Spring Rapeseed Cultivars Response to Water Stress in Winter Planting

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1 Spring Rapeseed s Response to Water Stress in Winter Planting Amir Hossein Shirani Rad Department of Oilseed Crops, Seed and Plant Improvement Institute, Karaj, Iran Abstract- A two year field experiment was carried out in Karaj, Iran during growing seasons to assess the drought tolerance of spring rapeseed (Brassica napus L.) cultivars in winter planting. The experiments was laid out in a fourreplicated-randomized complete block, split plot design with two irrigation levels (I: I 1 = irrigation on the basis of 80 ml evaporation from the class A pan (normal irrigation) and I 2 : interruption of irrigation from the flowering stage (water stress) as the main plot and cultivar including C 1 : RGS 003, C 2 : Amica, C 3 : Sarigol, C 4 : Option 500, C 5 : Hyola 401, C 6 : Hyola 42, C 7 : Hyola 60, C 8 : Hyola 420, C 9 : Hyola 330, C 10 : Hyola 308, C 11 : Kimberly, C 12 : RGS 006, C 13 : 19-H, C 14 : Syn-3, C 15 : PR- 401/16, C 16 : PP-401/15E, C 17 : PP 308/8, C 18 : PP 308/3, C 19 : ORS , C 20 : ORS , C 21 : RG 4403, C 22 : RG 405/03, C 23 : RGAS 0324 and C 24 : RG 405/02 as subplot. The results of combined analysis of two years revealed that under normal irrigation condition ORS cultivar by average of 2285 kg ha -1 and RG 405/03 cultivar by average of kg ha -1 produced the highest seed yield and biomass yield, respectively. Under water stress condition, RG 405/03 produced the highest seed yield and biomass yield by average of 1544 and 7359 kg ha -1, respectively. Key words: Rape seed; Brassica napus L.; Spring cultivars; Water stress; Winter planting. I. Introduction Rapeseed (Brassica napus L.) is a crop which is grown mainly for its high quality oil and protein although its yield is often restricted by water deficit and high temperatures during the reproductive growth. The effect of water stress on a crop is a function of genotype, intensity and duration of stress, weather conditions and developmental stages of rapeseed [1]. The occurrence time is more important than the water stress intensity. Severe stress decreases the duration of reproductive growth [2] and stress during flowering or ripening stages results in large yield losses as seed yield potential of Brassica crops depends on the events occurring prior to and during the flowering stage, while the reproductive period is most susceptible to stress [3]. Flowering is the most sensitive stage to water stress, probably due to susceptibility of pollen development, anthesis and fertilization leading to lower seed yield [4-5]. Since there is no logical way to increase precipitation in drought periods to modify its undesirable effects so using the most appropriate agricultural practices to avoid crop sensitive stages meeting dryness and also cultivars which are more tolerant than the others to dryness are the best solutions [6]. Therefore the main objective of this study is to assess the effects of water stress at flowering stage on yield and some agronomic traits of spring rapeseed cultivars in winter planting to find the most tolerant ones. II. Materials and methods These experiments were carried out at the experimental farm located in Karaj (50 75 E, 35 9 N; 1313 m a.s.l), Iran on a randomized complete block design arranged in split plot form with four replications during the and crop years. Karaj is a cold temperate and semi arid region. Treatments were included two agents: Irrigation in two levels including I 1 : irrigation on the basis of 80 ml evaporation from the class A pan (normal irrigation) and I 2 : interruption of irrigation from the flowering stage (water stress) as the main plots and cultivar including C 1 : RGS 003, C 2 : Amica, C 3 : Sarigol, C 4 : Option 500, C 5 : Hyola 401, C 6 : Hyola 42, C 7 : Hyola 60, C 8 : Hyola 420, C 9 : Hyola 330, C 10 : Hyola 308, C 11 : Kimberly, C 12 : RGS 006, C 13 : 19-H, C 14 : Syn-3, C 15 : PR-401/16, C 16 : PP- 401/15E, C 17 : PP 308/8, C 18 : PP 308/3, C 19 : ORS , C 20 : ORS , C 21 : RG 4403, C 22 : RG 405/03, C 23 : RGAS 0324 and C 24 : RG 405/02 as the subplots. Each experimental plot consisted of 4 rows, 4 m long with 30 cm spaced between rows and 4 cm distance between plants on the rows. According to soil analysis, N, P and K fertilizer rates recommended. P and K fertilizer applied pre-plant 62

