Qualitative and multivariate analyses of clonal cocoa resistance to cocoa pod borer (Lepidoptera : Gracillariidae).
Using morphological features, such as the husk thickness ratio, hardness and thickness of the sclerotic layer, average damage severity index and the number of eggs per pod, a resistance index to Conopomorpha cramerella was calculated for each of 53 cocoa clones in studies in Sabah, Malaysia. The clones were ranked and categorised into resistant, moderately resistant and susceptible classes. This qualitative grouping was then verified using linear discriminant analysis and classification and clusteranalysis. A total of 11, 24 and 18 clones were qualitatively categorised as resistant, moderately resistant, and susceptible, resp. The resistance index for the resistant category ranged from 4.2 for LAFI7 to 19.4 for NGK28; 20.2 for 1466 to 30.0 for NGK16 in the moderately resistant category; and 32.4 for NGK13 to 45.6 for ICS39 in the susceptible category. Two linear discriminant functions explained the total variation and correctly classified about 92.5% of the clones into their appropriate categories. Natural grouping using cluster analysis resulted in 22, 21 and 10 clones grouped into resistant, moderately resistant and susceptible categories, resp. This classification resulted in 52.8% being appropriately categorised into respective groups, qualitatively. There seemed to be slight discrepancies between the classification developed through the resistance index compared to that using the multivariate techniques. The classification of clones using the index into various resistant categories was justified as apparent error rate of reclassification using discriminant analysis and classification was very small (7.55%). Although correct classification of clones into respective categories using cluster analysis was low, this multivariate technique might be suitable for exploring the potential number of resistant groupings prior to the analysis using resistance index.
| Main Authors: | , , |
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| Format: | Texto biblioteca |
| Language: | d |
| Subjects: | agricultural entomology, analytical methods, beverage crops, clonal variation, Coco., control, insect pests, Malaysia, pest control, pest resistance, plant pests, stimulant plants, varietal resistance, varietal susceptibility, Control, Insect pests, Pests, Pest control, Plant parasites, |
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