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Pineapple [Ananas comosus (L.) Merr.] is an important fruit crop cultivated in Tanzania. However, the knowledge on genetic diversity of the pineapple cultivars grown in Tanzania is limited. This study was aimed at determining the genetic diversity and identity of pineapple cultivars from different growing regions in Tanzania using microsatellite markers also known as simple sequence repeat marker (SSR). Ten of the 18 microsatellite markers were polymorphic and generated a total of 22 distinct reproducible bands with an average of 2.2 bands per primer pair. The number of polymorphic bands detected with each primer pair ranged from 1 to 3 with an average of 1.5 per primer pair. The polymorphic information content (PIC) values of each primer pair ranged from 0.17 to 0.79 with an average of 0.41. Two microsatellite loci TsuAC010 and TsuAC039 revealed PIC values higher than 0.50 thus suggesting that such primers have high discriminatory ability. The consensus tree derived from the unweighted pair-group method with arithmetic means (UPGMA) revealed four different groups. Kinole-SCT sub-population formed a distinct group from Madeke-SCT and MD2 hybrid cultivar. Kinole-SC, Mukuranga-SC, and Kiwangwa-SCcultivars were closely related on the cluster analysis. This study demonstrated the existence of low genetic diversity in pineapples cultivated in Tanzania implying that a well-thought-out breeding strategies should be employed for genetic improvements of pineapple. Introduction of exotic clones and employment of modern breeding strategies such as marker assisted selection (MAS) and genetic engineering technologies is recommended. This will widen the current genetic pool of pineapple in Tanzania. Key words: Pineapple [Ananascomosus (L.) Merr.], microsatellite markers, genetic diversity, unweighted pair-group method with arithmetic means (UPGMA), polymorphic information content (PIC).

Transformation of a tropical maize inbred genotype (CML144) with the Xerophyta viscosa peroxiredoxin2 ( XvPrx2 ) gene was reported. The protective role of peroxiredoxin2 against the damage resulting from reactive oxygen species (ROS) under dehydration stress was further determined. Successful integration of XvPrx2 gene into maize we achieved and recovered 10 independent transgenic events. Transformation and regeneration frequencies were 12.9 and 31.3%, respectively. Reverse transcription polymerase chain reaction (PCR) revealed the expression of the XvPrx2 gene in transformed plants under dehydration. Stressed transgenic plants had higher relative water content (RWC) as compared to the conventional plants. Recovery irrigation showed higher RWC in transgenics than in conventional plants. Unlike in conventional plants, rapid morphogenic recovery was observed in transgenics within 24 h. Chlorophyll contents decreased faster in conventional plants than in transgenics with prolonged drought. Generally, transgenic plants were more tolerant to dehydration stress than conventional plants. This tolerance may be associated with the over expression of peroxiredoxin2 playing a role in managing ROS generated in plant cells. Keywords: Xerophyta viscosa , reactive oxygen species (ROS), transgenic drought tolerant maize, plant breeding

A total of 57 sweet potato genotypes with high dry matter content and resistant to sweet potato virus disease (SPVD) were characterized using four simple sequence repeat (SSR) markers. The germplasm included 20 genotypes identified as having high dry matter content and 25 accessions tolerant to SPVD in a study conducted in Tanzania in 2008. The total number of alleles within the 57 genotypes across 4 loci was 395, with an average of 4 alleles per locus. The unweighted pair group method with arithmetic mean (UPGMA) and analysis of molecular variance (AMOVA) using generated SSR data, grouped the 57 genotypes into two major clusters, with mean pair-wise genetic distance of 0.55. No specific grouping was observed in relation to SPVD resistance, dry matter content and geographic location. The four microsatellites markers distinguished the 57 Tanzanian sweet potato genotypes into two major clusters. The relatively high level of genetic diversity indicates broad genetic base for sweet potato breeding in Tanzania. The results obtained demonstrate the efficiency of SSR marker technique for the assessment of genetic relationships and distinguishing between Tanzanian sweet potato genotypes. The findings of this of this study, provide valuable information to breeders to facilitate cost effective germplasm conservation and development of improved sweet potato varieties resistant to SPVD and containing high dry matter. Key words: Simple sequence repeat (SSR), Ipomoea batatas, cluster analysis, genetic diversity.

