Genetic mapping of novel symptom in response to soybean bacterial leaf pustule in PI 96188

Abstract

Soybean bacterial leaf pustule (BLP) is a serious disease caused by Xanthomonas axonopodis pv. glycines. Typical symptoms of BLP are pustules surrounded by small yellow haloes. Interestingly, PI 96188 only exhibits pustules without chlorotic haloes which suggests a resistant response. The objectives of this study are to understand the inheritance mode of the novel symptom to BLP in PI 96188 and to investigate whether or not a gene controlling BLP resistance in PI 96188 is identical to the rxp gene. First, a new BLP resistant genotype, PI 96188 was crossed with the resistant cultivar SS2-2. All F1 plants showed the same phenotype as SS2-2 and the F2 population segregated into 75 typical symptoms (haloes presence: 28 novel symptoms (haloes absence) indicating the presence of a single recessive gene. To map the novel symptom to BLP in PI 96188, a population of 88 F7 recombinant inbred lines was developed from a cross between PI 96188 and the susceptible cultivar Jinjoo1. The BLP resistance gene from PI 96188 was mapped on chromosome (Chr.) 10 (LG O) rather than Chr. 17 (LG D2). This gene was linked with the simple sequence repeat marker, Sat_108 at the distal end of Chr. 10. Thus, the BLP resistance gene from PI 96188 was determined to be a new gene.