Marta Santalla

Allozyme evidence supporting southwestern Europe as a secondary center of genetic diversity for the common bean.

Abstract.Genetic diversity within a common bean (Phaseolus vulgaris L.) collection, comprising 343 accessions from the Iberian Peninsula, was examined using six allozyme markers. Two major clusters corresponding to the Andean and Mesoamerican gene pools were identified. Both gene pools were characterized by specific alleles, with the former exhibiting Skdh100, Me100, Rbcs100 or 98 and Diap-1100, and the latter exhibiting Skdh103, Me100, Rbcs100 and Diap-195. Some accessions from both clusters, deviating from these allozyme patterns, exhibited Skdh100, Me100, Rbcs100 and Diap-195 or Skdh103, Me100, Rbcs100 and Diap-1100 allozyme profiles and were considered as putative hybrids.The levels of genetic variation has not been eroded since the introduction of the common bean from the American centers of domestication to the Iberian Peninsula. Instead, obvious signs of introgression between the two gene pools were observed, mainly among white-seeded genotypes. The intermediate forms adapted to the Iberian Peninsula could have emerged from initial recombination between Mesoamerican and Andean gene pools. The Iberian common bean germplasm is therefore more complex than previously thought, and contains additional diversity that remains to be explored for genetic and breeding purposes. The Iberian Peninsula could be considered as a secondary center of genetic diversity of the common bean, especially the large white-seeded genotypes.

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.

Interactions of bush bean intercropped with field and sweet maize

Abstract Common bean, Phaseolus vulgaris L., is traditionally intercropped with maize by small-scale farmers in northwest Spain. Interactions of genotypes of beans with cropping systems and seasons were studied to determine if selection of bean in sole cropping would be a valid approach to genetic improvement for intercropping. In this experiment, 10 dry bush bean varieties were evaluated in sole cropping and intercropping with two types of maize (field and sweet maize) at two locations for 2 years. The performance of bean genotypes in each cropping system was compared with respect to developmental plant characteristics, seed yield and yield components and food quality traits. A significant bean genotype×cropping system interaction was found for period of flowering and seed yield, and there were significant differences between cropping systems for pods per plant, seed length and seed coat proportion. Intercropping with field maize reduced bean yield by 55% and intercropping with sweet maize reduced bean yield by 44%. Significant and high correlations of bean yields were obtained between sole cropping and intercropping with maize. Mean yields were used to calculate the land equivalent ratios (LERs), which averaged 1.12 for intercropping with field maize and 0.93 for intercropping with sweet maize. Specific variety combinations reached LER values greater than one. Net income was higher for some intercrop patterns than for bush bean sole crop. The most competitive bean varieties yielded the most when intercropped with maize but those varieties were not necessarily the highest yielding in sole cropping. The most competitive bean varieties were the latest to flower. The evaluation of bush bean genotypes for agronomic and food quality traits under sole cropping provides sufficient information to select varieties efficiently for the field maize-bean and sweet maize-bean intercropping systems. Greatest net income was realized when bush beans intercropped with sweet maize, provided a system with higher added value compared to intercropping with field maize.

Genome and transcriptome analysis of the Mesoamerican common bean and the role of gene duplications in establishing tissue and temporal specialization of genes

BackgroundLegumes are the third largest family of angiosperms and the second most important crop class. Legume genomes have been shaped by extensive large-scale gene duplications, including an approximately 58 million year old whole genome duplication shared by most crop legumes.ResultsWe report the genome and the transcription atlas of coding and non-coding genes of a Mesoamerican genotype of common bean (Phaseolus vulgaris L., BAT93). Using a comprehensive phylogenomics analysis, we assessed the past and recent evolution of common bean, and traced the diversification of patterns of gene expression following duplication. We find that successive rounds of gene duplications in legumes have shaped tissue and developmental expression, leading to increased levels of specialization in larger gene families. We also find that many long non-coding RNAs are preferentially expressed in germ-line-related tissues (pods and seeds), suggesting that they play a significant role in fruit development. Our results also suggest that most bean-specific gene family expansions, including resistance gene clusters, predate the split of the Mesoamerican and Andean gene pools.ConclusionsThe genome and transcriptome data herein generated for a Mesoamerican genotype represent a counterpart to the genomic resources already available for the Andean gene pool. Altogether, this information will allow the genetic dissection of the characters involved in the domestication and adaptation of the crop, and their further implementation in breeding strategies for this important crop.

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.

