As the disease progress all leaves became gradually yellow and necrotic (Stover & Espinoza 1992),then wilt, collapse and hang down. Red to brown necrotic marks are seen towards the centre of the pseudostem and/or peduncle whencut transversely. The male bud below the fruit may ooze droplets,especially from flower and bract scars in those genotypes that shed flowers and bracts. This is thought to be one reason why certain ABB cultivars are much more susceptible to infection than other bananas(Davis et al. 2001). An additional symptom may occur on ABB cultivars.
The Ralstonia solanacearum species complex includes R. solanacearum, R. syzygii, and the Blood Disease Bacterium (BDB). All colonize plant xylem vessels and cause wilt diseases, but with significant biological differences. R. solanacearum is a soilborne bacterium that infects the roots of a broad range of plants. R. syzygii causes Sumatra disease of clove trees and is actively transmitted by cercopoid insects. BDB is also pathogenic to a single host, banana, and is transmitted by pollinating insects. Sequencing and DNA-DNA hybridization studies indicated that despite their phenotypic differences, these three plant pathogens are actually very closely related, falling into the Phylotype IV subgroup of the R. solanacearum species complex. To better understand the relationships among these bacteria, we sequenced and annotated the genomes of R. syzygii strain R24 and BDB strain R229. These genomes were compared to strain PSI07, a closely related Phylotype IV tomato isolate of R. solanacearum, and to five additional R. solanacearum genomes.
Serdang Agriculture Station,
(12 Zulkaedah 1434H)