2 and N fertilizer applied in three stages: one-third pre plant, one-third in stemming stage and one-third in flowering stage. The crop was kept free from weeds by applying 2.5 L ha 1 Terfelan pre-plant. Cabbage aphid also controlled during the growing seasons using Metasistox at a rate of 1.5 L ha 1. Plant height, biomass yield, seed yield and harvest index were determined for each cultivar under both normal irrigation and water stress in both years of experiment. Simple analysis of variance (ANOVA) was performed for assessed traits at the end of each year. Combined analysis of variance was performed for assessed traits after two years of experiment. Also Duncan s Multiple Range Test (DMRT) (P = 0.05) was used to conduct means comparison. III. Results and discussion III.I. First year of the experiment Plant height- The simple effects of treatments and the interaction effect of them on plant height were all significant at P = 0.01 (Table 1). Normal irrigation by average of 99.4 cm showed a significant from the flowering stage by average of 88.5 cm. Also assessed cultivars from the plant height point of view placed in different statistical groups as Amica by average of cm and Hyola 308 by average of 79.8 cm produced the highest and lowest plant height, respectively (Table 2). Study of the trait revealed that assessed cultivars from the plant height point of view, in different levels of irrigation placed in different statistical groups as Sarigol by average of cm under normal irrigation condition and Hyola 42 by average of 59.4 cm under water stress condition produced the highest and lowest plant height, respectively. Generally Sarigol under normal irrigation condition and RGAS0324 under water stress condition produced the highest plants (Fig. 1). Seed yield- The simple effects of irrigation and cultivar and their interaction on seed yield were significant at P = 0.01 (Table 1). Normal irrigation by average of kg ha -1 showed a significant from the flowering stage by average of kg ha - 1. Also assessed cultivars from the seed yield point of view placed in different statistical groups as ORS by average of 1798 kg ha -1 and Hyola 401 by average of kg ha -1 produced the highest and lowest seed yield, respectively (Table 2). Study of the interaction effect of irrigation and cultivar on this trait revealed that assessed cultivars from the seed yield point of view, in different levels of irrigation placed in different statistical groups as ORS by average of 2241 kg ha -1 under normal irrigation condition and Hyola 401 by average of kg ha -1 under water stress condition produced the highest and lowest seed yield, respectively. Generally ORS under normal irrigation condition and RG 405/03 under water stress condition produced the highest seed yield (Fig. 2). Biomass yield- The simple effects of treatments and the interaction effect of them on biomass yield all were significant at P = 0.01 (Table 1). Normal irrigation by average of kg ha -1 showed a significant preference in comparison to interruption of irrigation from the flowering stage by average of kg ha -1. Also assessed cultivars from the seed oil yield point of view placed in different statistical groups as RG405/03 by average of 9906 kg ha -1 and Hyola 401 by average of 5406 kg ha -1 produced the highest and lowest biomass yield, respectively (Table 2). Study of the interaction effect of irrigation and cultivar on this trait revealed that assessed cultivars from the biomass yield point of view, in different levels of irrigation placed in different statistical groups as RG405/03 by average of kg ha -1 under normal irrigation condition and Hyola 401 by average of 3250 kg ha -1 under water stress condition produced the highest and lowest biomass yield, respectively. Generally RG405/03 under both irrigation conditions produced the highest biomass yield (Fig. 3). Harvest index- The simple effect of cultivar and interaction effect of irrigation and cultivar on harvest index were significant at P = 0.01 but the simple effect of cultivar on harvest index was not significant (Table 1). Assessed cultivars from the harvest index point of view placed in different statistical groups as ORS by average of 21.03% and 19-H by average of 12.86% produced the highest and lowest harvest index, respectively (Table 2). Study of the trait revealed that the assessed cultivars from the harvest index point of view, in different levels of irrigation placed in different statistical groups as SYN-3 by average of 24.76% in water stress condition and 19-H by average of 11.75% under the same irrigation condition produced the highest and lowest harvest index, respectively. Generally Kimberly under normal irrigation condition and 63

