In vitro regeneration of selected commercial Tanzanian open pollinated maize varieties

Four Tanzanian open pollinated maize varieties namely; Kito, Situka M-1, Staha and TMV-1 were regenerated in vitro using immature zygotic embryos as ex-plants. Callus induction was achieved using Murashige and Skoog (MS) basal medium supplemented with 1, 1.5, 2 or 2.5 mg/l of 2, 4-D. Callus induction was significantly affected by the genotype of the varieties. Among the varieties tested, Kito, Situka M-1 and Staha had significantly higher callus induction frequency of 84.4, 92.7 and 88.7%, respectively compared to TMV-1 (43.3%). Embryogenic callus induction percentage was significantly influenced by the genotype, 2, 4-D concentrations and their interaction effect implying differential response of the genotypes to 2, 4-D concentrations. Among the genotypes tested, Kito gave significantly (p<0.05) the highest embryogenic callus frequency of 69.5%. Great variations were observed among the genotypes with regard to regeneration frequencies. Staha was comparatively the most regenerable variety with RF of 32.6% than even Kito which had the highest callus induction and embryogenic callus formation. MS medium amended with 1 mg/l 2, 4-D was observed to be the optimum formulation for the induction of embryogenic calli for genotypes tested in this study. Using this regeneration system Situka M-1, Staha and TMV-1 can now be improved against various production constraints through genetic engineering.Key words: 2, 4-dichlorophexyacetic acid, embryogenic callus, immature zygotic embryos, regeneration frequency, somatic embryos, Tanzanian open pollinated maize

Identification of SNP and SSR Markers in Finger Millet Using Next Generation Sequencing Technologies

Finger millet is an important cereal crop in eastern Africa and southern India with excellent grain storage quality and unique ability to thrive in extreme environmental conditions. Since negligible attention has been paid to improving this crop to date, the current study used Next Generation Sequencing (NGS) technologies to develop both Simple Sequence Repeat (SSR) and Single Nucleotide Polymorphism (SNP) markers. Genomic DNA from cultivated finger millet genotypes KNE755 and KNE796 was sequenced using both Roche 454 and Illumina technologies. Non-organelle sequencing reads were assembled into 207 Mbp representing approximately 13% of the finger millet genome. We identified 10,327 SSRs and 23,285 non-homeologous SNPs and tested 101 of each for polymorphism across a diverse set of wild and cultivated finger millet germplasm. For the 49 polymorphic SSRs, the mean polymorphism information content (PIC) was 0.42, ranging from 0.16 to 0.77. We also validated 92 SNP markers, 80 of which were polymorphic with a mean PIC of 0.29 across 30 wild and 59 cultivated accessions. Seventy-six of the 80 SNPs were polymorphic across 30 wild germplasm with a mean PIC of 0.30 while only 22 of the SNP markers showed polymorphism among the 59 cultivated accessions with an average PIC value of 0.15. Genetic diversity analysis using the polymorphic SNP markers revealed two major clusters; one of wild and another of cultivated accessions. Detailed STRUCTURE analysis confirmed this grouping pattern and further revealed 2 sub-populations within wild E. coracana subsp. africana. Both STRUCTURE and genetic diversity analysis assisted with the correct identification of the new germplasm collections. These polymorphic SSR and SNP markers are a significant addition to the existing 82 published SSRs, especially with regard to the previously reported low polymorphism levels in finger millet. Our results also reveal an unexploited finger millet genetic resource that can be included in the regional breeding programs in order to efficiently optimize productivity

Identification of Candida strains isolated from Tanzanian pregnant women with vaginal candidiasis

Objective: To identify Candida strains isolated from Tanzanian women (13 to 45 years) with vaginal candidiasis. Design: A cross-sectional study. Setting: Antenatal clinic in llala district hospital in Dar es Salaam, Tanzania from March 1998 to December 2000. Results: The identities of the 272 isolates tested with API Candida were: Candida albicans 180(66.2%), Candida tropicalis 13(4.7%), Candida glabrata 20(7.35%), Candida famata 6(2.2%), Candida parapsilosis 6 (2.2%) and Candida lusitaniae one (0.37%). API Candida could not speciate 43 (15.8%) isolates of these; two (0.7%) fell between C. albicans and C. tropicalis, 17(6.25%) C. Iusitaniael, C. guilliermondii/C. famata, 14(5.15%) C. krusei, C. inconspicua, and C. norvegensis and nine (3.3%) either C. parapsilosis, C. krusei, C. incospicua or Geotrichum spp. Four (1.5%) isolates had an assimilation pattern of Trichosporo spp, but were all germ tube positive and had morphological features on cornemeal agar that were consistent with C. albicans. API 20C AUX was used for testing 29 isolates and results showed: 11/29 (37.9%) C. albicans, 1/29 (3.4%) C. tropicalis, 4/29 (13.8%) C. glabrata, 1/29 (3.4%) C. parapsilosis, 1/29 (3.4%) C. famata, 1/29 (3.4%) C. lusitaniae, 1/29 (3.4%) C. colliculosa/C. magnoliae, 5/29(17.2%) C. albicans/ C. tropicals 2/29 (6.8%) C. norvegensis/C. parapsilosis, and 2/29(6.8%) C. kruseil/C. inconspicua. Results of 20 isolates identified by Randomly Amplified Polymorphic DNA (RAPID) technique showed a 95% agreement with API Candida and a 100% agreement with API 20C AUX. Conclusion: Although most (66.3%) of the species isolated from Dar es Salaam women with vaginal candidiasis were C. albicans, a considerable percentage (33.7%) were nonalbicans, mainly C. glabrata, C. krusei and C. tropicalis. The high prevalence of non-albicans Candida spp observed in this population may have therapeutic implications.East African Medical Journal Vol. 82(5) 2005: 226-23

