Population genetics is an essential component for understanding population biology leading to effective disease management by reducing one or more of the most virulent populations of a pathogen. This is especially important when dealing with an epidemic that causes significant crop loss. New species/strains are introduced into Hawaii via imported materials including the food supply, seed sources and propagative plant stocks. Bacterial heart rot caused by Dickeya was first reported in 2005 in Hawaii on pineapples. The study conducted by Sueno et al (2014) on Dickeya isolates suggested that at least two separate introductions of distinct strains occurred through the imported planting materials. There are numerous other examples of introduction of economically important bacterial pathogens in Hawaii including Xanthomonas axonopodis pv. dieffenbachiae, Clavibacter michiganensis subsp. michiganensis, Pantoea stewartii, Ralstonia solanacearum race 2 etc. Moreover, bacteria are well known for rapid mutation rates and adaptability to new environments. Evidence is available that new populations can emerge and dominate in a region. A most recent study on a high consequence bacterium Rathayibacter toxicus (select agent in United States) showed emergence of a new population (RT-I) on annual ryegrass (Lolium rigidum) dominating in a particular geographical region in South Australia. This bacterium produces corynetoxins which are lethal to livestock (grazing animals) and have already caused thousands of deaths. Bacteria can easily jump from one host to another; a single nucleotide mutation could drive the host specificity, to cause the disease on a new host. Few studies on population genetics of important bacterial pathogens of the tropics have already been conducted. However, there are still many questions to answer about the species complexes within the genus of economically important bacteria e.g. Xanthomonas, Dickeya, Erwinia. Therefore, our interest is to map out the current population structure of important bacterial species/genera of the tropics to better understand the population biology for effective disease management strategies.
Expanded population genetics of Dickeya species
Population structure of Xanthomonas euvesicatoria
University of Hawaii at Manoa Collage of Tropical Agriculture and Human Resources Department of Plant & Environment Protection Sciences