Abstract
Most crops are sensitive to salt stress, but their degree of susceptibility varies among species and cultivars. In order to understand the salt stress adaptability of Brassica napus to salt stress, we collected the phenotypic data of 505 B. napus accessions at the germination stage under 150 or 215 mM sodium chloride (NaCl) and at the seedling stage under 215 mM NaCl. Genome-wide association studies (GWAS) of 16 salt tolerance coefficients (STCs) were applied to investigate the genetic basis of salt stress tolerance of B. napus. In this study, we mapped 31 salts stress-related QTLs and identified 177 and 228 candidate genes related to salt stress tolerance were detected at germination and seedling stages, respectively. Overexpression of two candidate genes, BnCKX5 and BnERF3 overexpression, were found to increase the sensitivity to salt and mannitol stresses at the germination stage. This study demonstrated that it is a feasible method to dissect the genetic basis of salt stress tolerance at germination and seedling stages in B. napus by GWAS, which provides valuable loci for improving the salt stress tolerance of B. napus. Moreover, these candidate genes are rich genetic resources for the following exploration of molecular mechanisms in adaptation to salt stress in B. napus.
Highlights
Salt stress is a leading cause of inhibition of crop growth and development in the world (Munns, 2005; Morton et al, 2019)
To study the response of the 505 B. napus accessions to salt stress, we analyzed the related traits at the germination stage under 0 mM, 150 mM (T1), and 215 mM NaCl (T2), and at the seedling stage under 0 mM and 215 mM NaCl (T2)
In order to better reflect salt stress responses, we focused on the salt tolerance coefficient (STC) calculated as the ratio of trait value under salt stress condition to that under normal condition, which was represented by the suffix type “trait_R1” under low salt stress and “trait_R2” under high salt stress (Supplementary Table 5; Guo et al, 2018)
Summary
Salt stress is a leading cause of inhibition of crop growth and development in the world (Munns, 2005; Morton et al, 2019). About 10% area of China is arable land is salt-affected (Song and Liu, 2017). Many methods have been used to improve the high yield of crops under salt stress, it is a challenge of maintaining the world food supplies (Hickey et al, 2019; Tyerman and Munns, 2019). Understanding the genetic and molecular mechanisms for enhancing salt tolerance is an important step toward improving the agricultural productivity of crops (Patishtan et al, 2018). Salt stress mainly includes ion stress and osmotic stress (Zhu, 2002; Julkowska and Testerink, 2015). Short-term salt stress can make the plants immediately appear the phenomenon of wilting
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