Registration of Common Bacterial Blight Resistant Cranberry Dry Bean Germplasm Line USCR‐CBB‐20

Abstract

Common bacterial blight (CBB; caused by Xanthomonas axonopodis pv. phaseoli ) is a serious disease of dry and green beans ( Phaseolus vulgaris L.) in warm humid climates. Crop loss up to 40% has been reported due to this disease, which is most prominent east of the continental divide in the United States. Cranberry beans are very susceptible to CBB, so our objective was to develop a cranberry dry bean with improved resistance to the disease. A combination of marker‐assisted selection for quantitative trait loci (QTL) for resistance in early generations followed by selection under disease pressure in later generations was used to develop the cranberry dry bean germplasm line USCR‐CBB‐20 (Reg. No. GP‐281, PI 659069), which has improved resistance to CBB. USCR‐CBB‐20, released in 2008 by the USDA‐ARS in cooperation with the Idaho and Michigan agricultural experiment stations, possesses the sequence‐characterized amplified region markers SU91 and SAP6, which are associated with CBB resistance QTL on linkage groups 8 and 10, respectively. USCR‐CBB‐20 had an average disease score of 5.3 in greenhouse tests, which is a remarkable improvement over the previous cranberry line released with CBB resistance, which scored 8.4 (9 = completely susceptible) in the same tests. Except for relatively small seed size, USCR‐CBB‐20 exhibits commercially acceptable agronomic traits for the cranberry bean market class. Yield potential was above average in Michigan and below average in Washington. USCR‐CBB‐20 will be useful for improving CBB resistance in the cranberry and other large‐seeded dry and green‐bean market classes of Andean origin.