Authors
Shi-En Lu, Department of Entomology and Plant Pathology, Mississippi State University, Mississippi State, MS 39762; and
Dennis C. Gross, Department of Plant Pathology and Microbiology, Texas A&M University, College Station, TX 77843-2132
ABSTRACT
Drippy pod is a unique bacterial disease of Mediterranean white lupine (Lupinus albus) that first appeared in commercial fields in Eastern Washington State in the mid-1980s. The disease is most noticeable in the field as water-soaked lesions on lupine pods that produce an abundance of whitish-colored ooze with a sticky and foamy consistency. As the disease progresses, yellowing of lupine plants occurs with ooze characteristically dripping down the infected pods and stems and solidifying. A gram-negative rod-shaped bacterium with facultative anaerobic growth was repeatedly isolated from infected lupine tissues, and subsequently confirmed by Koch's postulates to infect lupines. Physiological and biochemical tests, including the API 20E and 50CHE strip assays, showed a highly uniform phenotype for the lupine strains that was distinctive for the genus Brenneria and most closely resembled the oak pathogen Brenneria quercina. Furthermore, sequence analyses of the 16S rDNA gene and the 16S-23S intergenic region of lupine strains revealed the highest similarity (>97%) to the corresponding regions of B. quercina and less similarity to the next closest species, B. salicis. Fatty acid profiling demonstrated that lupine strains were qualitatively similar in composition to Brenneria spp., and supported placement of the drippy pod bacterium in the species B. quercina. Oak strains of B. quercina, however, did not incite drippy pod disease on lupine. Consequently, the lupine strains that cause bacterial drippy pod disease were classified as B. quercina pv. lupinicola pv. nov.
