Variations of glucosinolates in kale leaves (Brassica oleracea var. acephala) treated with drought-stress in autumn and spring seasons

The present study aimed to investigate the effects of drought stress on the accumulation of glucosinolates (GSLs) in the leaves of Kale cultivated in autumn and spring. HPLC analysis guided to identify seven GSLs including progoitrin, glucoraphanin, sinigrin, gluconapin, glucobrassicin, 4-methoxyglucobrassicin and neoglucobrasscin. Quantification of GSLs revealed that the contents of sigirin was the highest (45%) followed by the level of progoitrin (24%) in terms of total GSLs. The ranges of total GSL contents was 1.16 (84)-15.88 (89 DAS, ${\mu}mol/g$ dry wt. (DW)) in treatment plot and 1.23 (84)-7.05 (74 DAS, ${\mu}mol/g$ dry wt.) in control plot showed the enhancement in the contents of GSLs in treatment than in the control plot. The present results evidenced that the variation of total GSL contents were depending on the harvest period. In 105 DAS, comparatively no differences in the GSL contents on each sample in autumn season, whereas in spring season, although there was decrease in the GSLs tendency from 74 DAS to 84 DAS in both control and treatment plot, the GSL contents of treatment plot was dramatically increased in 89 DAS. In treatment plot, the GSL contents on 89 DAS (1.16) was 15 fold higher to 84 DAS ($15.88{\mu}mol/g$ DW). The variation in the contents of GSL in spring and autumn did not documented significant differences because of their differences in the growth time and cultivation conditions. In conclusion, the GSL contents in kale was likely to be affected by drought stress treatment. Scrutiny and further research for exact relation between drought stress and GSL contents in kale should be needed.

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