Anatomical and Biochemical Traits Associated with Field Resistance of Onion Cultivars to Onion Thrips and the Effect of Mechanical Injury on the Level of Biochemical Compounds in Onion Leaves

Michał Kruczek,Anna Kostecka-Gugała,Marta Olczyk,Maria Pobożniak,Ewa Hanus-Fajerska,Iwona Kamińska,Tomasz Wójtowicz

doi:10.3390/agronomy12010147

Michał Kruczek, Anna Kostecka-Gugała + Show 5 more

Open Access

https://doi.org/10.3390/agronomy12010147

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Journal: Agronomy	Publication Date: Jan 8, 2022
Citations: 2	License type: CC BY 4.0

Affiliation: University of Agriculture in Krakow

Abstract

Thrips tabaci Lind. is a global pest and also represents a serious threat to onion production in Poland. In 2 years (2015–2016) of field studies, 8 onion cultivars were evaluated to characterize the resistance to onion thrips and to determine if any biochemical and anatomical features of onion plants are associated with antixenotic and/or antibiotic mechanisms of resistance. Additionally, the influence of mechanical injury on the content of several biochemical compounds in onion leaves was made. The resistance to thrips colonization during the migration period, abundance, and thrips damage throughout the whole vegetation season was determined. We identified two cultivars, Tęcza and Wenta, resistant to thrips colonization and abundance, and one cultivar Wenta resistant to thrips damage. A positive correlation between concentrations of the reducing sugars and thrips abundance and conversely negative relationships between the total phenolic content and thrips damage was confirmed in both years. We suspect that a thinner epidermal layer, a smaller area of epidermal and mesophilic cells, and a lower diameter of vascular bundles may favor the resistance of onion cultivars to thrips. Thrips foraging resulted in a decrease in the content of soluble sugars, sucrose, and plant pigments in the leaves of all onion varieties.

Highlights

Onion is an important vegetable in terms of global production volume
A clear conclusion from this study is that thrips damage cannot always be predicted accurately based on the number of thrips, in many onion cultivars, a higher population of onion thrips promotes more extensive plant injuries caused by thrips
We identified two cultivars Tecza and Wenta useful for host resistance to thrips abundance and Wenta to thrips feeding damage and we suggest a link between concentrations of carbohydrates and phenolics and antixenotic and/or antibiotic resistance so that breeding for host plant resistance can be advanced more quickly

Summary

Introduction

Onion is an important vegetable in terms of global production volume. Is a global pest [3,4] and represents a serious threat to onion production in Poland [5]. Damage resulting from injuries caused by thrips appears as silvery patches, streaks on the leaves, or tiny black “tar” spots, which are thrips feces. The feeding thrips cause premature senescence of leaves, reduce the photosynthetic capacity, hinder the transport of nutrients to the bulb, and lead to their distortion and loss of biomass [3,8]. Tissue injury that results from thrips feeding causes increased vulnerability to infection by bacterial pathogens such as Pantoea ananatis, P. agglomerans, and P. alli that cause the onion center-rot complex, as well as Alternaria porri, the fungus that in turn causes purple blotch [14,15]. To prevent the opening of infection pathways, it is usually necessary to combat onion thrips, which requires frequent applications of insecticides [16], with the unfortunate consequence of increased resistance to commonly used pyrethroids and organophosphates [17,18], methomyl, and oxamyl (carbamates), abamectin [19], and spinetoram [20]

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