The F 3 was bulk selected for uniform maturity and seed color. From the F 4 to F 7 generations, it was yield tested along with other entries under rainfed conditions. Subsequently, the F 2-derived F 8 line was increased and yield tested in regional trials in the semiarid highlands from 1987 to 1990. Pathogen-free seed was produced in the winter of 1989-1990 in Los Mochis, Sinaloa. Pinto Villa possesses an indeterminate prostrate Type III growth habit, with 6 to 10 basal branches and a mean canopy height of 35 cm. It has white flowers with medium sized cordate bracteole and ovate leaves. Pinto Villa has shown broad adaptation and yield stability in the semiarid highlands; adaptation that is partially due to its phonological plasticity and tolerance to low night temperatures during seed filling (1). Under normal rainfed conditions, it requires =95 d to reach maturity. Under the variable semiarid environments, maturity ranges from 75 to 110 d. This variability in maturity may be partially due to its photoperiod sensitivity (1). It is highly resistant to anthracnose [caused by local isolates of Colletotrichum lindemuthianum (Sacc. & Magn.) Lams.-Scrib.]. It is tolerant to races of rust [caused by Uromyces appendiculatus (Pers.:Pers.) Unger var. appendiculatus] in the drier locations of the Mexican highlands, to halo blight [caused by Pseudomonas syringae pv. phaseolicola (Burkholder) Young et al.], to common bacterial blight [caused by Xanthomonas campestris pv. phaseoli (Smith) Dye], and to low soil fertility. Pinto Villa was tested at four to eight locations each year from 1987 to 1992 in the highlands of Mexico (from Chihuahua to Valle de Mexico). It is classified as a drought-tolerant cultivar (2). On the basis of yield response, it is better adapted to early planting dates in the less productive rainfed environments of than all other available cultivars. Under favorable rainfed environments of the humid highlands its mean yield has been above 2.0 mT ha" 1 and it has outyielded all landraces in the Pinto seed class. Pinto Villa has medium seed size (30 to 32 g 100 seed"'). Its seed color pattern of cream with brown spots is acceptable as a Pinto cultivar. Environmental conditions during maturation, however, may influence seed size and color intensity. Protein content and cooking time of Pinto Villa is within the average for this class (3). Pinto Villa has been released without plant protection rights to organized bean growers and registered public and private seed companies in Mexico. Breeder seed is maintained by the Valle del Guadiana Experimental Station of INIFAP-SARH, and is available upon request from F. Ibarra-Perez.

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In Mexico, high incidences of Fusarium affect common bean (Phaseolus vulgaris L.) production, reducing grain yields due to seedling death and crop standing reductions. Production of resistant germplasm could be an appropriate strategy for grain yield increasing. Bean breeding programs need the former analysis of plant-pathogen pathosystem to perform the selection of segregating populations with improved resistance to root rot pathogens and the best agroecosystem adaptation. Here, we report our results on characterization of genetic variability patterns of Fusarium solani f. sp. phaseoli (FSP) from Aguascalientes, México; the analysis of P. vulgaris germplasm reactions to highly and naturally FSP-infested field and controlled conditions; and the identification of genetic basis of resistance to FSP root rot in segregating common bean populations. Significant genetic variability in FSP isolates from Aguascalientes and other regions of México was found. Also, we found high variation on reactions to FSP root rots, resistance was more frequent on black seed-coated beans, and susceptibility was common in pinto beans. Resistance to FSP in BAT 477 seedlings was associated with one quantitative trait loci (QTL).