Bangladesh Agron. J. 2021, 24(1): 43-55 PHYSIOLOGICAL AND YIELD RESPONSES OF SOME SELECTED RAPESEED/MUSTARD GENOTYPES TO SALINITY STRESS F. Ahmed1, I.M. Ahmed1, A.F.M. Shamim Ahsan1, B. Ahmed1 and F. Begum2 1Plant Physiology Division, BARI, Gazipur-1701 2Oil Seed Research Center, BARI, Gazipur-1701 Corresponding E-mail: faruquebari@gmail.com (Received: 12 February 2021, Accepted: 19 February 2021) Keywords: Salnity, rapeseed/mustard, toerant genotypes, physiological parameters, seed yield Abstract An experiment on rapeseed/mustard genotypes was conducted during 2019-2020 rabi season in vinyl house of Plant Physiology Division of Bangladesh Agricultural Research Institute (BARI), Gazipur to find out the salt-tolerant genotypes based on the responses of their physiological parameters and yield. Five selected rapeseed/ mustard genotypes (V1= Jun-536, V2 = BJDH-12, V3 = BD-10115, V4 = BARI Sarisha-14, V5 = BD-6950) were tested at three salinity levels (S0= 0, S1= 5 and S2=10 dS m-1). Irrespective of the genotypes, salinity stress showed a negative effect on the measured physiological parameters as well as seed yield. Leaf chlorophyll contents, leaf area, leaf photosynthetic rate and total dry matter (TDM) were reduced due to salinity stress which ultimately affected seed yield irrespective of the genotypes. However, these parameters were less affected by the salinity in V1 and V2 genotypes compared to others. Sodium and potassium ion contents and their ratios (K+/Na+) in leaf tissues were significantly affected by salinity stress. Among the genotypes, V1 and V2 showed higher K+/Na+ ratios in leaf under both the salinity treatments, and that phenomenon indicated their higher tolerance to salinity than the other genotypes. Catalase (CAT), Peroxidase (POD) activity and Malondialdehyde (MDA) content of the genotypes increased due to salinity stress with variability among the genotypes. The higher CAT and POD activity with lower MDA content was found in V1 and V2 genotypes which indicated their better salt tolerance ability compared to others. These genotypes also showed higher seed yield under both the salinity levels (5 and 10 dS m-1) compared to other genotypes. Based on the responses of physiological parameters and seed yield to salinity, the genotypes Jun-536(V1) and BJDH-12(V2) could be considered relatively tolerant to salinity stress. Introduction Salinity is an important limiting factor that causes low crop yield with inferior quality. The adverse effects of salinization cause both osmotic stress and ionic toxicity in plants, leading to secondary stresses such as nutritional disorders and oxidative stress. One of the most detrimental effects of salinity stress is the accumulation of Na+ and Cl− ions in tissues of plants exposed to soils with high NaCl concentrations. Entry of both Na+ and Cl−into the cells causes’ severe ion imbalance and the excess uptake of them might cause significant physiological disorder(s). Generation of reactive oxygen species (ROS) like singlet oxygen, superoxide radical, hydrogen peroxide, and hydroxyl radicals exposed to salinity stress causes injury to plants. The genotypes which produce more ROS scavenging enzymes under stress can be considered as comparatively tolerant genotype. mailto:faruquebari@gmail.com 44 Ahmed et al. Among the oilseed crops grown in Bangladesh, rapeseed/mustard (Brassica spp.) holds the first position acarage and production. It constitutes an important source of edible oil and is grown under diverse agro-ecological situations. This crop can also be grown successfully in the coastal districts of southern Bangladesh where the cropping intensity is lower than in other parts of the country. However, most of the southern districts of the country are under saline zones which cover an area of 25-30% of the total cultivable land (SRDI, 2012). Though soil salinity is the most dominant factors limiting crop production in the coastal areas of Bangladesh during dry season, salt-tolerant rapeseed/mustard can bring substantial changes in the agricultural practices in those saline soils. Genetic variations in salt tolerance exist in the