In order to study effect of zeolite soil application and selenium foliar application on growth, yield and yield components of three canola cultivar under conditions of late season drought stress an experiment was conducted in two growing season in 2006 and 2007. Site study was field of Seed and Plant Improvement Institute, Karaj, Iran. The experimental design was a Randomized Complete Block arrangement in factorial split plot with three replications. Irrigation factors were chosen at two levels, included complete irrigation and irrigation holding at stem elongation stage. Zeolite was used at two levels, non application and 10 ton per hectare. Also selenium was sprayed at three concentrations, 0, 15 and 30 gr per liter from sodium selenate. These treatments were randomized in main plots while three canola cultivars ('Zarfam' , 'Okapi' and 'Sarigol') were randomized in sub plots. The results showed that, main effects of different irrigation levels have significant effect on all traits and drought stress decreased significantly all traits. Foliar application of selenium had significant and additive effect on plant height, number of pods in plant, number of seeds in pod, seed yield, biological yield, harvest index and oil yield. There was significant difference between zeolite application and non application on all traits except oil percent and harvest index. It was shown that canola cultivars were different in all of studied traits. Comparison of means showed that, four critical traits that is seed yield, biological yield, harvest index and oil yield were affected by experimental treatments. Different cultivars have different responses under unlike conditions inside upon traits. Under different treatment conditions especially drought stress, zeolite and selenium application have positive and significant effect on traits related to yield. In finally, zeolite and selenium application in dry lands that are exposure to late season drought stress can be helpful for yield improvement and prevent of decreasing yield.

To investigate the effects of sowing dates and late season water deficit stress on quantitative and qualitative traits of different canola cultivars, a 2-year field experiment was carried out in the 2014–2015 and 2015–2016 growing seasons. The experimental factors consisted of sowing date at two levels (7th and 27th October), irrigation at two levels (full irrigation and irrigation termination at silique formation stage) and four German canola cultivars including Trapper, Makro, Smilla, and Agamax. The results indicated that the main effects of sowing date, irrigation, and cultivar were significant on all studied characteristics except for harvest index. The interaction between sowing date and irrigation was also statistically significant on silique number per plant, oil percentage, linolenic acid, and erucic acid percentage. The results demonstrated that seed yield and its components oil percentage and oil yield, as well as oleic and linoleic acid percentage, decreased when sowing date was delayed until 27th October. Due to irrigation termination, all the studied traits decreased except for linolenic and erucic acid. Seed yield also decreased. The results suggest that to improve seed and oil yield, canola should be sown on 7th October and fully irrigated until physiological maturity stage in the study area.

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Drought is a wide spread problem seriously influencing rapeseed (Brassica napus L.) production, mostly in dryland regions. This study was conducted to determine drought tolerance genotypes with superiority in different stressed environments. Twenty three rapeseed genotypes were tested in a split plot design based on randomized complete block design (RCBD) with four replications in two years (2008- 2009 and 2009-2010) at Seed and Plant Improvement Institute of Karaj, Iran. Seven drought resistance indices include susceptible stress index (SSI), tolerance index (TOL), stress mean productivity (MP), geometric mean productivity (GMP), stress tolerance index (STI), yield index (YI) and yield stability index (YSI) were applied on the basis of seed yield in non stress and drought stress conditions. Based on different drought indices, genotypes ‘Modena’, ‘Geronimo’, ‘Elite’, ‘Syn-4’ and ‘SLM046’ had the best rank with low standard deviation. The results indicated that they have stable yield performance. Bi-plot display and cluster analysis cleared superiority of these genotypes in both years. The synthetic derived cultivars could perform well across all environments with better agronomic performance. Results showed MP, GMP and YI indices were more effective in identifying high yielding cultivars in diverse water scarcity.

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In order to investigate the effects of different sowing dates and humic acid foliar application on some agronomic traits of six canola cultivars a two-year experiment was carried out in 2015 and 2016 growing seasons. The experiments were laid out in a randomized complete block design arranged in factorial split plot with three replicates. The factorial combination of three sowing dates (7 th , 17 th and 27 th October) and two humic acid levels (0 and 0.2%) were allocated to the main plots and six canola cultivars (HW118, WPN6, HL3721, L14, Tassilo and Natali) were randomized in subplots. The results indicated that the main effects of experimental factors were significant on all studied traits, except for harvest index. Interaction between sowing date and cultivar was also significant on all traits except for branch number and harvest index. In general, early seed sowing caused the highest yield and yield component as well as oil percentage and yield. Similarly, humic acid foliar application could increase agronomic traits in canola cultivars. In sum, early seed sowing and humic acid foliar application are highly recommended in canola production.

Water stress is one of the main abiotic factors that reduces plant growth, mainly due to high evaporative demand and low water availability. In order to evaluate the effects of drought stress on certain morphological and physiological characteristics of two canola cultivars, we conducted a factorial experiment based on a completely randomized design. The findings show that drought stress exacerbations result in the plant's response to stress due to increased canola resistance caused by changes in plant pigments, proline, catalase, ascorbate peroxidase, peroxidase, superoxide dismutase and malondialdehyde, glucose, galactose, rhamnose and xylose. These in turn ultimately influence the morphological characteristics of canola. Drought stress reduces the concentration of carotenoids, chlorophyll a, chlorophyll b, total chlorophylls; however, glucose, galactose, rhamnose, xylose, proline, catalase, ascorbate peroxidase, peroxidase, superoxide dismutase, malondialdehyde (in leaves and roots) and the chlorophyll a and b ratios were increased. Reduction of plant height, stem height, root length, fresh and dry weight of canola treated with 300 g/l PEG compared to non‐treatment were 0.264, 0.236, 0.394, 0.183 and 0.395, respectively. From the two canola cultivars, the morphological characteristics of the NIMA increased compared to the Ks7 cultivar. Interaction effects of cultivar and drought stress showed that NIMA cultivar without treatment had the highest number of morphological characteristics such as carotenoid concentration, chlorophyll a, chlorophyll b, total chlorophylls a and b, whereas the cultivar with 300 g/l PEG (drought stress) had the highest amount of proline, malondialdehyde, soluble sugars and enzymes in leaves and roots. Increasing activity of oxidative enzymes and soluble sugars in canola under drought stress could be a sign of their relative tolerance to drought stress.

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