Patterns of genetic diversity in landraces of common bean (Phaseolus vulgaris L.) from Galicia

Knowledge of patterns of genetic diversity among existing cultivars helps to broaden the genetic base of new cultivars and maximizes the use of available germplasm resources. This study examined the organization of diversity for morphological traits in 66 landraces of cultivated common bean (Phaseolus vulgaris) from Galicia and its relationship with phaseolin seed protein diversity. Data on growth habit, seed and pod traits obtained from field evaluations at two locations during the 1989—91 cropping seasons were subjected to multivariate statistical analysis. Cluster analysis based on 14 quantitative variables and five qualitative variables identified 11 groups. The landraces were also characterized by phaseolin electrophoresis. The results allowed separation of these landraces into Middle and Andean American groups, which could be further divided into at least eight groups within the Andean American cultivars and three within the Mesoamerican cultivars. These groups in turn corresponded to the previously described races Nueva Granada and Peru of South American origin, and races Durango, Jalisco and Mesoamerica from the Middle American domestication centre. These results confirm the existence of two major groups of germplasm in the cultivated common bean landraces from Galicia, Mesoamerican vs. Andean American.     

Phenotypic variation in a core collection of common bean (Phaseolus vulgaris L.) in the Netherlands

Forty accessions, forming a core collection of mainly bush type of the common bean (Phaseolus vulgaris L.) germplasm in the Netherlands, were evaluated for 14 qualitative and quantitative traits at the Agricultural University, Wageningen (WAU), the Netherlands in 1992. These and an additional 117 Dutch accessions, mainly collected in private home gardens, were also evaluated for phaseolin seed protein pattern, and morphological and agronomic traits at the International Center for Tropical Agriculture (CIAT, Spanish acronym), Cali, Columbia between 1987 and 1997. Multivariate and principal component analyses at both WAU and CIAT indicated existence of one large group with no discernable patterns among Dutch common bean collections of landraces, garden forms and cultivars. However, when phaseolin, an evolutionary, biochemical marker, was used as an initial classification criterion followed by use of morphological markers, the two major gene pools; Andean and Middle American with two races in each (Chile and Nueva Granada in Andean, and Durango and Mesoamerica in Middle American) were identified. The Andean gene pool was predominant (136 of 157 accessions), especially the race Nueva Granada (126 accessions) characterized by the bush determinate growth habit type I and T phaseolin. The new core collection comprised 31 accessions. Bean races Chile, Durango, and Mesoamerica were represented by 10, 7, and 14 accessions, respectively. Of the 9 French or snap bean accessions six possessed characteristics of race Mesoamerica and three belonged to Durango race. Occurrence of these and a large number of other recombinants strongly suggested considerable hybridization and gene exchange between Andean and Middle American gene pools, thus blurring the natural boundaries and forming a large single group of common bean germplasm in the Netherlands. The inter-gene-pool recombinants of both dry and French beans should be of special interest to breeders for use as bridging-parents for development of broad-based populations. This revised version was published online in July 2006 with corrections to the Cover Date.     

Random amplified polymorphic DNA (RAPD) markers variability among cultivars and landraces of common beans (Phaseolus vulgaris L.) of south-Brazil

To evaluate the variability among cultivars and landraces of common bean(Phaseolus vulgaris L.), 15 cultivars and 18 landraces of common bean (Phaseolus vulgarisL.), a undefined species of Phaseolus,two landraces of Vigna angularis L., and a landrace of soybean (Glycine maxL.), were screened with fifteen oligonucleotide primers in PCR reactions. An average of 20.3 RAPD bands were scored per primer. A total of 304 amplification products were scored of which 88.8% were polymorphic among Phaseolus genotypes. Based on the RAPD markers, four major clusters were formed. Three clusters corresponded to the soybean, to the two Vigna angularis landraces, and to the Phaseolus sp. landrace, respectively. The fourth cluster include all the landraces and cultivars of Phaseolus vulgaris. This large group could be separated into three subgroups that were correlated with the phaseolin patterns and the average seed weight of the genotypes. The analysis shows that most of the landraces collected in South Brazil (17 out of 18) belong to the Andean gene pool, and most of the cultivars (13 out of 15) belong to the Middle American gene pool. This revised version was published online in July 2006 with corrections to the Cover Date.     

