Biochemical studies of resistance levels of cocoa varieties at cocoa research institute of Ghana, Tafo-Akim to cocoa swollen shoot virus

Abstract

Biochemical studies were carried out on ten cocoa types to find out their different levels of resistance to Cocoa Swollen Shoot Virus. The beans were inoculated via viruliferous nymphs of mealy bugs, and observed after planting for 3 months. Patches of barks of severe symptom bearing cocoa types were also tested through grafting on healthy Amelonado plants and observed for 3 months. Significant differences were observed in the cocoa types in terms of symptoms appearance and in severity. PAI50 X NA33, T63/967 X T65/326 and T85/199 X PA7 were observed to be the best resistant to the CSSVD whilst T85/799 X T65/238, Amelonado X Amelonado, T85/799 X Amelonado, T85/799 XT65/326, and T85/799 X T79/50I were observed to be poor in resistance. In the investigations, there was weak correlation (0.333) between total polyphenol content and susceptibility of cocoa types to the CSSV, whereas a significant correlation (-0.58) existed between total nitrogen content and susceptibility to the Cocoa Swollen Shoot Virus. PAI50 X NA33 had the highest nitrogen content, and statistically different. There were no differences between T85/799 X Amelonado, T63/967 XIMC60 and Amelonado X Amelonado. T85/799 X T65/238 had the lowest and different from the rest. From the polyacrylamide gel electrophoresis, protein with molecular weights ranged from 12.0 to 62.6 kDa. A pathogenic related protein of size 23.9 kDa was detected in PAI50 X NA33, T85/799 X Amelonado and on Amelonado X Amelonado. Another pathogenic related protein of size 46.6 kDa and 23.9 kDa were detected in T85/799 X T79/501.