Objective Physiological and biochemical properties and transcriptome characteristics of cherry rootstock in response to alkaline stress were studied.

Method Rootstocks of 6 cherry varieties, including Gisela 6 (G6), Gisela 17 (G17), Mahaleb (M), Landing (L), Krymsk 5 (K5), and Lu S-SST-PPA-012-2009 (Y1), were grown in pots at pH 7.0 (CK), 7.5, 8.0, 8.5, 9.0 or 9.5. Plant height and stem diameter as growth indicators as well as relative conductivity, contents of chlorophyll, malondialdehyde, proline, and soluble sugar, and activities of SOD and CAT in the leaves were measured 2 and 4 weeks after the treatments. Transcriptomes of representative alkaline-tolerant and susceptible rootstocks were analyzed.

Result All 6 rootstocks grew normally in the pots of pHs between 7.0 and 8.0. But at high alkalinity, e.g., pH 9.5, the growth was suppressed showing reduced plant height and stem diameter. And the leaf relative conductivity and contents of chlorophyll, malondialdehyde, proline, and soluble sugar and the activities of SOD and CAT in G6, G17, and L became lower than those in M, K5, and Y1, indicating differentiated tolerance of the two groups to the risen pH in soil. The treatments of pH 7.0, 8.5, and 9.5 induced transcriptome changes in the genes with 13 differentially expressed genes (DEGs) in M and 7 DEGs in L. The KEGG analysis indicated that the DEGs in the pH 9.5-treated alkaline-resistant M rootstock were enriched in the secondary metabolite biosynthesis and plant hormone signal transduction pathways, while those in the pH 9.5-treated L were largely related to the metabolic and secondary metabolite biosynthesis pathways.

Conclusion Preliminarily, the results obtained by this study suggested that the secondary metabolites played a major role in regulating alkaline tolerance of cherry rootstocks. The tolerant M, K5, and Y1 would be more appropriate than the other three cultivars for application in coastal areas with soil of high pHs.