Response of the molluscicidal berry plant (Phytolacca dodecandra) to different climatic and edaphic conditions
Keywords:Phytolacca dodecandra, Molluscicide, Berry, Ecotypes, Molluscicidal potency, Saponin content, Yield
AbstractClonal material from an imported Ethiopian cultivar (E44) and a local Zimbabwean cultivar (MS1) of the molluscicidal berry plant, Phytolacca dodecandra, was planted in eight ecological zones of Zimbabwe to assess the influence of different climatic and edaphic conditions on plant growth performance, berry yield, saponin content, and the molluscicidal potency of water ex-tracts of the berries. The locations were at altitudes ranging from 429 m to 1650 m above sea level and were chosen to represent the major ecological regions where the plant molluscicide would be required. The highest berry yield of 1057 g per plant was obtained from the Ethiopian cultivar cultivated at an altitude of 1650 m while the highest berry yield from the Zimbabwean cultivar was 683 g per plant at an altitude of 1100 m. Saponin content and molluscidical potency of berry extracts from the Ethiopian plants cultivated at all localities were higher than the Zimbabwean cultivar (P < 0.01). This indicated the greater ecological adaptability of the Ethiopian variety for use in schistosomiasis control programmes. The addition of cattle manure at planting reduced the nutrient differences in inherent soil chemical properties on berry saponin content and molluscicidal potency. Regular irrigation during the study period prevented the previously demonstrated water stress related increase in saponin content and po-tency of the berries from low rainfall areas. Saponin yield was highest (212 g per plant) in the Ethiopian cultivar at high altitudes. In lowland areas, however, this was highest for the Zimbabwean cultivar, notwithstanding the good growth of the Ethiopian cultivar.