Graphic analysis of genotype, environment and genotype × environment interaction for oil yield in coriander

Coriander is an annual herb of the umbel family and is belonged from North Africa to south-western of Asia. Coriander is one of the important medicinal plant that used in the pharmaceutical industry and it mainly cultivated and widely distributed for the fruits. The dried fruits are widely employed as a condiment, especially for flavoring of sauces, meat products and bakery and confectionery items. Also, coriander fruits are as a source of essential oils and fatty oil. Water deficit stress is one of the most important factors limiting the growth and survival of plants in arid and semi-arid regions of the world. Water is a major component of the fresh produce and significantly effects on weight and quality of plants. Also, water deficit may cause significant changes in the yield and composition of essential oils in aromatic and medicine plants. So that, was reported that water deficit increased essential oil percentage in coriander but decreased essential oil yield. Iran with an average annual rainfall of 240 mm is included among arid and semi-arid regions of the world. Of the million hectares of cultivated region, only five millions are under irrigation because of intense water limitations. However, Iran is one of the world’s commercial coriander producers. Coriander has been cultivated for many years in different parts of Iran. Therefore, development of drought-tolerant cultivars with high essential oil yield is important in coriander. This research was conducted in order to evaluate the effect of drought stress on morphological, physiological and phytochemical characteristics of endemic coriander genotypes.

F2 generations derived from half-diallel crosses of six endemic coriander genotypes including Isfahan, Hamedan, Bushehr, Mazandaran, Markazi and Alborz, together with their parents were evaluated in randomized complete block design with three replications in each experiment during growing season of 2016 in the research field of Tarbiat Modares University. Plants were treated with different levels of water treatment: well watered (WW), moderate water stress (MWS) and severe water stress (SWS). Data were collected on fruit yield, oil content and oil yield. GGE biplot statistical method (genotype effect + genotype × environment interaction) was used to study stability of genotypes in the studied environments.

Results of Combined analysis of variance indicated that the effects of environments, genotypes and genotype × environment interaction were significant, suggesting that the genotypes responded differently in the studied environment conditions. So, there was the possibility of stability analysis. Results of stability analysis using GGE biplot method indicated that the two first and second principal components of the GGE biplot explained 71.9% of the total essential oil yield variation. Based on the hypothetical ideal genotype biplot, the genotypes G17 (Mazandaran  Hamadan) and G4 (Alborz   Mazandaran) were better than the other genotypes across environments for essential oil yield and stability and had the high general adaptation to all environments. Furthermore, the genotype G18 (Mazandaran   Bushehr) in E2 and E3 environments and genotype G9 (Markazi   Mazandaran) in E1 environment were superior genotypes with the high specific adaptation. Comparison of the studied environments showed that the E2 and E3 environments were quite similar in ranking, grouping and assessing stability of the genotypes, whereas the E1 environment was different from the other environments. Overall, the results showed that all environments had high discriminating ability so that could able to show differences between genotypes. The moderate stress environment was the nearest environment to ideal environment that had the highest discriminating ability and representativeness.

Generally, the results indicated that all environments had high discriminating ability so that could able to show differences between genotypes. Also, the genotypes G17 and G4 as stable and drought tolerant genotype can be considered as donor parent which contains drought tolerance genes and could be used to improve coriander high essential oil yield in drought condition.