glycophytes, and the degree of salt tolerance varies with plant species and varieties within a species. There also exist differences in sensitivity to salinity among Brassica cultivars which need to be found out in a systematic study. Therefore, the present study was conducted to find the tolerant mustard- rapeseed genotype(s) based ontolerance of physiological and yield parameters. Materials and Methods A pot experiment on mustard-rapeseed was conducted in the vinyl house of Plant Physiology Division, BARI, Gazipur during the rabi season of 2019-2020. Five selected mustard/rapeseed genotypes, namely: V1= Jun-536, V2= BJDH-12, V3= BD-10115, V4= BARISarisha-14, V5= BD-6950 was grown in three salinity levels (S0 = 0, S1 = 5 and S2 =10 dS m-1) in pots inside a plastichouse of Plant Physiology Division, BARI, Gazipur during rabi season of 2019-2020. Salinity was imposed at 20 days after sowing by adding NaCl solution. Salt solution was prepared by dissolving calculated amount of Lab grade NaCl with pond water. Salt solution was applied with an increment of 5dS m-1 every alternate day until desired salinity levels were attained. In the control treatment, pond water was used which salinity level was 0.2 dS m-1. Salinity levels were maintained by monitoring and adding salt solution when required up to maturity. The experiment was laid out in a Factorial Randomized Complete Block design with 5 replications. Plastic pots (top dia: 25 cm, bottom dia: 18 cm and height 25 cm; 12 kg soil) were filled up with soil and cowdung (4:1). Seeds were sown in each pot on 12 November 2019. Fertilizers were applied @100-30-80-20-3-1 kgha-1NPKSZnB. Half of N and all other fertilizers were applied as basal and the remaining N was applied at 20 days after sowing (DAS). Irrigation was done as and when required for maintaining adequate soil moisture. After emergence plants were thinned to three plants in each pot. Plants from three pots were sampled for leaf area and dry matter measurement at different growth stages. Sampled plants were separated into leaf, stem, and siliqua depending on growth stages. Leaf area was measured by an automatic area meter (LI-3100 C; LI-Cor, USA). Plant parts were dried in an oven for 72 hours at 70oC and dry weight was recorded. At harvest yield and yield components data were collected from three pots and analyzed statistically and mean separation was done by LSD test at 5% level of significance using data processing software. Chlorophyll estimation Leaves of each genotype were properly cut into small pieces and weighed 0.5 g and were taken for chlorophyll estimation at 55 DAS. Chlorophyll a, chlorophyll b and total chlorophyll were estimated following Arnon’s method (Arnon, 1949). The absorbance of the solution was read at 645 and 663 nm for Chlorophyll a, Chlorophyll b and total chlorophyll. Calculation: Chlorophyll a (mg g-1) = {12.7 (D663) - 2.69 (D645)}V/(1000w) Chlorophyll b (mg g-1) = {22.9 (D645) - 4.68 (D663)}V/(1000w) Response of Rapeseed/Mustard Genotypes to Salinity Stress 45 Total chlorophyll (mg g-1) = 20.2 (D645) + 8.02 (D663)V/(1000w) Where, D = optical density; V = final volume of 80% acetone (ml); w = fresh weight of sample taken (g) Leaf photosynthesis measurement: Leaf photosynthetic rate was measured on 50 DAS by a portable photosynthesis system (Li-6800, USA). Fully expanded third leaf from the top was used for this purpose and the measurement was carried out from 10 am to 11.30 pm. Sodium and potassium ion uptake measurement: At 55 DAS, fully expanded third leaf from the top was collected from each treatment for determining of sodium and potassium ion content in leaf tissue. Cell sap of leaf was extracted from the leaf using mortar and pistil. LAQUAtwin Sodium Ion Meter (Na-11, Horiba, Japan) and LAQUAtwin Potassium Ion Meter (K-11, Horiba, Japan) were used for Na+ and K+ determination, respectively. Enzyme Extraction and Assays Using a pre-cooled mortar and pestle, 0.5 g of leaf tissue was homogenized in 1 ml of 50 mMice-cold K-phosphate buffer (pH 7.0) containing 100 mMKCl, 1 mMascorbate, 5 mMβ- mercaptoethanol, and 10% (w/v) glycerol. The homogenates were