菜豆种子蛋白的变异和品种鉴定

用两种线性浓度梯度(8—20%和12—20%)的SDS聚丙烯酰胺凝胶电泳分析了来自14个国家的54个菜豆品种的种子蛋白.结果表明:多数多肽在品种间有淌度变异,变异发生在8个分子量区域.我们推荐本方法用于菜豆品种鉴定.种子蛋白谱与种皮颜色没有相关性.除3个品种外,凡菜豆球蛋白含3主要多肽的品种都是茎直立的矮生类型;而只有2主要多肽的品种都是茎缠绕的蔓生类型.看来,种子蛋白还可能在育种中预测其他性状.     

A core collection of common bean from the Iberian peninsula

Characterization of crop germplasm from specific regions helps understand the patterns of genetic variation that facilitates further germplasm collection, characterization, management and their more efficient utilization in genetics, breeding and other studies. Common bean (Phaseolus vulgaris L.) is a traditional crop in the Iberian Peninsula (Spain and Portugal) where subsistence farmers have been growing and maintaining their own cultivars since their introductions from the Americas in the sixteenth century. Our objectives were to: (i) characterize diversity in the landraces collected from the Iberian Peninsula and (ii) form a core collection. Of 388 landraces from the major production regions characterized for 34quantitative and 13 qualitative characters, including morphological, agronomic and biochemical traits, 74.7% had an Andean origin, 16.8% a Mesoamerican origin and 8.4% had seed mixtures or were recombinants between the two gene pools. Landraces of indeterminate climbing growth habit Type IV(47.2%) and bush determinate Type I(26.4%) with large (52.9%) and medium(27.4%) seeds of white (38.8%) and cream(25.9%) colour were predominant. Similarly, the ‘T’ phaseolin pattern and common bean race Nueva Granada were the most frequent(51%). Some exceptionally large-seeded landraces of Andean (e.g., PHA-0917 with119 g 100-seed weight^-1) and Mesoamerican (e.g., PHA-0399 with 66 g100-seed weight^-1) were found. These and other possible recombinants between the two gene pools merit further investigation. Fifty two landraces (13%) were chosen to form a core collection representing the genetic diversity in the Iberian Peninsula. This revised version was published online in July 2006 with corrections to the Cover Date.     

Acid PAGE procedure for detection of phaseolins in field beans (Phaseolus vulgaris L.)

Summary A procedure based on acid polyacrylamide gel electrophoresis (acid PAGE) has been described. Resolution of phaseolin bands appears to be relatively superior to that obtained with basic PAGE system. The procedure discriminates S, T, C, M and B types of phaseolins; S, T and C have been reported previously while M and B types were identified in the present study.     

Environmental and Genotypic Effects on Pod Characteristics Related to Common Bean Quality

A collection of 121 common bean (Phaseolus vulgaris L.) landraces from Spain and Portugal (Iberian Peninsula) was evaluated in six environments (three locations and 2 years). Significant differences among landraces were found for period of flowering, pod maturity and pod morphology (weight, length, width/thickness and curvature). Wide variation among landraces was revealed by the range of variation observed. Environmental effects were not significant although year × location and landrace × year × location interactions were significant for all traits studied except for pod curvature. Poor consistent expression across the different environments for most of the traits studied was expressed by the low values of constancy (C) with the exception of width/thickness indicating that pod shape (round or flat) was expressed regularly across different environments. Principal component analysis enhanced differences among environments affecting the performance of the bean landraces evaluated. Analysis by environment showed that 51 landraces were adapted to specific environments and only four of them had broad geographical adaptability with similar performance under different conditions. These results could be a starting point for selection of new inbred lines adapted to distinct environments with potential for the improvement of current snap bean cultivars.     

Phaseolin Diversity in the Tepary Bean, Phaseolus acutifolius A. Gray

The tepary bean (Phaseolus acutifolius A. Gray) is grown mainly in and regions of Mexico and the southwestern U.S. as a subsistence crop by small farmers. It is also a store of genetic variability for traits such as disease and pest resistance and stress tolerance to improve the common bean (P. vulgaris L.). To determine geographic patterns of variation and the influence of domestication on genetic variability, the genetic diversity of phaseolin, the major seed storage protein, was characterized among 55 wild and 8 cultivated teparies using polyacrylamide gel electrophoresis. Fifteen electrophoretic phaseolin patterns were identified among wild forms, whereas only one pattern was exhibited by cultivars. This result suggests a single domestication in this species leading to a strong reduction in diversity. An additional finding is the divergence m phaseolin types between populations east and west of the Sierra Madre Occidental mountains.     

