QTL mapping of pod tenderness and total soluble solid in yardlong bean [Vigna unguiculata (L.) Walp. subsp. unguiculata cv.-gr. sesquipedalis]

Yardlong bean [Vigna unguiculata ssp. unguiculata cv.-gr. sesquipedalis] is an important vegetable legume, particularly in Asia. Tenderness and sweetness of fresh pods are the key factors in deciding the commercial acceptance of yardlong bean. We report here for the first time quantitative trait loci (QTL) mapping of these traits from crosses between the yardlong bean accession JP81610 and wild cowpea (V. unguiculata ssp. unguiculata var. spontanea) accession JP89083. Two SSR-based linkage maps developed from BC₁F₁ [(JP81610?×?JP89083)?×?JP81610] and F₂ (JP81610?×?JP89083) populations were used for QTL analysis of pod tenderness and total soluble solid (TSS) content. Composite interval mapping (CIM) identified three QTLs for pod tenderness with phenotypic variance explained (PVE) of 5.6?C50?% and alleles from JP81610 increased the tenderness. CIM detected two QTLs for pod TSS with PVE of 7 and 9?%, and alleles from JP89083 increased TSS. Locations of these QTLs were compared with those of QTLs controlling domestication-related traits identified in the same populations. All QTLs for pod tenderness co-localized with QTLs for pod length. QTLs for pod TSS co-located with QTLs for pod dehiscence and/or pod length. The implications of these QTLs in breeding new yardlong bean and cowpea cultivars are discussed.     

A procedure for combining a quantitative inheritance study with the first cycle of a breeding program

Summary The number of effective factors controlling the inheritance of a quantitative character can be estimated by analysis of F₃ lines where the parental lines are homozygous. The procedure is illustrated with data from a study of pod length inheritance in common bean (Phaseolus vulgaris L.). The mean pod length of Sprite, the parent with longer pods, was compared statistically with the means of F₃ progenies derived from F₂ plants obtained from the appropriate tail of the F₂ frequency distribution for pod length. The data indicate that analysis of F₃ progenies avoids much of the underestimation of the effective factor number which is characteristic of other procedures. The number of effective factors was estimated to be a minimum of 4 and the correlation between random F₂ parents and F₃ progeny means was r=0.82.Florida Agricultural Experiment Station Journal Series No. 406.     

Inheritance of pigmentation and pod shape in winged bean

Summary The inheritance of five qualitative character differences in winged bean was studied in two crosses. All five character pairs were based on a single gene difference with complete dominance of purple over green stem colour, purple over green calyx colour, purple over green pod wing colour, purple specks over green pod and rectangular over flat pod shape. Linkage was observed between stem and calyx colour and also pod wing colour and pod specks.     

A factor analysis of plant variables associated with architecture and seed size in dry bean

Summary A knowledge of the biological and functional relationships among traits would be of benefit to plant breeders in the choice of traits to use for increasing efficiency of selection in a breeding program. Principal factor analysis was used to identify biological and functional relationships among dry bean (Phaseolus vulgaris L.) traits in segregating populations of a phenotypic recurrent selection program designed to introduce upright architecture into medium-sized dry bean.Two biological interpretations were assigned to factors extracted in the analysis of four seed/pod traits. The first was a size factor, loaded with seed weight and pod width, and the second a number factor, which was loaded with number of seeds per pod and pod length. Similarly, three factors were extracted from the analysis of fifteen architectural traits. The first factor was interpreted as an elongation factor, and was loaded with internode length measurements, while the second factor was interpreted as a structural factor, and was further divided into two subclasses namely, sturdiness factor and profile factor. The sturdiness factor comprised hypocotyl diameter and hypocotyl length, while the profile factor comprised branch angle and number of basal branches. The third factor which was called a reproductive factor was loaded with pod distribution traits and the number and location of nodes on which pods were borne.     

