Resistance of some commercial walnut cultivars and genotypes to Aceria tristriata (Nalepa) (Acari: Eriophyidae) and its correlation with some plant features.

Abstract

The walnut leaf gall mite (WLGM) (Aceria tristriata (Nalepa)) is one of the major pests of walnut in western Iran. The use of a resistant variety is an economical and environment-friendly method of pest control. The aim of the present study is to assess resistance of some walnut cultivars and genotypes in relation to WLGM. Also, the current research aimed to study a possible correlation between resistance with plant morphological and biochemical features. Based on the leaf damage index (number of galls per leaf and plant, the percentage of infested leaves and the percentage of leaf injury area) induced by WLGM, the studied cultivars and genotypes were classified into four groups from susceptible to approximately resistant. Free-choice experiments indicated that Jamal and Chandler cultivars were colonized by lower densities of WLGM, whereas Seedling, Hartly, Lara and Z60 hosted denser populations. In antibiosis assay, the highest mite density was created in the galls on the leaves of Seedling and Hartly, whereas lowest mite density was observed in galled leaves of Chandler and Jamal cultivars. Results from biochemical assays showed that nearly all evaluated biomarkers had negative correlation with number of galls per leaf and mite density. Generally, resistant cultivars (Chandler, Jamal and Pedro) significantly produced defensive compounds more than those of controls after mite infestation. Also, it is worth noting that, the content of photosynthetic pigments significantly reduced in susceptible cultivars after mite infestation. The obtained results from this study can be useful for provisional resistance screening. © 2019 Society of Chemical Industry.