DNA from Coffea arabica leaves was used for RAPD analysis and a total of 144 leaf samples collected from 16 provenances in five regions of Tanzania were analysed. Ten arbitrary 10 mer primers were employed in the analysis and they produced a total of 86 fragments. Fragment sizes ranged from 100–1400 bp. The resulting dissimilarity matrix revealed values ranging from 0.11 to 1, while the average was 0.66. The cophenetic matrix and the original dissimilarity matrix showed a significant correlation of 78 %. Mean dissimilarity values within provenances showed a fairly uniform trend despite the large range from 0.31 to 0.65. The dendrogram based on genetic distances but showed two clusters with grouping of provenances similar to the dendrogram generated by Jaccard's coefficient. Bootstrap analysis showed low values, despite this, the resulting dendrogram grouped all provenances according to their geographical origin. The standard genetic distances were fairly uniform implying a narrow genetic base in the cultivated Arabica coffee.

SummaryA study was conducted to develop in vitro culture techniques relevant to the clonal multiplication of cashew (Anacardium occidentale L.) using the Tanzanian elite clone AC4. Cultural factors affecting shoot proliferation, shoot elongation, and node development were assessed using glasshouse-raised plants of various ages. MS salts medium containing full-strength macroelements was found to be best for shoot proliferation and shoot elongation. Increasing ages of stock plants resulted in drastic decreases in the abilities of axillary buds on nodal explants to sprout and elongate and best performances were obtained from juvenile explants of 1–6 month old explants. Out of six cytokinins compared, 6-benzylamino purine (BAP) applied at 30 μM and zeatin (Zea) at 5 μM were found to be optimal for axillary shoot proliferation and shoot elongation, respectively. Microshoots were rooted in vitro at a frequency of 50–60% when cultured for 3 d in woody plant medium (WPM) with 0.5 μM indole-3-butyric acid (IBA). A...

The Association for Strengthening Agricultural Research in Eastern and Central Africa (ASARECA) through its Agrobiodiversity and Biotechnology Programme is enhancing the utilization of biotechnology research and development innovations in Eastern and Central Africa (ECA). We present successes in the application of biotechnology to enhance the productivity of cassava, sweet potato, banana, maize and sorghum in ECA. These products—drought tolerant maize, sorghum resistant to striga, as well as the technology for producing and distributing disease free planting materials of cassava, sweet potato and banana to farmers—are central for the agro-ecological intensification of farming systems in the central African highlands.

SummaryRAPD (random amplified polymorphic DNA) markers were used to determine genetic diversity within and between populations of cashew (Anacardium occidentale L.). Efficient and novel procedures for extracting PCR-amplifiable, high molecular weight DNA from young cashew leaves were developed and the PCR conditions for RAPD analysis of cashew DNA using random 10.bp primers were defined. Optimized PCR-reaction conditions were then used to analyse differences in RAPD profiles within and between a selection of cashew varieties obtained from diverse geographical locations around the world and within a pool of twenty elite Tanazanian cashew lines. RAPD polymorphisms were obtained among the Tanzanian lines and between and within the geographically diverse lines. The relatively uniform RAPD profiles for the selection of random primers tested suggested a high degree of DNA level similarity between the Tanzanian accessions. Accessions from India, Mozambique and Tanzania showed the closest relationship, with acces...

Shoot tips excised from glasshouse-raised seedlings and field-grown plants of cashew (Anacardium occidentale L.) were micrografted by a modified side-grafting procedure using in vitro-raised seedling rootstocks. Factors affecting graft-take were optimised. The micro-scion take obtained was in the range 60–80%. The best growth of micro-scions was obtained with hypocotyls rather than with epicotyls as stock tissue. Rooting of micrografted shoots of mature tree origin was poor (13.3%) because the shoots were only partially rejuvenated.

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

DNA from Coffea arabica leaves was used for RAPD analysis and a total of 144 leaf samples collected from 16 provenances in five regions of Tanzania were analysed. Ten arbitrary 10 mer primers were employed in the analysis and they produced a total of 86 fragments. Fragment sizes ranged from 100-1400 bp. The resulting dissimilarity matrix revealed values ranging from 0.11 to 1, while the average was 0.66. The cophenetic matrix and the original dissimilarity matrix showed a significant correlation of 78%. Mean dissimilarity values within provenances showed a fairly uniform trend despite the large range from 0.31 to 0.65. The dendrogram based on genetic distances but showed two clusters with grouping of provenances similar to the dendrogram generated by Jaccard's coefficient. Bootstrap analysis showed low values, despite this, the resulting dendrogram grouped all provenances according to their geographical origin. The standard genetic distances were fairly uniform implying a narrow genetic base in the cultivated Arabica coffee.