centrifuged at 11,500×g for 10 min, and the supernatants were used for determining of enzyme activity. All procedures were performed at 0°C to 4°C. Determination of Protein The protein concentration of each sample was determined following the method of Bradford (1976) using BSA as a protein standard where 5, 10, 15, 20, 25 μgμl-1 protein concentrations were used to prepare the standard curve. Peroxidase (POD, EC 1.11.1.7): POD activity was estimated according to Hemeda and Klein (1990). The reaction mixture contained 25 mM K-P buffer (pH 7.0), 0.05% guaiacol, 10 mM H2O2 and enzyme. The activity was determined by the increase in absorbance at 470 nm due to guaiacol oxidation for 1 min using extinction coefficient of 26.6 mM-1 cm-1. Catalase (CAT, EC: 1.11.1.6): CAT activity was measured according to the method of Hossain et al. (2010) by monitoring the decrease of absorbance at 240 nm for 1 min caused by the decomposition of H2O2. The reaction mixture contained 50 mM K-phosphate buffer (pH 7.0), 15 mM H2O2, and enzyme solution in a final volume of 0.7 ml. The reaction was initiated with enzyme extract, and the activity was calculated using the extinction coefficient of 39.4 M−1 cm−1. Lipid peroxidation The level of lipid peroxidation in plant tissues was expressed as 2-thiobarbituric acid (TBA) reactive metabolites, mainly malondialdehyde (MDA), and was determined according to Hodges et al. (1999). Fresh samples (leaves) of around 0.5 g were homogenized in 4.0 ml of 1% trichloroacetic acid (TCA) solution and centrifuged at 10,000g for 10 min. The supernatant was added to 1ml 0.5% (w/v) TBA made in 20% TCA. The mixture was heated in boiling water for 30 min, and the reaction was stopped by placing the tubes in an ice bath. The samples were centrifuged at 10,000×g for 10 min, and the absorbance of the supernatant was recorded at 532 nm. Correction of non-specific turbidity was made by subtracting the absorbance value read at 600 nm. The level of lipid peroxidation was expressed as nmol g−1 fresh weight, with a molar extinction coefficient of 0.155 mMcm−1. 46 Ahmed et al. Results and Discussion Leaf chlorophyll content Interaction effect of genotypes and salinity showed significant influence on chlorophyll a content (Fig. 1). Under control conditions (non saline) chlorophyll-a content of the genotypes were identical while chlorophyll-b differed significantly. Fig.1. Interaction effect of genotype and salinity on leaf chlorophyll content of mustard/rapeseed at 55 DAS (Vertical bars indicate SE). V1= Jun-536, V2 = BJDH-12, V3 = BD-10115, V4 = BARISarisha-14, V5 = BD-6950 (S0= 0, S1= 5 and S2=10 dS m-1salinity). The maximum chlorophyll-b content was found in V2 which was identical with V3 but significantly higher than others. The lowest chl b was detected in V4 which was identical to that of V5. Total chlorophyll content was the highest in V2 which was identical with V3 but significantly higher than others and the lowest value was found in V4. At 5dS m-1 salinity, all the genotypes showed statistically similar chlorophyll-content except V4 which showed the lowest value. Chlorophyll-b content of V1 and V2 were identical and these values were significantly higher than V3, V4 and V5 genotypes which showed statistically similar values. The total chlorophyll content of V1 and V2 were identical but significantly higher than others. At 10dS m-1 salinity, chlorophyll-a content of V1, V2 and V3 was identical which were significantly higher than the other two genotypes. Again chlorophyll-a content of V4 and V5 were statistically similar. The lowest value was found in V4. Chlorophyll-b content was the highest in V2 which was identical with V1 and V5 but significantly higher than others. The lowest value was found in V4. The total chlorophyll content was the highest in V2 which was identical with V1 but significantly higher than others. Total chlorophyll content of V3 and V5 genotypes were identical and the lowest value was found in V4. In general, the photosynthetic pigments i.e. chlorophyll content decreased with the increase of salinity. Shah (2007) also reported reduced chlorophyll content in