African Journal of
Plant Science

  • Abbreviation: Afr. J. Plant Sci.
  • Language: English
  • ISSN: 1996-0824
  • DOI: 10.5897/AJPS
  • Start Year: 2007
  • Published Articles: 631

Full Length Research Paper

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

Paul Martial Téné Tayo
  • Paul Martial Téné Tayo
  • Department of Biochemistry, University of Yaoundé 1, PO Box 812 Ngoa Ekelle, Cameroon.
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Cécile Annie Ewane
  • Cécile Annie Ewane
  • Department of Biochemistry, University of Yaoundé 1, PO Box 812 Ngoa Ekelle, Cameroon.
  • Google Scholar
Pierre Onomo Effa
  • Pierre Onomo Effa
  • Department of Biochemistry, University of Yaoundé 1, PO Box 812 Ngoa Ekelle, Cameroon.
  • Google Scholar
Thaddée Boudjeko
  • Thaddée Boudjeko
  • Department of Biochemistry, University of Yaoundé 1, PO Box 812 Ngoa Ekelle, Cameroon.
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  •  Accepted: 22 January 2017
  •  Published: 31 August 2017

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 cm2) 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.

Key words: Theobroma cacao, Phytophthora megakarya, black pod disease, chitosan, snail shell, biocontrol agents.