Document Type : Research paper
Authors
1
Department of Horticulture, Michigan State University, East Lansing, MI, 48824
2
Department of Agronomy and Plant Breeding Science, College of Aburaihan, University of Tehran, Tehran, Iran
Abstract
Bitter fennel (Foeniculum vulgare var. vulgare) is a commercial subspecies of fennel that is widely used in food, pharmaceutical, and perfume industries. Despite the economic importance of this crop and a growing demand for its products, most farmers cultivate local bitter fennel populations that are not necessarily high-yielding. Genetic variation in bitter fennel and relevant heritability studies have suggested that selection can be an efficient breeding method to increase bitter fennel yield. This experiment was conducted in the College of Aburaihan, University of Tehran, Pakdasht, Iran, from 2010 to 2014. Fifty fennel populations from different parts of Iran were collected and assessed for their maturity habit, life span, seed yield, essential oil content, and essential oil yield in a five-year field experiment. Results
showed that these fennel populations, based on their maturity habits, comprised three distinctive groups of early, intermediate, and latematuring, requiring 120, 175, and 230 days from seedling emergence to seed harvest, respectively. The life span of the fennel populations ranged from three to four years. In general, fennel populations in arid regions with extreme temperatures in summer and winter were earlymaturing and had shorter life spans. Populations in humid or semihumid regions with a rather temperate climate were late- or intermediate-maturing and had longer life spans. These observations showed how the causes of growth limitation such as extreme seasonal temperature changes, water accessibility, and competition for sunlight have shaped the phenological features of these fennel populations. During the first three years of the study, considering the minimum life span of all populations, essential oil yield among the early maturing fennels ranged from 2.5 to 104.6 L ha-1 year-1 (average 26.1±0.1). The essential oil yield ranged from 10.1 to 152.2 L ha-1 year-1 (average 67.7± 1) in intermediate-maturing fennels and from 7.5 to 160.9 L ha-1 year-1 (average 46.4±0.2) in late-maturing fennels. Populations with four and five-year life spans had a dramatic decrease in yield after the third year, although they produced considerable amounts of green biomass. Regarding average values in three years, the highest essential oil yield a mong early-maturing fennels occurred in the Fasa population (51.4 L ha-1), among intermediate-maturing fennels in the Meshkin Shahr and Moqhan populations (140.5 and 124.9 L ha-1, respectively), and among late-maturing fennels in the Sari population (52.1 L ha-1). Identifying high-yielding early- and intermediate maturing populations provides a platform for further evaluations on high-yielding fennel populations with stable performance in future studies.
Keywords
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