Biochemical and gene expression profiling of five pear species under drought stress conditions.

Drought is one of the crucial abiotic stresses which affects growth, development, and performance of pear trees. This research was performed to investigate responses of five pear species including Pyrus communis L., Pyrus boissieriana Bushe., Pyrus glabra Boiss., Pyrus syriaca Boiss., and Pyrus salicifolia Pall. to different levels of drought stress. The potted trees were irrigated with water volume of 100%, 60%, or 30% of field capacity (FC) during 90 days. Based on the visual observation, the plant growth was restricted by severe drought in all species. Malondialdehyde (MDA) and glycine betaine (GB) contents, as well as the ascorbate peroxidase (APX), guaiacol peroxidase (GPX) and catalase (CAT) activities were indicated an uprising behavior under drought stress. Principal component analysis (PCA) analysis revealed P. glabra as tolerant and P. communis as sensitive to drought stress. The expression rates of stress-responsive transcription factors (TFs); WRKY29 and DREB6 and their responding genes, including LEA29 and Dehydrin1, were analyzed in the two differentially drought-responding pear species i.e., P. glabra and P. communis. The expression of the studied TFs was induced when both species were exposed to higher drought levels. The species P. glabra exhibited better osmoregulation, antioxidant response, and higher up-regulation of WRKY29, DREB6, LEA29 and Dehydrin1. In conclusion, among the studied pear species, P. glabra could best tolerate drought stress by boosting protective mechanisms.