Genetic Diversity and Variability among Papaya (Carica papaya L.) Genotypes Using Multivariate Analysis

Abstract

Multivariate analysis was used to group and study the pattern of genetic variability and relationship among ten papaya genotypes in Benin City, Nigeria. The experiment was conducted at the Teaching and Research Farm of the Faculty of Agriculture, University of Benin, Benin City, Nigeria (Latitude: 6° 33′N, Longitude: 5° 37′E; 79m asl). Field evaluation of the papaya genotypes was carried out from October 2012 to June 2013. The experiment was laid out as a randomized complete block design with three replications. The result of the Principal Component Analysis (PCA) indicated that the contribution of the first three factors with Eigen value greater than one accounted for 93.0% of the total variation. The first component loaded highly for fruit characters except fruit flesh thickness and fruit diameter which loaded highly in the third component. The vegetative components loaded highly in the second component. Thus the pawpaw genotypes can be distinguished based on either yield or vegetative characters with more reliability on the yield parameters which mostly accounted for the greater proportion of variation. Better resolution can be achieved when both are considered together. The accessions were allocated into three clusters by Cluster Analysis. The three clusters formed indicate intraspecific phenotypic dissimilarity among the ten genotypes especially with the separation of the genotypes that were collected from similar environments. PCA and Cluster Analysis produced similar results in classifying similar genotypes into their separate clusters. Between accessions, CP006 and CP012 had the highest genetic distance while the lowest genetic distance was between CP001 and CP011. The level of variability observed suggested a high diversity among the genotypes. The phenotypic variations could be explored for utilization, conservation and for future genetic improvement by selection of genotypes with promising agronomic characters.  CP012 was particularly superior with respect to the studied traits and was the only genotype in its cluster group. Molecular studies would be useful to confirm the genetic diversity and characterize these genotypes for more detailed examination.