Diseases cause severe losses (20–100%) to yield and quality of common bean (Phaseolus vulgaris L.) worldwide. Our objectives were to describe major bean disease problems in the Americas and review progress achieved in breeding for resistance. We also describe strategies to integrate genetic improvement for resistance to multiple diseases with cultivar development. Common bacterial blight, halo blight, and bacterial brown spot are the major bacterial diseases. Angular leaf spot, anthracnose, root rots, rust, and white mold are severe fungal diseases. Bean common mosaic virus (BCMV), Bean golden mosaic virus (BGMV), Bean golden yellow mosaic virus (BGYMV), and Beet curly top virus (BCTV) are important viral diseases. Breeding for resistance to one or two diseases at a time is emphasized. Backcross, pedigree, and bulk‐pedigree methods of breeding are used. The use of molecular markers has gradually increased. Substantial progress has been made in breeding and genetics of resistance to most of these diseases; however, improvement in resistance to bacterial brown spot, halo blight, root rots, and web blight has been slow and localized. Furthermore, cultivars with high levels of resistance to one or more quantitatively inherited diseases (e.g., common bacterial blight and white mold) are rare. Breeding strategies for simultaneous and integrated genetic improvement of multiple qualitatively and quantitatively inherited resistances and cultivar development are briefly described.

Onion (Allium cepa) is an economically important crop in the United States, generating over $900 million annually in farm receipts from 2000 to 2004 (88). U.S. onion production area ranges from 65,000 to 70,000 hectares annually, with over 80% of the summer production (54,000 hectares) in the western states. On average, 53 million metric tons of onion bulbs are harvested annually from nearly 3 million hectares worldwide. A significant portion of the U.S. and world supply of onion seed is produced in the western United States, primarily in the Pacific Northwest (124). The genus Allium includes various economically important cultivated species, including the bulb onion, chive (A. schoenoprasum), garlic (A. sativum), and leek (A. porrum) (10). At least 18 other Allium species are consumed as fresh vegetables, pickled, or used as flavoring. However, the bulb onion is the most economically valuable species. On average, worldwide production of garlic is valued at about 10% that of the bulb onion (10). Leek and bunching onion are the next most valuable species, with production concentrated in Europe and the Orient, respectively. Bunching onion (A. fistulosum) production also is important in some areas of the United States, such as California. The distinctive flavor or odor of Allium spp. is produced when plant tissues are bruised or cut, and the enzyme alliinase hydrolyzes S-alk(en)yl cysteine sulfoxide precursors to form volatile sulfur compounds (10). Onion, garlic, and their relatives, although primarily grown for food, are also used in traditional medicine, including the treatment of chicken pox, the common cold, influenza, measles, and rheumatism. Antimicrobial characteristics of alliums are likely the result of sulfur compounds. Research has demonstrated that extracts of onion and garlic decrease sugars, lipids, and platelet aggregation, and enhance fibrinolysis in blood, indicating that alliums may help prevent arteriosclerosis and other cardiovascular diseases (111).

Under favorable weather conditions white mold causes 100% loss of yield and quality of susceptible common bean (Phaseolus vulgaris L.) cultivars. The disease is endemic and widespread in North and South American countries including the United States, Canada, Argentina, and Brazil. Our objective was to review progress achieved in identifying sources of resistance in Phaseolus species, genetics, and breeding for resistance to white mold. We also describe an integrated genetic improvement strategy for resistance to the pathogen with germplasm enhancement and cultivar development using multiple‐parent crosses and gamete selection methods of breeding. Substantial progress has been made in understanding pathogenic variation in the white mold fungus, developing screening methods, identifying sources of resistant germplasm, genetics of resistance, and introgressing resistance from the secondary gene pool, and breeding for resistance to white mold. Also, molecular marker‐assisted selection for partial resistance is practiced. However, development of white mold resistant common bean cultivars in most market classes has been slow and localized. Breeding strategies for simultaneous and integrated genetic improvement of qualitatively and quantitatively inherited resistances to white mold and cultivar development are briefly described.

Sclerotium populations of Sclerotinia scierotiorum were germinated sclerotium in both crops. An apothecium variable during this 3-yr study; however, sclerotia did not continued to produce ascospores in the field for about 7 days. accumulate in increasing numbers in fields planted to Apothecium production was less beneath the open bush susceptible dry edible bean (Phaseolus vulgaris) cultivars canopy of dark red kidney Charlevoix and the upright semidespite annual white mold epidemics. Populations ranged vine canopy of small white Aurora when compared to between one and three sclerotia/kg air-dried soil in bean production beneath the dense compact bush canopy of Great fields. A 3-yr crop rotation did not reduce sclerotium Northern (G.N.) Code P #92 and the dense viny canopies of populations significantly. A low sclerotium population of G.N. U I #59 and G.N. Tara. Over 90% of the apothecia were 0.2/ kg soil produced sufficient inoculum (ascospores) to located either adjacent to the plant or on the side of the infect 46% of the plant canopy during 1975. Sclerotia were irrigation furrow, regardless of plant growth habit. An redistributed within a field by irrigation water. During irrigation application every 5 days increased apothecium August, numerous sclerotia germinated to form 11-14 and 7production, especially beneath Tara, when compared to a 10-II apothecia/m 2 in bean and sugar beet fields, respectively, day irrigation frequency. Each apothecium produced about An average of two apothecia were produced by each 2.3 X 106 ascospores under laboratory conditions.