Effect of selection for pollen grain size on various traits in common bean

Summary Selection among microgametophytes usually exploits variation in pollen grain germination. Studies of variation in pollen grain size in common bean (Phaseolus vulgaris L.) suggested that selection for size might lead to changes in sporophytic traits. To determine whether microgametophytic selection based on size would affect pollen grain size in subsequent generations or sporophytic traits that were correlated with pollen grain size, pollen grains from three crosses were separated into two size categories by sieving and then used to pollinate cv. Diacol Calima. Selection resulted in changes in pollen grain diameter for pollen from F₁, F₂ and F₃ plants for all crosses. In vitro germination indicated no differences between vigor of large and small grains, but extraction and sieving reduced germinability. F₁ seed from two of the crosses with size-selected pollen varied in weight according to pollen grain size, but in subsequent generations, the effect disappeared. Both size categories of selected pollen resulted in F₂ progeny with reduced numbers of seeds per pod as compared to controls, suggesting that the size selection process may have resulted in indirect selection for traits reducing seed set. The overall results suggested that genes determining pollen grain size in bean have little or no effect on sporophytic traits such as seed size and seed yield.     

Identification of Genes Controlling Pod Length in Spring Rapeseed, Brassica napus L., and their Utilization for Yield Improvement

Experiments were undertaken to determine the inheritance of pod length in a cross with spring rapesecd, Brassica napus, and to assess the value of pod length as a criterion of selection for high seed yield. Analyses of patterns of variation in F₂; and backcross populations derived from a cross between a short-pod line TB42 and long-pod line CA553 indicated that much of the variation in pod length could be attributed to two major genes interacting in a complementary manner. Short-pods were produced when cither one or both genes were homozygous for the recessive allele. Analyses of F₃ progenies of selected F₂ and inbred-backcross lines derived from the same cross supported the two-gene hypothesis but also indicated that the effects of the major genes on pod length were possibly modified by genes of minor effect. Field testing of families derived from random intermating between F₂, plants of the TB42 × CA553 cross showed that number of pods per plant varied independently of pod length, but seed weight per pod tended to increase with increasing pod length. As a result, families with the longest pods generally had significantly higher yields than those with short pods. It was concluded that yield improvement in B. napus could be achieved through introgression of long-pod genes into cultivars with an appropriate genetic background to ensure that selection for the long-pod character would be accompanied by an increase in seed weight per pod with little or no reduction in number of pods per plant.     

Development of common bean (Phaseolus vulgaris L.) lines resistant to the bean pod weevil,Apion godmani Wagner,in Central America

Summary The larva of the bean pod weevil (BPW), Apion godmani Wagner (Coleoptera: Curculionidae), causes serious yield losses in common bean (Phaseolus vulgaris L.) in Mexico and Central America, by consuming the seed as it develops in the immature pod. Resistance to the BPW was identified in bean germplasm of highland Mexican origin, and these sources of resistance were incorporated into a pedigree breeding program to recover locally adapted lines resistant to Bean Common Mosaic Virus and BPW, with commercial grain for Guatemala, Honduras and El Salvador. These lines yielded as well as or better than local cultivars in the absence of the insect, and better than local cultivars when the BPW was present. Resistance appeared to be governed by several genes, and was stable across geographic areas, seasons and planting systems.     

Inheritance of yield components and their correlation with yield in cowpea (Vigna unguiculata (L.) Walp.)

Summary The inheritance of yield components was studied in a cross of two varieties of cowpea (Vigna unguiculata), and the relationships among the components and yield were examined in the F₂ of a cross and in a trial of 22 varieties. The main objective was to determine the suitability of using the components as selection criteria for increasing seed yield. All the components appeared to be under polygenic control and transgressive segregation in the F₂ was observed for pod length and number of seeds per pod. Narrow sense heritability estimates ranged from 19.8% for number of pods per plant to 60.3% for pod length. Most of the genotypic correlations between pairs of yield components were significant. Correlation of yield per plant was negative with pod length, but positive with the other components. Number of pods per plant was consistently correlated with yield. However because of low heritability for number of pods per plant, this component may only be used as a preliminary selection criterion while the final selection is based on yield itself.     

