Differences in Leaf Morphological Parameters of Pear (Pyrus communis L.) Based on Their Susceptibility to European Pear Rust Caused by Gymnosporangium sabinae (Dicks.) Oerst.

Katrīna Kārkliņa,Gunārs Lācis,Baiba Lāce

doi:10.3390/plants10051024

Katrīna Kārkliņa, Gunārs Lācis + Show 1 more

Open Access

https://doi.org/10.3390/plants10051024

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Abstract

European pear rust is an important disease; however, the relationship between its causal pathogen Gymnosporangium sabinae (Dicks.) Oerst. and host Pyrus communis L. is poorly understood. In this study, disease severity was measured, and leaf samples were collected over three years, and their leaf water content; leaf area; leaf mass per area; and epidermis, mesophyll, and vascular tissue width and stomatal density were measured and compared between susceptible and resistant genotypes for each year. Most genotypes either showed consistent disease symptoms or showed no symptoms during the study in terms of their susceptibility. A correlation between disease severity and mesophyll tissue thickness, and stomatal density and differences between several morphological parameters were found depending on the genotype’s susceptibility. The study showed that the following pear morphological traits were stable between the years: water content, leaf mass per area, spongy mesophyll thickness, phloem thickness, and stomatal density. When selecting for breeding, we found that candidates for traits that discern susceptible genotypes from resistant were mesophyll layer width, stomatal density, epidermis width, and xylem tissue width.

Highlights

European pear rust (EPR) is an important disease found on pears and junipers, widespread where the hosts are growing together [1,2]
G. sabinae belongs to the division Basidiomycota and the rust fungus order Pucciniales, which are characterized by being obligate biotrophs—rust fungi can only infect living host cells [4]
This study aimed to identify pear morphological traits related to resistance towards EPR and evaluate the applicability of these traits in selecting resistant and susceptible genotypes

Summary

Introduction

European pear rust (EPR) is an important disease found on pears and junipers, widespread where the hosts are growing together [1,2] It is caused by Gymnosporangium sabinae (Dicks.) Oerst., a parasitic fungus commonly found in Europe, Asia, Africa, and North America [3]. The infection on pear leaves is characterized by bright orange spots, where the spermagonium grows in the middle in small, dark dots [8]. These formations are harmful to the plant as they inhibit photosynthesis, increase respiration, and lead to the death of the infected organs [9]

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