Citrus rootstocks modify scion antioxidant system under drought and heat stress combination

Abstract

The activation of the antioxidant system under stress combination is a transmissible trait from the rootstock to the scion. Therefore, rootstock selection is key to improve crop performance and a sustainable production under changing climate conditions. Climate change is altering weather conditions such as mean temperatures and precipitation patterns. Rising temperatures, especially in certain regions, accelerates soil water depletion and increases drought risk, which affects agriculture yield. Previously, our research demonstrated that the citrus rootstock Carrizo citrange (Citrus sinensis × Poncirus trifoliata) is more tolerant than Cleopatra mandarin (C. reshni) to drought and heat stress combination, in part, due to a higher activation of the antioxidant system that alleviated damage produced by oxidative stress. Here, by using reciprocal grafts of both genotypes, we studied the importance of the rootstock on scion performance and antioxidant response under this stress combination. Carrizo rootstock, under stress combination, positively influenced Cleopatra scion by reducing H₂O₂ accumulation, increasing superoxide dismutase (SOD) and ascorbate peroxidase (APX) enzymatic activities and inducing SOD1, APX2 and catalase (CAT) protein accumulations. On the contrary, Cleopatra rootstock induced decreases in APX2 expression, CAT activity and SOD1, APX2 and CAT contents on Carrizo scion. Taken together, our findings indicate that the activation of the antioxidant system under stress combination is a transmissible trait from the rootstock to the scion and highlight the importance of the rootstock selection to improve crop performance and maintain citrus yield under the current scenario of climate change.

Keywords: Abiotic stress; Climate change; Grafting; H2O2; Stress combination.

Fig. 1

Carrizo citrange and Cleopatra mandarin self- and reciprocal grafts (a). Experimental design to study the effect of drought and heat stress combination (WS + HS) in citrus grafted plants (b). Images created with BioRender.com

Fig. 2

Leaf damage index (a), leaf relative water content (b), Φ_PSII (n = 15) (c) and photosynthetic rate (n = 10) (d) of Carrizo and Cleopatra plants self-grafted or grafted into each other after drought and heat stress combination. Data are mean values ± standard errors. Different letters show statistical significance at p ≤ 0.05

Fig. 3

Representative images of Carrizo plants grafted onto Carrizo (a) or Cleopatra (b) and Cleopatra plants grafted onto Carrizo (c) or Cleopatra (d), subjected to control or drought and heat stress combination conditions

Fig. 4

H₂O₂ leaf content (a) and enzymatic activity of SOD (b), APX (c) and CAT (d) of Carrizo and Cleopatra plants self-grafted or grafted into each other after drought and heat stress combination. Data are mean values ± standard errors (n = 3). Different letters show statistical significance at p ≤ 0.05

Fig. 5

Relative gene expression of SOD1, APX2 and CAT genes (Top) and protein blots and quantitative bar graphs (Bottom) of SOD1, APX2 and CAT proteins. Both analyses were performed in Carrizo and Cleopatra plants self-grafted or grafted into each other after drought and heat stress combination. Data are mean values ± standard errors (n = 3). Asterisks denote Student’s t test significant at p < 0.05 between control and stressed plants within each grafting group