Based on its highly diverse phenotypes and genotypes, strains of Pseudomonas syringae pv. actinidiae (Psa), causal bacterium of kiwifruit canker, have been subdivided into biovars 1–3, 5 and 6. In comparative genomic analyses of numerous strains with various histories by our research group and others around the world, to clarify the genetic background that contributes to biovar differences, repertories of toxin biosynthesis gene clusters and genes encoding type III secreted effectors were found to differ greatly among biovars. Many mobile genetic elements, such as plasmids and genomic islands including integrative and conjugative elements (ICEs) and integrative and mobilizable elements (IMEs), were also found in the Psa genomes and may also have contributed to the diversification.
Fruitlet core rot of pineapple (Ananas comosus) has been found in Okinawa Prefecture, Japan since a few decades ago. A fungus frequently isolated from the diseased fruits was identified as Fusarium ananatum based on morphological and cultural characteristics and molecular analyses of EF-1α,β-tubulin and histone H3 DNA sequences. The isolates reproduced the symptoms on pineapple fruits after inoculation using toothpicks and were reisolated from the inoculated symptomatic fruits. This is the first report of fruitlet core rot of pineapple caused by F. ananatum in Japan, and we propose the Japanese name “shoka-fuhai-byo” of pineapple.