Capture of genetic variation by vegetative propagation: processes determining success
Vegetative propagation offers the opportunity to rapidly overcome the limitations to domestication imposed by long generation times, irregular fruiting/flowering and outbreeding. Vegetative propagation techniques are increasingly being applied to a wide range of tree species, of both moist and dry tropics. Identification of the critical factors determining adventitious root development is crucial to sustained, cost-effective propagation, even in 'species in which these factors are not currently limiting.
Over the past ten years, research at ITE has identified a wide range of factors which influence rooting, including the stockplant growth environment, cutting origin, post-severance treatments applied to cuttings, and the propagation environment. In order to understand the influence of these different factors and their interactions, an appreciation of the physiological, biochemical and cytological processes involved in rooting is required. The primary processes occurring in the leaf are net photosynthesis and transpiration, while those in the stem are starch hydrolysis, translocation of sugars, water and nutrients, respiration, mitosis and cell differentiation. Each of these processes is influenced by a number of environmental, morphological and physiological variables, such as leaf area and thickness, internode length, chlorophyll content, stomatal density stem Uglification, etc.
Suggestions are made for experimental approaches to improve further the understanding of the mechanisms of rooting of leafy stem cuttings. These approaches include the development of a mechanistic model of adventitious root development. The practical implications arising from a process-based approach to propagation are also discussed.
In: Tropical trees: the potential for domestication and the rebuilding of forest resources. Leakey, R.R.B. and Newton, A.C. (Eds.). pp. 72-83. HMSO, London, UK.