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POSTERS: Population biology and genetics

Phylogeny of Dickeya zeae isolated from different hosts and irrigation water using multilocus sequence analysis
Gamze Boluk - University of Hawaii at Manoa. Mohammad Arif- University of Hawaii at Manoa, Anne Alvarez- University of Hawaii at Manoa, Shefali Dobhal- University of Hawaii at Manoa

Soft rot Dickeya species (formerly known as pectinolytic Erwinia species) in the Enterobacteriaceae cause economically important diseases on vegetable and other crops. Both bacterial heart rot of pineapple and bacterial stalk rot of corn are caused by strains of Dickeya zeae. Recently, we found D. zeae associated with diseases of kale and taro, which are economically important crops in Hawaii and other areas. In this research, we used Multi-Locus Sequence Typing (MLST) to define the relationships among the strains isolated from different sources including pineapple, corn, taro and irrigation water. The housekeeping genes, dnaA (chromosomal replication initiator) and gapA (glyceraldehyde-3-phosphate dehydrogenase A), were selected based on their higher resolution capabilities for Dickeya species compared to the other housekeeping genes. In addition to 40 strains of D. zeae, 15 and 20 strains other Dickeya species and Pectobacterium species, respectively, were included in the study. The phylogenetic tree revealed a high nucleotide discrepancy among the D. zeae strains. The D. zeae strains found associated with kale and taro showed close relationships with the strains isolated from corn and irrigation water. However, strains from both kale and taro were in the same clade with strains isolated in 2006-07 from irrigation water.