Study of Genetic Variation and Heritability of some Flower Traits in different Chrysanthemum (Chrysanthemum morifolium) Genotypes

Introduction The evaluation of morphological, phenological and agronomical characteristics is one of the first steps for the initial study of germplasm. It can also be conferred as basic information for the breeder to study genetic diversity for particular purposes. Chrysanthemum (Chrysanthemum morifolium) is a perennial herbaceous plant of the family Asteraceae with simple coniferous leaves and alternate arrangement on its branched stems and has composite flowers. The first stage in breeding programs is to study genetic variation of the selected plants. This study was conducted in order to evaluate the genetic variation of flower traits for selected Chrysanthemum genotypes for three years. Researchers use different methods to estimate genetic diversity of plants including DNA markers, isozymes and morphological traits. Use of morphological traits that are easily measured and have high heritability is a convenient tool to assess the level of genetic diversity of plants.Materials and Methods The origin of the tested genotypes was from the gene bank of the Research Institute of Flowers and Ornamental Plants. The results of random crosses between different chrysanthemum clones were evaluated. The research was conducted for four consecutive years. The aim of the first year experiment was positive selection of genotypes. In fact, the best genotypes were selected. In addition, negative selection of different genotypes was performed. During this selection period, similar genotypes were removed. Selected genotypes (20 genotypes) were evaluated based on a completely randomized design with three replications using seven morphological traits including number of flower per plant, period of flowering, flower diameter, number of petal row, petal length, Fresh weight and dry weight of flower. Statistical analyses including analysis of variance, correlation coefficient, and heritability, phenotypic and genotypic coefficient of variation were estimated using SAS 9.0 software.Results and Discussion After performing Bartlett test and confirming the uniformity of variances, combined analysis was performed for three years. The results of analysis of variance showed that the effect of the year was significant only for the number of flowers per plant and the flowering period. The results of three-year analysis of variance showed that there was significant difference among the genotypes for the number of flowers per plant, flowering period, number of petal rows, fresh and dry flower weight. There was a significant difference (p≤0.05) among the years only in flowering period and number of flowers per plant. The highest variation observed between flowering period and flower diameter. The highest coefficient of phenotypic and genetic variation obtained for the number of petal rows, flower fresh weight and petal length. The lowest coefficient of phenotypic and genetic variation obtained for fresh and dry flower weight and number of flowers per plant. The highest positive genetic and phenotypic correlation coefficient estimated between flowering period with flower diameter, number of rows of petals and fresh weight of flowers which is important for the simultaneous breeding of these traits. The results of this study showed that flower diameter, flowering period, petal length and number of petal rows showed high general heritability. Therefore these results indicate that the selection process for these traits is effective and can be used in the breeding programs. The results of this study showed that highest number of petal rows belonged to B136 genotype. Genotype 31 with forty-three days of flowering period had the highest flowering length compared to other genotypes. GenotypeC85 had 202 flowers per plant. These genotypes can be used as parents especially to increase the flowering period and the number of petal rows due to the general heritability of over fifty percent of these traits. It is also suggested that traits such as petal color and resistance to important pests (including black chrysanthemum aphid, flower thrips pest) and important diseases (including Fusarium wilt, verticillium wilt and leaf spot) should be studied. The superior genotype can be selected if statistically significant difference observed among of genotypes. Conclusion It is a fact that chrysanthemums has characteristics such as variation of flower shape and color, plant size, form and flowering period that is widely used in landscape. In this research significant difference observed among the genotypes. Also some of measured traits had a high general heritability due to the positive and significant correlation of these traits that can be used to improve other genotypes and their traits.