Production, local trade and diversity of avocado (Persea americana Mill.) in the southern highlands of Tanzania
Abstract: Avocado (Persea americana Mill) has a long cultivation history in Tanzania and adds to the country’s revenue through trading within (local and commercial avocado cultivars) and outside (commercial cultivars) the country. Research has been, however, scanty to characterize the country’s avocado production, local trading and diversity. In order to contribute to this research area, the present study was conducted in eight districts of Tanzania’s southern highlands. For the purpose of describing aspects of avocado production and trading throughout the value chain, 275 avocado growers, 231 traders and 16 key informers were interviewed. As for the diversity study, 226 seed-originated avocado trees were sampled in the eight districts and 14 morphological and 10 simple sequence repeat (SSR) loci genetic characters were evaluated. The analyses of the data generated through the interviews showed that the average avocado yield per district varied from 52 to 156 kg/plant. Approximately, 28 and 79% of the growers and the traders were content with the earnings from the avocado trading. The majority of the growers and traders mentioned some challenges affecting the value chain including limited extension services, drought, pathogens and pests, poor marketing environment, and the short shelf life of the fruits. Resolving these issues is the key towards the improvement of the earnings and living standards of avocado farmers and traders, which is also applicable to many other crops sharing similar challenges. The sampled trees showed great variation in the investigated morphological features. These included 11, 21 and 17 different shapes of the leaf, mature fruit and seed, respectively. As for the genetic characteristics, an average of 16.7 ± 1.3 alleles per locus, 0.65 ± 0.04 and 0.84 ± 0.02 observed and expected heterozygosity, respectively, and a Shannon’s information index of 2.17 ± 0.10 were obtained. These results imply a high genetic diversity of the trees investigated. Most of the observed morphological and genetic characters were not unique for a particular area as revealed by the district/region-free clustering of the trees in the principal coordinates and components analyses or by dendrograms. Introduction of highly similar (overlapping) germplasm to more than one districts and cross-transfer of seeds (propagules) among the districts/regions could be the reason for this distribution.
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