttings) was poorly related to their breeding value (measured on seedlings). It is suggested that this is due to physiological differences between cuttings and seedlings.     

An analysis of hybrid sterility in rice using a diallel cross of 21 parents involving indica, japonica and wide compatibility varieties

Summary There is much interest in the inter-varietal fertility of Asian cultivated rice. In this study, we analyzed the fertility of hybrids in a diallel set of 210 crosses involving 21 parents representing a broad range of the cultivated rice germplasm including landraces, primitive cultivars, modern elite cultivars and parents of hybrid rice. The materials were also carefully selected with respect to indica-japonica classification including typical indica/japonica, more or less intermediate and wide compatibility varieties. The level of hybrid fertility varied widely among the crosses from almost completely sterile to fully fertile. In general, hybrid fertility of intra-subspecific crosses, i.e., indica by indica (I×I) and japonica by japonica (J×J), is much higher than inter-subspecific crosses (I×J or J×I). The fertility varied widely in hybrids involving wide compatibility varieties and also in inter-subspecific crosses not involving wide compatibility varieties. An analysis of variance showed that both the main effects of indica and japonica parents and the interaction between the parents are highly significant in determining hybrid fertility. We speculate that, in addition to wide compatibility, the overall genetic difference between the indica and japonica parents, that may involve a series of minor mutations, play an important role in determining the hybrid fertility. There are also genes of sizable effect that influence fertility in hybrids resulting from specific combinations of the parents.Abbreviations I×I indica by indica cross - I×J indica by japonica cross - J×I japonica by indica cross - J×J japonica by japonica cross - WCV wide compatibility variety     

Genetic control of agronomic traits in alfalfa (<Emphasis Type="Italic">M. sativa</Emphasis> ssp. <Emphasis Type="Italic">sativa</Emphasis> L.)

The objective of this study was to develop diallel population hybrids by crossing selected germplasm and to determine the gene effects and genetic control of yield and yield components using diallel analysis. A complete diallel including reciprocals was made during 2003 and 2004 between five alfalfa cultivars of different geographic origin. For each pairwise cross, five plants were chosen at random from each of the two cultivars (~100 florets per plant) to obtain the F₁ generation. A spaced plant field was established in 2006 which included the five alfalfa cultivars (parents) and their 20 diallel hybrids (F₁). The results of the diallel analysis suggest that the genetic control of major agronomic traits is determined by both additive gene action (accumulation of frequency of desirable alleles represented by significant GCA effects) and nonadditive gene action (complementary gene interactions represented by significant SCA effects). This type of gene action expression in alfalfa also determines the way in which breeding is carried out and brings about changes in the methods used and has given rise to the idea of the semi-hybrid breeding of this crop. The concept involves: breeding alfalfas within the population, identification of heterotic germplasm, and the production of seed of the population hybrid (PH).     

甘蓝型油菜品质性状的配合力分析及低硫甙种质新开发的理论探讨

本研究以5个有代表性的甘蓝型油菜品种(系)进行双列杂交设计,采用 Griffing 方法1和2分别对其主要的品质性状含油量、硫甙总量和蛋白质含量进行了配合力分析,同时对这些性状的杂种优势和劣势问题进行了一些讨论。结果表明,含油量有少量的杂种优势可供利用,蛋白质含量表现为完全的杂种劣势,而控制硫甙总量的基因系统的显性效应     

Genetic variation and heritability of forage yield in Mediterranean tall fescue

The genetic control of tall fescue forage yield has been poorly investigated. Full‐sib families from diallel crosses of Mediterranean germplasm were evaluated for forage yield over 34 months in a Mediterranean environment with severe drought stress (diallel 1, with 20 parents) and over 16 months under irrigation in a heated greenhouse simulating the Mediterranean temperature pattern (diallel 2, with 15 parents). Genetic parameters were estimated for fresh biomass in diallel 1 and dry‐matter yield in diallel 2. Additive genetic variance was always larger than non‐additive (dominance) variance. Narrow‐sense heritability was fairly high (h² = 0.61) in diallel 1 and moderate (h² = 0.45) in diallel 2. Predicted yield gains from one selection cycle were larger in the former diallel (23.9%) than in the latter (10.5%), suggesting that gains can be enhanced by selection under severe drought stress and over a time span sufficient to allow the variation in persistence to fully emerge. General combining ability effects of eight parents that were common to both diallel crosses were highly correlated (r = 0.94) across the contrasting evaluation environments. The extent and consistency of additive genetic effects across environments suggest that rapid improvement of forage yield is possible.     

