Study On Biochemical Mechanism Of Resistance To Carya Cathayensis Canker Of Grafted Hickory

Carya cathayensis canker is a main disease of hickory which which seriously affects the sustainable development of hickory industry.In plantation,Linan carya cathayensis has a serious degree of disease while carya cathayensis grafted on carya hunanensis’ rootstock(grafted C.hunanensis)and carya cathayensis grafted on carya illinoensis’ rootstock(grafted C.illinoensis)has a lighter degree of disease.The experiment was taken with two-year-old and ten-year-old Linan C.cathayensis,C.hunanensis,C.illinoensis,grafted C.hunanensi and grafted C.illinoensis,determining the contents of phenolic acids,alkaloid,CAT,POD,PPO and SOD in tree trunks and roots,and analysing the correlation between those components and disease index of canker disease.Then the mechanism of resistance to Canker in grafted hickories was discussed,which could provide scientific basis for prevention and control of Canker in Lin’an C.cathayensis.The results were as following:1 Through investigating the disease of hickory forests,it was found that Linan C.cathayensis had the highest index of disease and a serious degree while the two grafted hickories had the lighter disease index.Besides,The 2-year-old hickories were less likely to be infected with Canker while the 10-year-old hickories were seriously affected.2 Using HPLC-SPE method to determine the composition and contents of phenolic acids in trunks and roots of five species of hickories.It was found that all varieties contained gallic acid and chlorogenic acid.In the trunks,the content of total phenolic acids in grafted hickory was significantly higher than that in Linan.In the two-year-old roots,the content of total phenolic acids in the grafted hickory was lower than that in Lin’an,and in the two-year-old roots,it was higher than Lin’an.As the tree age increased,the contents of total phenolic acids in trunks and roots all increased.Among Linan C.cathayensis,grafted C.hunanensi and grafted C.illinoensis,there was a significant negative correlation between the contents of total phenolic acids in the trunk and the index of canker disease.The correlation coefficients between two-year-old as well as ten-year-oldtrunkand the index of canker disease were 0.943 and 0.768,respectively.But there was significant negative correlation between the contents of total phenolic acids in the trunk and the index of canker disease.The results showed that the higher the content of total phenolic acids in the trunk,the lower the index of disease and the stronger the resistance of canker.3 There were no significant differences in the total alkaloid contents in the trunk and root of C.cathayensis,grafted C.illinoensis and grafted C.hunanensiss.With the increase of tree age,the contents of total alkaloids in the trunks of the five varieties were significantly reduced,and in the oots,except for C.illinoensis increased significantly,there was no significant change in other varieties.Besides,there was a weak negatively correlation between the two-year-old trunk and roots and the disease index of canker.As for the ten-year-old trunk and roots,there were a non-significant positively correlation with the disease index.The total alkaloid contents in the trunks and roots might affect the resistance of hickory,but this correlation was not obvious.4 The activities of CAT and POD in trunks and roots of the two grafted hickories were higher than those in Linan C.cathayensis.With the increase of tree age,the CAT activity,POD activity,and SOD activity of different varieties of hickory were increased,in contrast,PPO activity was decreased.The correlation coefficients of CAT activity and the index of canker disease in 2 year and 10 year old hickory trees were 0.834 and 0.645 respectively.The correlation coefficient of POD activity and sthe index of canker disease of 2 year and 10 year old was 0.834 and 0.645 respectively.And the correlation between the activity of CAT as well as POD and the index of disease was significant negatively.But,the correlation between the activity of PPO as well as SOD and the index of disease were both small,so there was no obvious correlation.On the other hand,there was no significant correlation between roots’ enzyme activity and disease index of canker.Therefore,the higher the activity of CAT and POD in the trunk,the stronger the disease resistance of hickory.