School of Agriculture, Food and Ecosystem Sciences - Theses

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Subject: biodiversity × Author: Kuman, Noel Yori ×

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    Comparative analyses of genetic diversity, cocoa quality and flavour characteristics in selected Papua New Guinea cocoa genotypes
    Kuman, Noel Yori ( 2001)
    This study explored three aspects of cocoa breeding: (1) evaluating the quality characteristic of new breeding lines to select genotypes that have good flavour and quality attributes (2), DNA fingerprinting of selected genotypes to assess genetic diversity of selected breeding lines and (3), evaluating the influence of genotype x environment (GE) interactions on bean quality. The quality of Papua New Guinea (PNG) beans has deteriorated in recent years. Manufacturers are very critical of this situation. In 1999, the International Cocoa and Confectionary Organisation (ICCO) reduced PNG's Fine/Flavour status from 75% to 30%. This has had a negative impact on the industry because PNG's cocoa exports will be subjected to quota restrictions, unlike previously. There is an urgent need to re-establish PNG's Fine/Flavour status and address other quality problems. Flavour and quality related problems are now being addressed through a selective plant breeding programs. Genotypes with high fat content, large bean size, good chocolate and pronounced fruity flavours were selected for this study. These genotypes will be integrated into the breeding programs to replace current genotype, which lacks desirable bean flavours and quality. DNA fingerprinting of the selected genotypes showed high levels of genetic diversity. The genetic dissimilarity between any two genotypes ranged from 14% to 52%, with an average of 29%. A mixed model analysis of variance used to determine the genotype x environment interaction on bean quality showed that fat content, bean count, shell content and recovery rates of the genotypes were significantly influenced by genotype x replicate interaction. The month x genotype interaction also influenced fat content; shell content and bean count were significantly influenced by the plant size. Pearson correlation was used to evaluate correlations between each of the bean quality parameters, and showed that there was a significant correlation only between fat content and recovery rate.