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Common bean rust, Bean golden yellow mosaic virus (BGYMV), Bean common mosaic virus (BCMV), and Bean common mosaic necrosis virus (BCMNV) are devastating diseases of dry bean (Phaseolus vulgaris L.) in Central America and the Caribbean. The development of dry bean cultivars with enhanced levels of genetic resistance to these and other diseases is an important goal of the University of Puerto Rico (UPR) and other dry bean breeding programs in Central America and the Caribbean. PR1572‐19 (Reg. no. GP‐308, PI 692976) and PR1572‐26 (Reg. no. GP‐307, PI 692975) are multiple virus‐ and rust‐resistant pinto bean germplasm lines adapted to the humid tropics that were developed and released cooperatively in 2019 by the UPR Agricultural Experiment Station, the Instituto Dominicano de Investigaciones Agropecuarias y Forestales, and the USDA–ARS. Both PR1572‐19 and PR1572‐26 possess the bgm‐1 gene for resistance to BGYMV, the I and bc‐3 loci that provide broad resistance to all strains of BCMV and BCMNV in the United States and the Caribbean, and the Ur‐3 and Ur‐11 loci that confer comprehensive resistance to all known races of the bean rust pathogen. PR1572‐26 also has the SW12 quantitative trait locus marker associated with resistance to BGYMV. PR1572‐19 and PR1572‐26 produced mean seed yields similar to the check cultivar 'Santa Fe' in trials conducted in Puerto Rico and mean seed yields comparable to the pinto cultivar 'La Paz' in the Cooperative Dry Bean Nursery conducted in Puerto Rico. Both lines should serve as useful sources of resistance to BGYMV, BCMV, BCMNV, and bean rust for common beans of the Durango race that includes the pinto and great northern market classes. [ABSTRACT FROM AUTHOR]

Examines the variability of Rhizoctonia solani isolates causing web blight (WB) of the common bean Phaseolus vulgaris. Polymerase chain reaction-restriction fragment length polymorphism analysis of the internal transcribed regions; Analysis of DNA repeat; Genetic variability of the WB pathogen.

Diseases are a major constraint to production of beans in developing countries, reducing yields and seed quality. Contributing factors include poor disease management, lack of resistant cultivars, and the limited availability of certified disease-free seed. From the outset the Bean/Cowpea Collaborative Research Support Program (CRSP) has emphasized integrated disease management, and breeding for resistance to bean rust (Uromyces appendiculatus), common bacterial blight (Xanthomonas campestris (=X. axonopodis) pv. phaseoli) (CBB) and web blight (Thanatephorus cucumeris (anamorph Rhizoctonia solani)) (WB). Later in the 1990s, angular leaf spot (Phaeoisariopsis griseola) (ALS), and virus induced bean common mosaic (BCM) and bean common mosaic necrosis (BCMN) became more widespread and epidemic. The research included development of disease-resistant germplasm and studies of pathogenic variation and epidemiology.During the early 1990s bean golden yellow mosaic (BGYM), became a major disease of common bean in the Caribbean and Central America. No cultivar resistant to the gemini virus causing BGYM was available in the Dominican Republic (DR) and pesticides were used to reduce transmission of the virus by white flies (Bremisia tabaci) biotype A. A change in the bean-production system to limit reproduction of the vector through a host-free period and concentrate the bean growing season to a four month period reduced BGYM significantly. Improved resistant cultivars and disease management resulted in high yields and self-sufficiency of beans in the DR.Evidence for co-evolution of the pathogens causing ALS, CBB, and rust in the two major bean gene pools (Andean and Middle American) was found. Variation in the WB pathogen on bean indicated independent genetic populations and the presence of different anastosmosis subgroups. WB disease management practices should be designed for the sub-group of the pathogen. Seed transmission was found to be a significant source of R. solani inoculum. Specific (Ur-9 gene) and adult-plant resistance (Ur-12 gene) to rust was identified for PC-50 (Andean origin) in the DR, and the genes were mapped. A mobile rust nursery was developed to monitor races of rust in a region and assist in resistance-gene deployment in bean germplasm and varieties. DNA based diagnostic methods were developed to differentiate X. campestris pv. phaseoli from X. campestris pv. phaseoli var fuscans (prevalent in East Africa) and P. griseola isolates. DNA hybridization methods also were developed to identify BGYM and bean golden mosaic viruses. Research in USA and East Africa has helped define bean common mosaic virus (BCMV) and bean common mosaic necrotic virus (BCMNV) as separate viruses and has demonstrated that BCMNV appears to be indigenous to Africa. Serological tools were developed that assist in the detection and identification of potyviruses, BCMV and BCMNV. These tools are now used worldwide. [Copyright &y& Elsevier]