Waterlogging stress tolerant sesame lines: Towards mitigating climate change

Abstract

Cultivated sesame (Sesamum indicum L., 2n = 2x = 26), one of the world’s most important and ancient oilseed crop is cultivated in subtropical and tropical regions of the world, including India. Waterlogging is one of the adverse factors constraining sesame production (Li et al., 2017). Loss of sesame seed yields due to waterlogging ranges from 30 % to 100 % worldwide (Li et al., 2017) and 15 % to 80 % in India (Sreepriya and Girija, 2020), depending on the duration of waterlogging, growth stage of the crop, and type of soil (Sarkar et al., 2016). Therefore, identification of waterlogging tolerant sesame lines is crucial to waterlogging tolerant sesame breeding program. With this background, an experiment was conducted to identify waterlogging stress tolerant sesame lines. METHODOLOGY An experiment was conducted during Rabi season of 2020 at the research farm of ICAR-Indian Institute of Oilseeds Research, Hyderabad, India. A panel of 120 sesame lines were sown in 3 metre rows following alpha lattice design with triplication. A spacing of 10 cm plan-to-plant and 45 cm row-to-row was followed with recommended package of practice. The crop was exposed to 10 days waterlogging stress at the seedling establishment stage, followed by six days during flowering stage. Data on seed yield and related traits were recorded from five random individual plants and the statistical analyses were performed with AGRICOLA package in R software. RESULTS AND DISCUSSIONS A studied set of 120 sesame genotypes were subjected analysis of variance (ANOVA) and genetic variability and results are summarized in tables 1 and 2 respectively. Sesame genotypes varied significantly for most of the traits (Table 1), and most of the traits showed statistical significance p<0.01 and for the average yield per plant it was p<0.05. This suggests that genotypes responded differently under waterlogging stress. Further, plant height (cm) was maximum (99.8 cm) in IC-204843; average number of primary branches was maximum (4.2) in TMV7; average number of capsules per plant was highest (69.75) in IC-131943; average capsule length was maximum (3.3 cm) in IC-96226; average capsule width was maximum (0.72 cm) in IC-131936; average seed yield per plant was highest (23.23 g) in IC-500423; and, average dry weight per plant recorded highest (23.38 g) in IC-132300. This suggests that landraces IC204843, IC-131943, IC-96226, IC-131936, IC-500423 and IC-132300; and, variety TMV7 are tolerant to waterlogging stress in terms of various yield and related traits. Table 1: Analysis of variation (ANOVA) for yield traits under waterlogged stress. Character MSS F Prob (Pr) Sig CV (%) Mean Range Plant height (cm) 220.56 4.07 2X10-7 * * * 11.8 62.48 36.22 to 99.8 Average no. of primary branches per plant 0.58 1.87 5e-6 * * * 24.1 2.31

1 to 4.2 Number of capsules per plant (cm) 230.41 1.06 0.36 NS 52.7 27.98

14.07 to 69.77 Capsule length (cm) 19.11 4.23 2X10-16 * * * 8.9 23.81 1.7 to 3.37 Capsule width (cm) 0.44 2.43 1e-18 * * * 7.4 5.75 0.46 tom 0.72 Average seed yield per plant (g/plant) 81.26 1.37 0.03 * 92.7 8.32

1.3 to 23.23 Average dry weight per plant (g/plant) 48.18 2.01 6X10-16 * * * 54.8 8.92

3.09 to 23.38

Seed yield per plant recorded highest genetic, phenotypic, and environmental coefficients of variance (Table 2). While heritability in broad sense was highest for capsule length, genetic advancement (percent of mean) was highest in average dry weight of the plant at harvesting. Results of the present study hold significance as the duration of waterlogging stress imposed during seedling establishment was severe than that of the other reports: for instance, three hours (Wang et al., 2016) to six days (Wei et al., 2013).

Table 2: Genetic variability for yield traits under waterlogged stress Traits Genetic Coefficient of Variance (%) Phenotypic Coefficient of Variance (%) Environmental Coefficient of Variance (%) Heritability (H2, Broad Sense) Genetic Advancement (% of mean) Plant hight (cm) 11.29 17.61 13.51 0.41 14.92 No of primary branches per plant

13.25

27.07

23.61

0.24

13.37 No of capsules per plant 6.16 53.55 53.20 0.01 1.46 Capsule length (cm) 9.13 13.04 9.31 0.49 13.18 Capsule width (cm) 5.19 8.88 7.20 0.34 6.25 Seed yield (g/plant) 35.49 95.99 89.19 0.14 27.02 Dry weight (g/plant) 31.14 64.15 56.08 0.24 31.13

CONCLUSION Sesame is more sensitive to waterlogging at seedling establishment stage (Sarkar et al, 2016). Waterlogging tolerant sesame genotypes IC204843, IC-131943, IC-96226, IC-131936, IC-500423, IC-132300, and TMV7, identified in the present work are useful for waterlogging tolerance breeding. However, they need to be further studied using molecular, physiological, and anatomical approaches to decipher waterlogging stress tolerance mechanisms.