10th U6+ Consortium of African Universities International Conference

Guizotia abyssinica (L.f.) Cass. and Guizotia scabra (Vis.) Chiov. are common stubborn broadleaf weeds in maize-growing fields of Uasin Gishu County, Kenya. However, information on their morphological variation across agro-ecological zones and their distribution is limited. This study evaluated the morphological characteristics and distribution of Guizotia populations to support species identification and weed management. Field surveys were conducted across the upper highland, upper midland, and lower highland agro-ecological zones using a roadside sampling approach. Mature plants were collected, georeferenced using a Global Positioning System (GPS), and identified using established taxonomic keys. Plant height, number of branches, leaves, and flowers were recorded, and data analyzed using one-way analysis of variance (ANOVA), Kruskal–Wallis, and Mann–Whitney U tests at a 5% significance level. The results showed significant morphological variation in G. abyssinica among sampling sites. Plant height differed significantly (F0.05 (9,90) = 3.48, p = 0.001), with the tallest plants recorded at Chirchir Farm (3.49 ± 5.15 m) and Kerita Lessos Farm (3.05±0.16 m), and the shortest at Matharu Scheme (0.54 ± 0.14 m) and Kap Francis (0.61±0.06 m). Significant differences were also observed in the number of branches, leaves, and flowers (p < 0.001), with plants from Juakali and Kerita Lessos Farm exhibiting greater vegetative growth and reproductive capacity. In contrast, G. scabra was found only at Kahuho and Kap Francis, where plant height (F0.05 (1,15) = 18.58, p = 0.001) and leaf number (Mann–Whitney U = 10.5, p = 0.014) differed significantly, while branch and flower numbers did not. The findings indicate substantial morphological variation in G. abyssinica and a restricted distribution with lower variability in G. scabra. This information provides a useful baseline for distinguishing Guizotia ecotypes, improving species identification and understanding the distribution of these economically important weedy species for purposes of better management.