mustard under salinity stress. Photosynthesis Interaction effect of genotype and salinity showed significant influence on leaf photosynthetic rate (Fig. 2). Under control conditions, the highest photosynthetic rate was found in V5 (23.55 0 0.2 0.4 0.6 0.8 1 1.2 1.4 V1 V2 V3 V4 V5 V1 V2 V3 V4 V5 V1 V2 V3 V4 V5 S0 S1 S2 C h lo ro p h y ll ( m g g -1 F W ) Treatments Chl a C hl b Response of Rapeseed/Mustard Genotypes to Salinity Stress 47 µmol m-2s-1) which were identical with all other genotypes except V4 which showed the lowest value. At 5dS m-1 salinity, the highest photosynthetic rate was observed in V5 which was identical with V3 and V2. Again, V2 and V1 were identical and the lowest value was found in V4 genotype. At 10 dS m-1 salinity, the highest rate was recorded in V2 (15.05 µmolm-2s-1) which were identical with other genotypes, except V4, which showed the lowest value (12.67 µmol m-2 s-1). In general, with the increase of salinity levels photosynthetic rate was reduced irrespective of the genotypes. Salt-induced reduction in photosynthesis is associated with the partial stomatal closure and/or the non-stomatal limitation which is involved in the dark enzymatic processes of CO2 assimilation e.g. the decrease in Rubisco activity and content, or Pi-regeneration capacity (Ashraf and Harris, 2013). Fig. 2. Interaction effect of genotype and salinity on leaf photosynthesis of mustard/ rapeseed at 55 DAS (Vertical bars indicate SE) V1= Jun-536, V2 = BJDH-12, V3 = BD-10115, V4 = BARI-14, V5 = BD-6950S0= 0, S1= 5 and S2=10 dSm-1 salinity. Leaf area and dry matter production Leaf areaplant-1 of the mustard-rapessdgenotypes differed significantly under different levels of salinity stress (Table 1). Under control conditions at 45 DAS, the maximum leaf area was observed in V2 (410 cm2), which was identical with V1 and V3. At 5 dS m-1salinity, the highest leaf area was found in V2 (396.67 cm2), which was identical with V1, V3 and V5 genotypes. The lowest value was found in V4 (217.67 cm2) genotype. Under 10 dS m-1, V2 produced the highest leaf area (248.33 cm2), which was identical with all other genotypes and the lowest value was observed in V4 (167.67 cm2). In general leaf area was reduced with increased salinity levels irrespective of the genotypes. Salinity-induced osmotic stress is considered responsible for the reduced leaf area in Canola and wild mustard (Huang and Redmann, 1995). Furthermore, high salinity is known to induce ionic stress, which causes premature abscission and senescence of adult leaves, thus reducing the available photosynthetic area (Munns, 2002). At 55 DAS, under control condition (no salinity), the maximum leaf area was found in V2 (438.33 cm2), which was identical with all other genotypes, except V4 which produced the lowest leaf area. At 5 dS m-1salinity, V2 (401.67 cm2) produced the highest leaf area which was identical with all other genotypes except V4 which produced the lowest leaf area (246.67 cm2). 0 5 10 15 20 25 30 V1 V2 V3 V4 V5 V1 V2 V3 V4 V5 V1 V2 V3 V4 V5 S0 S1 S2 P h o to sy n th e si s (µ m o l m -2 S -1 ) Treatments 48 Ahmed et al. At 10 dS m-1 salinity, the highest leaf area was found in V2 and was identical with all other genotypes except V4 which produced the lowest leaf area (197 cm2). Total dry matter production of the genotypes was identical at 45 DAS under control conditions, although comparatively higher values were observed in V2 (8.0 g plant-1) and V1 (7.83 gplant-1) and the lowest (6.93 g plant-1) in V4. At 5 dSm-1 salinity, the highest TDM was found in V2 (6.98 gplant-1) which were identical with all other genotypes except V4 which produced the lowest dry matter. At 10 dSm-1 salinity, all the genotypes showed identical values except V4 which showed the lowest TDM (4.07 g plant-1). At 55 DAS under control condition, TDM production of V1, V2, V3 and V5 was identical and the lowest value was found in V4. At 5dS m-1salinity, statistically similar TDM was observed in all the genotypes except V4 which was lowest among the genotypes. At 10 dS m-1salinity, the maximum TDM was observed in V1 which was identical with V2, similarly V2 and