Genetic diversity in pod and seed quality traits of common bean populations from northwestern Spain

Common bean (Phaseolus vulgaris L.) is an important food in the northwest of Spain where it is consumed as either green pods or dry seeds after cooking. Quality properties play a major role in cultivar acceptance by processors and consumers. To determine if sufficient variation in important culinary and nutritional traits exists within common bean, fifty-nine populations (plus five commercial cultivars) were grown in the northwest of the Iberian Peninsula in three different environments and evaluated for sixteen fresh pod and dry seed quality traits. Populations showed significant differences for pod curvature, length/width and width/thickness ratios of pod and seed, pod and seed texture, volume, hardness, seed coat percentage and water absorption of seed, crude protein, crude fat, crude fiber, toal sugars and starch content. Genotype × environment interaction was significant for fresh pod traits such as curvature, length/width and width/thickness ratios, and texture, and for dry seed traits such as length/width and width/thickness ratios, volume, hardness and water absorption. Estimates of heritabilities and constancies (genotypic/environmental variance) were higher than 0.5 and 1.0 respectively for pod curvature, length/width and width/thickness ratios of pod and seed, seed volume and seed water absorption. There were high correlations of pod texture with seed length/width and width-thickness ratios, seed coat percentage, seed water absorption, crude fat, total sugars, starch content and crude fiber. Pod texture could be used as an important parameter for evaluating both seed culinary and nutritional quality. In addition, 17 populations showed promise as parental material in a breeding program for pod and seed culinary quality and protein content. The culinary and nutritional quality potential of the accessions such as PHA-0171, PHA-0253 and PHA-0257 which are known as Alubias de riñón could be the base material in a breeding program to obtain accessions with a good seed quality.     

The variability of certain bean characteristics of cacao (Theobroma cacao L.)

Summary The variability of the following characteristics of fresh cacao beans were studied, using samples of clones of different genetic origin: wet weight, length, width, thickness, and shell percentage, pulp percentage, and number of beans per pod.All these characteristics showed highly statistical differences between clones and a very high discriminative value P to differentiate clones. It was also estimated that the best sample size, taking as a basis wet weight (the most variable character), was 3 seeds of 20 pods per clone.     

Temporal profiles of pod production and pod set in soybean

The distribution of flower and pod production during flowering may be an important determinant of pod and seed number in grain crops. We characterized the dynamics of small pod production and survival to maturity on indeterminate and determinate soybean [Glycine max (L.) Merrill)] cultivars growing in the field or greenhouse. Two soybean cultivars (maturity group IV, indeterminate and determinate) were grown in the field near Lexington, KY (38°N latitude) in 2001 and 2002 in 0.76 cm rows using late May and late June (2002 only) planting dates, and normal (24 plants m⁻²) and low (9 plants m⁻², 2002 only) plant populations. Cultivar Elgin 87 (indeterminate, maturity group II) was grown in a greenhouse in 3.0 L pots with one plant per pot. All unmarked pods that were ≥10 mm long were marked with acrylic paint at the base of the pod at 3-day intervals. Paint color was changed at each marking to provide a temporal profile of pod production and pod survival. The pod production (marked pods) period was longer in the indeterminate cultivar (nearly 50 days after R1) than the determinate cultivar (≤40 days after R1). Delayed planting shortened the pod-production period, but a two- to three-fold difference in pods per plant, created by changing plant population, did not affect it. The temporal distribution of small pods that survived to maturity (full sized pods with at least one normal seed) closely followed the distribution of pod production in all experiments. Some surviving pods initiated growth after the beginning of seed filling (i.e., between growth stage R5 and R6), but most of the pods were initiated in a much shorter interval (up to 84% were initiated in <40% of the period) before R5. Abortion of pods >10 mm long was relatively low (20–30%), so production of a pod ≥10 mm long seems to be a key event in the pod set process. The average length of the pod set period at individual nodes on the main stem was larger for the determinate cultivar (14 days) than for the indeterminate (9 days), so the longer total period in the indeterminate cultivar resulted from the delay in initating pod production at the upper nodes on the main stem. Temporal profiles of pod production and pod set seem to be more sensitive to changes in flower and main stem node production than to changes in photosynthesis per plant (created by varying plant population). These results provide some of the information needed to integrate time into models predicting pod and seed number.     