3 SYN-3 under water stress condition produced the highest harvest index (Fig. 4). Table2. Effects and mean comparisons (simple effect) of irrigation and cultivar for assessed traits ( ) S.O.V. DF PH SY BY HI Replication 3 Irrigation 1 ** ** ** ns Error 3 23 ** ** ** ** Irrigation 23 ** ** ** ** Error 138 Total CV (%) *, ** significant at 5 and 1% respectively, ns: not significant Table1. Analysis of variance for assessed traits ( ) Fig.1. Interaction effect of irrigation and cultivar on plant height (cm) ( ) Treatment Irrigation Normal irrigation Water Mean PH(cm) SY(Kg ha -1 ) BY(Kg ha -1 ) HI(%) 99.4 a a a a 88.5 b b b a stress RGS h 1502 c-g 7531 e-h a Amica a 1277 hij 7500 e-h fg Sarigol a 1336 hi 8406 bcd fg Option d 1245 ijk 6156 i a Hyola h l 5406 j c-g Hyola i 1240 ijk 7219 gh efg Hyola fg 1167 jk 7281 fgh g Hyola c 1369 f-i 7938 d-g fg Hyola fg 1345 hi 6969 h a-e Hyola i 1165 jk 6188 i a-f Kimberly 92.1 ef 1383 e-i 7000 h a-d RGS gh 1362 ghi 7094 h a-d 19-H abc 1127 k 8500 bcd h SYN c 1313 hij 7406 e-h abc PR-401/ bc 1298 hij 8063 cde 16.3 fg PP fg 1371 f-i 7969 d-g a-g 401/15E PP-308/ a 1282 hij 8031 c-f g PP-308/3 89 g 1516 c-f 8750 bc d-g ORS ab 1538 cd 8625 bcd a-g 3006 ORS g 1798 a 8813 b a 3008 RG a 1716 ab 8594 bcd ab RG 405/ de 1641 bc 9906 a b-g RGAS a 1528 cd 7875 d-g abc 0324 RG 405/ i 1419 d-h 8031 c-f a-g Any two means sharing a common letter not differ significantly from each other at 5% probability Fig.2. Interaction effect of irrigation and cultivar on seed yield (kg ha -1 ) ( ) Fig.3. Interaction effect of irrigation and cultivar on biomass yield (kg ha -1 ) ( ) 64

4 irrigation condition and Hyola 401 by average of 507 kg ha -1 under water stress condition produced the highest and lowest seed yield, respectively. Generally ORS under normal irrigation condition and RG 405/03 under water stress condition produced the highest seed yield (Fig. 6). Fig.4. Interaction effect of irrigation and cultivar on harvest index (%) ( ) III.II. Second year of the experiment Plant height- The simple effects of treatments and the interaction effect of them on plant height were all significant at P = 0.01 (Table 3). Normal irrigation by average of cm showed a significant from the flowering stage by average of cm. Also assessed cultivars from the plant height point of view placed in different statistical groups as Amica by average of cm and Hyola 308 by average of cm produced the highest and lowest plant height, respectively (Table 4). Study of the trait revealed that assessed cultivars from the plant height point of view, in different levels of irrigation placed in different statistical groups as Sarigol by average of 120 cm under normal irrigation condition and Hyola 42 by average of cm under water stress condition produced the highest and lowest plant height, respectively. Generally Sarigol under normal irrigation condition and RGAS0324 under water stress condition produced the highest plants (Fig. 5). Seed yield- The simple effects of treatments and the interaction effect of them on seed yield were significant at P = 0.01 (Table 3). Normal irrigation by average of kg ha -1 showed a significant from the flowering stage by average of kg ha - 1. Also assessed cultivars from the seed yield point of view placed in different statistical groups as ORS by average of 1870 kg ha -1 and Hyola 401 by average of 1009 kg ha -1 produced the highest and lowest seed yield, respectively (Table 4). Study of the interaction effects of irrigation and cultivar on this trait revealed that assessed cultivars from the seed yield point of view, in different levels of irrigation placed in different statistical groups as ORS by average of 2330 kg ha -1 under normal Biomass yield- The simple effects of treatments and the interaction effect of them on biomass yield all were significant at P = 0.01 (Table 3). Normal irrigation by average of kg ha -1 showed a significant preference in comparison to interruption of irrigation from the flowering stage by average of kg ha -1. Also assessed cultivars from the seed oil yield point of view placed in different statistical groups as RG405/03 by average of kg ha -1 and Hyola 401 by average of 5568 kg ha -1 produced the highest and