BANANA - BLOOD DISEASE

BLOOD DISEASE disease for banana (Musa spp) is a wilt caused by a bacterium that invades the vascular tissues. The name blood disease was originally adoptedbecause droplets of a thick milky white, yellow or red-brown liquid often ooze out of the vascular tissues of infected plants at cut surfaces. The disease affects cultivars of both AAA and ABB genomic groups (See photo above). In Malaysia this disease severely cause as the major impact on banana industry since 2006 but recentky recovered. As a reference, Gäuman (1921, 1923) found that the bacteria can survive for over a year in soil infested by decaying diseased plant tissues and can infect the banana plant through wounds on suckers, pseudostem and fruits. The sequence of symptoms depends on the route of infection and the growth stage of the plant. There is evidence that this disease is probably transmitted by insects visiting the male flowers. The cultivar Pisang Kepok (ABB group) in Indonesia is thought to be highly susceptible because the male flower nectar has high sugar content, making it particularly attractive to insects that spread the bacterium from male bud to male bud. Following this route of infection, blackening and shrivelling of male flowers is frequently found. Then, the bacteria move into the fruit and cause a reddish dry rot of the pulp. Afterwards the bacteria move down into the pseudostem towards the suckers. This article I would like to share knowlwedge about the symptoms and the scientific study of blood disease or locallny known as Moko Disease in "Anim Agriculture Technology" from verious technical papers.

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.

 

Healthy banana.

Whole-genome comparisons confirmed previous phylogenetic results: the three phylotype IV strains share more and larger syntenic regions with each other than with other R. solanacearum strains. Furthermore, the genetic distances between strains, assessed by an in-silico equivalent of DNA-DNA hybridization, unambiguously showed that phylotype IV strains of BDB, R. syzygii and R. solanacearum form one genomic species. Based on these comprehensive data we propose a revision of the taxonomy of the R. solanacearum species complex. The BDB and R. syzygii genomes encoded no obvious unique metabolic capacities and contained no evidence of horizontal gene transfer from bacteria occupying similar niches. Genes specific to R. syzygii and BDB were almost all of unknown function or extrachromosomal origin. Thus, the pathogenic life-styles of these organisms are more probably due to ecological adaptation and genomic convergence during vertical evolution than to the acquisition of DNA by horizontal transfer.

 

By,

M Anem,

Senior Agronomist,

Serdang Agriculture Station,

Serdang, Selangor,

Malaysia.

(12 Zulkaedah 1434H)