Common bacterial blight (CBB) in common bean (Phaseolus vulgaris L.), caused by Xanthomonas campestris pv. phaseoli (Xcp), reduces bean yields and quality throughout the world. Pinto `Chase' is a high-yielding variety with moderate resistance to Xcp derived from great northern Nebraska #1 selection 27, whose resistance is derived from an unknown tepary (P. acutifolius) bean source. XAN-159 is a black mottled small seeded breeding line with different genes for high resistance to Xcp derived from a different tepary source (PI 319443). Our objective was to pyramid different genes for Xcp resistance from the donor parent XAN-159 into the rust-resistant recurrent parent Pinto `Chase' using the classical back-cross breeding method with confirmation of resistance using RAPD molecular markers. Resistance was confirmed in some BC2F2 generation plants. Seven RAPD markers and the V locus (flower color) previously identified were confirmed in the BC1 and BC2 populations. Smaller seed size, purple flower color, and black mottled seed coat color were coinherited with resistance to Xcp. However, a recombinant plant with enhanced CBB resistance and moderate-sized pinto seed was identified. Backcross breeding is being continued.
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