lowest biomass yield, respectively (Table 4). Study of the interaction effect of irrigation and cultivar on this trait revealed that assessed cultivars from the biomass yield point of view, in different levels of irrigation placed in different statistical groups as RG405/03 by average of kg ha -1 under normal irrigation condition and Hyola 401 by average of 3348 kg ha -1 under water stress condition produced the highest and lowest biomass yield, respectively. Generally RG405/03 under both irrigation conditions produced the highest biomass yield (Fig. 7). Harvest index- The simple effect of cultivar and interaction effect of irrigation and cultivar on harvest index were significant at P = 0.01 but the simple effect of cultivar on harvest index was not significant (Table 3). Assessed cultivars from the harvest index point of view placed in different statistical groups as ORS by average of 21.24% and 19-H by average of 12.98% produced the highest and lowest harvest index, respectively (Table 4). Study of the trait revealed that the assessed cultivars from the harvest index point of view, in different levels of irrigation placed in different statistical groups as SYN-3 by average of 25% in water stress condition and 19-H by average of 11.86% under the same irrigation condition produced the highest and lowest harvest index, respectively. Generally Kimberly under normal irrigation condition and SYN-3 under water stress condition produced the highest harvest index (Fig. 8). 65

5 S.O.V. DF PH SY BY HI Replication 3 Irrigation 1 ** ** ** ns Error 3 23 ** ** ** ** Irrigation 23 ** ** ** ** Error 138 Total CV (%) *, ** significant at 5 and 1% respectively, ns: not significant Table3. Analysis of variance for assessed traits ( ) Fig.5. Interaction effect of irrigation and cultivar on plant height (cm) ( ) Treatment Mean PH(cm) SY(Kg ha -1 ) BY(Kg ha -1 ) HI(%) Irrigation Normal a a a a irrigation Water 93.8 b b b a stress RGS h c-g 7757 e-h 20.5 a Amica a 1328 hij 7725 e-h 16.6 fg Sarigol a 1389 hi 8658 bcd fg Option d 1294 ijk 6431 i a Hyola h 1009 l 5568 j c-g Hyola i 1289 ijk 7435 gh efg Hyola fg 1214 jk 7500 fgh g Hyola c 1424 f-i 8176 d-g 16.5 fg Hyola fg 1399 hi 7178 h a-e Hyola i 1211 jk 6373 i a-f Kimberly ef 1438 e-i 7210 h a-d RGS gh 1416 ghi 7307 h a-d 19-H abc 1172 k 8755 bcd h SYN c 1365 hij 7628 e-h abc PR-401/ bc 1350 hij 8304 cde fg PP fg 1426 f-i 8208 d-g a-g 401/15E PP-308/8 110 a 1333 hij 8272 c-f g PP-308/ g 1577 c-f 9013 bc d-g ORS ab 1599 cd 8884 bcd a-g 3006 ORS g 1870 a 9077 b a 3008 RG a 1784 ab 8852 bcd ab RG 405/ de 1706 bc a b-g RGAS a 1589 cde 8111 d-g abc 0324 RG 405/ i 1476 d-h 8272 c-f a-g Any two means sharing a common letter not differ significantly from each other at 5% probability Fig.6. Interaction effect of irrigation and cultivar on seed yield (kg ha -1 ) ( ) Fig.7. Interaction effect of irrigation and cultivar on biomass yield (kg ha -1 ) ( ) Table4. Effects and mean comparisons (simple effect) of irrigation and cultivar for assessed traits ( ) 66

6 Fig.8. Interaction effect of irrigation and cultivar on harvest index (%) ( ) III.III. Both years of the experiment Plant height- The simple effects of treatments and the interaction effect of them on plant height were all significant at P = 0.01 (Table 5). Normal irrigation by average of cm showed a significant from the flowering stage by average of 91.2 cm. Also assessed cultivars from the plant height point of view placed in different statistical groups as Amica by average of cm and Hyola 308 by average of cm produced the highest and lowest plant height, respectively (Table 6). Study of the trait revealed that assessed cultivars from the plant height point of view, in different levels of irrigation placed in different statistical groups as Sarigol by average of cm under normal irrigation condition and Hyola 42 by average of cm under water stress condition produced the highest and lowest plant height, respectively. Generally Sarigol under normal irrigation condition and RGAS0324 under water stress condition produced the highest plants (Fig. 9). Decrease in plant height is due to decrease in cell division and assimilates transport. In many reports decrease of vegetative growth and plant height under drought stress condition was observed [7]. Seed yield- The simple effects of treatments and the interaction effect of them on seed yield were significant at P = 0.01 (Table 5). Normal irrigation by average