R.T. Wurster, J. Kori
Potatoes are grown in many parts of Uganda, the estimated area in production being 7 000 hectares (table 1). In recent years, however, imports of potatoes into Uganda have been increasing annually while yields have declined (table 2). Even at higher elevations, such as the area of Kigezi which is the major potato growing area of Western Uganda, yields can be attributed to a combination of factors, including the lack of suitable varieties, a low standard of management and pathogenic organisms. A number of diseases, including 'Bacterial Wilt' (Pseudomonas solanacearum), 'Early Blight' (Alternaria solani), 'Cercospora Leaf Spot' (Cercospora spp.) and several kinds of virus greatly reduce yields. The incidence of 'Late Blight' (Phytophthora infestans) is probably the most serious factor limiting potato production in Uganda since this disease can quickly reach epiphytotic proportions wherever potatoes are grown. 'Late Blight' was first reported in the East Rift Valley of East Africa in 1941 and the disease quickly spread over most of the potato growing areas of Kenya (Nattrass, 1944). A year later, 'Late Blight' had spread to the foothills of Mount Elgon and to Uganda.

The importation of blight-resistant lines and tests for blight resistance began in 1943, at the former Scott Laboratories in Nairobi (Cox & Large, 1960). Most of the work in Kenya has centred around Black's R-gene resistant hybrids, imported from Scotland. One of Black's seedlings, B-53, proved to be resistant to the prevalent races of Phytophthora infestans and was widely distributed in Kenya, replacing older blight-susceptible varieties such as 'Kerr's Pink', 'Dutch Robijn' and others.

The entire potato crop in Uganda is produced by subsistence cultivators and control of 'Late Blight' by spraying is therefore not feasible for most farmers. The only practical approach to increasing potato yields in Uganda appears to be through the use of high yielding blight-resistant varieties. Potato varieties which have been introduced into Uganda in the past apparently become more susceptible to the disease; this could be an indication of the extreme pathogenic variability of Phytophthora infestans. This loss of resistance emphasises the need for a survey of the pathogenic races present in Uganda so that breeders can identify the type of resistance which should be incorporated in new varieties (Gallegly, 1969).

Wurster, R.T. and Kori, J. (1971). POTATO IMPROVEMENT IN UGANDA. Acta Hortic. 21, 125-131
DOI: 10.17660/ActaHortic.1971.21.21

Acta Horticulturae