Diversity of <I>Xanthomonas axonopodis</I> pv. <I>glycines</I>, the Causal Agent of Bacterial Pustule of Soybean and Specific Primer for Detection

Abstract

The 171-novel strains of Xanthomonas axonopodis pv. glycines, the bacterial pustule pathogen, were isolated from infected leaves of different commercial soybean fields in Chiang Rai, Chiang Mai, Lamphun and Lampang provinces. The genetic diversity was determined with physiological and molecular analyzed. All strains were tested for their pathogenicity on differential soybean cultivars including Williams 82, Spencer, PI520733 and SJ.5 under greenhouse conditions; then molecular diversity was analyzed by BOX-PCR fingerprinting. The pathogenicity tests showed 2 groups with a large amount of phenotypic variation between strains. Most strains were highly virulent. Using rep- PCR fingerprinting, a relationship between BOX-PCR fingerpring and phenotype was observed. Two major groups were obtained within the soybean cluster and relationship of the virulence levels of the strains was revealed. The fingerprinting with BOX primer was more relatively unique, stable, and reproducible in that it produced a 650 bp band in all 171 strains tested. We designed primers specific for X. axonopodis pv. glycines, XagF: 5'ATGGATGCCACCGCACAG3' and XagR: 5'GCGTCGAACCGCACATC3', that amplify a 788 bp product from hrpB. To our knowledge, this is the first report of specific primer for identification of X. axonopodis pv. glycines, the causal pathogen of soybean bacterial pustule.