2-DE-based proteomic analysis of common bean (Phaseolus vulgaris L.) seeds

Common bean (Phaseolus vulgaris L.) is the most important grain legume for direct human consumption. Proteomic studies in legumes have increased significantly in the last years but few studies have been performed to date in P. vulgaris. We report here a proteomic analysis of bean seeds by two-dimensional electrophoresis (2-DE). Three different protein extraction methods (TCA-acetone, phenol and the commercial clean-up kit) were used taking into account that the extractome can have a determinant impact on the level of quality of downstream protein separation and identification. To demonstrate the quality of the 2-DE analysis, a selection of 50 gel spots was used in protein identification by mass spectrometry (MALDI-TOF MS and MALDI-TOF/TOF). The results showed that a considerable proportion of spots (70%) were identified in spite of incomplete genome/protein databases for bean and other legume species. Most identified proteins corresponded to storage protein, carbohydrate metabolism, defense and stress response, including proteins highly abundant in the seed of P. vulgaris such as the phaseolin, the phytohemagglutinin and the lectin-related α-amylase inhibitor.

Food and feed potential breeding value of green, dry and vegetable pea germplasm

Pea is an important grain legume and vegetable in the South of Europe where it is grown on small farms and gardens using traditional varieties and methods during the winter. Variability in old, unimproved varieties needs to be determined in order to create useful genetic variation for broadening the narrow genetic base of commercial cultivars and for making efficient use of available resources. One hundred and four unimproved pea varieties and ten elite cultivars were evaluated in 1991 and 1992 at two locations for seed and vegetable quality, canopy and agronomic traits. Significant genotype by environment (G × E) interactions were found for protein concentration, fresh seed size and weight, canopy traits, pod length and weight, days to flowering, and days to fresh seed and pod maturity. There were significant differences between unimproved pea varieties for all traits studied except for seed soluble sugars and seed tenderness. Most of the significant differences for seed and vegetable quality traits were...

Efficient in vitro shoot regeneration responses of Phaseolus vulgaris and P. coccineus

Phaseolus vulgaris L. is the most important economic species within the genus Phaseolus, and it is grown in all parts of the world. Genetic improvement by conventional breeding has met considerable success, although production of hybrids between species within the genus has been limited due to sexual incompatibility or other evolutionary lethalities. Recent advances in tissue culture have offered the opportunity to produce cultivars which could not be obtained by conventional breeding methods, but regeneration protocols are influenced by the genotype. A standard regeneration procedure was assessed for its applicability to elite breeding lines of P. vulgaris L. and landraces of P. coccineus L. from seedling explants containing a cotyledon and a small portion of the split embryonic axis. In vitro culture response and regeneration ability varied significantly between species and amongst genotypes. P. coccineus produced more shoots per explant with a higher rooting efficiency than P. vulgaris. These significant genotype effects suggest that genetic factors are important in the response to in vitro tissue culture. Different genotypes were identified, which were more competent to in vitro culture and could produce highly responsible hybrids. This in vitro culture system carry a high potential for propagation of P. vulgaris and P. coccineus, and subsequent exploitation of hybrid forms, which could also be incorporated into somatic cell approaches to improve these species.

Genetic diversity of Argentinean common bean and its evolution during domestication

Wild populations of common bean pertainingto the Andean gene pool are distributedfrom southern Peru to northern Argentina.The objectives of this study were todetermine the genetic structure of Andeanlandraces from northern Argentina, as oneof the potential domestication sites of theAndean domesticated gene pool, and toestablish a correspondence between Andeanprimitive landraces and wild populationsthat might have served as the source ofdomesticated bean. Forty-four landraces and21 wild populations representing thediversity of common bean in northernArgentina were included in this study. Results indicated that Andean gene pool inArgentina has a large genetic base on thebasis of morphological and adaptivevariability and biochemical analysis. Theexistence of introgressed populations withsympatric wild forms was evidenced.

Effect of intercropping bush bean populations with maize on agronomic traits and their implications for selection

Abstract The effect of intercropping bush bean with maize on several agronomic traits was studied for 25 populations of bush bean. These populations were grown in two field trials in the northwest of Spain in two consecutive years. Population means differed little between cropping systems. Significant differences among populations were found for all characters except end of flowering, period of flowering and pod yield. There were neither cropping system nor populations × cropping system effects for the characters studied. There were significant environment × population interactions in some cases, and this could cause difficulties for future breeding programs. The results suggest that under these environmental conditions, selection under either cropping system would be effective for both.