Morphological and Genetic Characterization of Jackfruit (Artocarpus heterophyllus) in Kayunga and Luwero districts of Uganda

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Abstract Background Jackfruit (Artocarpus heterophyllus), is an economically valuable fruit tree. Despite its potential, the production of jackfruit in Uganda is currently low, and may face further reduction due to deforestation. As a result, genetic erosion of the tree resource is predicted, before its documentation and exploitation for possible crop improvement and sustainable conservation. As a prerequisite for crop improvement and conservation, 100 A. heterophyllus tree isolates from Kayunga and Luwero districts in Uganda were characterized using 16 morphological and 10 microsatellite markers. Results The results from the morphological analysis showed variation in the tree height, diameter at breast height (DBH), and crown diameter traits, with coefficients of variation (CV) values of 20%, 41%, and 33% respectively. Except for taste, various forms of the 13 assessed qualitative traits were observed. Genotyping showed that the number of alleles amplified per microsatellite locus ranged from 2 to 5, with an average of 2.90, and totalling to 29. The mean observed (Ho) and expected (He) heterozygosity were 0.71 and 0.57 respectively. Analysis of molecular variance (AMOVA) indicated that 81% of the variation occurred within individual trees, 19% among trees within populations and 0% between the two populations. The gene flow (Nm) in the two populations was 88.72. The results from further analysis using ‘Partitioning Around Medoids’ (PAM), Principal Coordinate Analysis (PCoA) and genetic cluster analysis further revealed no differentiation of the A. heterophyllus populations. In addition, the Mantel test revealed no significant correlation between the genetic and geographic distances, and the morphological and geographic distances, and a negligible correlation between the morphological and genetic distances. Discussion Diversity was observed in the assessed A. heterophyllus because the crop is crossly pollinated. However, there was no differentiation of the jackfruit populations probably because of continuous gene flow in the adjacently located districts. Morphological resemblance did not imply genetic similarity probably because morphology is influenced by the environment. Conclusions Both morphological and genetic analyses revealed variation of jackfruit within a single interbreeding population. The observed diversity can be exploited to establish breeding and conservation strategies to increase production of jackfruit. However, selecting germplasm depending on morphological assessment alone may be misleading.

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