A Comparative Salt Shock Stress Response in the Wild Brassica Oleracea and Doubled Haploid Genotypes

The study was conducted to compare the early response between the wild (S1), founder (DHLS150), and doubled haploid (DH) lines to salt shock. A single dose of 250 mM NaCl was used to expose the plants to salt shock. Data analyzed at a two-point time; 24 hr post-treatment (24 hr pt), and 14 days post-treatment (2 wk pt) showed a significant increase 24 hr pt in leaf Na+ content (P<0.05) in the parent and DH lines, however, K+ and Ca2+ levels remained significantly unchanged (P>0.05), and K+/Na+ ratio reduced, which indicates osmotic shock. Similarly, the K+/Na+ ratio showed an improvement of 2 wk pt in some of the S1 parent and DH lines, recuperating phase. The qRT-PCR analysis showed significant variation in gene expression, that show an mRNA level of sodium/proton exchanger (NHX1), potassium transporter 9 (KT9) and potassium uptake permease (KUP11), vacuolar H+ adenosine triphosphatase (V- ATPase -G), and chloride gated channel (V-CLC) in both the parent and DH lines. The results further revealed that the S1 and DH lines maintained higher levels of K+, Ca2+, and K+/Na+ ratio in leaves through ion-selective capacity. Therefore, our results conclude that the adaptability of Brassica oleracea to salt shock and prolonged salt stress could be associated with ion selectivity, and Na+ exclusion and the response between the parent and DH lines are similar hence the DH lines can be used for the brassica breeding program.