Analysis of Carya cathayensis resistance to Botryosphaeria dothidea using grafting on pecan in China

Grafting technology is applied to control the trunk canker disease of Chinese hickory (Carya cathayensis). In this study, the grafting of Chinese hickory hybrids onto American pecan (C. illinoinensis) and Hunan pecan (C. hunanensis) as rootstocks was investigated in the field. The trunk canker was significantly more serious in self-grafted C. cathayensis (CC), and the disease of C. hunanensis-grafted C. cathayensis (HC) was less serious than that of C. illinoinensis-grafted C. cathayensis (IC). The causal agent of Botryosphaeria dothidea was characterized by comparison of the fungal morphology and its combined DNA sequence data. Seedlings of CC, IC and HC were inoculated with B. dothidea, and we observed that the phloem and xylem tissues of CC were more damaged by B. dothidea mycelia than those in IC and HC at 2 and 4 days, respectively, using a scanning electron microscope (SEM). The phenol contents in the trunk bark tissues of HC, the total phenylalanine ammonia-lyase (PAL) activities of HC and IC were significantly increased, and the total polyphenol oxidase (PPO) activity of HC was higher than that of other pecans at 5 days. The expression levels of the CHS gene were significantly upregulated in HC, and the expression levels of PAL, C4H, 4CL, and CHS in IC and HC were high at 1, 3, and 5 days. In summary, the grafted pecan IC and HC showed higher phenol content, PAL activity, and C4H, CHS, and PAL gene expression levels. This study explains the potential of using C. hunanensis as a rootstock to control the Botryosphaeria canker disease in C. cathayensis.

Automated summary

Grafting technology is used to control the trunk canker disease of Chinese hickory. In this study, it was found that the disease was more serious in self-grafted Chinese hickory, while it was less serious in Chinese hickory grafted onto Hunan pecan. The causal agent of the disease was identified as Botryosphaeria dothidea. This study demonstrates the potential of using Hunan pecan as a rootstock to control the canker disease in Chinese hickory.