Fennel ( Foeniculumvulgare Mill, Umbelifera) family is a perennial and one of the oldest spicy and medicinal plants of Iran. Inbreeding is crossing between individuals related together compared to those crossing randomly in a population. The most extreme state of inbreeding is selfing which means cross of individuals by themselves via self-pollination. This experiment was conducted to estimate the effect of inbreeding on morphological traits and essential oil percent of fennel genotypes derived from self-pollination during 2012-2013. The first trial was conducted to estimate percent self-pollination and generation of selfed seeds in 20 accessions of fennel. Data analysis was performed according to split plots in a completely randomized block design to evaluate the effect of self-pollination on the genotypes. Results showed that the effect of pollination type (self or cross) was significant on all traits. Similarly, genotypes affected all traits significantly suggesting high variation in studied germplasm. The results of mean comparisons indicatedthat under cross pollination, Tabriz and Kerman genotypes showed the highest and lowest number of seeds per plant, respectively. Under self-pollination, Isfahan II and Kerman showed the highest and lowest number of seeds, respectively. Under both conditions, the traits of seed number per plant, seed number in umbrella, seed weight in umbrella and seed weight per plant showed significant and positive correlations. The second trial was conducted to estimate the effect of inbreeding on morphologic traits and essential oil content of offsprings from self and cross pollinations in a simple lattice design. Among 20 studied genotypes, 32 plants with enough seed under both self and cross pollination (64 genotypes overall) were selected and evaluated.The results of variance analysis based on lattice design showed that studied genotypes differed significantly in terms of all traits except canopy cover diameter. Except for days to 50% emergence, days to 50% flowering and canopy cover to height ratio means of other traits were reduced due to inbreeding. According to correlation results, height was correlated to days to 50% flowering, number of secondary branches and height to secondary branch ratio in both self and cross pollinated plants. Based on factor analysis, five and four factors were extracted in cross and self-pollinated genotypes, accounting for 89 and 78% of variations,respectively. Keywords : fennel, self-pollination, cross pollination, inbreeding
