Rapeseed (Brassica napus) Varieties Performance under Soil Moisture Stressed and Non-stressed Condition in Terai Region of Nepal

World Research Journal of Agricultural Sciences Vol. 4(1), pp. 120-125, July, 2017. www.premierpublishers.org.issn: XXXX-XXXX WRJAS Research article Rapeseed (Brassica napus) Varieties Performance under Soil Moisture Stressed and Non-stressed Condition in Terai Region of Nepal 1 Roshan Babu Ojha, 2 Himal Prasad Timalsina, 3 Razan Malla 1 Scientist, Soil Science Division, Nepal Agricultural Research Council, Nepal 2 Senior Scientist, National Wheat Research Program, Nepal Agricultural Research Council, Nepal 3 Technical Officer (soil science), Oilseed Research Program, Nepal Agricultural Research Council, Nepal Soil moisture is limiting factor of production during rapeseed growing period of Nepal. An experiment was conducted in research farm of oilseed research program (ORP), Sarlahi, Nepal in order to evaluate the performance of elven pipeline varieties of rapeseed under soil moisture stress condition. They were laid out in the randomized complete block design with three replications for two years 2014 to 2016. Separate field blocks for irrigated (non-stress) and drought (stressed) condition were made. Yield from moisture stress (Ys) and non-stress (Ys) were recorded to calculate different drought indices. Variety ICT 2010-3 performs better with the highest tolerance index (TOL), marginal productivity (MP), gross mean productivity (GMP), yield index (YI), yield stability index (YSI), stress tolerance index (STI) and the lowest stress susceptibility index (SSI) and percentage yield reduction (%YR). But in the second-year variety ICT 2001-14 has the highest MP, GMP, YI and STI. Variety ICT 2001-19 has the highest TOL and YSI, and the lowest SSI and %YR. On an average ICT 2001-14 has the highest MP, GMP and STI and these indices are significantly positively correlated with stressed and non-stressed yield. So, ICT 2001-14 is the best choice for drought resistance in case of inner-terai ecological belt of Nepal. Key Words: Drought indices, Drought resistance, Non-Stressed yield, Stressed yield, Rapeseed. INTRODUCTION Rapeseed (Brassica napus) is a popular oilseed crops of Terai, inner-terai and upland mid-hills of Nepal where moisture is always a limiting factor of crop production. Nepal is in subtropical climatic zones. It receives heavy monsoon rainfall during June-July and less winter rainfall during November-December. So, there is moisture stress during rapeseed growing period (winter). There are two critical stages of moisture in rapeseed, first is at vegetative stage and next is at flowering stage. Winter rainfall is not sufficient to supply enough moisture during this stage and winter rainfall may not coincide these two growing stage of rapeseed. Soil moisture stress during reproductive period is more sensitive than vegetative stage (Ahmadi and Bahrani, 2009). Various factors like weather conditions, rapeseed developmental stages, stress intensity and duration, and crop genotype determines the effect of stress on crop plant (Robertson and Holland, 2004). So, rapeseed yield gap between research farm and farmer field is very high. So, best rapeseed variety under soil moisture stress condition is necessary to identify. Drought indices are important agronomic practice to select drought tolerant varieties despite genetic improvement (Richards et al., 2002). *Corresponding Author: Roshan Babu Ojha, Scientist, Soil Science Division, Nepal Agricultural Research Council, Nepal. E-mail: roshanbachhan@gmail.com

Ojha et al. 121 So, drought indices are used to determine the yield loss under moisture stressed (drought) condition compared to non-stressed (irrigated) condition. This index provides the basis to select drought resistant varieties (Mitra, 2001). Various drought indices have been proposed on the basis of empirical findings (Sio-Se Mardeh et al., 2006; Shirani Rad and Abbasian, 2011). Stress susceptibility index (SSI) indicate the susceptibility of the variety to yield loss during soil moisture stress condition (Fischer and Maurer, 1978). Stress tolerance index (STI) in the other hand is helpful to identify the varieties that have higher productivity under moisture stress and non-stress condition (Fernandez, 1992). Further, Farshadfar and Sutka (2002) proposed a modified stress tolerance index (MSTI) in which a separate correction coefficient is calculated and multiplied to STI. Percent reduction in the yield is another important parameter of drought