Evaluation of Carya cathayensis resistance to Botryosphaeria trunk canker using grafting on pecan

Trunk canker of Chinese hickory (Carya cathayensis), caused by Botryosphaeria dothidea, is a catastrophic disease in China, and currently no effective pesticide control methods or resistant varieties are available. Therefore, alternative measures for the management of this disease are required. In this study, the efficacy of grafting Chinese hickory hybrids onto American pecan (C. illinoensis) as rootstocks was examined in two field trials in Tuankou town and Longgang town, Zhejiang Province, China, from May 2005. Compared with self-grafted C. cathayensis (CC), C. illinoensis-grafted C. cathayensis (IC) exhibited significant resistance against Botryospharia canker in both field trials. In 2017, the average numbers of cankers per tree were 2.52 +/- 0.76 and 3.25 +/- 0.35 in the Tuankou and Longgang trials, respectively, significantly lower than the 35.65 +/- 3.15 and 31.65 +/- 3.06 for CC (P < 0.05), respectively. Furthermore, IC produced 9.74 +/- 0.69 kg and 9.78 +/- 057 kg of fresh nuts per tree in the Tuankou and Longgang trials, respectively, whereas CC produced only 6.13 +/- 0.35 kg and 5.56 +/- 0.34 kg, respectively. Levels of phenylalanine ammonia lyase and polyphenol oxidase from the trunk bark tissue of B. dothidea-inoculated IC seedlings were significantly higher than those in inoculated CC seedlings after 24 h incubation. Phenolic compounds in the trunk bark tissue of IC also increased throughout the experimental period. The present study accordingly demonstrated the potential of using C. illinoensis as a rootstock to control Botryosphaeria canker of C. cathayensis.