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.     

Phytochemical distribution and antioxidant activities of Korean adzuki bean (<Emphasis Type="Italic">Vigna angularis</Emphasis>) landraces

Total polyphenol content (TPC), total phenolic acid content (TPA), and total flavonoid content (TFC) in 209 Korean adzuki bean landraces were determined by colorimetric methods. Antioxidant effects were evaluated with the DPPH, ABTS, ferric reducing antioxidant power (FRAP), reducing power (RP), and SOD assays. TPC, TPA, and TFC in the 209 Korean adzuki bean landraces ranged from 1.1 to 11.7 mg gallic acid equivalents/g, 0.37 to 5.03 mg caffeic acid equivalents/g, and 0.17 to 0.91 mg quercetin equivalents/g, respectively. Antioxidant activities as assessed by the DPPH, ABTS, FRAP, PR, and SOD assays showed wide variation, ranging from 12.2 to 86.3 (IC₅₀), 0.85 to 5.25 mg ascorbic acid equivalents (ASC)/g, 0.41 to 5.44 mg ASC/g, 0.54 to 1.83 mg ASC/g, and 60.4 to 142.8 (IC₅₀), respectively. Using the relative antioxidant capacity index (RACI), we found that the IT189394 had the highest antioxidant activity. In clustering analysis, 209 Korean adzuki bean landraces were classified into three clusters. Among them, cluster I contained 22 landraces with higher antioxidant activities, TPC, TFC, and TPA and smaller seed sizes than the other clusters. We anticipate that these results will provide useful information for the development of adzuki bean-based functional foods.     

Agronomical and quality traits of runner bean germplasm and implications for breeding

White runner bean landraces are greatly appreciated in the North highlands of Spain due to their excellent culinary seed quality. Runner bean cultivars are grown like pole beans. Diversity within a runner bean collection of 31 accessions from the Iberian Peninsula (Spain and Portugal) was examined using morphological, agronomical and seed quality traits. Landraces showed significant differences for most of the agronomical and seed quality traits studied except for seeds per pod, water absorption, seed coat tenderness and floury texture. Runner bean landraces showed sufficient variability to select inbred lines for future breeding. Genotype × environment interaction was significant for days to first flowering, days to first dry pod, seeds per pod and seed length. The majority of physical and nutritional seed quality traits studied which are important to determine the commercial value of a variety were not subject to environmental influences. Different selection pressures affecting to the runner bean genetic material could have occurred in several regions of the Iberian Peninsula. Extra-large and high yielding runner bean germplasm was identified and represents a valuable source of genetic diversity that has potential for development of improved cultivars to be chosen for commercialisation. This revised version was published online in July 2006 with corrections to the Cover Date.     

Pattern of variation for seed size traits and molecular markers in Italian germplasm of Phaseolus coccineus L.

Variation in Italian germplasm of Phaseolus coccineus L. was assessed for seed traits and molecular markers. A total of 130 seeds and seedlings, five for each of 21 Italian landraces, an Italian commercial cultivar and four Mesoamerican landraces of P. coccineus, were analysed using seven selected PCR markers: three RAPDs, two ISSRs and two ETs. Seed weight of the Mesoamerican landraces was ≤1 g, whereas that of the Italian landraces varied from 1 g to 2.5 g and was related to their origin. Oval shape was more frequent, with round shape observed only in Mesoamerican landraces. Three seed coat colours were observed: white, violet mottled or spotted black and buff spotted brown, also this trait was related to the origin. The level of polymorphism detected by molecular markers was low but with significant discriminant power. ISSRs were the most effective markers prone to unravel molecular polymorphism. The within accession component of variation exceeded that among accessions, as expected for an allogamous species. However correct classification of the individuals was achieved performing either discriminant analysis of the seed phenotypic traits or cluster analysis of seedling similarity measure based on the whole banding patterns obtained by the three marker types. Our data suggest that the Italian farmers, starting with ancestral Mesoamerican runner bean introductions in Europe, bred their own landraces through selection for seed size and seed coat colour, but occasional gene flow maintained variability within landraces bred by different farmers in the same Italian Region. Selection favored molecular and seed trait uniformity within several landraces making them suitable for certification.     