Characterization and PCR multiplexing of polymorphic microsatellite loci in cashew (Anacardium occidentale L.) and their cross-species utilization

Cashew (Anacardium occidentale L.) is the most economically important tropical nut crop in the world, and yet there are no sequence tagged site (STS) markers available for its study. Here we use an automated, high-throughput system to isolate cashew microsatellites from a non-enriched genomic library blotted onto membranes at high density for screening. Sixty-five sequences contained a microsatellite array, of which 21 proved polymorphic among a closely related seed garden population of 49 genotypes. Twelve markers were suitable for multiplex analysis. Of these, 10 amplified in all three related tropical tree species tested: Anacardium microcarpum, Anacardium pumilum and Anacardium nanum

Identification of SNP and SSR markers in finger millet using next generation sequencing technologies

Finger millet is an important cereal crop in eastern Africa and southern India with excellent grain storage quality and unique ability to thrive in extreme environmental conditions. Since negligible attention has been paid to improving this crop to date, the current study used Next Generation Sequencing (NGS) technologies to develop both Simple Sequence Repeat (SSR) and Single Nucleotide Polymorphism (SNP) markers. Genomic DNA from cultivated finger millet genotypes KNE755 and KNE796 was sequenced using both Roche 454 and Illumina technologies. Non-organelle sequencing reads were assembled into 207 Mbp representing approximately 13% of the finger millet genome. We identified 10,327 SSRs and 23,285 non-homeologous SNPs and tested 101 of each for polymorphism across a diverse set of wild and cultivated finger millet germplasm. For the 49 polymorphic SSRs, the mean polymorphism information content (PIC) was 0.42, ranging from 0.16 to 0.77. We also validated 92 SNP markers, 80 of which were polymorphic with a mean PIC of 0.29 across 30 wild and 59 cultivated accessions. Seventy-six of the 80 SNPs were polymorphic across 30 wild germplasm with a mean PIC of 0.30 while only 22 of the SNP markers showed polymorphism among the 59 cultivated accessions with an average PIC value of 0.15. Genetic diversity analysis using the polymorphic SNP markers revealed two major clusters; one of wild and another of cultivated accessions. Detailed STRUCTURE analysis confirmed this grouping pattern and further revealed 2 sub-populations within wild E. coracana subsp. africana. Both STRUCTURE and genetic diversity analysis assisted with the correct identification of the new germplasm collections. These polymorphic SSR and SNP markers are a significant addition to the existing 82 published SSRs, especially with regard to the previously reported low polymorphism levels in finger millet. Our results also reveal an unexploited finger millet genetic resource that can be included in the regional breeding programs in order to efficiently optimize productivity

Identification of SNP and SSR markers in finger millet using next generation sequencing technologies

Finger millet is an important cereal crop in eastern Africa and southern India with excellent grain storage quality and unique ability to thrive in extreme environmental conditions. Since negligible attention has been paid to improving this crop to date, the current study used Next Generation Sequencing (NGS) technologies to develop both Simple Sequence Repeat (SSR) and Single Nucleotide Polymorphism (SNP) markers. Genomic DNA from cultivated finger millet genotypes KNE755 and KNE796 was sequenced using both Roche 454 and Illumina technologies. Non-organelle sequencing reads were assembled into 207 Mbp representing approximately 13% of the finger millet genome. We identified 10,327 SSRs and 23,285 non-homeologous SNPs and tested 101 of each for polymorphism across a diverse set of wild and cultivated finger millet germplasm. For the 49 polymorphic SSRs, the mean polymorphism information content (PIC) was 0.42, ranging from 0.16 to 0.77. We also validated 92 SNP markers, 80 of which were polymorphic with a mean PIC of 0.29 across 30 wild and 59 cultivated accessions. Seventy-six of the 80 SNPs were polymorphic across 30 wild germplasm with a mean PIC of 0.30 while only 22 of the SNP markers showed polymorphism among the 59 cultivated accessions with an average PIC value of 0.15. Genetic diversity analysis using the polymorphic SNP markers revealed two major clusters; one of wild and another of cultivated accessions. Detailed STRUCTURE analysis confirmed this grouping pattern and further revealed 2 sub-populations within wild E. coracana subsp. africana. Both STRUCTURE and genetic diversity analysis assisted with the correct identification of the new germplasm collections. These polymorphic SSR and SNP markers are a significant addition to the existing 82 published SSRs, especially with regard to the previously reported low polymorphism levels in finger millet. Our results also reveal an unexploited finger millet genetic resource that can be included in the regional breeding programs in order to efficiently optimize productivity

Micrografting of Protea cynaroides

The inability to induce rooting of in vitro-established Protea cynaroides microshoots has prevented the production of complete plantlets. A successful shoot-tip micrografting technique was developed using in vitro-germinated P. cynaroides seedlings as rootstocks and axenic microshoots established from pot plants as microscions. Thirty-day old seedlings, germinated on growth-regulator-free, half-strength Murashige and Skoog medium, were decapitated and a vertical incision made from the top end. The bottom ends of microshoots established on modified Murashige and Skoog medium were cut into a wedge (‘V’) shape, and placed into the incision. The micrografted explants were cultured in a growth chamber with the temperature adjusted to 25 ± 2°C, with a 12-h photoperiod. Best results were obtained by placing the microscions directly onto the rootstock without any pre-treatments. Dipping the explants in anti-oxidant solution or placing a layer of medium around the graft area led to the blackening of the microscion. Abbreviations EDTA Ethylenediaminetetraacetate - BAP 6-Benzylaminopurine - GA3 Gibberellic acid - PAR Photosynthetic active radiatio