Morphological Response, Grain Yield and Essential Oil of Three Fennel Ecotypes to Different Times of Planting

Environment condition and appropriate planting date are the most important factors in producing optimal yield. Different planting dates lead to adaptation of plant vegetative growth period to different temperatures, daytime, and solar radiation. Therefore, it affects the development, production of biomass and ultimately plant yield. The effect of environmental factors on phenological stages of the plant makes the planting date differ from region to region and between genotypes in one region. The characteristics of the growth and performance of ecotypes vary from region to region that indicates interaction among ecotype, regions and environment. The interaction between genotype and environment indicates that selection of cultivars based on the performance of an environment is not suitable standard. It is better to evaluate genotypes in a wide range of environmental changes in different locations and times. For this purpose, the information obtained from the estimation of compatibility and stability of genotypes performance is a more reliable criterion for the development of cultivars and their cultivation and will increase the efficiency of selection and introduction of cultivars. In Khuzestan, due to the lack of suitable and recommended planting dates for fennel plants, decision making about optimal planting time is very important and it is one of the important factors for achieving maximum plant yield. Therefore, the present study aimed at evaluating three fennel ecotypes in different planting dates and determining the best planting time for this plant under Ahwaz climatic conditions.
This experiment was carried out as split plot based on randomized complete block design with three replications at research farm of Agriculture and Natural Resources Science University of Khuzestan in 2016-2017. Seven planting date (22-Oct, 6-Nov, 21-Nov, 6-Dec, 21-Dec, 5-Jan, 20-Jan) were assigned as main plots and three ecotypes (Bushehr, Hamedan, Esfahan) were assigned made up of sub plots. Number of nodes, stem diameter, second internode length, umbrella number per main stem, umbrella number per sub branch, seed yield, essential oil percentage, essential oil yield and biological yield were evaluated after harvesting. The data were analyzed by the SAS statistical package (Ver.9.2) and means were compared with LSD test at the 5% level of probability.
The results showed that different planting dates had significant effect on fennel ecotypes. The maximum internode length and umbrella number per branch were obtained from the first planting date in the Bushehr ecotype. The delayed sowing date had a decreasing effect on morphological traits, so that the highest number of nodes in the main stem (6.7), stem diameter (1.97 cm), umbrella number per main stem (4.55) were observed at sowing date October 22. By delaying planting to January, the amount of traits decreased. The highest grain yield (2026.5 kg ha-1) was obtained from the sowing date of October 22 and Bushehr ecotype (1774.12 kg ha-1). The highest percentage of essential oil was obtained from sowing date of January 20 (46.4%) and Isfahan ecotype (4.27%). The highest essential oil yield of Isfahan ecotype was 67.66 kg ha-1, which had no significant difference with Bushehr ecotype (67.15 kg ha-1) and were in a group.
According to the results, the first planting date had the highest yield and components yield, due to the favorable environmental factors in the occurrence of the genetic potential of ecotypes. Also, with delaying planting date from October 22 to January 20, the percentage of essential oil reached the highest. This is probably due to the reduction of reproduction period and the occurrence of this period with increasing heat at the end of the season. Among ecotypes, Bushehr ecotype due to more adaptation to the region, as well as the highest grain yield and number of umbrellas is proposed as the most suitable ecotype for cultivation in the study area and if the objective is the production of essential oils, Isfahan ecotype is recommended for cultivation in the study area.