Iris yellow spot virus (IYSV) is an emerging and potentially devastating disease of onion that was recently detected in Colorado and other onion producing regions in the western United States. In annual surveys, IYSV was confirmed in one of 18 fields (5.6%) in 2001, four of 24 (16.7%) in 2002, and 41 of 56 (73.2%) in 2003. IYSV was confirmed on volunteer onions in 2003 at all four locations where IYSV was observed in the onion crop the previous year. The disease was detected in six of seven western Colorado onion fields surveyed in 2003, but was not observed any year in southern or northeastern Colorado. The spatial variability of disease incidence, yield, and plant population also was mapped in two fields in 2003 using the global positioning system and a geographic information system. Disease incidence varied among cultivars, plant population, fields, and location in the field. Distinct disease gradients were observed in both fields with susceptible cultivars Teton and Granero, but not in the moderately resistant cultivar Sterling. In fields planted to the susceptible cultivars, disease incidence was highest on the field edges and lowest near the field centers. Plant population was negatively correlated with IYSV incidence in cultivar Sterling (R2 = 0.56, P = 0.003), but not with the susceptible cultivars. Yield of jumbo market class onions, but not total yield, was negatively correlated with increasing IYSV incidence (R2 = 0.37, P = 0.012) in cultivar Teton. Colossal market class yield, but not other yield components, was negatively correlated with IYSV incidence in cultivar Sterling (R2 = 0.28, P = 0.061). The results of these studies indicate the distribution of IYSV is rapidly expanding in Colorado and is associated with a general reduction in bulb size.

A periodic comparison of cultivars is essential to assess selection gains, determine deficiencies, define objectives, and set breeding priorities. Our objective was to assess the progress, or lack thereof, achieved in improving yield, plant type, maturity, and resistance to major bacterial, fungal, and viral diseases of dry bean of the western USA from 1918 to 1998. Twentyfive great northern, pink, pinto, and red cultivars were evaluated for seed yield at three locations in Idaho and for anthracnose,

P1 603038) were released by the USDA-ARS in 1997. A major advantage of these lines is their moderate resistance to white mold [caused by Sclerotinia sclerotiorum (Lib.) de Bary], White mold is a major disease problem of dry edible beans grown worldwide, and cultivars grown throughout the United States are susceptible. These four lines also exhibited high yield potential in both tropical (Puerto Rico) and temperate (Michigan, Nebraska, North Dakota, Washington) environments, resistance to bean common mosaic and necrosis viruses (BCMV and BCMNV), and resistance to rust [caused by Uromyces appendiculatus (Pers.) Unger var. appendiculatus; syn. U. phaseoli]. These four lines were evaluated for physiological reaction to white mold in straw tests (1) conducted at the University of Nebraska (2), Cornell University (M.H. Dickson), North Dakota State University, and the USDA-ARS at Prosser, WA, from 1995 to 1997. Reactions of these four lines to white mold were evaluated in Michigan, Nebraska, and North Dakota in the field from 1995 to 1997 (3). 19365-3 is a small, red dry bean developed from an interspecific Population II (Florida 6-19/Pc-46) using a modified bulk selection of 10 plants for three continuous generations. Population II was cooperatively released in 1985 by the USDA-ARS and the Agricultural Experiment Stations of Puerto Rico and Florida as a heterogeneous Fo bulk possessing different disease resistances, plant habits, and seed sizes, shapes, and colors (4). The common bean parent, Florida 6-19, was an F 4 bulk selection for reclining foliage and short internodes from the cross Guatemala 14-2 (Cambridge collection)/'Remus'. The Phaseolus coccineus L. parent, Pc-46, was developed by recurrent selection for multiple disease resistance by N.G. Vakili in Puerto Rico and released by the USDA-ARS in 1979.19365-3 averaged 98 d to harvest maturity at Othello, WA (1997), and exhibited an upright indeterminate Type Ilb-IIIa growth habit (5). Weight of 100 seeds averaged 24 g. In field and greenhouse tests the reaction of 19365-3 to white mold was comparable to 'Bunsi' (known in Canada as 'Ex Rico 23'). Bunsi navy bean has been widely used as a check cultivar because it has some resistance to white mold (2,3,6). 19365-3 exhibited a top necrosis, black root response to BCMNV strains confirming presence of the / gene for resistance to BCMV and BCMNV. This line is resistant to rust pathotypes in Colorado that overcame the Ur-6 rust resistant gene (7) present in 'Olathe' pinto bean but not the Ur-3 gene (7) present in 'Chase' pinto bean. 19365-5 is a small, pink dry bean developed from an interspecific cross (P. vulgaris/P. coccineus/V233B) using a modified bulk selection of 10 plants, from the F 5 to F 7 generations. The original P.-vulgaris parent was a dry bean derived by recurrent selec

White mold (WM) caused by Sclerotinia sclerotiorum (Lib.) de Bary is a severe disease of common bean (Phaseolus vulgaris L.) in North America. Common bean has only partial resistance. However, some accessions of P. coccineus L. and other species of the secondary gene pool (SGP) are highly resistant. The objectives of this study were to (i) introgress WM resistance from the SGP and (ii) compare resistance of interspecific breeding lines (IBL) VCW 54 and VCW 55, developed by congruity backcrossing between ‘ICA Pijao’ and P. coccineus accession G 35172, and VRW 32, derived from recurrent backcrossing of ICA Pijao with P. costaricensis accession S 33720 with known sources of resistance. The three IBL, ICA Pijao, and susceptible (‘Othello’) and resistant (92BG‐7, A 195, G 122, I9365–25, ‘ICA Bunsi’, and VA 19) genotypes were screened in the greenhouse in Colorado and Idaho in 2007 and 2008 and in the field in Idaho in 2007. White mold resistance was successfully introgressed from two of the three Phaseolus species (P. coccineus and P. costaricensis) of the SGP. VCW 54 had the highest WM resistance, and VCW 55 and VRW 32 had similar resistance as previously reported. These sources of WM resistance should be introgressed into common bean cultivars.