夏大豆产量性状的遗传力和配合力分析

用６个夏大豆品种进行双列杂交试验，估算了主要产量性状的遗传力、配合力效应。结果表明：大豆有效分枝数，每荚粒数，百粒重的狭义遗传力较高，可以进行早代选择；单株数、单株产量的狭义遗传力较低，在中高世代进行选择效果较好。大豆产量性状的加性遗传效应都是主要的，并以单株产量表现较大的特殊配合力效应。新品系８５２１２．８４２４０Ｂ１、７７２４９都是高产育种较理想的亲本材料，尤以品系７７２４９育种的效果最佳。     

Effects of Competition upon the Productivity of White Clover-Perennial Ryegrass Mixtures. Genetic Analysis

A diallel cross amongst four contrasting white clover varieties was used to provide genetic information on those characters which affect the productivity of white clover-perennial ryegrass mixtures when grown under a cutting-only management regime. Generally speaking those characters recorded on the clover families and in mixtures exhibited highly significant additive and non-ad dative genetic effects, though for1 sortie characters the latter could not be ascribed solely to dominance effects. For two of the clover characters, stolon and leaf number, the genetic picture was radically altered in mixtures by the effects of inter-specific competition Pseudo-genetic effects were also detected for the grass characters, bur it was suggested that the two ryegrass varieties used here were exhibiting phenotypic plasticity. As a group the four intra-varietal crosses performed significantly better than the six intra-varietal crosses for all clover and mixture characters. Only one of the inter-varietal crosses had significantly positive specific combining ability effects for most characters and that was between the two long established varieties ‘S. 184’ and ‘S. 100’. The implications of these results for the breeding of white clover varieties for use in mixtures are briefly discussed.     

Origin,diversity and utilization of the Cuban germplasm of common bean (Phaseolus vulgaris L.)

Summary Wheat root characters which influence vital plant processes have scarcely been explored for their genetic control. This study was conducted to i) examine the diversity of root traits and associated shoot traits in spring wheat (Triticum aestivum L.) cultivars; ii) study the nature of genetic control of selected traits; and iii) examine associations among root and shoot traits. Three experiments were conducted in the greenhouse with plants grown in the vermiculite medium in clear plastic tubes. In the first experiment, 42 spring wheat cultivars were grown for three weeks and measurements were taken on root length, leaf length, root number, leaf number, root dry weight, and top dry weight. In the second study, 15F₁'s originating from a partial diallel mating of six cultivars along with the parents were evaluated for 4 weeks. The data on root length, leaf length, and root number were subjected to diallel analysis according to Griffing's method 4, fixed model. A third experiment consisted of studying 2 F₂ populations with 141 plants per population. In the first study the 42 cultivars exhibited a wide range of variation for all six traits. Diallel analysis revealed significant effects of both general combining ability (GCA) and specific combining ability (SCA) for root length, leaf length, and root number. Parents with high GCA estimates were identified. Significant positive correlation coefficients were found among root and shoot traits. Analysis of F₂'s for root length indicated quantitative nature of inheritance of root length.     

Inheritance of two components of early maturity in groundnut (Arachis hypogaea L.)

