Effects of chitosan and snail shell powder on cocoa (Theobroma cacao L.) growth and resistance against black pod disease caused by Phytophthora megakarya

Abstract

Chitosan and chitin sources have emerged as promising groups of biological substances that can induce plant growth and resistance to diseases. This study is aimed at investigating the potential effect of chitosan and snail shell to promote cocoa growth and induce resistance against Phytophthora megakarya. The results showed that treatment of cocoa seeds with chitosan at 1.5 to 2.0% and snail shell at 2.0% increases the percentage of germination and also reduces the time of germination. 12 weeks after planting, a series of morphological changes was observed on the plants treated with chitosan and snail shell. Plant height (34 to 39.5 cm), leaf number (11 to 13 leaves/plant), leaf area (88 to 130 cm 2 ) and fresh weight of roots and shoots (25 to 44 g/plant) increased significantly in the chitosan and snail shell treated soils. Pods inoculated with chitosan and/or snail shell treated soil suspensions presented very slight necrotic lesions. This could be linked to a decrease in the P. megakarya load of the soil suspension. Leaf inoculation showed variation among the treatments with the lowest index (highest level of resistance) recorded in plants treated either with chitosan or snail shell. The treatment of plants with chitosan and snail shell powder before and after inoculation showed higher level of phenolic compounds than in the control plants. Furthermore, the inoculation induced a significant accumulation of proteins in the cocoa plants treated with chitosan and snail shell. The level of proteins accumulation after inoculation was higher in plants treated with snail shell than those treated with chitosan. In conclusion, the effect of snail shell on cocoa growth and resistance showed that it is possible for snail shell powder to be a biofungicide and biofertilizer used in the control of cacao Black Pod Disease in nurseries.

Potential Biostimulant Effect of Clam Shells on Growth Promotion of Plantain PIF Seedlings (<i>var</i>. Big Ebanga & Batard) and Relation to Black Sigatoka Disease Susceptibility

“…It was hypothesized that clam shells treatment could biostimulate the growth of plantain PIF seedlings and their susceptibility to black Sigatoka disease. Our data confirmed this hypothesis and provided evidence for wide variations in the germination rate, in the growth characteristics (number of shoots, height of shoots, diameter of pseudo-stems, area of leaves, length of roots), in the susceptibility to BSD, and in the accumulation of total proteins and polyphenols before and after inoculation for the treated plantain PIF seedlings as previously shown on different plants treated with shells in nursery and/or in the field [8] [9] [19] [20].…”

“…Such effects of shells or chitin-source treatments on growth promotion and/or host resistance have also been reported for other pathosystems such as cocoa/snail shells/Phytophthora megakarya [9], tobacco/nanochitin/Fusarium spp. [21], chilli/chitosan/Colletotrichum capsica [22], millet/chitosan derivatives/Pyricola grisea [23], tomato/crab shells/Fusarium oxysporum [24] and cocoa/oyster shells/P.…”

“…So far, the potential impact of clam shells in agriculture as biofertilizer and/or as biocontrol agent has received limited attention. However, a recent study carried out in Cameroon has demonstrated that snail shell powder has a strong influence on cocoa growth and resistance in nurseries by acting as a biofertilizer and as a biofungicide in the control of cocoa black pod disease [9]. Moreover, the clam shells are abundant waste products regularly found along the coasts of rivers that become pollutants for the environment when accumulated for a long time.…”

Enhancement of <i>Theobroma cacao</i> Seedling Growth and Tolerance to <i>Phytophthora megakarya</i> by Heat-Treated Oyster Shell Powder

“…For the determination of total native protein content, extraction was performed as described by [22]. One g of fresh tissue of inoculated and healthy leaves was ground separately in 10 ml of extraction buffer (Tris-HCl 10 mM pH 7.5, Triton X-100 1%) at 4˚C, stirred for 10 min and kept on ice.…”

“…The evaluation of the suppressive effect of heat-treated and non-treated oyster shell powder in the soil P. megakarya load after 12 weeks was done by infecting healthy cocoa pods with some suspension of the soil as described by [22] with modification. 3-month-old healthy pods (SNK10, susceptible clone) were harvested, washed with tap water, sterilized with 70% ethanol (for 1 min), 10% (v/v) commercial sodium hypochlorite (for 5 min) and rinsed 3 times with sterilized distilled water.…”