Estimation of genetic variability in turmeric (Curcuma longa L.) germplasm using agro-morphological traits

Turmeric is an important medicinal plant and cultivated spice crop in Pakistan. The present study was conducted to determine the extent of genetic variation and relationship among turmeric genotypes using 21 qualitative and quantitative traits. A total of 20 genotypes collected from three eco-geographical areas (Bannu, Haripur and Kasur) of turmeric cultivation in Pakistan were studied under field conditions. In qualitative trait light green leaf color, light orange yellow rhizome color and greenish white flower color were found in abundance in most of the genotypes. The leaves, rhizomes and flowers of turmeric plants collected from Bannu and Haripur were light green, yellow and yellowish-white in color, while those of Kasur area were dark green, dark orange and whitish green in color, respectively. A considerable level of variability was displayed by various genotypes for some of the quantitative traits measured. Pattern of variation among the genotypes was different for different agro-morphological traits. The largest variation was observed for plant height, leaf length, leaf width, total and fresh number of leaves, whereas relatively, a low level of variability was detected in most of the remaining quantitative traits. Agro-morphological data was also analyzed by numerical taxonomic techniques using two complementary procedures: cluster and principal component analysis (PCA). Phenogram based on Euclidean distance coefficients placed 20 genotypes into two main clusters with three sub-groups in the 2nd cluster. Genotypes groups were primarily associated with morphological differences among the collections and secondly with the consumer preference and horticulture use. Principal component analysis re-ordered genotypes into four broad groups that had within cluster similarities and inter-cluster morphological variation. Our study revealed that the evaluated germplasm of turmeric appeared to have narrow genetic base which underwent high level of genetic erosion and selection pressure. This is perhaps due to the use of same ancestors and similar seed source by the farmers for cultivation of crop in selected areas of the country. However, this preliminary study of traditional turmeric landraces from Pakistan provided useful information regarding their horticultural and medicinal potential. The given method of analysis may be helpful in selecting diverse parents and broadening local germplasm base of turmeric for future breeding programs.