Mapping Tomato Cultivar Distribution and Production Constraints across Three Distinct Agroecological Zones in Kenya
Grace Kiruki
Agripack Seeds Company Limited, Ruiru, Kenya and Department of Plant Science and Crop Protection, University of Nairobi, P.O. Box 29053-00625, Nairobi, Kenya.
Felister Nzuve *
Department of Plant Science and Crop Protection, University of Nairobi, P.O. Box 29053-00625, Nairobi, Kenya.
John Muhia
Agripack Seeds Company Limited, Ruiru, Kenya.
*Author to whom correspondence should be addressed.
Abstract
Modern commercial tomato hybrids of Solanum lycopersicum L. display a narrowed genetic base containing only about 5% of the genetic variation found in wild relatives, leading to severe genetic erosion and extreme vulnerability to pests and diseases. In Kenya, where tomato production has been reported to reach 410,033 tonnes annually, continuous pesticide application has triggered the evolution of local pathogens, creating an urgent need to identify resilient germplasm with low chemical demands. This study investigated 168 tomato accessions collected across contrasting agroecological areas in Kajiado, Baringo, Laikipia and Kirinyaga to document variety distribution, farmer-recalled challenges, and biotic stressors. Using an open questionnaire alongside observations and fruit sampling, data were analysed through descriptive statistics, canonical variable analysis, principal component analysis and hierarchical clustering with Ward linkage. The geographic distribution of the collected samples comprised Kajiado at 41.1%, Kirinyaga/Laikipia at 32.1%, and Marigat at 26.8%. Among the reported variety categories, farmers relied heavily on two principal accessions, namely BIG ROCK (22.6%) and ANSAL (20.2%), which also had the highest numbers of reported stress incidences with 28 stress incidences each. Tuta absoluta was the most frequently reported stressor with 22 reports in the stated-pressure summary and 36 cumulative mentions in the variety-level matrix and formed a prominent column across nearly all commercial favourites. While farmers prioritised high yield (37.0%) and long shelf life (32.6%), a distinct difference in post-harvest characteristics was reported: SALA and BIG ROCK suffered from short shelf lives, whereas KILELE and STVE 8444 displayed soft fruit traits. Dendrogram-based clustering revealed that Kajiado and Kirinyaga/Laikipia share highly similar complex stress profiles, whereas Marigat stood out due to unique localized pressures such as frost, red mites and high soil salinity. This descriptive characterisation provides a crucial core collection and passport dataset, which may guide targeted crossing programmes, minimise pesticide misuse, and build climate-resilient tropical varieties.
Keywords: Solanum lycopersicum, genetic diversity, landraces, wild relatives, climate resilience