Relationship between the characteristics sclerotic layer of cocoa pods and their resistance to cocoa pod borer
2006
Susilo, Agung W., Indonesian Coffee and Cocoa Research Institute, Jl. PB. Sudirman 90 Jember 68118 (Indonesia)
A study to characterize the sclerotic (SCL) of selected cocoa clones with different levels of cocoa pod borer (CPB) infestation was carried out to determine its relationship to CPB resistance. Genetic materials for this study were 5 clones that appeared to show a range of CPB resistance and intensity of larvae activity in the pods. To assess the resistance, a more detailed study of the infestation and characteristics of pods were required to facilitate further selection for resistance. The SCL of the clones was characterized by preparing cross-sections from three fresh-mature pods of each clone. Three pieces, each 30-60 µm thick, were cut from the pod husk using a sliding microtome before staining. The stained tissue of SCL allowed visualisation of the non- lignin tissue, so-called channels,and allowed measurement of the thickness. Three up to six other fresh-mature pods of each clone were tested for hardness of the SCL using a penetrometer at points in the primary furrow, three each in the bottom, middle, and tip area of the pod. The results indicated that there were differences in the channel distribution in the SCL among the tested clone. Appearance of channels was significantly related to the thickness at the node and the hardness at the bottom of the pod in negative correlation. The number of channels positively corresponded to the number of exit holes and entry holes, and the ratio of exit and entry holes. However, of the tested clones, KW 514, KW 546 and KW 566 had a diverse response to CPB the number of channels, exit holes, and the exit/entry ratio. It could be intpreted that the channels facilitate the emerging larvae out of the pod rather than penetration of larvae into the pods.
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