Development of Early Maturing Upright Pinto Bean Resistant to Multiple Diseases
Pinto bean is by far the most important market class of dry bean (Phaseolus vulgaris L.) grown in Idaho, the USA, and North America. In Idaho and the USA, pinto bean occupies more than half of the acreage. Pinto (and other market classes of race Durango) dry bean cultivars are highly susceptible to white mold [caused by Sclerotinia sclerotiorum (Lib.) de Bary], an endemic and widely spread disease. Moreover, Bean common mosaic virus (BCMV, aphid-vectored potyvirus) and Beet curly top virus (BCTV, leafhopper-vectored curtovirus) are endemic to Idaho and other western states, and broadly adapted cultivars also would require resistance to rust [caused by Uromyces appendiculatus (Pers:Pers.) Unger]. Most pinto cultivars are of full-season (taking 100 days or longer to maturity) and have a prostrate growth habit Type III, which enhances white mold
and is not suitable for direct harvest. Early maturing upright multiple disease resistant cultivars would minimize yield losses, reduce pesticide use, and facilitate direct harvest thus reducing fuel use, farm labor, and production costs. We aim to (1) identify sources of upright growth habit and early maturity in pinto bean germplasm and cultivars, (2) pyramid resistance to the four diseases, and (3) combine the upright growth habit, early maturity, and pyramided multiple disease resistance into slow darkening (i.e., taking longer than six months for an appreciable change in seed coat color) high yielding broadly adapted pinto bean breeding lines and cultivars. Multiple-parent crosses, gamete selection, and direct disease screening will be used. Also, greenhouse nurseries may be complemented with field crops to facilitate and expedite selection for seed yield, upright plant type, and
early maturity. New pinto breeding lines will be evaluated in the greenhouse for reaction to multiple diseases and in the field for seed yield, early maturity, upright plant type, and adaptation within and outside (through the Western Regional Bean Trial and national Cooperative Dry Bean Nursery) of Idaho to identify broadly adapted pinto bean breeding lines and cultivars.