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They were collected from plants with symptoms of yellowing and wilting in commercial chickpea fields in five municipalities in southern Guanajuato, Mexico. From these, the pathogens present in the stem and root were isolated and identified. Of the isolates obtained, those with morphological characteristics of Sclerotium rolfsii had their identity confirmed by sequencing the ITS fragments obtained with the oligonucleotides: NsiF and Nlb4R; the sequences obtained were compared with the NCBI database. Of the two isolates identified as S. rolfsii by both methodologies, the most virulent was identified, which was used to inoculate 181 chickpea genotypes of the kabuli and desi types. The results indicate that, according to the mortality percentage, the genotypes of the desi type ICC3287, ICC 4874, ICC1882, ICC 10259 and WR-315, and kabuli type CUGA 08-3160 presented moderate resistance to the pathogen. Of these resistant genotypes, ICC 10259 stands out, which has genetic resistance to four races of Fusarium oxysporum f. sp. ciceris and M. phaseolina. [ABSTRACT FROM AUTHOR]

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Common bean (Phaseolus vulgaris L.) is one of the most consumed legumes in the human diet and a substantial source of dietary protein. A major problem for this rainfed crop is the decrease in grain yield caused by prolonged drought periods during the reproductive stage of plant development (terminal drought). Terminal drought remains a prevailing threat to the farming of this staple, with losses reaching >80%. Based on the high correlation between the resistance of common bean to terminal drought and efficient photoassimilate mobilization and biomass accumulation in seeds, we aimed to identify mechanisms implicated in its resistance to this stress. We used two representative Durango race common bean cultivars with contrasting yields under terminal drought, grown under well-watered or terminal drought conditions. Using comparative transcriptomic analysis focused on source leaves, pods, and seeds from both cultivars, we provide evidence indicating that under terminal drought the resistant cultivar promotes the build-up of transcripts involved in recycling carbon through photosynthesis, photorespiration, and CO2-concentrating mechanisms in pod walls, while in seeds, the induced transcripts participate in sink strength and respiration. Physiological data support this conclusion, implicating their relevance as key processes in the plant response to terminal drought. [ABSTRACT FROM AUTHOR]

Common bean (Phaseolus vulgaris L.) is the most widely consumed grain legume in the world. This cultigen was domesticated from wild P. vulgaris, an indeterminate viny from Mexico to Argentina in midaltitude neotropical and subtropical regions, To colonize such diverse ecological niches, the species possesses many adaptation traits and a wealth of genetic diversity. However, breeding programs are limited by me under-utilization of the available genetic diversity because of me necessity of prebreeding exotic material. Due to partial reproductive isolation between the domesticated Andean and Mesoamerican gene pools, hybridizations between wild and domesticated types of P. vulgaris from the same gene pool offer greater potential to enhance the variation in the crop. Evaluations of wild P vulgaris accessions have shown resistance to insects and diseases and higher N, Fe, and Ca content in seeds which will ultimately contribute to improvements in nutritional quality and yield. Recurrent and inbred backcross methods are being used for the transfer of both qualitative and quantitative traits from wild into domesticated forms of P. vulgaris; specific data on yield and 100-seed weight are presented. The prebreeding efforts will be enhanced by (i) information on gene pool origins, domestication syndrome traits, molecular diversity, and mapping data of the wild forms; (ii) indirect screening for biotic and abiotic stresses; and (iii) marker-assisted selection.

Sucrose was the predominant sugar in seeds of five cultivars of common bean (Phaseolus vulgaris L.) grown under controlled conditions. The concentration of soluble sugars was higher in seeds from nodulated plants than seeds from N-fertilized or control (uninoculated and unfertilized) plants. Trehalose was detected in seeds but only from nodulated plants, and average values ranged from undetectable levels in seeds from control plants to 18 mg [kg.sup.-1] in seeds from nodulated plants. Nodulated plants also produced larger and heavier seeds of higher quality; sucrose and trehalose contents were highly correlated with germination rate and with the vigor index of artificially aged seeds. Seeds of nine common bean cultivars grown in the field showed soluble sugar contents similar to those observed in seeds from nodulated plants raised in a growth chamber, except that the trehalose levels were significantly higher (23-111 mg [kg.sup.-1]). Trehalose was not detected in seeds from nonnodulating control plants. Seed trehalose level was significantly correlated with germination rate and with the vigor index of artificially aged seeds. Seed glucose concentrations were negatively related to all of the seed quality parameters used. In general terms, the recognition of the natural presence of trehalose in seeds has been limited to reports on the expression of the trehalose biosynthetic genes in a few plants. Our data show that in seeds produced by nodulated bean, plants trehalose occurs at high levels, suggesting that strategies to maximize nodulation may result in improvement of seed quality.

