Seed yield and physiological responses to deal with drought stress and late sowing date for promising lines of rapeseed (<i>Brassica napus</i> L.)

Abstract

The introduction of new genotypes of crop plants is among the most strategic research programmes, especially in arid and semi-arid regions. To study the effect of drought stress on seed yield and some physiological traits of promising lines of rapeseed at different sowing dates, an experiment was conducted for two years (2015-2017) in a semi-arid region of Iran. In this research, two conventional sowing dates were set in October 12 and November 1 (late sowing). Irrigation was carried out at two levels: normal irrigation (control) and irrigation interruption from the silique formation stage to the next stage (late-season drought stress). The genotypes included four promising lines (L1112, L1091, L1093, L1206), and a cultivar (Okapi) as a control. Results showed that delayed sowing and drought stress increased carbohydrate content and decreased seed yield, with the highest carbohydrate content and highest yield loss in L1112 and the lowest carbohydrate and lowest yield loss in the L1206 line. Among the physiological traits measured, stomatal resistance had the highest degree of correlation and the highest direct negative effect on seed yield, which declined with increasing stomatal resistance. L1112 had the highest stomatal resistance (52.76 s cm-1) in delayed sowing and drought stress conditions. Therefore, L1206 and L1112 were revealed to be resistant and sensitive lines, respectively.

Grain yield and associated physiological traits of rapeseed (<em>Brassica napus L.</em>) cultivars under different planting dates and drought stress at the flowering stage

“…Furthermore, despite the inappropriate distribution of rainfall in the second year of the experiment under late sowing conditions, the ES Hydromel cultivar was able to keep the LRWC at a higher level. The results regarding the late planting date and late-season drought stress showed an increased SR among the studied cultivars under the experimental condition which is in the same direction with the results of other researchers (Shirani Rad et al, 2014b;Moradi Aghdam et al, 2018;Teymoori et al, 2020). In response to drought stress, the plant may have closed the stomata as the most vital strategy to slow down perspiration and prevent the spread of water deficiency in the tissues.…”

Effect of water stress on yield stability, water productivity, and canopy temperature of rice genotypes

“…The GT-biplot analysis also showed that CT was negatively correlated with GMP, STI, MP, HM, WP, Yp, and Ys. Therefore, CT measurement should be introduced as a practical and immediate method to evaluate the drought tolerance of rice genotypes (Yan et al, 2012;Khorsand et al, 2020;Teymoori et al, 2020). Similar to the present study, Sharifi and Ebadi (2018) and Sabouri et al (2022) also used a GT-biplot analysis to identify superior rice genotypes under drought stress conditions.…”

“…Since the CT depends on the transpiration rate, water absorption capacity, and water productivity, a low CT indirectly indicates the high ability of roots to absorb (Yan et al, 2012). Also, since CT is correlated with crop RWC and yield, genotypes with a lower CT show an improved water potential and will have more tolerance to drought stress (Khorsand et al, 2020;Teymoori et al, 2020). 5.…”

“…Another method of identifying drought-tolerant genotypes is to use stress tolerance indices (such as TOL, STI, SSI, MP, GMP, HM, RSI, YI, and YSI) and to rank the genotypes based on them (Krishnamurthy et al, 2016;Mariey and Khedr, 2017). In addition, it is possible to identify drought-tolerant genotypes by evaluating their water productivity and canopy temperature (Khorsand et al, 2020;Teymoori et al, 2020).…”