The effect of potassium gibberellate and naphtaline acetamide on pod setting in intervarietal crosses of common bean,Phaseolus vulgaris L.

Summary The potential effects of two hormones, namely potassium gibberellate (P.G.) and naphtaline acetamide (N.A.), on pod setting in bean were investigated in three crossing programs, set up with five varieties of bean. Shortly after each crossing, a cut was made on the calyx and a mixture of lanoline + P.G. (2%) or of lanoline + P.G. (2%) + N.A. (1%) was applied. Lanoline alone was used as a control. When compared with the control, lanoline + P.G. (2%) increased the number of pods, although significantly so only in two of the programs. Lanoline + P.G. (2%) + N.A. (1%) increased the number of pods by 23.39 to 25.46%.     

Interrelationships between cropping systems for pod and seed quality components and breeding implications in common bean

Breeding programmes in common bean (Phaseolus vulgaris L.) have mainly focused on performance under monoculture conditions. Interactions among cultivars and cropping systems do occur and genotypes bred for pure cropping may not be suitable for intercropping. This study was undertaken to obtain estimates of genetic parameters of quality traits for bush bean landraces grown in two cropping systems, and the interrelationships of these traits between pure cropping and intercropping with maize (Zea mays L.). Field experiments were conducted at two locations for two years. Expression of most traits was not strongly influenced by genotype × environment interactions. Heritability estimates were similar in both cropping systems for most pod and seed quality traits. Positive correlations were observed between pure cropping and intercropping for pod characters (weight, length, width and texture) and seed characters (dry and imbided weight, length, hardness, coat proportion, water absorption and crude protein). Use of a selection index is suggested for breeding for seed size, water absorption,coat proportion and crude protein for both cropping systems. However, larger gains would be expected in pure cropping for most traits. Bean accessions PHA-0267, PHA-0285, PHA-0286 and PHA-0299 should be used for developing acceptable culinary and high protein breeding lines for either cropping system. This revised version was published online in August 2006 with corrections to the Cover Date.     

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.     

Characterization of the interspecific cross Cicer anetinum L. ×C. judaicum (Boiss)

An interspecific cross involving Cicer anetinum L. and C. judaicum (Boiss) No. 182 was established. The F₁ could be distinguished from the parents by its prostrate growth habit at the seedling stage and through isozyme patterns for peroxidases and esterases. The inheritance of PRX-3 was found to be relatively simple and behaved as a monomer. Meiotic studies indicated the occurrence of six bivalents and four uni-valents in about 6% of F₁ PMC's at metaphase I, but normal 8–8 chromosomal distribution in anaphase I, indicating near complete homology. The F₁ hybrid was characterized for three morphological and six agronomical characters. A large F₂ was studied for secondary branches per plant, 100-seed weight (g), pods per plant, and grain yield per plant (g). Distributions of F₂ for pod number and grain yield displayed high C.V. and were highly skewed in a positive direction. F₂ recombinants were isolated with a very large number of secondary branches and a high pod number and yield. Such wide variability is not normally encountered in intevarietal crosses.     

