[show abstract][hide abstract] ABSTRACT: Drought is a major constraint to common bean (Phaseolus vulgaris L.) production, especially in developing countries where irrigation for the crop is infrequent. The Mesoamerican genepool is the most widely grown subdivision of common beans that include small red, small cream and black seeded varieties. The objective of this study was to develop a reliable genetic map for a Mesoamerican × Mesoamerican drought tolerant × susceptible cross and to use this map to analyze the inheritance of yield traits under drought and fully irrigated conditions over 3 years of experiments. The source of drought tolerance used in the cross was the cream-seeded advanced line BAT477 crossed with the small red variety DOR364 and the population was made up of recombinant inbred lines in the F5 generation. Quantitative trait loci were detected by composite interval mapping for the traits of overall seed yield, yield per day, 100 seed weight, days to flowering and days to maturity for each field environment consisting of two treatments (irrigated and rainfed) and lattice design experiments with three repetitions for a total of six environments. The genetic map based on amplified fragment length polymorphism and random amplified polymorphic DNA markers was anchored with 60 simple sequence repeat (SSR) markers and had a total map length of 1,087.5 cM across 11 linkage groups covering the whole common bean genome with saturation of one marker every 5.9 cM. Gaps for the genetic map existed on linkage groups b03, b09 and b11 but overall there were only nine gaps larger than 15 cM. All traits were inherited quantitatively, with the greatest number for seed weight followed by yield per day, yield per se, days to flowering and days to maturity. The relevance of these results for breeding common beans is discussed in particular in the light of crop improvement for drought tolerance in the Mesoamerican genepool.
[show abstract][hide abstract] ABSTRACT: A diversity survey was used to estimate allelic diversity and heterozygosity of 129 microsatellite markers in a panel of 44 common bean (Phaseolus vulgaris L.) genotypes that have been used as parents of mapping populations. Two types of microsatellites were evaluated, based respectively on gene coding and genomic sequences. Genetic diversity was evaluated by estimating the polymorphism information content (PIC), as well as the distribution and range of alleles sizes. Gene-based microsatellites proved to be less polymorphic than genomic microsatellites in terms of both number of alleles (6.0 vs. 9.2) and PIC values (0.446 vs. 0.594) while greater size differences between the largest and the smallest allele were observed for the genomic microsatellites than for the gene-based microsatellites (31.4 vs. 19.1 bp). Markers that showed a high number of alleles were identified with a maximum of 28 alleles for the marker BMd1. The microsatellites were useful for distinguishing Andean and Mesoamerican genotypes, for uncovering the races within each genepool and for separating wild accessions from cultivars. Greater polymorphism and race structure was found within the Andean gene pool than within the Mesoamerican gene pool and polymorphism rate between genotypes was consistent with genepool and race identity. Comparisons between Andean genotypes had higher polymorphism (53.0%) on average than comparisons among Mesoamerican genotypes (33.4%). Within the Mesoamerican parental combinations, the intra-racial combinations between Mesoamerica and Durango or Jalisco race genotypes showed higher average rates of polymorphism (37.5%) than the within-race combinations between Mesoamerica race genotypes (31.7%). In multiple correspondance analysis we found two principal clusters of genotypes corresponding to the Mesoamerican and Andean gene pools and subgroups representing specific races especially for the Nueva Granada and Peru races of the Andean gene pool. Intra population diversity was higher within the Andean genepool than within the Mesoamerican genepool and this pattern was observed for both gene-based and genomic microsatellites. Furthermore, intra-population diversity within the Andean races (0.356 on average) was higher than within the Mesoamerican races (0.302). Within the Andean gene pool, race Peru had higher diversity compared to race Nueva Granada, while within the Mesoamerican gene pool, the races Durango, Guatemala and Jalisco had comparable levels of diversity which were below that of race Mesoamerica.