Summary Knowledge of inheritance of early maturity or its components is important to groundnut breeders in developing short-duration cultivars. This study was conducted to determine the inheritance of two components of early maturity: days to first flower from sowing, and days to accumulation of 25 flowers from the appearance of first flower, using three groundnut genotypes. Two early-maturing (Chico and Gangapuri) and one late-maturing (M 13) genotypes were crossed in all possible combinations, including reciprocals. The parents, F₁, F₂, F₃, and backcross populations were evaluated for days to first flower from sowing, and for days to accumulation of 25 flowers. The data suggest that days to first flower in the crosses studied is governed by a single gene with additive gene action. Chico and Gangapuri possess the same allele for this component of earliness. Three independent genes with complete dominance at each locus appear to control the days to accumulation of 25 flowers. In crosses between late (M 13) and early (Chico or Gangapuri) parents, a segregation pattern suggesting dominant-recessive epistasis (13 late:3 early) was observed for this component. Segregation in the F₂ generation (1 late:15 early) of both early parents (Chico x Gangapuri) indicated that the genes for early accumulation of flowers in these two parents are at different loci.Submitted as ICRISAT J.A. No. 1557.     

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.     

三种不同类型大豆及其杂种后代主要农艺性状的配合力分析

利用具有明显差异的3种不同进化类型的大豆，采用双列杂交方式配制类型内及类型间共15个杂交组合。结果表明，不同类型大豆主要农艺性状的一般配合力明显不同。秣食豆在株高、节间长、分枝数、单株荚数和单株粒数等性状上具有增效作用；在粒茎比和收获指数等性状上具有减效作用。亚有限类型大豆则有降低株高和节间长度，提高     

Reciprocal cross differences in a 6×6 diallel set of groundnut (Arachis hypogaea L.) in the F1 generation

Summary Reciprocal cross differences were studied in a 6×6 diallel full set comprising of thirty hybrid combinations of groundnut in the F₁ generation.Reciprocal cross differences were observed for growth habit in four pairs of crosses, for leaf colour, flower colour and stem pigmentation in two pairs of crosses each. It was observed that the inheritance of flower colour, stem pigmentation and testa colour which exhibited different shades of purple colour was likely to be governed by pleiotropic gene(s). Among the quantitative characters significantly positive reciprocal effects were observed in different crosses for number of mature pods per plant, weight of pods per plant and shelling percent. Marked reciprocal cross differences were observed for pod and kernel characters like pod filling, pod beak, pod constriction and testa colour.     

The Nutritive Value and Yield of Alfalfa in Relation to Nitrogen Fertilization on Sulphur Industry Reclaimed Lands

The aim of this study was to determine the direction and magnitude of change in morphological and agronomical characters of spring barley ( Hordeum vulgare L.) in Germany over a period of 80 years and to assess the value of various strategies for further crop improvement. Old and new two-rowed cultivars, eight in each case, were tested together with their F₂ intra-group diallel crosses in a field trial at Braunschweig-Völkenrode in 1994. New parents and their crosses showed a higher dry matter grain and total biomass yield, a lower plant height, and a higher harvest index as compared to the respective old germplasm. The annual genetic gain in grain yield was estimated at 0.15%. The superior grain yield of the new germplasm was attributable to the higher number of ears per plant and the larger kernel weight. The F₂ mid-parent heterosis in grain yield was 7.6 and 7.2 % for the old and new crosses, respectively. The differences between the two types of crosses were nonsignificant except for the higher heterosis for plant height in the new crosses. General combining ability effects were significant for all characters in both types of crosses, whereas specific combining ability effects were significant in a few cases only. In the new crosses, a significant positive correlation was found between grain yield and straw yield (r = 0.52), whereas no such association was observed between grain yield and harvest index. For further gain in grain yield, improvement of the straw yield is more promising than increasing harvest index.     

The biological characters and polyploidy of progenies in hybridization in 4×–2× crosses in <Emphasis Type="Italic">Dianthus caryophyllus</Emphasis>

Crosses were carried out between tetraploid Dianthus caryophyllus cv ‘Butterfly’ (2n = 4×= 60) and seven diploid cultivars (2n = 2×= 30). Fewer seeds were obtained and the low seed germination was found which suggested the post-fertilization barrier in 4×–2× crosses. 12 progeny were obtained from 5 crossing combinations. Chromosome analysis revealed that they consisted of 5 triploid hybrid plants and 7 tetraploid hybrid plants, suggesting that unreduced male gamete maybe be involved in polyploid formation. Various flower shapes and colours were observed in the polyploid progenies, showing that sexual polyploidization results in greater variability and fitness. The hybrids obtained by 4×–2× crosses showed the flower-size intermediate between the parents or larger than the parents. Some favourable characters of parents such as flower shape, flower colour and resistance to Fusarium oxysporum, were successfully transmitted to the hybrids. Since polyploid hybrids have some of the profitable characters of the parents, they are expected to be used for future breeding in carnation.     

