Heat and drought stress and their implications on potato production under dry African tropics

Abstract

The two most important abiotic factors affecting potato productivity in many areas of the world and especially in the dry African tropics are drought and high temperature. The situation is worsened by global warming. High temperature and drought reduce not only yields but also quality of potatoes. The effects of drought depend on the genotype, timing, duration and severity of the stress; plant emergence and tuberization are two critical periods when water stress most affects the final tuber yield. The susceptibility of potato crops to high temperature largely depends on genotype, development stage and stress duration; tuber initiation and bulking are critical stages. High temperature, particularly high night temperature, is reported to delay tuber induction, prolong tuber setting, and delay the onset of rapid tuber growth. The optimum soil temperature range for tuber initiation and tuber growth is 15–20 0C, and the colder the soil temperature, the more rapid the initiation of tubers and the greater the number of tubers formed. At high temperature more photoassimilates are partitioned to the vegetative parts than tubers resulting in acceleration of haulm growth and inhibition of tuber initiation and growth. In tropical Africa, potato production is moving to the dry mid and low altitudes due to high population pressure in the moist highlands. In these dry areas, potato production is facing the double tragedy of high temperature and water stress. This has led to low yields and poor quality since there is no available commercial potato variety which is tolerant to high temperature and water stress. Breeding for heat and drought tolerance in potatoes is hard because in most cases, especially in dry tropics, these two conditions occur concurrently. In addition, the two traits are polygenic with low inheritance making conventional breeding difficult; more progress could be achieved through molecular breeding and/or genetic engineering.