Effects of Phenolic Compounds on Walnut Bacterial Blight in the Green Husk of Hungarian-Bred Cultivars

Abstract

The Persian walnut (Juglans regia L.) is the most grown nut tree crop in Central Europe. The aim was to study the full Hungarian walnut assortment with a distinct early spring phenology to detect the difference in phenolic profile in their green husks. Furthermore, the relationship between the presence and concentration of phenolic compounds and the tolerance/resistance of the observed cultivars to walnut bacterial blight was investigated. Examining the samples, significant differences were found between the concentrations of the different groups of phenolic compounds. Walnut blight immunity tests were also performed to clarify the role of phenolic compounds in the nut derived from a non-irrigated orchard. The Hungarian-bred local cultivars contained phenolic compounds in higher concentrations than the domesticated ones. There was a significant correlation between the budburst, as well as the pistillate flowers’ receptivity and the concentration of juglone. Cultivars with a low concentration of phenolic compounds were the most susceptible to walnut bacterial blight, except ‘Bonifác’.

Responses of Persian walnut on foliar applications of different biostimulants

“…According to Wielgolaski (2001) climatic factors correlated well to the phenological stages, and the air temperature is reported to be the major force for the onset of the early spring phenological stages (Rodriguez-Rajo et al, 2003;Wielgolaski, 2003;Crepinsek et al, 2009;Cosmulescu et al, 2010;Crepinsek et al, 2012;Bırsanu Ionescu and Cosmulescu et al, 2017;Cosmulescu et al, 2015;Bujdosóet al, 2022) such as pistillate flower receptivity. Negative relationships between the heat demand of early spring phenological stages and daily air temperatures indicate that warm weather is required for early flowering (Emberlin et al, 2007).…”

“…It is a proterandric cultivar. It has an oval, large nut size, which means 33 to 35 mm in diameter, large kernel recovery (40 to 45%), and a light brown shell and kernel color ( Bujdosó et al., 2022 ).…”

Effects of Leaf Wetness Duration, Temperature, and Host Phenological Stage on Infection of Walnut by Xanthomonas arboricola pv. juglandis

“…These results give evidence of differential host susceptibility among plant organs within the same cultivar. Contents of phenolics implicated in defense against walnut blight may partially explain this differential susceptibility of fruit and leaves of susceptible walnut cultivars depending on the organ and the phenological stage [25,[29][30][31].…”

Role of the Green Husks of Persian Walnut (Juglans regia L.)—A Review

“…Similar variations were also observed on Hungarian-bred cultivars. Bujdosó et al [3] established that 'Bonifác' had the highest phenolic content; however, their nuts were very susceptible to Xanthomonas arboricola pv. juglandis.…”

“…The United States of America and Iran produced 592,390 tons and 321,074 tons of dried nuts with shells, respectively [1,2]. Annual production is steadily increasing in Central Europe [3]. In 2019, statistics show that Hungary's production was estimated at 6820 tons of dried nuts with shells [2].…”