黄淮夏大豆形态性状的遗传研究

本文以黄淮地区6个夏大豆品种(系)通过双列杂交保留下来的F_3代材料,研究大豆6个形态性状的遗传特性.结果表明,株高、有效分枝数、主茎节数、主茎荚丛数和茎粗5个性状均符合加性—显性模型.而底荚高则存在非等位基因之间的互作效应.株高、有效分枝数、主茎节数和主茎荚丛数为部分显性,茎粗存在超显性现象.主茎节数和主茎荚丛数可能有相似的遗传特点.豫豆8号大豆带有较多的控制株高的显性基因,油84-30大豆带有较多的控制分枝和茎粗的显性基因,而尖顶大白角大豆控制主茎节数和美丛数的显性基因较多.     

栽培大豆(G.max)×半野生大豆(G.gracilis)后代主要农艺性状遗传参数的初步分析

本试验利用三个不同结荚习性的栽培大豆(G.max)做母本,分别与三个半野生大豆(G.graeilis)按NCⅡ设计配制的9个杂交组合,估测了F_1、F_2代主要农艺性状的优势指数;F_2代主要农艺性状的平均数、变幅、遗传变异系数、遗传力和预期遗传进度。试验结果表明:F_1代除百粒重、主茎有效节数以外,其余性状均有明显的杂种优势;F_2代除有效分枝、主茎粗以外,其余性状的优势指数均明显下降;F_2代遗传变异幅度大小的趋势为有限组合>亚有限组合>无限组合;生育日数、株高的遗传力高,可在早期世代进行选择;单株粒数、单株荚数、主茎粗的遗传力低,应在较晚世代选择;单株粒重及其主要构成因素均有较大的遗传进度绝对值,无限组合的遗传进度明显低于有限、亚有限组合。     

Combining ability and correlations for yield components in early generations of potato breeding

A partial diallel set of crosses was made between 14 potato cultivars chosen for their fertility, from those included in a potato breeding programme at the NEIKER – Basque Institute for Agricultural Research. The progeny were grown in completely randomized trials from 1997 to 1999. Performance for yield, tuber number and average tuber weight was analysed in seedling and two clonal generations. Variance estimates due to both general combining ability (GCA) and specific combining ability (SCA) were significant in all generations for all traits under study. However, SCA was more important than GCA in almost all cases. Correlation coefficients among characters, generations, GCA and SCA effects were examined. For tuber yield no relation was obtained between generations; however, average tuber weight and yield were positively associated in all generations. The results indicate that appropriate selection criteria depend strongly on the particular cross. The implication for a breeding strategy are discussed.     

Inheritance of salt tolerance in rice

Summary The genetic behavior of salt tolerance was studied in artificially salinized conditions at the International Rice Research Institute.Divergent selection, carried out at a salinity level where the ECe was 15.2 mmhos/cm at 25 C in F₃ lines from two crosses confirmed the effects of salt tolerance on F₄ progeny with realized heritability values of 0.39 and 0.62, respectively.In a cross between two tolerant cultivars there was clear over-dominance for tolerance, despite the high environmental fluctuation which resulted in a low genetic response as indicated by a low but significant repeatability of 0.20–0.25, and many progeny lines more tolerant than the parents were recovered. The superior tolerance of these progenies compared to the parents was confirmed subsequently at 3 different salt levels. In the same experiment a cross between tolerant and susceptible cultivars produced some progeny of comparable tolerance with tolerant sources.In a 6×6 diallel cross experiment with two tolerant, moderate, and susceptible varieties each, both general and specific combining ability were significant.The findings indicate the possibility of breeding rices more tolerant than existing tolerant cultivars through cumulative crosses of tolerant cultivars. Further improvement can be attained by crossing highly tolerant lines with donors of good agronomic traits and pest and disease resistance.