V3 were identical and the lowest value was found in V4. At harvest under control condition, TDM production of the genotypes was identical except V4 which produced the lowest. At 5dS m-1 salinity TDM of the genotypes were statistically identical. Under 10 dS m-1 salinity, the maximum TDM was found in V1 which was identical with V2, V3 and V5 but lowest in V4. Dry matter production which is considered as an index of photosynthetic activity (Essa and Al-Ani, 2001) was reduced under saline conditions. Reduction in total dry matter accumulation under saline conditions was also reported by Shamsul et al. (2011) in Indian mustard (Brassica juncea). Table 1. Interaction effect of genotype and salinity on leaf area and TDM of mustard/ rapeseedgenotypes Salinity Genotype Leaf area (cm2) Total dry matter (g plant -1) 45 DAS 55 DAS 45 DAS 55 DAS Harvest S0 V1 396.67 437.33 7.83 9.24 10.80 V2 410.00 438.33 8.00 9.17 10.20 V3 389.67 401.77 7.50 9.00 10.47 V4 326.00 342.67 6.93 7.27 9.90 V5 380.33 410.67 7.10 9.00 10.20 S1 V1 380.00 398.67 6.83 8.88 9.33 V2 396.77 401.67 6.98 8.98 9.53 V3 378.33 388.33 6.22 8.10 9.10 V4 217.67 246.67 5.49 6.83 8.20 V5 365.00 391.67 6.20 8.77 9.17 S2 V1 244.33 303.67 5.85 7.80 8.87 V2 248.33 310.00 5.98 7.65 8.63 V3 240.00 302.00 5.63 7.67 8.25 V4 167.67 197.00 4.07 5.99 7.98 V5 243.33 298.67 5.87 7.77 8.60 LSD (0.05) 27.68 38.51 1.42 1.27 1.50 CV (%) 5.2 6.6 11.2 9.4 9.6 S0=0, S1=5 and S2=10 dS m-1 salinity. V1= Jun536, V2 = BJDH-12, V3 = BD-10115, V4 = BARI-14, V5 = BD-6950. Potassium and Sodium ion in leaf tissue The interaction effect of genotype and salinity on potassium content in leaf tissue was significant (Table 2). Under control conditions, the maximum K+ was observed in V3 (2700 ppm) which Response of Rapeseed/Mustard Genotypes to Salinity Stress 49 was identical with V1 and V2 but significantly higher than others. At 5dS m-1, the highest K+ was recorded in V4 (2900 ppm) and the lowest value was found in the V5 (2300 ppm) genotype. At 10dS m-1 salinity, the highest K+ was recorded in V1 (4800 ppm) genotype and the lowest value was found in V4 which was identical with V2. The adverse effect of salinity on plant growth may be due to ion cytotoxicity and osmotic stress. High levels of K+in young expanding tissue are associated with salt tolerance in many plant species (Bandeh-Hagh et al., 2008; Shabala, 2009). Sodium content in leaf tissue was significantly lower in the control treatment than other salinity levels irrespective of the genotypes, and the maximum Na+ content under no salinity condition was found in V4 which was identical with V5 but significantly higher than others. Sodium content in leaf tissues increased significantly due to salinity stress irrespective of the genotypes. At 5dS m-1 salinity, the highest Na+ content was found in V4 (650 ppm) and the lowest value was observed in V3 (170 ppm) which was identical with V2. At 10dS m-1 salinity, the highest Na+ content was found in V4 (1400 ppm) which was significantly higher than all other genotypes. The lowest Na+ content was found in V2 (260 ppm). The potassium and sodium ion ratio in leaf tissue was drastically reduced due to salinity stress. Genotypes showed significant variability in K+/Na+ ratios in leaf tissue under control conditions. The highest value was found in V2 (44.14) which was significantly higher than others. Genotypes V2 and V5 showed moderate ratios of K+/Na+ content in leaf tissue and the lowest in V4 (14.34). At 5dS m-1 salinity, the maximum value was observed in V2 (13.73) which was identical with all other genotypes and the lowest value was found in V4 (4.50). At 10 dS m-1 salinity, the maximum value was observed in V2 (12.70) which was identical with V1 (10.97) and V3 (10.92) but significantly higher than other genotypes. The lowest value of K+/Na+ ratio was found in V4 (2.23 ppm) and V5 showed the moderate value. A decrease in uptake of potassium (K) and consequent decrease in growth at higher sodium (Na) concentration has been reported earlier by Ashraf and McNeilly (2004). Table 2. Interaction effect of genotype and salinity on potassium and sodium ion uptake and their ratios in mustard/rapeseed genotypes at 55 DAS Salinity Genotype K+ (ppm) Na+(ppm) K+/Na+ S0 V1 2500 68 36.87 V2 2600 59 44.14 V3 2700 120 22.78 V4 2400 170 14.34 V5 2200 110 20.03 S1 V1 2500 210 11.91 V2 2600 190 13.73 V3 2300 170 13.55 V4 2900 650 4.50 V5 2500 220 11.52 S2 V1 4800 440 10.97 V2 3300 260 12.70 V3 4000 370 10.92 V4 3100 1400 2.23 V5 4400 580 7.61 LSD (0.05) 225.86 72.25 2.78 CV (%) 4.5 11.9 10.5 S0=0, S1=5 and S2=10 dS m-1 salinity. V1= Jun536, V2 = BJDH-12, V3 = BD-10115, V4 = BARI-14, V5 = BD-6950. 