Theoretical and Applied Genetics 07/2006; 113(1):100-9. · 3.66 Impact Factor
[show abstract][hide abstract] ABSTRACT: Both wild and cultivated Phaseolus germplasm were characterized over several years using RAPD and/or AFLP to determine the genetic structure of the species and the association of genetic structure with phenotypic traits. In most cases, multivariate analysis was carried out using Multiple Correspondence Analysis (MCA), which adjusts the weight of each datum inversely to its frequency in the population. For present purposes this implies that rare DNA polymorphisms that occur together get especially high value in the analysis, a phenomenon that is interpreted evolutionarily as reflecting descent from a common ancestor. A core collection of wild P. vulgaris was created, based on geographic distribution and seed protein classification of phaseolin, lectins and alpha-amylase inhibitors (Tohme et al, 1996). A total of 114 accessions were analyzed by AFLP. Reported gene pools of Andean, Mesoamerican and northern Andean (Ecuador and northern Peru) origins were recognized, and additional diversity was found in Colombia, suggesting a fourth wild bean gene pool. This latter pool has been incorporated into a breeding program together with other wild accessions, and one Colombian accession appears to have contributed yield genes that are expressed in the temperate region of the United States (J. Kelly, pers. comm., 2002). Wilds from Guatemala separated only slightly from Mexican wilds, but relatively discreet groups were observed in the Andean pool. It is suggested that the rugged Andean terrain serves to isolate genetic groups more effectively than the topography of Middle America. Diversity in cultivated bean as revealed by RAPD analysis mirrored the structure of the wild bean gene pools and was largely consistent with results reported by other authors. Two major gene pools, one Middle American and one Andean, were revealed (Gepts et al, 1986). Within the Middle American gene pool, races Durango, Jalisco and Mesoamerica were distinguishable, and groups formed by DNA analysis were consistent with morphological traits associated with these races (Singh et al, 1991). However, a fourth race was distinguished among climbing beans in the south of Mexico and in Guatemala, which separated from race Jalisco climbers in the MCA (Beebe et al, 2000). This race was designated as race Guatemala and was characterized by having several sources of resistance to angular leaf spot. G2333, a widely studied source of anthracnose resistance, also pertains to this race. The distinction of races Jalisco and Guatemala may reflect the a geographical separation created by the isthmus of Tehuantepec in southern Mexico, with a maximum altitude of about 1000 m above sea level Furthermore, some internal structure was distinguished within races Mesoamerica and Durango (Beebe et al, 2000). Race Mesoamerica separated into two closely related subgroups, one designated M1 that consisted of type 2 habit genotypes (largely black seeded) and one with wide diversity in seed color and type 3 growth habits. Race Durango presented two subgroups with differences in seed size, color and growth habit. Sub-group D1 represented the more commercial types, while subgroup D2 presented less attractive (black or cream) colors, and more type 4 growth habits. The Andean pool of cultivated bean displayed a surprisingly narrow genetic base (Beebe et al, 2001). Thus, races in the Andean pool have a different meaning that in the
[show abstract][hide abstract] ABSTRACT: Plant root development can be largely affected through the association of roots with plant growth-promoting rhizobacteria
(PGPR). However, little is known about the identity of plant genes enabling such PGPR-plant root associations. Differences
in the responsiveness to PGPR among cultivars suggest genetic variation for this trait within germplasm. In this study, two
genotypes of common bean (Phaseolus vulgaris L.), BAT477 and DOR364, were identified showing contrasting responsiveness in root development to inoculation with the PGPR
Azospirillum brasilense Sp245. Inoculation with an A. brasilense Sp245 mutant strain strongly reduced in auxin biosynthesis or addition of increasing concentrations of exogenous auxin to
the plant growth medium, indicated that the differential response to A. brasilense Sp245 among the bean genotypes is related to a differential response to the bacterial produced auxin. To further assess the
role of the plant host in root responsiveness, a population of Recombinant Inbred Lines (RILs) of the DOR364×BAT477 cross
was used to evaluate the efficacy of exogenous auxin on root development. We detected significant phenotypic variation among
the RILs for basal root formation during germination upon addition of auxin to the growth medium. Genetic analysis revealed
two quantitative trait loci (QTLs) associated with basal root responsiveness to auxin of which one explained 36% of the phenotypic
variation among the RILs. This latter QTL mapped to the same location as a QTL for root tip formation at low P, suggesting
that the host effect on root responsiveness to IAA interacts with specific root development. Also, significant correlations
between basal root responsiveness to auxin and growth, root tips and root dry weight at low P were identified. To our knowledge,
this is the first report on QTL detection for root responsiveness to auxin.
Plant and Soil 302(1):149-161. · 2.64 Impact Factor