Survey on the chemical compounds of the galls formed by oak gall wasps (Hym.: Cynipidae) in Kermanshah province (case study: Javanroud city)

Oak trees (Quercus infectoria) are one of the main components of forest communities in western Iran and play a vital role in preserving water and soil in this region. Oak gall wasps (Hymenoptera: Cynipidae) cause gall on different parts of oak trees. This research was conducted to investigate the concentration of some plant metabolites in different tissues of oak trees and some leaf galls formed by gall wasps and their changes during the growing season in the Javanroud region. For this purpose, four types of galls (Neuroterus numismalis Geoffroy, Neuroterus quercusbaccarum L., Cynips divisa Harting, and Cynips quercusfolii L.), leaves containing gall, and healthy leaves were collected as a sampling unit from oak forests in Javanroud city. This study measured the concentration of some food compounds and secondary metabolites, such as soluble and insoluble sugars, total phenol, total tannin, and condensed tannin. The results of the variance analysis of the data showed that the concentration of different metabolites during the season in four different types of gall and the two investigated tissues were significantly different. The results showed that the peak concentration of carbohydrates and starch in all four types of galls and two types of plant tissue occurs in October, while the highest amount of total nitrogen and crude protein is found in September. Because gall tissue is considered the only food source for the gall-producing wasps, the quality of its food seems very important to them.