Metabolomic and transcriptomic analyses of Prunus davidiana reveal the key resistance compound to green peach aphid, betulin

Prunus davidiana, a close wild relative of the cultivated peach, has been identified as having a strong resistance to Myzus persicae Sülzer (green peach aphid, GPA), one of the major pests of peach. However, the resistance mechanism of P. davidiana remains unclear. In this study, combined analysis of metabolome and transcriptome was conducted using aphid-resistant (R-32) and aphid-susceptible (S-27) lines, from a segregating population, to investigate the defense mechanism of P. davidiana. These results showed that R-32 continuously accumulated higher levels of betulin than S-27 during aphid infestation. Besides, betulin displayed a strong toxic effect on GPA. Transcriptome analysis revealed that the expression of genes involved in the betulin biosynthesis pathway responded highly to GPA infestation, especially CYP716A1. Our results demonstrate that betulin play an important role in the mechanism of resistance of P. davidiana to GPA.

Effects of Chitosan on Soluble Sugar Content in Prunus davidiana Seedlings

A pot experiment was conducted to study the effects of different concentrations of chitosan solutions (0, 1, 2, 4, 6 g/L) on soluble sugar content in Prunus davidiana seedlings. The result showed that there was no significant difference of the soluble sugar content in roots, stems, leaves and shoot in P. davidiana seedlings between at 1 g/L concentration and the control. All concentration treatments were reduced the soluble sugar content in roots and stems of P. davidiana seedlings compared with the control. On the contrary, all concentration treatments were improved the soluble sugar content in leaves and shoot of P. davidiana seedlings compared with the control and the concentration treatment of 2 g/L and 4 g/L was at a higher level. All concentration treatments were improved the content in relative conductivity of blade in P. davidiana seedlings and the concentration treatment of 4 g/L was at a higher level. On the contrary, all concentration treatments were reduced the content in soil conductivity. Therefore, the chitosan solutions concentration of 2 g/L and 4 g/L concentration was beneficial to soluble sugar content in P. davidiana seedlings. On the contrary, high concentration of chitosan solutions was not good for soluble sugar content.

Effects of Different Selenium Concentrations on Physiology of Prunus davidiana Seedlings

To study the effects of selenium on physiology, Prunus davidiana seedlings were treated with the irrigation of different selenium concentrations solution. The result showed that the photosynthetic pigment content was relatively higher at selenium concentrations of 0, 0.05 and 0.1 mg/L except for carotenoid content which was the highest at 0.1 mg/L but the lowest in control seedlings. In terms of antioxidant enzyme activity, the activities of peroxidase (POD), catalase (CAT) and superoxide dismutase (SOD) in selenium-treated seedlings were all higher than that in control seedlings and especially at the selenium concentration of 1 mg/L. The soluble protein content accumulated most at 0.25 mg/L selenium concentration. The content of malondialdehyde (MDA), as membrane lipid peroxidation index, was the lowest at selenium concentration of 0.5 mg/L. In a word, irrigating lower selenium concentrations could increase the photosynthetic pigment content and higher selenium concentrations enhanced the antioxidant enzyme activity to increase cell protection and kept the P. davidiana seedlings good growth and resistance to adverse environments.

Study on the selenium accumulation of peach seedlings

An experiment was conducted to study the effect of peach seedlings (Prunus davidiana) grown in nutrient solution with different selenium concentration. The results showed that selenium concentration were 0.05 and 0.10 mg/L which caused a marked increase of roots and shoorts biomass, and the root/shoot ratio were relatively low (0.180 and 0.170) compared with control, and other selenium treatments decreased significantly the biomass. Consequently, 0.05 and 0.10 mg/L selenium treatments were conducive to peach seedlings growth, while the peach seedlings was inhibited significantly by the increasing concentration of selenium (≥ 0.10 mg/L). Selenium content of peach seedlings increased remarkably with the increase of selenium concentration that indicated the accumulation of selenium in peach seedlings had a linear relation with the dose of selenium. Above all, when selenium concentration in the range of 0-0.10 mg/ L, which not only promotes peach seedlings growth, but also increases peach seedlings selenium content.