پديد آورندگان :
جبّاري، حميد سازمان تحقيقات، آموزش و ترويج كشاورزي - موسسه تحقيقات اصلاح و تهيه نهال و بذر , خوش خلق سيما، نيراعظم سازمان تحقيقات، آموزش و ترويج كشاورزي - پژوهشكده بيوتكنولوژي كشاورزي , شيراني راد، اميرحسين سازمان تحقيقات، آموزش و ترويج كشاورزي - موسسه تحقيقات اصلاح و تهيه نهال و بذر
چكيده لاتين :
Introduction: Plants are exposed to various environmental stresses such as drought, salinity and high or low temperatures. Of which, drought is the most serious problem for global agriculture, approximately affecting 40% of the world’s land area (Zhang et al., 2014). Furthermore, climate change is likely to lead to changes in global temperature and precipitations patterns in some parts of the world, which will have a dramatic impact on crop growth and productivity (Trenberth et al., 2014). Thus, there is an urgent need to develop varieties that can maintain optimum yield levels under drought conditions. It is estimated that approximately 85% of Iran is located in arid, semi-arid or hyper arid regions. Among the oilseed crops, Brassica species are more affected by drought, as these crops are mainly grown in arid and semiarid areas. The objective of the present study was to evaluate oil fatty acids composition of Rapeseed cultivars under drought stress conditions in different growth stages. Materials and Methods: The experiment was conducted as a split-plot based on a randomized complete block design with three replications at Yazd, Iran in 2011-2012 growing season. Irrigation treatments included control (irrigation after 80 mm evaporation from evaporation pan class A) and drought stress (irrigation termination at stem elongation, flowering and silique formation stages until physiological maturity stages) were allocated to the main plots and three winter type rapeseed cultivars (GKH2005, Opera and Okapi) were assigned to the subplots. The measured traits included oil percentage, oleic acid, linoleic acid, linolenic acid, palmitic acid, gadoleic acid, stearic acid, arachidonic acid, palmitoleic acid, erucic acid, seed yield and oil yield. SAS statistical software was used for data analysis and means were compared with LSD test at 5% probability level.Results and Discussion: The results of variance analysis indicated that seed yield was significantly affected by the individual effects drought stress and cultivar (P≤0.01), but was not affected by their interactions. The greatest seed yield from the investigated cultivars (2856 kg. ha-1) was obtained from the control treatment, however, with termination of irrigation at stem elongation, flowering and silique formation stages, the trait decreased by 62, 51 and 27 %, respectively. The oleic acid content of rapeseed oil varied from 64 to 68 % and the linoleic acid concentration fluctuated from 15 to 18 %. Among the three saturated fatty acids (palmitic, stearic and arachidonic), the irrigation treatment only affected arachidonic acid and among the six unsaturated fatty acids (palmitoleic, oleic, linoleic, linolenic, gadoleic and erucic), the effect of irrigation was only significant on oleic, linoleic and linolenic fatty acids. When Irrigation was terminated at the rapeseed vegetative and reproductive stages, the oleic acid content significantly increased as compared to control treatment, while the amount of linoleic acid markedly decreased. Tohidi-Moghaddam et al. (2011) showed that the concentration of seed unsaturated fatty acids diminished in canola plant subjected to drought stress. This was more conspicuous when the stress was applied at flowering stage. They attributed the observed decrease to the reduced plant growth period induced by water-deficit conditions. The response of the three rapeseed cultivars to irrigation levels in terms of their linoleic and linolenic fatty acid contents was different. The cultivar Opera exhibited the highest amount of linoleic acid under the control treatment and irrigation termination at silique formation stage. However, the highest content of linoleic acid for the cultivar GKH2005 was associated with the irrigation termination at stem elongation and flowering stages. Under the control treatment, all the three cultivars were grouped for the content of linolenic fatty acid in the same statistical category, however, with the cessation of irrigation, cultivar GKH2005 was statistically superior to the other cultivars. Conclusions: In general, it seems that irrigation termination resulted in the enhanced oleic acid content in the seeds of the rapeseed cultivars as compared to linoleic fatty acid. Moreover, among the rapeseed cultivars, there was a significant difference in the oil fatty acids content. Our findings indicated that GKH2005 produced higher seed yield and good quality fatty acid oils under drought stress than the other cultivars.
