ISHS Acta Horticulturae 218: XII African Symposium on Horticultural Crops
POTATO CLONES IN EAST AFRICA RESISTANT TO BACTERIAL WILT CAUSED BY PSEUDOMONAS SOLANACEARUM |
| Authors: | A.H. Ramos, A.O. Michieka |
| Abstract:
Planting of 52 potato clones in 1983, some with parents resistant to bacterial wilt, in a field containing only residual soil inoculum of Pseudomonas solanacearum race 3 from Kenya, resulted in a wilting incidence of 14%, with the wilted plants randomly distributed according to a Poisson series, thus excluding the existence of immunity, symptomless infection and disease escape mechanisms. This method did not detect tolerance to infection. The latter was assessed using speed of wilting by measuring the number of wilting plants. The procedure required uniformity of soil inoculum which was simulated by pouring aqueous bacterial suspension containing 108 viable cells/ml over roots without damaging them. Wilting was increased from 14% to 70%. however, the speed of wilting of individual plants fluctuated greatly. Nevertheless, reproducible results were obtained. Pot and field experiments done at N.A.L. and a field experiment done at Embu, 100 km from N.A.L. in 1983/84 and 1985 clearly showed that clones 720118, 800212, 800223 and 800224 were the most tolerant. These clones are products of crosses between S. phureja parents (resistant to bacterial wilt) and 720054 'Atzimba' (a susceptible parent). Environment influenced speed of wilting significantly, but environment-clone interaction was significant in the pot but not in the field experiments. Implications of the various results are discussed. | |
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