Variation in traits affecting nodulation of common bean under intercropping with maize and sole cropping

Common bean (Phaseolus vulgaris L.), an important food crop in Europe, America, Africa and Asia, is thought to fix only small amounts of atmospheric nitrogen. It contributes significantly to the sustainability of traditional cropping systems because of the predominance of small-scale farmers who cultivate beans in those areas. The objectives of this work were to evaluate bush bean varieties under common agronomic cropping systems and to evaluate breeding lines under low N-fertility sole cropping and intercropping systems. The purpose of the study was to characterize the genotype and cropping system's variability in symbiotic and plant characters and to identify the most suitable genotypes to establish an effective symbiosis with indigenous strains of Rhizobium. No significant differences among the bush bean varieties evaluated under typical fertilization practices were observed for N₂-fixation and plant traits except for seed nitrogen. Significant differences among the bean lines studied under low N-fertilization conditions were detected for plant growth,plant component and N₂-fixation traits. A significant interaction of bean genotype x cropping system was found for number of nodules per plant and nodule moisture on the bush bean varieties studied, and for days to emergence, days to flowering, end of flowering, shoot length, root dry weight and shoot nitrogen on the bean lines evaluated. Nodulation parameters were correlated positively with the yield components, shoot and root parts and duration of flowering, and correlated negatively with seed crude protein, pod and seed dimensions and seed dry weight. These observations indicate that it may be possible to increase both the symbiotic N₂-fixation and seed yield through plant breeding. This revised version was published online in August 2006 with corrections to the Cover Date.     

Genetic diversity of some surviving on-farm Italian common bean (Phaseolus vulgaris L.) landraces

This study was undertaken to estimate the level of variation among and within 33 local populations belonging to seven Italian common bean landraces, by analysing the polymorphism of seed storage proteins, simple sequence repeat (SSR) and amplified fragment length polymorphism (AFLP) molecular markers. The nutritional seed quality of the landraces studied was also investigated. Results showed that the landraces retain a considerable level of heterogeneity. Use of both biochemical and molecular approaches provided a picture of the genetic diversity of each landrace. Cluster analyses based on Nei's genetic distances and Jaccard's similarity index as defined by SSR and AFLP markers, respectively, showed that all populations clustered into two groups corresponding to the Andean and the Mesoamerican gene pools. Knowledge of the genetic structure of a landrace is fundamental in elaborating strategies, which involve the local farmers, allowing us to improve and, at the same time, safeguard the genetic integrity of landrace genetic resources.     

Variation for dry matter yield,seed yield and other agronomic traits in Ladino white clover landraces and natural populations

Summary A set of Ladino white clover ecotypes including the last available landraces and some natural populations collected from old permanent meadows, together with some white clover varieties of various origins, were evaluated as monocultures for dry matter (DM) and seed yield assessed in separate field experiments. Other agronomic traits were also recorded. The best performing variety, Espanso, was significantly outyielded by some ecotypes for DM and seed production. Compared to landraces, natural populations yielded on average far less seed but as much DM and tended towards higher persistence indicating that domestication of the native Ladino at the farm level only improved seed yield of the crop. Natural populations showed, besides lower values of most seed yield components, a distinct canopy architecture characterized by smaller leaves, longer internodes and denser stolons. Seed weight proved the best character discriminating between the two ecotype groups. Significant variation for most traits was found both among landraces, in which it was mostly relatable to differences among provenances, and among natural populations. The relations between the main multivariate patterns of phenotypic variation and a set of environment collecting variables suggested that evolutive adaptation to different agronomic practices was a major determinant of the overall variation found in landraces. Evidence is provided that a relevant part of the variation observed among ecotypes for some important traits could be genetic.Abbreviations DM dry matter - DMY dry matter yield - NRH number of ripe heads - NFH number of florets per head - PL petiole length - LS leaf size - IL internode length - NS number of stolons - PRO protein content - SY seed yield - TSW thousand seed weight - NSF number of seeds per floret - PCA principal components analysis - PC principal component     

Characterization of common bean wild populations for their in situ conservation in Northwestern Argentina

