Abstract
The aim of this study was to evaluate the ability of oyster shell powder soil amendment to enhance cocoa seedling growth and induce resistance against Phytophthora megakarya in nurseries. The results showed that heat-treated oyster shells powder at 1% (w/w) soil amendment significantly increased plant height, leaf number, leaf area, dry shoot and root weight more than chemical fungicide and control treatment after twelve weeks of growth. The results showed that heat-treated oyster shell powder raised soil pH significantly and reduced P. megakarya load of the soil suspension by 82%. Assessment of resistance stimulation by leaf inoculation showed the highest level of resistance recorded in plants treated either with heat-treated or non-treated oyster shell powder. Furthermore, total phenolic compounds contents, total soluble proteins contents, polyphenoloxidase, chitinase, peroxidase and β-1,3-glucanases activities increased in both healthy or infected leaves from cacao plants treated with oyster shell powder more than those treated with chemical fungicide. These findings demonstrated that heat-treated oyster shell powder could be used as biofertilizer and biofungicide to improve the quality of cocoa seedling production and protect the plant against P. megakarya.
Highlights
Cacao (Theobroma cacao L.), is an important economic crop in numerous developing countries
These findings demonstrated that heat-treated oyster shell powder could be used as biofertilizer and biofungicide to improve the quality of cocoa seedling production and protect the plant against P. megakarya
Many Phytophthora species such as P. megakarya have a soil-borne phase in their natural life cycles even though disease expression often occurs on aerial plant parts such as cocoa seedling black pod disease [3]
Summary
Cacao (Theobroma cacao L.), is an important economic crop in numerous developing countries. In Cameroon Black Pod Disease (BPD) is caused by P. megakarya [2]. Many Phytophthora species such as P. megakarya have a soil-borne phase in their natural life cycles even though disease expression often occurs on aerial plant parts such as cocoa seedling black pod disease [3]. Cocoa seedling production is a key step in the establishment of new cocoa plantations and generally requires forest soil as the production substrate. This soil used to produce the cocoa seedling is usually taken from areas already contaminated by P. megakarya [4]. Biological control of soil, possible vector of fungal pathogens, is poorly investigated [5]
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