indices which gives how much yield has been reduced at stressed condition compared to nonstressed condition (Choukan et al., 2006). The main objective of this study is to select the drought tolerant variety of rapeseed at inner Terai ecological belt of Nepal. MATERIALS AND METHODS A field trial was conducted at research farm of oilseed research program (ORP), Nawalpur, Sarlahi during 2014 to 2016. The soil of research farm is sandy loam with very acidic (5.1) soil reaction, medium organic matter content (3.2), medium to high available phosphorous (26 kg/ha), high potassium (198 kg/ha) and medium nitrogen content (0.12%) (SSD, 2015). Eleven different pipeline varieties of rapeseed (Goldee Tori, ICT 2003-15, ICT 2001-14, ICT 2006-4, ICT 2001-19, ICT 2001-12, ICT 2010-3, ICT 2002-8, ICT 2002-25, Preeti (check variety) and Uttara) have been selected as treatments. They were arranged in randomized complete block design in three replications. Variety Preeti was chosen as the standard check variety because it already a released variety by ORP and the most cultivated variety of the region. Two separate field plots, 25 m apart, for irrigated (non-stressed) and non-irrigated (stressed) were made in order to avoid water entering into non-irrigated plot. However, winter rainfall is very minimum which did not affect the soil moisture level. Two irrigations were given to meet the crop water requirement of the rapeseed in irrigated plot once at active vegetative stage and next at reproductive stage (critical stage) up to the field capacity level by surface flooding method. Except irrigation, all other activities and treatments were same for irrigated and non-irrigated plots. Each experimental plot consisted seven rows with 2m x 5m area. The row to row spacing is 30 cm and plant to plant spacing is continuous. Later manual thinning maintained approximately 10 cm plant to plant spacing. Seed yield of irrigated plot (Yp) and non-irrigated plot (Ys) was recorded after the final harvest of both years, February, 2015 and 2016. After then drought resistance indices were calculated based on the following formulas: SN Drought index Formula Cited from a Tolerance Index (TOL) Yp Ys Rosielle and Hamblin 1981; b Marginal Productivity (MP) (Ys+Yp)/2 Hossain, 1990 Rosielle and Hamblin, 1981; Hossain et al., 1990 c Geometric Mean Productivity (GMP) (Yp x Ys) Fernandez, 1992 d Stress [1 (Ys/Yp)] / Fisher and Maurer, Susceptibility Index (SSI) [1 (Ŷs/Ŷp)] 1978 e Stress Tolerance Index (STI) (Yp x Ys) / Ŷp Fernandez, 1992 f Yield Index (YI) Ys/ Ŷs Lin et al., 1986 g Yield Stability Index (YSI) Ys/Yp Bouslama and Schapaugh, 1984 h Percent Yield (Yp-Ys)/Yp x Choukan et al., Reduction (%YR) 100 2006 Where, Ys is the yield at stressed condition, Yp is the yield at non-stressed condition, Ŷs and Ŷp are average yield at stressed and non-stressed condition respectively. Data were analyzed by using GenStat software. Means were separated by Tukey s test at 5% level of significance. Sigma plot version 10 was used for graphics. Wilkinson Test of normality was done. All data was found normal distribution and normal data were subjected to ANOVA analysis. RESULTS AND DISCUSSIONS Except the varieties ICT 2003-15 and ICT 2001-19 other varieties yielded more than standard check variety in irrigated condition in 2016. However, in stressed condition only three varieties viz. ICT 2001-14, ICT-2010-3 and Uttara yielded more than standard check variety (Figure 2). Similarly, in first year variety ICT 2010-3 yielded the highest followed by ICT-2001-14, ICT 2003-15 and Goldee Tori in stressed condition (Figure 1b). Comparing yield only with the standard check might be misleading during selecting the drought tolerant varieties. So, various drought indices are calculated. In the first year, tolerance index of ICT 2001-12 was found the highest. Similarly, the highest marginal productivity was obtained from ICT 2001-19 with the least yield reduction from Goldee Tori. Rest of all drought indices viz. Gross mean productivity, yield stability index, yield index and stress tolerance index was found highest from variety ICT 2010-3 with the least stress susceptibility index. However, in second year variety ICT 2001-14 has the highest marginal productivity, gross marginal productivity, yield index and stress tolerable index (Table 2). Marginal productivity, Gross marginal productivity, yield index and stress tolerance index indicate the efficiency of the variety. There exist highly significant positive correlation between these indices (Table 3).

