Morphological and genetic characterization of jackfruit (Artocarpus heterophyllus) in the Kayunga and Luwero districts of Uganda.

BACKGROUND: Jackfruit (Artocarpus heterophyllus) is an economically valuable fruit tree in Uganda. However, the production of jackfruit in Uganda is low. Additionally, because of deforestation, genetic erosion of the resource is predicted before its exploitation for crop improvement and conservation. As a prerequisite for crop improvement and conservation, 100 A. heterophyllus tree isolates from the Kayunga and Luwero districts in Uganda were characterized using 16 morphological and 10 microsatellite markers. RESULTS: The results from the morphological analysis revealed variations in tree height, diameter at breast height (DBH), and crown diameter, with coefficient of variation (CV) values of 20%, 41%, and 33%, respectively. Apart from the pulp taste, variation was also observed in qualitative traits, including tree vigor, trunk surface, branching density, tree growth habit, crown shape, leaf blade shape, fruit shape, fruit surface, flake shape, flake color, flake flavor and pulp consistency/texture. Genotyping revealed that the number of alleles amplified per microsatellite locus ranged from 2 to 5, with an average of 2.90 and a total of 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 the 'partitioning around medoids' (PAM), principal coordinate analysis (PCoA) and genetic cluster analysis further revealed no differentiation of the jackfruit populations. The Mantel test revealed a negligible correlation between the morphological and genetic distances. CONCLUSIONS: Both morphological and genetic analyses revealed variation in jackfruit within a single interbreeding population. This diversity can be exploited to establish breeding and conservation strategies to increase the production of jackfruit and hence boost farmers' incomes. However, selecting germplasm based on morphology alone may be misleading.

Roles of Arbuscular Mycorrhizal Fungi on Soil Fertility: Contribution in the Improvement of Physical, Chemical, and Biological Properties of the Soil.

Many of the world's soils are experiencing degradation at an alarming rate. Climate change and some agricultural management practices, such as tillage and excessive use of chemicals, have all contributed to the degradation of soil fertility. Arbuscular Mycorrhizal Fungi (AMFs) contribute to the improvement of soil fertility. Here, a short review focusing on the role of AMF in improving soil fertility is presented. The aim of this review was to explore the role of AMF in improving the chemical, physical, and biological properties of the soil. We highlight some beneficial effects of AMF on soil carbon sequestration, nutrient contents, microbial activities, and soil structure. AMF has a positive impact on the soil by producing organic acids and glomalin, which protect from soil erosion, chelate heavy metals, improve carbon sequestration, and stabilize soil macro-aggregation. AMF also recruits bacteria that produce alkaline phosphatase, a mineralization soil enzyme associated with organic phosphorus availability. Moreover, AMFs influence the composition, diversity, and activity of microbial communities in the soil through mechanisms of antagonism or cooperation. All of these AMF activities contribute to improve soil fertility. Knowledge gaps are identified and discussed in the context of future research in this review. This will help us better understand AMF, stimulate further research, and help in sustaining the soil fertility.

Local varieties of cassava: conservation, cultivation and use in Uganda.

The study explored the theory that on-farm conservation of cassava germplasm is influenced by farmers' traditional and cultural preferences of particular varieties. Traditional knowledge practices that are used for on-farm conservation of cassava germplasm as well as cassava attributes for selection were assessed. The findings obtained from the study indicated that farmers use traditional knowledge to select and preserve cassava germplasm for future use. It was also clear that farmers have their preferences such as culinary attributes, storability in the ground, early maturity and cooking quality to mention but a few that influence the decisions taken to retain or abandon cultivation of varieties. Therefore, by planting varieties in multiples plots, replanting immediately after harvesting, sharing with others in the community and planting disease-free materials, farmers ensure that they preserve varieties of interest for decades. The information generated during this study could inform development policies tailored toward ensuring sustainable on-farm conservation of cassava genetic resources.

Celoporthe dispersa gen. et sp. nov. from native Myrtales in South Africa.

In a survey for Cryphonectria and Chrysoporthe species on Myrtales in South Africa, a fungus resembling the stem canker pathogen Chrysoporthe austroafricana was collected from native Syzygium cordatum near Tzaneen (Limpopo Province), Heteropyxis canescens near Lydenburg (Mpumalanga Province) and exotic Tibouchina granulosa in Durban (KwaZulu-Natal Province). The fungus was associated with dying branches and stems on S. cordatum, H.canescens and T.granulosa. However, morphological differences were detected between the unknown fungus from these three hosts and known species of Chrysoporthe. The aim of this study was to characterise the fungus using DNA sequence comparisons and morphological features. Pathogenicity tests were also conducted to assess its virulence on Eucalyptus (ZG 14 clones), H.natalensis and T. granulosa. Plants of H. canescens were not available for inoculation. Results showed distinct morphological differences between the unknown fungus and Chrysoporthe spp. Phylogenetic analysis showed that isolates reside in a clade separate from Chrysoporthe and other related genera. Celoporthe dispersa gen. et sp. nov. is, therefore, described to accommodate this fungus. Pathogenicity tests showed that C.dispersa is not pathogenic to H. natalensis, but that it is a potential pathogen of Eucalyptus and Tibouchina spp.