American Journal of Agriculture and Forestry 2014; 2(6): 262-266 Published online November 20, 2014 (http://www.sciencepublishinggroup.com/j/ajaf) doi: 10.11648/j.ajaf.20140206.15 ISSN: 2330-8583 (Print); ISSN: 2330-8591 (Online) Relationship between physiological and seed yield related traits in winter rapeseed (Brassica napus L.) cultivars under water deficit stress Gader Ghaffari 1 , Mahmoud Toorchi 2 , Saeid Aharizad 2 , Mohammad-Reza Shakiba 2 1 Department of Agricultural Engineering, Payame Noor University, East Azarbaijan Province, Iran 2 Department of Crop Production and Breeding, Faculty of Agriculture, University of Tabriz, Iran Email address: ghaffari314@yahoo.com (G. Ghaffari) To cite this article: Gader Ghaffari, Mahmoud Toorchi, Saeid Aharizad, Mohammad-Reza Shakiba. Relationship between Physiological and Seed Yield Related Traits in Winter Rapeseed (Brassica Napus L.) Cultivars under Water Deficit Stress. American Journal of Agriculture and Forestry. Vol. 2, No. 6, 2014, pp. 262-266. doi: 10.11648/j.ajaf.20140206.15 Abstract: Finding the relationship between physiological traits and seed yield components is an important objective in crop breeding programs. Canonical correlation analysis has been adopted to study the strength of association between the physiological traits and seed yield under water deficit stress and to obtain the physiological traits that have the largest effect on seed yield and its components. This study revealed that leaf water potential, relative water content, leaf osmotic potential and chlorophyll index had the largest influence on seed yield and its components under severe water deficit. Under mild water deficit, leaf water potential and relative water content were also important for improving seed yield. Leaf water potential, relative water content, chlorophyll fluorescene and chlorophyll index were had the largest effect on seed yield and its components under well watered condition. Keywords: Canonical Correlation, Water Deficit Stress, Winter Rapeseed 1. Introduction Rapeseed is the third most important oilseed cropoily plant in the world after soybean and palm (FAO, 2007). New seed varieties naturally contain 40- 45% of oil which is used as raw material to produce industrial and hydraulic oil, cleaner, soap and biodegradable plastics (Friedt, 2007). After extracting the oil, the remained oil cake, which contains 38- 44% high-quality proteins, is used for animal nutrition (Walker and Booth, 2001). Drought and its stress is one of the common environmental stresses which limit farm productions in around 25% of world's land (Mendham and Salisbury, 1995). Access to water is one of the main limitations in realization of full yield and quality of most species and it may erupt during the whole growth stage or in critical conditions (Parry et al., 2005). Plants employ a range of particular responses in order to minimize the effects of water shortage or to increase water absorbing rate (Morison et al., 2008). The effect of water stress is a function of genotype, stress race, weather condition, growth and development stage of rapeseed (Robertson and Holland, (2004). Water stress in particular stages of rapeseed phonology affects seed qualitative properties such as percentage of oil and protein and the amount of glucosinolates (Strocher et al., 1995). Liang et al, (1992) by evaluating the morphological and physiological responses to water stress showed that Brassica juncea is more adaptable to water stress than B. napus. The results of Kumar and Singh (1998) indicate that in Brassica oilseeds, the cell turgidity is maintained up to 2.4 Mega Pascal leaf water potential by the genotypes with high osmotic adjustment but with low osmotic adjustment, the fall rate in pressure potential was fast accordingly. Also, Valeric et al, (2002) remarked that when the separately planted rapeseed leaves were positioned under high osmotic- laboratory, huge amount of proline flocked in leaves. Zulini et al, (2002) found a significant correlation between Fv/Fm and leaf water potential in stressed plants so when leaf water potential decreases to less than 0.9 Mega Pascals, decrease in Fv/Fm can be observed. Numerous experiments suggest rapeseed yield is influenced by high number of pods per plant or per area unit (Rao and Mendham, 1991). Jensen et al, (1996) reported that the eruption of water stress in vegetative