Correlations between Phytohormones and Drought Tolerance in Selected Brassica Crops: Chinese Cabbage, White Cabbage and Kale.

Ondřej Novák,Danuše Tarkowská,Ivan Petřík,Iva Pavlović,Branka Salopek-Sondi,Hrvoje Lepeduš,Sandra Radić Brkanac,Valerija Vujčić Bok

doi:10.3390/ijms19102866

Abstract

Drought is one of the major abiotic stresses affecting the productivity of Brassica crops. To understand the role of phytohormones in drought tolerance, we subjected Chinese cabbage (B. rapa ssp. pekinensis), white cabbage (B. oleracea var. capitata), and kale (B. oleracea var. acephala) to drought and examined the stress response on the physiological, biochemical and hormonal levels. The phytohormones abscisic acid (ABA), auxin indole-3-acetic acid (IAA), brassinosteroids (BRs), cytokinins (CKs), jasmonates (JAs), and salicylic acid (SA) were analyzed by ultra-high-performance liquid chromatography–tandem mass spectrometry (UHPLC-MS/MS). Based on the physiological and biochemical markers the Chinese cabbage exhibited the lowest tolerance, followed by the white cabbage, while the kale appeared to be the most tolerant to drought. The drought tolerance of the kale correlated with increased levels of SA, ABA, IAA, CKs iP(R) and cZ(R), and typhasterol (TY), a precursor of active BRs. In contrast, the drought sensitivity of the Chinese cabbage correlated with a significant increase in ABA, JAs and the active BRs castasterol (CS) and brassinolide (BL). The moderately tolerant white cabbage, positioned between the kale and Chinese cabbage, showed more similarity in terms of the phytohormone patterns with the kale. We concluded that the drought tolerance in Brassicaceae is mostly determined by the increased endogenous levels of IAA, CKs, ABA and SA and the decreased levels of active BRs.

Highlights

Brassica vegetables, belonging to the family Brasiccaceae, include many economically important species that are grown worldwide
Three Brassica cultivars—Chinese cabbage (B. rapa), white cabbage (B. oleracea var. capitata), and non-headed kale or black cabbage (B. oleracea var. acephala)—were investigated under drought stress and recovery
abscisic acid (ABA) is the main regulator of photosynthesis, since it regulates the stomatal closure in conditions of water deficit and causes a decrease in the photosynthetic performance, as we identified in drought-sensitive B. rapa

Summary

Introduction

Brassica vegetables, belonging to the family Brasiccaceae, include many economically important species that are grown worldwide. The most utilized Brassica vegetables are B. oleracea and B. rapa, comprising different headed and non-headed cabbages, kale, broccoli, cauliflower, and Brussels sprouts. Around 70 million tons of cabbages are produced worldwide every year [1], and about 90% of the world’s cabbage is produced in Europe and Asia. In light of the current changes observed in the climate, drought is considered to be one of the most serious problems for global agriculture, affecting approximately 40% of the world’s land area [2,3]. Since Brassica crops are mainly cultivated commercially in Mediterranean, semi-arid and arid environments, their growth, and the crop yield and quality, can be greatly impaired by drought [3]. Future projections are even worse, since a gradual, but consistent, increase in aridity and drought is estimated for most of the Mediterranean region [4]

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