Dry Beans and Pulses Production, Processing, and Nutrition. Группа авторов

2.1. Major bean breeding programs in the US, location and seed type focus prior to 1980.

Institution	State	Seed types	Breeders
Cornell	NY	Light red kidney, black	D. Wallace
MSU	MI	Navy, dark, light red kidney	M.W. Adams
UNL	NE	Great northern	D.P. Coyne
CSU	CO	Pinto	D. Woods
UI	ID	Pinto, pink	J. Kolar, M. LeBaron
USDA‐ARS	WA	Small red, pink	D. Burke
UCD	CA	Kidney, pink, cranberry	C. Tucker

BEAN GENETICS

      Bean species

The genus Phaseolus is New World in origin in contrast to Old World Vigna species, which includes related grain legumes such as cowpea, adzuki, and mung beans. Bean breeders are limited in their improvement efforts to working within the genus Phaseolus due to speciation barriers that prevent successful hybridization. Phaseolus includes five cultivated species separated into four gene pools (Figure 2.3) and over 70 wild species (Freytag and Debouck 2002). Within the five species of cultivated Phaseolus, common bean is the most widely adapted and economically important member compared to other species that include lima and tepary beans. Breeders have successfully transferred traits from the scarlet runner bean (P. coccineus) and P. costaricensis in the secondary gene pool (Schwartz and Singh 2013) and from members of tepary bean (P. acutifolius) in the tertiary gene pool (Singh and Miklas 2015; Kusolwa et al. 2016), but no successful introgression with lima bean (P. lunatus) in the quaternary gene pool has occurred.

Fig. 2.3. Genus Phaseolus includes five cultivated species that reside in four separate gene pools based on genetic distance. There is no restriction to intercrossing between members of the primary gene pool; crossing between primary and secondary gene pool requires that P. vulgaris is used as the pollen parent; crossing between primary and tertiary gene pool requires special techniques to rescue hybrid embryo; crossing is not possible between the primary and quaternary gene pools. In addition to the five cultivated species, there are over 50 wild Phaseolus species (Freytag and Debouck 2002).

      Figure adapted from Gepts (2000).

Gene pools

      Common bean originated from central Mexico (Bitocchi et al. 2012). From that region, wild P. vulgaris moved north and south and can be found today from northern Argentina to Chihuahua in northern Mexico (Ariani et al. 2018). There were more domestication events in the Mesoamerican than Andean gene region, which may explain the narrower genetic variation within the Andean gene pool observed in many genetic studies. The two gene pools of common beans have been clearly defined based on morphological, biochemical, and molecular characterization (Gepts 1988). One of the most noticeable differences is the larger seed sizes found in Andean gene pool in contrast to members of the Middle American gene pool. Interestingly, similar seed size differences are observed between the Andean (large‐seeded) and Middle American (smaller‐seeded) gene pools for lima bean. A further classification of gene pools of common bean into six races based on agronomic and adaptive characteristics was proposed by Singh et al. (1991). A fourth race, named Guatemala, was added as the climbing beans from Chiapas, Mexico, are unique from the three other MA races (Beebe et al. 2000). Beans also differ in plant growth habit, ranging from determinate types to climbing pole beans that require support.

Singh (1982) classified beans into four types that differ in growth habit (Table 2.2). The typical type‐I determinate bush bean does not produce a vine and vegetative growth ceases at flowering. Most large‐seeded kidney and green beans are determinate. The other three types have an indeterminate growth habit and differ in vine extension. Type‐II is an upright short vine habit similar to soybean that is best suited to direct harvest. Type III is a decumbent long vine habit best suited to semiarid production areas where harvest loss due to wet weather is rare. Type‐IV is the climbing bean that is not grown commercially in the US other than as pole beans in gardens, but is widely grown in many parts of Latin America or East Africa, where they are supported on either trellises, or poles or grown in association with corn.

Table 2.2. Gene pools, races, and growth habits of US dry bean market classes.

Gene pool	Race	Growth habit	US market class
Andean:	Nueva Granada	Determinate Type I	Kidney
			Bush cranberry
	Chile	Indeterminate Type III	Vine cranberry
	Peru	Determinate Type I	Yellow, Mayacoba
Middle American:	Mesoamerican	Indeterminate Type II	Black
		Indeterminate Type II & Determinate Type I	Navy
	Durango	Indeterminate Type II & III	Pinto
			Great northern
	Jalisco	Indeterminate Type II & III	Small red
			Pink
	Guatemala	Climbers Type IV	Red and blacks – Mexico, Central American only

      Bean germplasm collections include contemporary and heirloom varieties, landraces, exotic plant introductions from foreign countries, and wild accessions of P. vulgaris (Acosta et al. 2007).