Genetic divergence studies in tulip (Tulipa gesneriana L.)

摘要

Twenty one tulip genotypes were assessed for their genetic divergence based on 16 agro-morphological traits following Mahalanobis D-2-statistic. On the basis of D-2 values, the 21 genotypes were grouped in to five clusters, of which cluster II accommodated 6 genotypes, while cluster IV had single genotype. The high magnitude of D-2 cluster means indicated that there is a considerable diversity in the population studied. The D-2 and inter-cluster coverage divergence were utilized for the choice of parents to decide the cross combination to produce heterotic effect. The highest inter cluster D-2 value was recorded between clusters III and V (11005.75) indicating that crosses may be attempted between the genotypes of cluster III (Character, Christian Dream, Hamilton and Horizon) and cluster V (Apeldoorn, Blushing Apeldoorn, Golden Apeldoorn, Strong Gold, Tulip Hb) to obtain new desirable recombinants in tulip. The study of cluster mean value of 5 clusters indicated high range of variation for days to sprout, days to flower, wrapper leaf area, percent sprouting & flowering, plant height and scape length among the different clusters. The cluster V includes genotypes with earliness and exhibited longest duration of flowering, highest wrapper leaf area and bulb weight. Genotypes of this cluster also possessed desirable floral traits (scape length, floral size and scape thickness) and bulb traits (number of bulbs per plant and bulb weight). Hence, genotypes from this cluster could serve as valuable parents to develop superior cultivars. Out of 16 principal components first six accounted 91.88% of total variability. The first principal component accounted for 57.25% of variability, while, the second and third accounted for 12.37 and 7.54% of total variability, respectively. Hierarchical cluster analysis (HCA) was performed for getting more clear idea among the genotypes. Based on HCA one dendrogram was constructed with two major clusters. These clusters could be divided into 8 minor sub-clusters.