Simple sequence repeat markers linked to a major QTL controlling pod shattering in soybean

Shattering of soybean pods prior to harvest leads to a reduction in yield. In order to identify simple sequence repeat (SSR) markers linked to quantitative trait loci (QTLs) conditioning pod shattering, QTL analysis was conducted using an recombinant inbred line (RIL) population segregating for this trait. The degrees of pod‐shattering resistance were evaluated by heat treatment applied to pods harvested from plants in the field and in a growth chamber. Composite interval mapping identified one major QTL between SSR markers Sat_093 and Sat_366 on linkage group J for both environments. The position and the effect of this QTL were confirmed in an F₂ population derived from a cross between the pod shattering‐susceptible parental cultivar and a pod shattering‐resistant RIL. The SSR markers linked to the major QTL will be useful for marker‐assisted selection in soybean‐breeding programmes.     

Variability of various pod characters as a factor in cacao selection

The total annual pulp production and the average weight of seeds are among the most important criteria in selecting new parent trees in a seedling population of cacao.Until now in Netherlands New Guinea the pulp production per tree was computed by multiplying the number of pods harvested with the average wet seed weight per pod, which magnitude, like the average weight per seed, was derived from the data of 20 average pods per tree which had been chosen by eye.Computations from the results of 20 pod analyses per tree in a group of 50 seedlings have shown that the values of the total pulp production established in this way and the average weight per seed can deviate considerably from the true values.As concerns the total pulp production, determination of the total weight of the pods harvested and multiplication of that figure with the average quotient pulp weight/pod weight of 20 average pods chosen on the basis of their weight as a rule gives much better results. By sampling in this way a better impression is also gained of the average bean size.     

Genetic gain in agronomic traits of common bean in the region of Planalto Catarinense

The purpose of this study was to predict the genetic progress in the selection for common bean agronomic traits based on the trait expression, using two indices of adaptive selection. The existence of correlation between various traits in common bean breeding is a major restriction, but some tools that allow breeders to predict the expected gains could optimize results. The following traits were evaluated: (1) plant cycle (days), (2) plant height (in cm), (3) stem diameter (cm), (4) insertion of the first pod (cm); (5) number of pods per plant; (6) number of grains per pod; (7) pod length (cm). Results show the possibility of selecting accessions for several agronomically important traits evaluated together. The only genotype selected by both indices was UDESC 03, confirming the possibility of selecting plants with superior agronomic traits among genotypes of common bean landraces.     

长豇豆几个数量性状杂种优势的研究

此试验利用长豇豆（Vignaunguiculatassp.Sesquipedalis(L)Verd.）7个品种，采用Griffing第2套方案配制21个杂交组合，对长豇豆的7个数量性状进行了杂种优势分析和配合力分析。结果表明，单株结荚数、单荚重、荚长、早期产量等性状为正向优势，第一花序节位、开花前天数、开花至嫩荚成熟天数为负向优势。     

Heritability of quantitative traits in segregating common bean families using a Bayesian approach

Genetic parameters for six quantitative traits in the early generation of segregating populations of common beans (Phaseolus vulgaris L.) were evaluated. A Bayesian approach was used for estimating the variance components, breeding values and broad sense heritability of the quantitative traits under analysis. The Markov Chain Monte Carlo method was utilized to analyze the contribution of genes affecting complex traits. Twenty-four F₃ families were evaluated in the field during 2005 in Santa Catarina, southern Brazil. With regard to the grain yield and yield components, the additive variances were relatively similar to the dominance variances. This result is confirmed by the 95% credible set from the posterior distribution. The mean estimates of broad-sense heritability (H²) varied from 11.5% to 64.2%. The heritability estimates of yield and yield components were higher than the estimates for the number of days until flowering and reproductive period. However, for grain yield, the 95% heritability credible set included the heritability estimates from point of crop duration. The predicted genetic gain reached the highest value for the number of pods per plant (10.95%). Days to flowering and reproductive period had the lowest values of genetic advance. One hundred seed-weight, grain yield and seeds per pod exhibited a similar predictable level of genetic gain: GA = 5.73%, 5.81% and 4.77%, respectively. The Bayesian framework provided information that is useful for a breeding program, since it contributes to the understanding of how quantitative traits are genetically controlled.