In situ conservation of wild species is a method of conservation that allows keeping populations in their natural environments, and set the strategies for maintaining the natural populations. The Active Bank of Northwestern Argentina (BANOA) is in charge of the in situ conservation of wild populations of common bean (Phaseolus vulgaris L.) in Northwestern Argentina (NOA), and has an ex situ collection of 401 landraces and 221 wild accessions from the NOA. We evaluated the phenotypic diversity of 68 common bean wild populations from the NOA both in protected and unprotected areas, finding a moderate variation among them. Ten phenotypic reproductive characteristics related to pod and seed displayed significant differences in the analysis of variance; these traits together with the seed weight were the basis for the multivariate analysis. The cluster analysis ordered the populations in 12 groups but trends in geographical distribution or phenotypical variation were not recognized. For the conservation in situ of the wild bean populations, their diversity should be considered. Two types of populations can be highlighted: (i) candidates for in situ conservation in order to preserve the novel variation generated by convergence with cultivated sympatric germplasm (populations 433, 437, 471, 509, 513 and 517) and (ii) those whose phenotype represents clearly the wild status and should be preserved in situ as such in their current status (populations 480, 495, 496, 525 and 533).     

Indonesian mungbean landraces I. Pure-line selection for yield when intercropped with maize

Summary When mungbean landraces from East Java were intercropped with maize, genetic variation for grain yield was observed. Three cycles of selection resulted in a yield increase of 24% as compared to the original landraces. The yield of the maize component in the mixture was not affected by the increase of the mungbean yield.     

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.     

Breeding the common bean (Phaseolus vulgaris L.) for resistance to bean common mosaic virus: alternatives to backcrossing

A series of field experiments was undertaken in order to determine whether resistance to bean common mosaic virus (BCMV) could be incorporated into genotypes of the common bean (Phaseolus vulgaris L.) suitable for cultivation in Zimbabwe without recourse to backcrossing. Six inbred genotypes carrying the resistance-conferring alleles at the loci I and Bc-3 were crossed with five locally-adapted inbred genotypes. The first experiment comprised F₃ progeny rows, each derived from a single unselected F₂ plant, the second, F₃ bulks selected for resistance, and the third, a comparison of selected and unselected F₂-derived F₄ lines. The number of days to flowering and to maturity, the incidence of mosaic and necrosis symptoms, seed yield and seed size were recorded. There was evidence that late flowering and maturity were associated with BCMV resistance in some crosses, though not strongly enough to present an obstacle to plant breeding. The incidence of virus symptoms and seed yield were influenced by genetic factors additional to the major resistance genes, and variation in seed yield was present not only between bulk populations of crosses, but also between single-row plots of lines within crosses. This indicates that early-generation selection for yield in the presence of BCMV, even among progeny selected for BCMV-resistace, is likely to be effective. However, the variation in yield among F₄ lines was least in the highest-yielding crosses, which may represent a limit to successful selection for yield. Seed size was partly under additive genetic control, but there was also evidence of non-allelic interactions. There was no association between large seed size, preferred by consumers, and susceptibility to BCMV in the progeny, indicating that the association between these characters in the parent lines is fortuitous and will not present an obstacle to plant breeding. It is noted that a considerable amount of useful genetic information can be obtained without recourse to elaborate crossing schemes, provided that unselected progeny are included in experiments as controls. The evidence presented indicates that resistance to BCMV can be combined with appropriate values of maturity date, yield and seed size without the need for backcrossing.     

Variation within and among Ladino white clover ecotypes for agronomic traits

Summary One set of 285 genotypes from three landraces and one natural population and a second set of 165 genotypes from two landraces and one natural population were evaluated in separate trials. Variation among populations was mostly accounted for by the difference between landrace and natural population genotype groups, the former showing features related to higher seed yield and short-term aerial dry matter (DM) yield and to lower persistence, cold tolerance and protein content. Compared to variance among ecotypes, that within ecotypes was never lower and it was at least four-fold higher for important traits such as aerial and total (aerial plus stolon) DM yield, stolon density, production of seed heads and cold tolerance. Landraces and natural populations showed similar levels of intra-population variation for all traits except cold tolerance, for which landraces tended to somewhat greater variation. Trait associations were less definite at the genotype level than what previously found in terms of mean values of the ecotypes. This finding and the relatively high broad sense heritability which was observed for all components of DM and seed yield can support the breeding activity on this clover. The level of variation and of heritability found for protein content do not suggest the routine evaluation of this trait in breeding programmes.