Browsing by Author "Osei, M.K."
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Item First report of bacterial wilt caused by Ralstonia solanacearum in Ghana, West Africa(Plant Disease, 2015-01) Subedi, N.; Gilbertson, R.L.; Osei, M.K.; Cornelius, E.; Miller, S.A.Tomato and pepper plants exhibiting wilt symptoms were collected from fields in seven villages in Northern (Vea, Tono, Pwalugu), Ashanti (Agogo, Akumadan), and Brong Ahafo (Tanoso, Tuobodom) regions of western Ghana in November 2012. The plants were wilted without leaf yellowing or necrosis. Disease incidence was generally low, with less than 20% symptomatic plants observed. Most of the plants collected produced visible bacterial ooze in water in the field. Ooze was plated on 2,3,5-triphenyltetrazolium chloride-amended (TZC) medium. Isolated colonies were fluidal, irregularly round, white with pink centers, gram-negative, and oxidase positive. One strain from each of seven fields was selected for further study. All strains induced a hypersensitive reaction on tobacco. Randomly selected strains SM855-12 and SM857-12 tested positive in R. solanacearum ImmunoStrip assays (Agdia Inc., IN). An end-point PCR assay with primer set 759/760 (3) generated an R. solanacearum-specific 280-bp amplicon for all seven strains. Two of these strains were biovar I and the remaining five were biovar III based on utilization of cellobiose, lactose, maltose, dulcitol, mannitol, and sorbitol. A phylotype-specific multiplex PCR assay that recognizes four geographically linked monophyletic groups within R. solanacearum (1) indicated that one strain (SM855-12) was phylotype III (African origin), whereas the other six were phylotype I (Asian origin). All strains were subjected to repetitive sequence-based PCR (Rep-PCR) with BOXA1R and REP1R/REP2 primers (4). Strain SM855-12 was grouped with the phylotype III reference strain UW 368 and the remaining six strains were grouped with the phylotype I reference strain GMI 1000. A pathogenicity test was performed with bacterial wilt-susceptible tomato line OH7814. Inoculum was prepared from 48-h cultures of strains SM855-12, SM856-12, and SM858-12 grown on casamino acid peptone glucose (CPG) medium at 30°C. Roots of ten 4-week-old tomato plants per strain were drench-inoculated with 5 ml of a 108 CFU/ml bacterial suspension after wounding with a sterile scalpel. Non-inoculated control plants were drenched with 5 ml distilled water after root wounding. Plants were kept in a greenhouse at 25 to 30°C. By 12 days after inoculation, 80 to 100% of inoculated plants were wilted, whereas no symptoms appeared in non-inoculated plants. Bacteria re-isolated from wilted plants were confirmed to be R. solanacearum using techniques mentioned above. Although an association of bacterial wilt with tomato/pepper was mentioned previously (2), to our knowledge, this is the first documented report of bacterial wilt caused by R. solanacearum in Ghana. The presence of Asian strains (phylotype I) may be the result of one or more accidental introductions. Awareness of this disease in Ghana will lead to deployment of management strategies including use of resistant varieties and grafting desirable varieties onto disease-resistant rootstocks.Item Hybridity testing of tomato F 1 progenies derived from parents with varying fruit quality and shelf life using single nucleotide polymorphism (SNPs)(Scientific African, 2020-07) Osei, M.K.; Danquah, E.; Danquah, A.; Blay, E.; Adu-Dapaah, H.The demand for tomato is increasing day by day mostly because of the increased per capita fresh fruit consumption. Nonetheless as a perishable fruit crop, it has relatively short life after ripening thus experiences remarkable post-harvest losses. The study was to select true F1 hybrids using SNPs for the development of inbred lines with long shelf life character through marker assisted backcrossing. Nine out of the one hundred and forty SNP markers failed, 93 were uninformative and 38 were polymorphic and spread across the 12 chromosomes. The major allele frequency, gene diversity, heterozygosity and Polymorphic Information Content (PIC) for each locus were calculated for SNP markers using Power Marker 3.5. The mean value of the major allele frequency was 0.673, ranging between 0.529 and 0.794. The average gene diversity and Heterozygosity values were 0.419 and 0.125 respectively. The PIC ranged from 0.273 (Sly11-Rx4) to 0.375 (Sly04-9) with a mean of 0.329. Of the 31 polymorphic SNPs, two SNPs (Sly04-9 and Sly07-2) exhibited the maximum PIC and a gene diversity value of 0.50. The markers Sly11-13 and Sly11-Rx4 were found to be the least informative with PIC and gene diversity values equaling 0.327 and major allele frequency of 0.794. The maximum heterozygosity was observed with SNP markers Sly03-8, Sly06-7, Sly08-1, Sly08-8, while the minimum heterozygosity was observed with SNPs marker Sly02-9, Sly06-1, Sly10-4, Sly10-5, Sly11-13, Sly11-Rx4, and Sly12-9.The SNPs tested for shelf life genes rin (Sly05-rin1 and Sly05-rin2) and nor (Sly10-nor) were monomorphic within the seven different plants (parentals). The SNP (Sly10-alc) tested for the alc gene was however, polymorphic within the seven lines. The result indicates that only one SNP (Sly10-alc) is a functional SNP to detect a long shelf life gene. Tomato genotypes CSIR/CRI-P002 and CSIR/CRI-ATS064 were however, polymorphic for alc. The other SNPs for rin and nor were not useful and new SNPs are needed to be redesigned. The molecular test revealed two superior F1 hybrids which were selected for evaluation as lines for improvement. The advantage is the reduction in cost, time, labor and field space requirement.Item Validation of SNP marker linked to alc gene for long shelf life of tomato(JOURNAL OF CROP IMPROVEMENT, 2019-08-14) Osei, M.K.; Danquah, E.; Danquah, A.; Massoudi, M.; Maxwell, D.; Adu- Dapaah, H.; Blay, E.Tomato (Solanum lycopersicum L.) fruits are naturally perishable and have short shelf life. Post-harvest losses can be devastating and can be associated with rapid ripening. The objective of this study was to identify a single nucleotide polymorphism (SNP) marker associated with alc gene conferring long shelf life in tomato. The tomato line CSIR/CRI-AT06 was crossed with Alc- LA3134 to develop an F2 population. A total of 72 plants were screened for the target loci. Genotypic data of the F2 population were generated following the scoring system as [T:A] for heterozygous individuals, [A:A] and [T:T] for plants homozygous for the donor and recipient parents, respectively. An assessment of the Sly10–14 SNP marker was completed by comparing SNP score against fruit shelf life of the 72 F2 entries. The pattern of segregation of SNP marker for the alc gene was tested for goodness of fit to a 1:2:1 ratio using Chi-square test (χ2) test. The results showed that the marker segregated in the expected ratio. The analysis from 72 F2 population plants indicated that SNP marker (Sly 10-14) had significant association with shelf life at 1% significance level. From the analysis, it can be established that a locus linked to Sly10-14 is significant. The homozygous marker (A:A) has an effect of increasing shelf life by 22 days and explains 87% of the observed variation. This marker (Sly10-14) is linked to a gene that controls the shelf life of tomato fruits. The effect of this gene is additive and it increases the shelf life.