Avocado crop in Tanzania is sparingly investigated regardless of being an important fruit commodity. This study was undertaken to explore the yield and the value chain of this crop in the country. Data were collected mainly by face-to-face interviews with 275 avocado farmers, 231 avocado traders and 16 key informants. Descriptive statistics, Chi-square test and one-way analysis of variance were used for data analysis. The average crop yield ranged from 76 to 124 kg plant⁻¹ between regions. The average price for the farmers’ produce ranged from US$ 0.30 to 0.45 kg⁻¹ between regions. About 72% of the farmers were dissatisfied with avocado business whereas 79% of the traders were pleased with it. A number of challenges were found hindering the development of the avocado industry in Tanzania, which in turn affects the fruit yield and the value chain. Addressing these challenges at the national, regional, district and village levels is important for improving the livelihood of Tanzanian farmers growing this crop, given the fact that a good proportion of the country’s population is employed in the agricultural sector and most of the reported challenges also affect the value chain of other crops.

Two-hundred and twenty-six old avocado trees (Persea americana Mill) derived from seeds were selected from eight districts of the Mbeya, Njombe and Songwe regions in Tanzania. The tree, leaf, fruit and seed characteristics were studied using the descriptors for avocado (Persea spp.) from the International Plant Genetic Resources Institute. Cross tabulation and Chi-square tests were conducted in order to assess the distribution of traits between districts and altitude ranges. Principle coordinate analysis (PCoA) and hierarchical cluster analysis (HCA) were used to assess variation of traits within and among districts. Various morphological features were observed among the samples which point to the existence of the Mexican, Guatemalan and West Indian avocado races in Tanzania. The biplot from PCoA revealed extensive variation between the sampled trees at the district level but no clear groupings of the samples based on geographic location. Likewise, dendrograms ensuing from the neighbor–joining and Wards methods displayed that the avocado samples from the same district and even region differed considerably. This morphological trait variation suggests high diversity that may help in planning germplasm management and conservation, as well as breeding strategies in the future.

Background: Avocado is an important cash crop in Tanzania, however its genetic diversity is not thoroughly investigated. This study was undertaken to explore the genetic diversity of avocado in the southern highlands using microsatellite markers. A total of 226 local avocado trees originating from seeds were sampled in eight districts of the Mbeya, Njombe and Songwe regions. Each district was considered as a population. The diversity at 10 microsatellite loci was investigated. Results: A total of 167 alleles were detected across the 10 loci with an average of 16.7 ± 1.3 alleles per locus. The average expected and observed heterozygosity were 0.84 ± 0.02 and 0.65 ± 0.04, respectively. All but two loci showed a significant deviation from the Hardy-Weinberg principle. Analysis of molecular variance showed that about 6% of the variation was partitioned among the eight geographic populations. Population F_ST pairwise comparisons revealed lack of genetic differentiation for the seven of 28 population pairs tested. The principal components analysis (PCA) and hierarchical cluster analysis showed a mixing of avocado trees from different districts. The model-based STRUCTURE subdivided the trees samples into four major genetic clusters. Conclusion: High diversity detected in the analysed avocado germplasm implies that this germplasm is a potentially valuable source of variable alleles that might be harnessed for genetic improvement of this crop in Tanzania. The mixing of avocado trees from different districts observed in the PCA and dendrogram points to strong gene flow among the avocado populations, which led to population admixture revealed in the STRUCTURE analysis. However, there is still significant differentiation among the tree populations from different districts that can be utilized in the avocado breeding program.

Tanzania has been growing avocado for decades. A wide variability of the avocado germplasm has been found, and the crop is largely contributing to the earnings of the farmers, traders, and the government, but its genetic diversity is scantly investigated. With the purpose of comparing morphological and genetic characteristics of this germplasm and uncovering the correlation between them and the geographical location, 226 adult seedling avocado trees were sampled in southwestern Tanzania. Their morphological characters were recorded, and their genetic diversity was evaluated based on 10 microsatellite loci. Discriminant analysis of principal components showed that the germplasm studied consisted of four genetic clusters that had an overall average gene diversity of 0.59 and 15.9% molecular variation among them. Most of the phenotypes were common in at least two clusters. The genetic clusters were also portrayed by multivariate analysis and hierarchical clustering for the molecular data but not for the morphology data. Using the Mantel test, a weak significant correlation was found between the genetic, morphological, and geographical distances, which indicates that the genetic variation present in the material is weakly reflected by the observed phenotypic variation and that both measures of variation varied slightly with the geographical sampling locations.

Avocado is a healthy fruit and the consumption is continuously growing worldwide. The fruit contains polyphenolic compounds with antioxidant effects. Globally, research has been devoted to exploring the fruit quality, especially compounds with antioxidant effects, from different avocado-growing sites. However, the fruit quality of the Tanzanian avocado has so far not been investigated. In this study, the contents of polyphenols in peel, pulp and seed of avocados sampled in south-western Tanzania are described. The levels of total polyphenolic and flavonoid contents were measured, and antioxidant activity was evaluated using a 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. The total polyphenolic content was highest in the seed and lowest in the peel (424 and 200 mg GAE/100 g DW, respectively). As for the total flavonoid content, the pulp had the highest value of 36.98 mg RE/100 g DW, while the seed had the lowest value of 32.54 mg RE/100 g DW. The overall average half maximal effective concentration (EC50) values in decreasing order, corresponding to an increasing antiradical activity, were 4.90 (peel), 3.63 (seed) and 3.24 µg/mL (pulp). The seed and peel possessed high levels of total polyphenolic and flavonoid content, thus demonstrating substantial antioxidant capacity. Seed and peel can potentially be processed and included in the diet to provide inexpensive antioxidant ingredients of natural origin. Consumption of the seed will not only improve human health but also reduce the environmental pollution, as many thousand tonnes of avocado seeds are produced in Tanzania per year; a huge amount currently remains as waste. Keywords: Flavonoid contents; Free radicals; EC50; Polyphenolic content