Pattern of Genetic Variability in Nsukka Yellow Pepper (Capsicum Annuum L.) Genotypes

ABSTRACT 

Nsukka yellow pepper genotypes were evaluated in 2009 and 2010 planting seasons to determine the pattern of genetic variability in its population. The initial collection comprising eighteen genotypes were assembled from the local farmers and evaluated in 2009 planting season. Forty nine promising genotypes were selected on individual plant basis and reevaluated in 2010 planting season. The results of the performance of the genotypes in both years showed that there was considerable variability in the population with respect to qualitative and quantitative traits. The high coefficients of variation observed in most of the quantitative traits showed that there is a wide scope for improvement in the germplasm. The results of the principal component analysis (PCA) in 2009 planting season revealed that, the first four principal components accounted for 80.87% of the total variation in the population. The number of fruits per plant, total fruit weight and fruit yield were identified as the most effective traits for genotype detection and discrimination. The results of the cluster analysis based on the traits associated with the first and second principal components classified the eighteen genotypes into three groups, A, B, C and an outlier (Ny-15). The groups had a coefficient of similarity of about 0.850. A comparison of the cluster means showed that Cluster A comprised six genotypes characterized with moderate fruit yield; Cluster B had eight genotypes endowed with early flowering and poor fruit yield; cluster C consisted of three genotypes with high potentials for fruit set and yield. The outlier, showed the best adaptation with respect to all the traits studied. Similarly, the 2010 data were also subjected to PCA, the results showed that the first four principal components explained 73.19% of the total variation in the population and implicated the fruit girth, number of primary branches per plant, number of fruits per plant, total fruit weight and fruit yield as the most discriminatory traits accountable for the genetic divergence in the germplasm. The scatter plot based on the traits associated with the first two principal components differentiated the xii forty nine genotypes into four clusters, A, B, C and D. Cluster A comprised 21 genotypes with average performance in yield; cluster B consisted of 3 genotypes characterized with tall plants, early flowering and poor yield. Cluster C had 23 genotypes associated with moderate yield, while cluster D comprised two genotypes endowed with the best agronomic and yield potentials. The results of the correlation analysis showed that, number of fruits per plant had highly significant correlation with fruit yield in 2009, whereas the associations between yield and the other remaining traits were positive but non-significant. In 2010 however, all but fruit length and plant height significantly correlated with fruit yield. The path coefficient analysis implicated number of fruits per plant and average fruit weight as having highest direct positive effects on fruit yield in both years. Analysis of the biochemical composition of five promising Nsukka yellow pepper genotypes showed a wide range of variation for ascorbic acid from 183.0-400.0 mg/100g, while a lower variation was observed for capsaicin, ranging from 0.32 mg/100g in Ny-08-2 to 0.405 mg/100g in Ny-15-3. Thirty nine genotypes with promising agronomic and breeding potentials were selected for further breeding work.

TABLE OF CONTENTS

Title page - - - - - - - - - - i

Certification - - - - - - - - - - ii

Dedication - - - - - - - - - - iii

Acknowledgement - - - - - - - - - iv

List of co-authored articles from this work - - - - - - v

Table of Contents - - - - - - - - - vi

List of Tables - - - - - - - - - - vii

List of Figures - - - - - - - - - - ix

List of plates - - - - - - - - - - x

Abstract - - - - - - - - - - xi

Introduction - - - - - - - - - - 1

Literature Review - - - - - - - - - 5

Materials and Methods - - - - - - - - 22

Results - - - - - - - - - - - 34

Discussion - - - - - - - - - - 77

Conclusion - - - - - - - - - - 93

References - - - - - - - - - - 95

Appendices - - - - - - - - - - 107