of kg ha -1 showed a significant from the flowering stage by average of kg ha - 1. Also assessed cultivars from the seed yield point of view placed in different statistical groups as ORS by average of 1834 kg ha -1 and Hyola 401 by average of kg ha -1 produced the highest and lowest seed yield, respectively (Table 6). Study of the interaction effects of irrigation and cultivar on this trait revealed that assessed cultivars from the seed yield point of view, in different levels of irrigation placed in different statistical groups as ORS by average of 2285 kg ha -1 under normal irrigation condition and Hyola 401 by average of kg ha -1 under water stress condition produced the highest and lowest seed yield, respectively. Generally ORS under normal irrigation condition and RG 405/03 under water stress condition produced the highest seed yield (Fig. 10). It seems that water stress caused yield reduction probably by inducing pod abortion via limiting photosynthesis. It appears that water stress hampered flowering and reduced the probability of developing flower to pod and its occurrence during flowering and pod formation resulted in pod abortion [8]. Gammelvind et al. (1996) reported that water deficient in late vegetative and early reproductive growth stages reduces photosynthetic rate in leaves and yield [9]. Masoud Sinaki et al. found that the highest rapeseed yield reduction was obtained when water stress occurred at flowering and then at pod developmental stages [4]. Biomass yield- The simple effects of treatments and the interaction effect of them on biomass yield all were significant at P = 0.01 (Table 5). Normal irrigation by average of kg ha -1 showed a significant preference in comparison to interruption of irrigation from the flowering stage by average of kg ha -1. Also assessed cultivars from the seed oil yield point of view placed in different statistical groups as RG405/03 by average of kg ha -1 and Hyola 401 by average of 5487 kg ha -1 produced the highest and lowest biomass yield, respectively (Table 6). Study of the interaction effect of irrigation and cultivar on this trait revealed that assessed cultivars from the biomass yield point of view, in different levels of irrigation placed in different statistical groups as RG405/03 by average of kg ha -1 under normal irrigation condition and Hyola 401 by average of 3299 kg ha -1 under water stress condition produced the highest and lowest biomass yield, respectively. Generally RG405/03 under both irrigation conditions produced the highest biomass yield (Fig. 11). Deepak and Wattal showed that water stress decreased significantly seed yield and biological yield [10]. Decrease of biological yield and pod dry matter has been observed in two canola cultivars under conditions of water deficit by Thomas et al.(2004) too [11]. 67

7 Harvest index- The simple effect of irrigation on harvest index was significant at P = 0.05 and the simple effect of cultivar and the interaction effect of irrigation and cultivar on harvest index were significant at P = 0.01 (Table 5). Interruption of irrigation from the flowering stage by average of 18.48% showed a significant preference in comparison to normal irrigation by average of 17.82%. Assessed cultivars from the harvest index point of view placed in different statistical groups as ORS by average of 21.13% and 19-H by average of 12.92% produced the highest and lowest harvest index, respectively (Table 6). Study of the trait revealed that the assessed cultivars from the harvest index point of view, in different levels of irrigation placed in different statistical groups as SYN-3 by average of 24.88% in water stress condition and 19-H by average of 11.8% under the same condition produced the highest and lowest harvest index, respectively. Generally Kimberly under normal irrigation condition and SYN-3 under water stress condition produced the highest harvest index (Fig. 12). There are many reports that late season drought stress apart from decrease of total dry matter, decrease assimilates transportation to seeds and lead to decrease harvest index [7-12]. S.O.V. DF PH SY BY HI Year 1 ** * ns ns Error 6 Irrigation 1 ** ** ** * Year 1 ns ns ns ns Irrigation Error 6 23 ** ** ** ** Year 23 ns ns ns ns Irrigation 23 ** ** ** ** Year 23 ns ns ns ns Irrigation Error 276 Total CV (%) *, ** significant at 5 and 1% respectively, ns: not significant Treatment Mean PH(cm) SY(Kg ha -1 ) BY(Kg ha -1 ) HI(%) Irrigation Normal a a a b irrigation Water 91.2 b b b a stress RGS i 1532 cd 7644 f-i 20.4 ab Amica a 1303 fg 7613g-j g Sarigol a 1363 efg 8532 bcd g Option e 1269 gh 6249 l ab Hyola i j 5487 m efg Hyola k 1265 gh 7327 ijk fg Hyola fgh 1191 hi 7390 ijk g Hyola d 1396 ef 8057 d-g g Hyola fg 1372 efg 7073 k a-d Hyola k 1188 hi 6280 l b-e Kimberly f 1410 ef 7105 jk abc RGS h 1389 ef 7200 ijk abc 19-H bc 1150 i 8628 bc h SYN d 1339 efg 7517 h-k abc PR-401/ cd 1324 fg 8183 cde g PP fg 1399 ef 8088 d-g c-f 401/15E PP-308/ a 1308 fg 8152 c-f g PP-308/ gh 1547 c 8881 b fg ORS ab 1568 c 8754 b 18.6 b-f 3006 ORS gh 1834 a 8945 b a 3008 RG a 1750 ab 8723 b abc RG 405/ e 1673 b a 17.6 d-g RGAS a 1559 c 7993 e-h abc 0324 RG 405/ j 1447 de 8152 c-f b-f Any two means sharing a common letter not differ significantly from each other at 5% probability Table6. Effects and mean comparisons (simple effect) of irrigation and cultivar for assessed traits ( ) Table5. Combined analysis of variance for assessed traits ( ) Fig.9. Interaction effect of irrigation and cultivar on plant height (cm) ( ) 68

8 Fig.10. Interaction effect of irrigation and cultivar on seed yield (kg ha -1 ) ( ) for cultivation in a region with cold temperate and semi arid region like Karaj. Our results showed generally ORS and RG 405/03 produced the highest seed and biomass yield, respectively, under normal irrigation condition and RG 405/03 produced the highest seed and biomass yield under water stress condition. Therefore ORS recommended as the best cultivar if there is no water deficit in winter planting for a cold temperate region and RG 405/03 recommended as the best cultivar under late season drought condition in the same condition. References [1] Robertson, M.J. and J.F. Holland, Production risk of canola in semiarid subtropics of Australia. Aust. J. Agric. Res., 55: [2] Hall, A.E., Breeding for heat tolerance. Plant Breed. Rev., 10: Fig.11. Interaction effect of irrigation and cultivar on biomass yield (kg ha -1 ) ( ) [3] Mendham, N.J. and P.A. Salisbury, Physiology, crop development, growth and yield. In: Kimber, D.S. and D.I. McGregor. (Ed.). Brassica Oilseeds: Production and utilization. CAB International, London. pp: [4] MasoudSinaki, M.J., E. MajidiHeravan, H. Shirani Rad, G. Noormohammadi and G.H. Zarei, The effects of water deficit during growth stages of canola (Brassica napusl.), Am-Euras. J. Agric. Environ. Sci., 2: [5] Faraji, A., N. Lattifi, A. Soltani and A.H. Shiranirad, Seed yield and water use efficiency of canola (Brassica napusl.) as affected by high temperature stress and supplemental irrigation. Agric. Water Manage., 96: Fig.12. Interaction effect of irrigation and cultivar on harvest index (cm) ( ) IV. Conclusions Flowering is the most sensitive stage for water stress damage resulting in a drastic reduction in yields. Using tolerant cultivars to water stress help to modify the water stress effect not only in flowering stage but also in whole plant growth stages. This study provides new information about the effect of water stress from the flowering stage on plant height, seed yield, biomass yield and harvest index of spring rapeseed cultivars in winter planting which helps us to choose the most appropriate and tolerant cultivars [6] Ahmadi, M. R. and F. Javid Far Evaluation and drought tolerance improvement methods in oil species of Brassica genus. Agricultural Research and Education Organization Press. (In Persian) [7] Wright, P. R., J. M. Morgan, R. S. Jossop and A. Cass Comparative adaptation of canola (Brassica napus L.) and indian mustard (Brassica Juncea) to soil water deficit. Field Crop Res. 42: [8] Kimber, D.S. and D.I. McGregor, Brassica Oilseeds: Production and utilization. 1st Ed. CAB International. Oxon UK. pp:

9 [9] Gammelvind, L. H., Schjoerring, J. K., Mogensen, V.O., Jenson, C.R., Bock, J. G. H. (1996). Photosynthesis in leaves and siliques of winter oilseed rape (Brassica napus L.) Plant Soil. 186, [10] Deepak, M.and P.N. Wattal Influence of water stress on seed yield of Canadian rape at flowering and role of metabolic factors. Plant physiol and Biochem. New Dehli.22(2): [11] Thomas, M. et al., The effect of timing and severity of water deficit on growth, development, yield accumulation and nitrogen fixation of mungbean. Field Crops Research, Amsterdam, v. 86, n. 7, p , [12] Kajdi, F Effect of irrigation on the protein and oil content of rape varieties.actaagronomica. 36: