The effects of pH and growing medium type on the susceptibility of Moringa oleifera to fungal diseases during seedling emergence

Moringa oleifera seed germinates poorly and most seedlings die during early establishment. To solve this problem, the effects of pH and growing medium type on the susceptibility of M. oleifera to fungal diseases during seed emergence and early seedling establishment were evaluated in a 3 x 6 factorial experiment arranged as a randomized complete block design with three replications in a greenhouse experiment. Six growing medium types (sandy soil, clay soil, pine bark, clay + sandy soil, clay + pine bark and sand + pine bark) were evaluated at pH 6.2, 8.2 and in situ pH for each growing medium type. The control was the sterilised media of in situ pH. Seed viability tests showed 90% viability. Analysis of the seed showed the presence of Fusarium spp., Pythium spp., Dreschlera spp., Rhizopus spp. and Chactomium spp. Thus, seed was sterilised prior to planting to eliminate any pathogen from the surface of the seed. Media and pH were found to have a significant effect on the emergence of seeds. In situ, sterilised pine bark and clay gave the highest emergence. After emergence, no seedlings showed any infection indicating that reported seedling deaths could be a result of seed borne diseases. Observations indicated Fusarium spp. infection in the seed that had failed to germinate, whilst those in the sterilised media showed no evidence of fungal attack. This means media used for Moringa ought to be sterilised with hypochlorite or another material or procedure to ensure good seed emergence.