50 Ahmed et al. Antioxidant activity Antioxidant activity was significantly affected due to salinity stress (Fig. 3). Under control treatment, higher catalaze (CAT) activities were found in V5 and lower in V2. At 5dS m-1 salinity, the highest CAT activity was observed in V2 which was significantly higher than others. Fig. 3. Effect of salinity stress on the catalyze activity in rapeseed/mustard genotypes at 55DAS. (Vartical bar indicate SE). V1= Jun-536, V2 = BJDH-12, V3 = BD-10115, V4 = BARI- 14, V5 = BD-6950.S0= 0, S1= 5 and S2=10 dS m-1salinity. At 10 dS m-1salinity CAT activity was higher than control and 5dS m-1salinity and the maximum activity was observed in V2 which was identical with V1 but significantly higher than others. CAT activity of V3 and V5 were identical and the lowest was found in V4. Peroxidase (POD) activity also increased due to temperature stress compared to control (Fig.4). Under control conditions, comparatively higher POD activity was found in V5 followed by V2 and V1 and the lower in V4 and V3. At 5dS m-1salinity the highest POD activity was observed in V2 which was significantly higher than other. At 10 dS m-1salinity POD activity of V1, V2 and V5 were satirically identical, V3 showed moderate activity while the lowest was found in V4. The reduced rate of photosynthesis increases the formation of reactive oxygen species (ROS) and increases the activity of enzymes (CAT and POD) that detoxify the ROS (Foyer and Noctor, 2005). Fig. 4. Effect of salinity stress on the POD activity in rapeseed/mustard genotypes at 55 DAS (Varticalbars indicateSE).V1= Jun-536, V2 = BJDH-12, V3 = BD-10115, V4 = BARI-14, V5 = BD-6950S0=0, S1= 5 and S2=10 dS m-1salinity. 0 0.1 0.2 0.3 0.4 0.5 0.6 V1 V2 V3 V4 V5 V1 V2 V3 V4 V5 V1 V2 V3 V4 V5 S0 S1 S2 C A T ( m m o l g -1 F W m im -1 ) Treatments 0 0.5 1 1.5 2 2.5 3 V1 V2 V3 V4 V5 V1 V2 V3 V4 V5 V1 V2 V3 V4 V5 S0 S1 S2 P O D ( m m o l g - 1 F W m im -1 ) Treatments Response of Rapeseed/Mustard Genotypes to Salinity Stress 51 Malondialdehyde (MDA) content also increased due to salinity stress compared to control (Fig. 5). Under control conditions, the genotypes showed variability in MDA activity which increased with the increase in salinity levels. At 5dS m-1salinity, the maximum MDA activity was foun in V4 followed by V5 and V3, and the lowest was found in V2. At 10 dS m-1salinity, almost a similar trend was observed where the highest MDA was found in V4 and the lowest in V2. Higher MDA content in the cell is correlated with salt stress sensitivity while lower MDA content displays higher antioxidative ability, reflecting higher tolerance to stress (Noreen and Ashraf, 2009). Fig. 5. Effect of salinity stress on the MDA activity in rapeseed-mustard genotypes at 55 DAS (Vertical bars indicate±SE). V1= Jun-536, V2 = BJDH-12, V3 = BD-10115, V4 = BARI- 14, V5 = BD-6950. S0= 0, S1= 5 and S2=10 dS m-1salinity. Yield and yield contributing characters Effect of genotypes Genotypes showed significant difference in plant height (Table 3). The tallest plant was found in V3 (127.33 cm) which was significantly higher than all other genotypes. Siliquaplant-1 of the genotypes also varied significantly. The highest number of siliquaplant-1 was recorded in V5 (115.82) and the lowest siliquaplant-1 was recorded in V4 (57.37) genotype. The number of seedssiliqua-1 of the genotypes differed significantly. Table 3. Effect of genotype on yield and yield component of mustard/rapeseed Genotype Plant height (cm) No. of siliqua plant-1 No. of seeds siliqua-1 1000-seed weight (g) Seed yield plant-1 (g) V1 117.96 94.56 13.44 2.97 3.55 V2 100.59 95.26 13.99 3.19 3.91 V3 127.33 79.74 15.69 3.10 3.59 V4 73.56 57.37 25.84 3.27 2.91 V5 110.37 115.82 13.24 2.80 3.26 LSD (0.05) 7.56 13.45 2.22 0.27 0.31 CV (%) 7.50 10.50 11.40 9.30 9.60 V1= Jun536, V2 = BJDH-12, V3 = BD-10115, V4 = BARI-14, V5 = BD-6950. 