World Res. J. Agric. Sci. 122 Figure: 1a Figure: 1b Figure 1: Boxplot showing the yield of rapeseed at non-stressed (figure 1a) and stressed condition (figure 1b), 2015. Numbers 1, 2, 3,..., 11 in x-axis represent the varieties entry number (refer Table 1 for their respective varieties). Table 1: Drought tolerance indices of different rapeseed varieties at ORP, Nawalpur, in 2015 Entry No. Varieties TOL MP SSI GMP %YR YI YSI STI 1 Goldee tori 123.58 458.69 0.69 454.51 21.45 1.05 0.76 0.62 2 ICT 2003 15 213.76 493.21 1.03 481.49 37.09 1.02 0.64 0.70 3 ICT 2001 14 187.60 506.85 0.90 498.09 32.55 1.10 0.69 0.75 4 ICT 2006 4 250.50 495.99 1.17 479.92 43.47 0.98 0.60 0.69 5 ICT 2001 19 255.51 513.53 1.15 497.38 44.34 1.02 0.60 0.74 6 ICT 2001 12 296.15 490.42 1.34 467.54 51.39 0.91 0.54 0.66 7 ICT 2010 3 139.72 534.12 0.67 529.53 24.25 1.23 0.77 0.84 8 ICT 2002 8 188.71 473.45 0.96 463.95 32.75 1.01 0.67 0.65 9 ICT 2002 25 280.56 509.35 1.25 489.65 48.69 0.98 0.57 0.72 10 Uttara 221.55 451.46 1.14 437.65 38.45 0.90 0.61 0.58 11 Preeti 33.00 316.50 0.29 316.07 5.73 0.80 0.90 0.30 TOL = Tolerence Index; MP = Marginal Productivity; SSI = Stress susceptibility Index; GMP = Gross Mean productivity; %YR = percentage in yield reduction; YI = Yield index; YSI = Yield stability index and STI = Stress tolerance index Table 2: Drought tolerance indices of different rapeseed varieties at ORP, Nawalpur, in 2016 Entry No. Varieties TOL MP SSI GMP %YR YI YSI STI 1 Goldee tori 144.30 332.75 1.53 324.83 40.31 0.95 0.64 0.82 2 ICT 2003 15 20.30 267.75 0.31 267.56 5.67 0.94 0.93 0.56 3 ICT 2001 14 29.60 400.30 0.31 400.03 8.27 1.40 0.93 1.25 4 ICT 2006 4 170.40 260.00 2.12 245.64 47.60 0.64 0.51 0.47 5 ICT 2001 19 2.40 242.40 0.04 242.40 0.67 0.88 0.99 0.46 6 ICT 2001 12 106.50 299.55 1.30 294.78 29.75 0.90 0.70 0.68 7 ICT 2010 3 32.50 393.85 0.34 393.51 9.08 1.38 0.92 1.21 8 ICT 2002 8 173.60 329.00 1.79 317.34 48.50 0.88 0.58 0.79 9 ICT 2002 25 161.80 286.50 1.89 274.84 45.20 0.75 0.56 0.59 10 Uttara 47.30 354.55 0.54 353.76 13.21 1.21 0.87 0.98 11 Preeti 28.50 312.25 0.37 311.92 7.96 1.09 0.91 0.76 TOL = Tolerence Index; MP = Marginal Productivity; SSI = Stress susceptibility Index; GMP = Gross Mean productivity; %YR = percentage in yield reduction; YI = Yield index; YSI = Yield stability index and STI = Stress tolerance index The highest tolerance index and yield stability index was obtained from variety ICT 2001-19. Similarly, the lowest stress susceptibility index and percentage yield reduction was also obtained from variety ICT 2001-19. Tolerance index, yield stability index, stress susceptibility index and percentage yield reduction are consistency parameters for

Ojha et al. 123 Table 3: Simple correlation coefficient of different drought indices with yield of 11 varieties of rapeseed Variables Ys Yp TOL MP SSI GMP YR YI YSI STI Ys 1.406ns -.642 *.865 ** -.690 *.909 ** -.642 * 1.000 **.688 *.920 ** Yp 1.441ns.809 **.374ns.749 **.441ns.403ns -.379ns.728 * TOL 1 -.170ns.992 ** -.265ns 1.000 ** -.644 * -.993 ** -.293ns MP 1 -.238ns.995 ** -.170ns.863 **.234ns.991 ** SSI 1 -.331ns.992 ** -.692 * -1.000 ** -.356ns GMP 1 -.265ns.908 **.327ns.997 ** YR 1 -.644 * -.993 ** -.293ns YI 1.689 *.919 ** YSI 1.352ns STI 1 Ys = yield at stressed condition, Yp = yield at non-stressed condtion, TOL = Tolerence Index; MP = Marginal Productivity; SSI = Stress susceptibility Index; GMP = Gross Mean productivity; %YR = percentage in yield reduction; YI = Yield index; YSI = Yield stability index, STI = Stress tolerance index, * = significant at P<0.05, ** = significant at P < 0.01 and ns = non-significant Figure: 2a Figure: 2b Figure 2: Boxplot showing the