Busitema University celebrates a landmark achievement as Dr. Carol Kawuma, Lecturer in the Faculty of Science and Education, earns her Doctor of Philosophy (PhD) in Botany from Makerere University. Her groundbreaking research on indigenous Solanum species strengthens Uganda’s scientific capacity in plant taxonomy, biodiversity conservation, and agricultural innovation.

Dr. Kawuma’s study, focused on clarifying the taxonomy, diversity, and distribution of species within this group. The Leptostemonum clade is the most species-rich subgroup within the genus Solanum, containing approximately 550 species worldwide. In Uganda, the clade is particularly significant because many of the country’s indigenous vegetables belong to this group. These plants play an important role in nutrition, agriculture, and livelihoods, while their wild relatives possess traits that could help improve cultivated crops, particularly in resistance to diseases, drought, and pests.

The study was guided by three main objectives: to assess the diversity and distribution of Leptostemonum species in Uganda, to establish their evolutionary relationships using molecular data, and to analyse the morphological variations within Solanum campylacanthum and its relationship with Solanum cerasiferum.

To achieve these objectives, extensive field surveys were conducted across different regions of Uganda. During these surveys, plant specimens were collected and their geographic locations recorded using handheld GPS devices. For molecular analysis, young leaves from each plant specimen were carefully dried in silica gel and preserved for later DNA extraction. Voucher specimens were also pressed, dried, and identified at the Makerere University Herbarium (MHU). In addition to field data, the study incorporated specimen records from the Global Biodiversity Information Facility (GBIF) and herbarium collections at Makerere University to enrich the dataset.

In total, 186 plant samples were collected during fieldwork, enabling the researcher to conduct a detailed analysis of species diversity and distribution. Geographic distribution maps were generated using ArcMap software, while ecological modelling was conducted using MaxEnt software to determine environmental factors influencing the distribution of the species.

The molecular component of the study involved DNA extraction using the EZNA Plant Mini Kit, followed by DNA amplification targeting two gene regions, trnL-trnF and Waxy. Sequence editing and analysis were conducted using Geneious Prime, while evolutionary relationships among species were reconstructed using Bayesian inference and Maximum Likelihood methods implemented in the software MrBayes and IQ-Tree.

Dr. Kawuma also conducted morphological studies focusing on Solanum campylacanthum and its relationship with Solanum cerasiferum. Using phenetic analysis, the research examined variations in plant characteristics such as leaf structure and prickle density. Statistical analyses, including dendrograms and box plots, were generated using PAST software to visualise patterns of variation among the species.

The findings of the study provide new insights into the diversity of Leptostemonum species in Uganda. A total of 18 species within the clade were recorded, with Southwestern Uganda and the Karamoja region identified as areas with particularly high species richness. Importantly, the research documented Solanum chrysotrichum as a new record for Uganda, while also confirming the presence of Solanum forskali, which had previously been uncertain.

Environmental analysis further revealed that temperature and rainfall are key factors influencing the distribution of Solanum species in the country. These findings highlight the importance of ecological conditions in shaping plant diversity and may help guide conservation strategies and agricultural planning.

The molecular phylogenetic analysis strongly supported the monophyly of the Leptostemonum clade, confirming that the species studied share a common evolutionary lineage. Ugandan species were found to align with five major clades already recognised globally: Aculeastrum, Eggplant, Coagulans, Giganteum, and the New World clade. This alignment strengthens the scientific understanding of how local species fit within the broader evolutionary framework of the Solanum genus.

The morphological analysis also yielded important findings. Within Solanum campylacanthum, the study identified three distinct morphological clusters:

1. Unarmed Solanum campylacanthum

2. Sparsely armed Solanum campylacanthum

3. Moderately to densely armed Solanum campylacanthum

In addition, a separate morphological group corresponding to Solanum cerasiferum was identified. The research further revealed that prickle density and leaf tip angles can serve as reliable morphological characteristics for distinguishing variations within Solanum campylacanthum. This is the first time these traits have been reported as useful characters for intraspecific classification within the species.

Dr. Kawuma’s research contributes significantly to the taxonomy, conservation, and utilisation of indigenous plant species in Uganda. By clarifying species relationships and distribution patterns, the study provides valuable information that can support plant conservation, biodiversity research, and crop improvement programmes. The identification of wild relatives of cultivated crops is particularly important for future agricultural innovation, as these plants may contain genetic traits that help crops adapt to climate change and emerging agricultural challenges.

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