Journal of Applied Biosciences (J. Appl. Biosci.) [ISSN 1997 - 5902]
Volume 17: 913 - 921. Published May 8, 2009.
Evaluation of cacao (Theobroma cacao L.) clones for resistance to root-knot nematode Meloidogyne incognita(Kofoid & White) Chitwood
Okeniyi, M. O.^*, Afolami, S. O**, Fademi, A. O.* and Aikpokpodion, P.**
*Plant Pathology Section, Cocoa Research Institute of Nigeria, P. M. B. 5244,Ibadan.
**Department of Crop Protection, University of Agriculture, P. M. B. 2240, Abeokuta.
*Corresponding author e-mail: michael_okeniyi@yahoo.co.uk
ABSTRACT
Objective: To evaluate cacao clones for reaction to Meloidogyne incognita, the most common root-knot nematode species in Nigeria.
Methodology and results: Experiments were carried out in the screen house and in nursery, laid out in a completely randomized design with four replicates. The two factors were M. incognita inoculum at two levels (0 and 5000 eggs per seedling) and the twelve cocoa clones (MXC67, T86/2, PA150, LCTEEN, T12/11, T53/5, T101/15, T65/7, ICS1 and AMAZ 15-15). Effect of nematode on plant height, number of leaves, stem girth, fresh root weight, fresh shoot weight, fresh leaf weight and total dry matter were considered. Based on gall index, nematode reproduction factor and growth parameters, it was concluded that clones MXC67, T86/2, PA150, T101/15 and T53/5 were susceptible to the nematode while clones T65/7 and ICS1 were tolerant. A high degree of resistance was exhibited by LCTEEN, T12/11 and AMAZ 15-15. Compared to F3 Amazon and Amelonado varieties, the two most famous cocoa varieties in Nigeria, four clones (LCTEEN, T65/7, ICSI and AMAZ 15-15) were superior to the check (F3 Amazon and Amelonado).
Conclusion and application of findings: This study showed that among clones that had been previously screened and certified as being resistant to black pod disease caused by Phytophthora megakarya, only three are resistant to root-knot nematode and only two are tolerant (are able to tolerate nematode reproduction). Breeding for disease resistance in cocoa can therefore no longer neglect the effect of nematodes, particularly the root-knot group.
Key words: Cocoa, Meloidogyne incognita, nematode, resistance
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