Investigation into fungal seedborne pathogens of farmer-saved seed maize (Zea mays L.) collected from three ecological zones of Ghana and efficacy of plant extracts in controlling the pathogens

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Seedborne fungal pathogenic infections of maize (Zea mays L.) were studied using fifty-four (54) seed samples, collected from locations in the Forest, Transitional and Guinea Savannah ecological zones in Ghana. The deep-freeze blotter method was used to detect fungal pathogens on the seed maize. Four pathogens identified were Acremonium strictum (infection ranging from 0.5 to 22%), Bipolaris maydis (0.5 to 1.5%), Botryodiplodia theobromae (1 to 19%) and Fusarium moniliforme (5 to 84.5%). Aqueous extracts of Cymbopogon citratus (lemongrass), Chromolaena odorata (siam weed) leaf and Azadirachta indica (neem) seeds were tested for their inhibitory activity against seedborne fungal pathogens in the infected seed maize, using 50% (w/v) concentrations for 1, 3, 6 and 24 hours each. Neem seed extract exhibited the best control, reducing infection of F. moniliforme from 68 to 18% with the 24 hours of treatment and eliminating Acremonium strictum at 1 and 24 hours of treatment. Botryodiplodia theobromae infection was eliminated at all the soaking periods. Neem had no effect on germination but reduced vigour slightly. Chromolaena odorata leaf extract also exhibited control on F. moniliforme reducing infection from 68 to 36.5% at 24 hours of treatment but had no significant effect on germination and vigour of seeds. Lemongrass extract did not have significant control effect on F. moniliforme but increased germination and vigour of seeds. There is therefore a potential of using neem seed extract as seed maize disinfectant against F. moniliforme, Acremonium strictum and Botryodiplodia theobromae.  
A thesis submitted to the Board of Postgraduate Studies, Kwame Nkrumah University of Science and Technology, Kumasi, in partial fulfilment of the requirements for the award of the Degree of Master of Science in Seed Science and Technology