yield of rapeseed at non-stressed (figure 2a) and stressed condition (figure 2b), in 2016. Numbers 1, 2, 3,..., 11 in x-axis represent the varieties entry number. selecting variety against drought. There also exists a perfect positive significant correlation between tolerance index, percentage yield reduction and stress susceptibility index (Table 3). It indicate the variety ICT 2001-19 is more consistence and stable than other variety. The correlation between the yield indices also follow the normal trend. In mean of two year variety ICT 2001-14 is superior in marginal productivity, gross marginal productivity, yield index and stress susceptibility index. Similarly, variety ICT 2001-19 is superior in tolerance index, yield stability index, stress susceptibility index and percentage yield reduction (figure 3a and 3b) but considering yearly mean variety ICT 2010-3 shows both consistent and stable character in first year which is not observed in second year. A significant positive correlation found between non-stress yields (Yp) and MP, GMP, YI and STI (Golabadi et al., 2006; Shirani Rad and Abbasian, 2011) similar with our findings. So, these indices are good indicator of drought tolerant rather other indices. Drought tolerant cultivar must have index partly high correlation with grain yield under stress and non-stress condition (Farshadfar et al., 2001). There are various research paper with similar conclusion in different crops like Golabadi et al. (2006) in wheat, Farshadfar and Sukta (2002) in maize and Fernandez (1992) in mungbean. During selection of appropriate drought severity index, the correlation between the yield under stressed and non-stressed condition and several drought indices should be taken into consideration. Shirani Rad and STI, GMP and MP are best indicator to select variety that produce high yield both under stressed and non-stressed environment (Abbasian, 2011; Shafazadeh et al., 2004).

World Res. J. Agric. Sci. 124 Ys Yp TOL MP GMP %YR Uttara ICT 2002 25 Preeti Goldee tori 500 400 300 200 100 0 ICT 2003-15 ICT 2001 14 ICT 2006-4 ICT 2002 8 ICT 2001 19 ICT 2010 3 ICT 2001 12 Figure: 3a SSI YI YSI STI Preeti Goldee tori 2.50 2.00 ICT 2003-15 Uttara ICT 2002 25 1.50 1.00 0.50 0.00 ICT 2001 14 ICT 2006-4 ICT 2002 8 ICT 2001 19 ICT 2010 3 ICT 2001 12 Figure: 3b Figure 3: Two years average mean relationship between Ys, Yp and drought indices (figure 3a and 3b) of eleven pipeline varieties of rapeseed. The values of Ys, Yp and drought indices are two year mean values. Under moderate stress condition MP, GMP and STI were best indices for selecting drought tolerant varieties (Sio-Se Mardeh et al., 2006). But under very severe stress none of indices are useful in selecting drought tolerant cultivars (Shirani Rad and Abbasian, 2011). However, Anwar et al. (2011) found significant positive correlation of Yp with MP, GMP andsti and Ys with MP, GMP, STI, YI, TOL, SSI and YSI. So, they concluded all drought indices other than TOL, SSI and YSI are better indicator for selecting drought resistant varieties. Significant positive correlation of Yp with MP, GMP and STI and Ys with MP, GMP, YI, YSI and STI (Table 3) was found. Hence, MP, GMP and STI are better predictor of potential yield under stress and nonstress condition. CONCLUSION Among different drought indices marginal productivity, geometric mean productivity and stress tolerance indices are selective indices in our study to identify the stress tolerant rapeseed varieties. In the first year, variety ICT 2010-3 has the highest MP, GMP and STI. However, in the second year and two year average value, variety ICT

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