In common bean (Phaseolus vulgaris L.), some nutritional traits such as proteins and mineral content are lower in the cultivated form as compared with the wild counterpart. To assess the feasibility of wild bean as the putative source of desirable traits such as minerals or tannins, this study was performed to identify quantitative trait loci (QTL) associated with seed mass, Ca, Fe, Zn, and tannin content in bean seed. Two-hundred-ninety-one amplified fragment length polymorphism (AFLP) markers were scored in 120 [F.sub.23] segregating individuals derived from a cross between cultivated 'Bayo Baranda' and wild common bean accession G-22837. Seed weight and minerals and tannin contents were quantified on the seed harvested from the 120 individual plants. Significant transgressive segregation was observed among the F2:3 individuals for some characteristics. A total of 57 AFLP markers were distributed among five linkage groups with a coverage of 497 centiMorgans (cM). Five putative QTL were significantly associated with seed mass, two with Ca, two with Fe, one with Zn, and four with tannin content in the seed. These QTL explained ≅42, 25, 25, 15, and 42% of the phenotypic variance, respectively. Due to known environmental effect on most nutritional traits, the use of QTL with larger effects could be used to screen segregating populations that include wild genotypes, wild populations, and ancestral landraces from the region where outstanding wild populations are identified., INCREASING THE AMOUNT of bioavailable micronutrients in plant foods for human consumption is a challenge that is particularly important in developing countries. Cereal grains and some legumes are the primary [...]

Cooking time is an important trait in the breeding of common beans (Phaseolus vulgaris L.), especially in Mexico where 96% of beans consumed are prepared in the household. Because of the characteristics of the cooking time trait, a method of indirect selection would increase selection efficiency. The objective of this study was to identify random amplified polymorphic DNA (RAPD) markers associated with the trait and estimate genetic parameters of cooking time. For that purpose, 104 recombinant inbred lines (RILs), derived from contrasting cooking time bean cultivars were evaluated for three consecutive generations ([F.sub.5] to [F.sub.8]). In each generation, cooking time was determined and plants in the [F.sub.7] generation were genotyped. One marker was associated with cooking time. The polymorphic UNAM-16 of 310 base pairs (bp) explained 23% of the variation in cooking time of the lines studied. Narrow sense heritability ([h.sup.2]) was estimated for cooking time, as was the number of genes involved in the trait. A high value of [h.sup.2] (0.74) was estimated for cooking time. Also, it was estimated that two genes control the cooking time trait., FOR MANY Latin American countries, common beans are an important source of dietary protein. However, bean consumption is limited by the long cooking time required to achieve the tenderness acceptable [...]

Drought is the second major constraint to common bean (Phaseolus vulgaris L) production after disease. This study examined yield under drought, yield potential, drought susceptibility index, harvest index, and geometric mean as potential indicators of drought resistant genotypes. The performance of two common bean populations, consisting of 78 and 95 recombinant inbred lines, was examined under moisture stress and nonstress regimes. Experiments were conducted at seven locations (1990-1994) in Michigan and Mexico to identify effective selection criteria for drought resistance. Two genotypes from each population yielded in the top 10% under both stress and nonstress conditions. Heritability estimates for yield in the Sierra/AC1028 population, based on 5 yr of data, ranged from 0.55 to 0.59 for stress and nonstress, respectively, and from 0.20 to 0.19 for stress and nonstress, respectively, in the Sierra/Lef-2RB population. Heritability for plant biomass was 0.52 for stress and 0.55 for nonstress in the Sierra/ AC1028 population and 0.15 under stress and 0.05 under nonstress in the Sierra/Lef-2RB population. One-hundred seed weight was the most highly heritable trait in both populations with heritability estimates of 0.80 for the Sierra/AC1028 population and 0.65 for the Sierra/Lef-2RB population. The geometric mean of the two moisture regimes was the single strongest indicator of performance under stress and nonstress, and a breeding strategy that involves selection based first on the geometric mean, followed by selection based on yield under stress, was suggested as the most effective strategy to improve drought resistance in common bean., Sixty percent of common bean production worldwide is grown under water stress, making drought the second largest contributor to yield reduction after disease (Singh, 1995). One of the largest production [...]

Under rainfed conditions in the semi-arid highlands of Mexico, time to first flower and to maturity of some cultivars of common bean (Phaseolus vulgaris L.) is strongly reduced with late plantings. Consideration of rainfall patterns in the region suggested that this response might be an adaptation to growing seasons of variable length, where length is determined by time of onset of summer rains and by risk of water deficit or low temperatures at the end of the season. Analysis of weather patterns at two sites in the highlands suggested that when rains commenced in early June, there was a high probability of adequate precipitation during the season. When rains commenced in mid- to late-July, total precipitation was lower. For a third site, total precipitation showed no relation with date of onset of rains. Evaluations of 20 bean genotypes planted at five dates each in 2 yr at Pabellon, Aguascalientes, (20 [degrees] 11 [minutes] N latitude, elevation 1910 m) demonstrated large differences in plasticity of the pre-flowering and reproductive periods. Cultivars Garbancillo Zarco and Tlaxcala-475 were late to flower and mature under early plantings, but were similar to other genotypes in late plantings. Other genotypes of highland origin showed little or no plasticity, suggesting that this trait is not universal among cultivars currently grown there. Furthermore, cultivars and breeding lines from other regions showed no plasticity. Marked phenological plasticity occurred only in genotypes from the highlands which were highly photoperiod sensitive, but several highly sensitive genotypes showed no or little plasticity. Similar patterns were noted in a survey of 81 genotypes that included a wider range of highland germplasm.