Drought is a worldwide constraint to dry bean (Phaseolus vulgaris L.) production. The objective of this research was to determine the response of three dry bean landraces and 13 cultivars evaluated under non-stressed (NS) and intermittent drought-stressed (DS) environments at Kimberly, Idaho in 2003 and 2004. The NS received seven irrigations in 2003 and five in 2004, and DS only four in 2003 and two in 2004. Most water use occurred within the top 0.5 m soil in both the NS and DS. Drought reduced biomass and seed yield, harvest index, and seed weight. Maturity was delayed in severe drought, but was similar or shortened by 1 to 6 d under moderate drought. Mean seed yield was reduced by 62% in 2003 and by 27% in 2004. Common Red Mexican and CO 46348 had high seed yield in both NS and DS environments, whereas 'Matterhorn' and 'Othello' yielded comparatively high under DS but moderately in NS environment. Drought resistance was inadvertently reduced from Common Red Mexican landrace to intermediate levels in 'NW-63' and 'UI 239' released in 1979 and 1993, respectively, and more recently released 'LeBaron ' (1999) and 'UI 259' (1996) were susceptible. Conversely, drought resistance was increased in newer pinto (Othello 1986; CO 46348) and great northern (Matterhorn 1998) releases compared to the landraces and older cultivars tested for those market classes. Seed yield in NS and DS was positively correlated. Seed yield was also correlated with harvest index in DS and NS. All early maturing cultivars except Othello (e.g., UI 59, US 1140, Common Pinto, Topaz, UI 320, and LeBaron) were susceptible. Common Red Mexican did not have any reduction in seed weight due to drought stress. Drought resistant genotypes should be used for determining irrigation frequency, amount of water to be applied, and mechanisms of resistance and for identifying, mapping, and pyramiding favorable genes for dryland and irrigation-assisted sustainable production systems.

Moderate to high drought stress can reduce biomass, number of seeds and pods, days to maturity, harvest Drought is a major constraint to common bean (Phaseolus vulgaris index, seed yield, and seed weight in common bean L.) production worldwide. Our objectives were to (i) identify sources of drought resistant germplasm in common bean cultivars and (ii) (Acosta-Gallegos and Adams, 1991; Ramirez-Vallejo and compare drought resistant germplasm with lines selected from interra- Kelly, 1998). A moderate drought stress has reduced cial and intergene pool populations. We included in this study 12 of yield by 41% without altering nitrogen (N) partitioning the most promising drought resistant cultivars from race Durango (Foster et al., 1995). However, severe drought stress has and 11 from race Jalisco, nine drought resistant lines selected from reduced yield by 92%, N harvest index, and N-and interracial or intergene pool populations, and two drought resistant water-use efficiency in common bean. Severe drought and two susceptible checks. The 36 genotypes were evaluated in during reproduction has reduced nodulation by an averdrought-stressed (DS) and nonstressed (NS) environments in four age of 43% and N 2 fixation to one sixth of a well-irricropping seasons between 1996 and 1998 at the International Center gated control (Castellanos et al., 1996). Root rots caused for Tropical Agriculture (CIAT), Palmira, Colombia. Drought stress by Macrophomina phaseolina (Tassi) Goid., Fusarium reduced seed yield by 53%, 100-seed weight by 13%, and days to maturity by 3%. Race Durango cultivars had higher yield, larger seed solani f. sp. phaseoli (Burk.) Snyder & Hansen, and other weight, and earlier maturity than race Jalisco cultivars in DS and NS fungi may aggravate drought stress. Similarly, DS bean environments. Large variations within the two races were found for crops may become prone to damage by leafhoppers (Emthe three traits. Drought resistant selected lines out-yielded drought poasca kraemeri Ross & Moore) in the tropics and subresistant checks by 44% in DS and 15% in NS and cultivars from tropics.race Durango by 48% in DS and 30% in NS and race Jalisco by 96%Genotypic differences for drought resistance have in DS and 46% in NS environments. Seed yield in DS was correlated been reported for common bean (Abebe et al., 1998; negatively with the percent reduction (PR) because of drought stress Acosta et al., 1999). The most effective selection criteand drought susceptibility index (DSI), whereas a positive correlation rion, among various morphological, physiological, pheexisted between PR and DSI. Drought resistant selected lines and nological, yield, and yield related traits, for identifying race Durango cultivars had similar maturity. Mean 100-seed weight of selected lines (23 g) was less than race Durango (34 g) and race

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,

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.

The fungus Sclerotinia sclerotiorum, cause of white mold, is known to attack >400 plant species. It is a widespread problem in dry bean (Phaseolus vulgaris) in the United States, causing >30% average yield losses. Low to moderate levels of resistance are found in dry bean. However, some accessions of P. coccineus (commonly known as scarlet runner bean) possess a relatively higher level of resistance. Our objective was to verify the reaction of 13 known white mold-resistant P. coccineus germ plasms and determine inheritance of resistance in accessions PI 433246 and PI 439534. Pinto Othello was crossed with PI 433246, and the resulting interspecific F1 was back-crossed onto Othello and allowed to produce F2 seed. Similarly, pinto UI 320 was crossed with PI 439534. The F1 was backcrossed onto UI 320 and allowed to produce F2 seed. The two parents, F1, F2, and backcross to dry bean of each set were evaluated in the greenhouse using the straw test at Fort Collins, CO in 2004. All 13 P. coccineus accessions and the two F2 also were evaluated using the modified petiole test at Kimberly, ID in 2005. All 13 P. coccineus accessions were variable in a 2002 straw test when rated for white mold reaction on a 1-to-9 scale, because the mean disease score ranged from 1.9 for PI 433246 to 4.4 for PI 189023 and 8.8 for the susceptible check Bill Z. For the petiole test, when rated on a 1-to-9 scale, the accessions exhibited an intermediate white mold score of 4 or 5 in 2005. In 2004, the susceptible check Othello exhibited a mean score of 7.9 compared with 3.4, 3.2, and 2.1 for PI 433246, UI 320, and PI 439534, respectively. The white mold reaction of PI 433246 and PI 439534 was dominant in their respective F1. The F2 segregation further indicated that white mold resistance in PI 433246 and PI 439534 was controlled by a single dominant gene. These two and other white mold-resistant P. coccineus accessions and selected breeding lines from the interspecific crosses should be useful for future improvement of white mold resistance of pinto and other market classes of dry and green or snap bean.