Nyadanu D.,College of Agriculture Science and Education |
Nyadanu D.,Kwame Nkrumah University Of Science And Technology |
Nyadanu D.,Cmoa Research Institute of Ghana |
Akromah R.,Kwame Nkrumah University Of Science And Technology |
And 8 more authors.
American Journal of Biochemistry and Molecular Biology | Year: 2013
Black pod disease caused by Phytophthora palmivora and Phytophthora megakarya is an important disease of cocoa and host plant resistance is one of the important components of management of this disease. Therefore, a diverse array of 12 cocoa genotypes was evaluated to identify biochemical characteristics conferring resistance to black pod disease. Resistance to black pod disease measured as leaf disc scores, pod lesion numbers, pod lesion sizes and natural field infection was associated with amounts of nitrogen, protein, soluble sugars, insoluble sugars, total polyphenols, flavonoids, tannins and lignin in leaf and pod of cocoa. The levels of these biochemical compounds in leaf and pod increased after inoculation with P. megakarya. Principal component analysis shows that 90% of the total variability in the eight original biochemical variables is captured in the first two principal components and 95% in the first three principal components. The first two principal components were defined by healthy pod lignin and healthy pod insoluble sugar and principal component three was mainly defined by healthy leaf protein. Phytochemical characterization of the 12 cocoa genotypes by cluster analysis revealed two major clusters. Cluster one consisted of Imc67, Na33, T79/501, T63/971, Imc53 and Sca9 which were susceptible to black pod and cluster two was made up of Pa150, T60/887, Sca6, Imc76, Pa7/808 and T85/799 which were resistant. Correlation coefficients, multiple and step-wise regressions indicated that insoluble sugar, flavonoid, tannins and lignin were the most reliable biochemical factors and these could be used as marker traits to screen and select for resistance to black pod disease of cocoa. © 2013 Academic Journals Inc.