Relationship between phenolic content in walnut branches and its resistance.

Considering walnut's resistance performance,the total phenolic content,flavonoids content,phenolic acids types and content in walnut branches were determined to study the relationship between phenolic content and its resistance.There are significant(P≤0.01) difference among different walnut cultivars in total phenolic contents.Of all the five cultivars tested,Zhonglin No.1 is the highest and Jinlong No.1 is the lowest.The flavonoids content of Zhonglin No.1 and Jinglong No.1 are significant(P≤0.01) higher than that of Jing861 and Bokexiang,and Lipin No.2 middle.Seven phenolic acids are detected in the five cultivars which were gallic acid,p-hydroxybenzonic acid,vanillic acid,caffeic acid,syringic acid,p-coumaric acid and ferulic acid.The content of gallic acid is relative high(accounting for 70% of the sum of the phenolic acids).P-hydroxybenzonic acid,vanillic acid and caffeic acid are not detected in some cultivars.Zhonglin No.1 with strong cold resistance is very different from the other four cultivars in which the total phenolic content(45.46mg/g),gallic content(4.50mg/g) and the sum of phenolic acids content(5.14mg/g) are all the most,and the vanillic acid and caffeic acid are detected which they are not or few in the other four cultivars.The p-hydroxy benzoic acid were not detected which were all detected in the other four cultivars.The syringic acid(0.084mg/g) and p-coumaric acid(0.065mg/g) levels were significantly lower than that in the other four varieties.However,the syringic acid(0.371mg/g) and p-coumaric acid(0.296mg/g) contents were relatively high in Bokexiang which had strong disease resistance.