Diversity, Distribution and Propagation Methods for Cacti Species (Cactaceae) from Arid and Semi-Arid Lands of Kenya

Abstract

Cactaceae is an important family of plants of Arid and Semi-Arid Lands (ASALs) in the world. It is useful as an ornamental plant (Cereus peruvianus and Thrixanthocereus blossfeldiorum), food, fodder and industrial purposes (Opuntia spp). There is minimal documentation about Cacti growing in the ASALs of Kenya. The objective was to enhance understanding and utilization of Cacti in Kenya through determination of distribution, diversity and propagation methods. A field survey of the ASAL areas was carried out and samples taken for molecular analysis and propagule evaluation. There were at least three different species of Cacti in Baringo, Laikipia, Machakos and Makueni Counties as opposed to Nakuru County that had two species (Opuntia ficus-indica and Opuntia exaltata). Majority of Cacti in the studied counties were either grown as fencing material (Thrixanthocereus blossfeldiorum, Opuntia stricta, Opuntia monacantha, Opuntia exaltata, Opuntia ficus-indica) in farms or as ornamentals (Thrixanthocereus blossfeldiorum, Cereus peruvianus) while some grew intermittently in uncultivated lands (Euphorbia ingens, Euphorbia abyssinica) . Sixty nine distinct populations of Cacti were characterized in-situ using a list of descriptors by the International Union for the Protection of New Varieties of Plants (UPOV). Results indicated that eight species namely, Opuntia exaltata, Opuntia monacantha, Opuntia ficus-indica, Opuntia stricta, Thrixanthocereus blossfeldiorum, Euphorbia abyssinica, Euphorbia ingens and Cereus peruvianus were present in Kenya. Opuntia ficus-indica xvi was the most diverse and was found in four of the five counties studied. Euphorbia abyssinica was found in four counties while Opuntia stricta and Thrixanthocereus blossfeldiorum were found in a single county each. The results indicated that vegetative propagation through cladodes; immature fruits and stem cuttings of Cacti are effective planting material and this can be enhanced by curing of the propagules for more than seven days. The results indicated significant variations among Cacti species in Kenya. The eleven simple sequence repeat (SSR) markers used were not polymorphic and did not sufficiently distinguish the Opuntia species investigated. The low genetic distances for some of the populations between counties call for further investigation and confirmation. Further research is needed through molecular characterization using more informative markers. This should be carried out to cover other parts of the country so as to identify other species available in these areas, their mode of distribution and their productivity to influence the choice species for utilization.