0 10 20 30 40 50 60 70 80 V1 V2 V3 V4 V5 V1 V2 V3 V4 V5 V1 V2 V3 V4 V5 S0 S1 S2 M D A ( n m o l g -1 F W m im -1 ) Treatments 52 Ahmed et al. The highest number of seedssiliqua-1 was observed in V4 (25.84) which were significantly higher than other genotypes and the lowest value was observed in V5 (13.24). The seed size of the genotypes varied significantly. The highest 1000-seed weight was recorded in V4 (3.27 g) which was significantly higher than others and the lowest was recorded in V5 (2.80 g). Seed yieldplant-1 of the genotypes varied significantly. The highest seed yield was found in V2 which significantly higher than others. But the lowest yield was observed in V4. Effect of salinity Salinity stress significantly affected yield and yield contributing characters of rapeseed/mustard genotypes (Table 4). Plant height was significantly reduced due to salinity stress. The tallest plant was recorded in control (125.44 cm) condition while the shortest in 10 dS m-1salinity treatment (86.29 cm). Table 4. Effect of salinity on yield and yield components of rapeseed/mustard Salinity Plant height (cm) No. of siliqua plant-1 No. of seeds siliqua-1 1000-seed weight (g) Seed yieldplant-1 (g) S0 125.44 91.64 17.39 3.29 4.16 S1 100.16 85.18 16.50 3.09 3.38 S2 86.29 76.82 15.42 2.82 2.79 LSD(0.05) 5.85 10.42 1.72 0.21 0.24 CV (%) 7.50 10.50 11.40 9.30 9.60 S0= 0, S1= 5 and S2=10 dS m-1 The most common undesirable effect of salinity on the crop of Brassica is the reduction in plant height, component characters of yield as well as deterioration of the product quality (Zamani et al., 2010). Siliquaplant-1 was significantly reduced due to salinity stress, the highest number was observed in the control (91.64) condition which was identical with 5dS m-1salinity level and the lowest (76.82) in 10 dSm-1. A negative effect of salinity on the number of siliqua plant-1 of Indian mustard was also observed by Kripa et al. (2011). The highest number of seedssiliqua-1 was found in the control conditions (17.39) which was identical with 5 dS m-1and the lowest (15.42) in 10 dS m-1salinity. These results corroborate the findings of Ahmad (2010). Reduced seed size was observed due to salinity stress. The highest 1000-seed weight was found in the control conditions (3.29 g) which was significantly higher than others and the lowest (2.82 g) in 10 dS m-1salinity. Seed yield was also reduced due to salinity stress and the highest seed yield (4.16gplant-1) was recorded in the control conditions and the lowest (2.79 gplant-1) in 10 dS m-1 salinity. This finding is supported by Kripa et al. (2011). Interaction effect of genotype and salinity on seed yield Interaction effect of genotype and salinity showed significant influence on seed yieldplant-1 (Fig.6). Under control conditions, the seed yield of V1 and V2 were identical. At 5 dS m-1salinity the maximum seed yield was found in V2 which was identical with V1, V3 and V5 but significantly higher than V4. At 10 dS m-1salinity V2 showed the highest seed yield which was significantly higher than other. The lowest yield was found in V4 genotype. Salinity may reduce the crop yield by upsetting the water and nutritional balance of plants (Francois, 1994; Islam et al., 2001). Response of Rapeseed/Mustard Genotypes to Salinity Stress 53 Fig. 6. Interaction effect of genotype and salinity on the seed yield of rapeseed/mustard (Vertical barsindicate SE) V1= Jun-536, V2 = BJDH-12, V3 = BD-10115, V4 = BARI Sarisha-14, V5 = BD-6950. S0= 0, S1= 5 and S2=10 dS m-1salinity. Conclusion Results revealed that genotypes Jun-536 and BJDH-12 were comparatively salt-tolerant as evaluated based on seed yield and important physiological parameters. References Ahmad, B. 2010. Effects of salinity on yield and component characters in canola (Brassica napus L.) cultivars. Not. Sci. 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