The Fungicide Tetramethylthiuram Disulfide Negatively Affects Plant Cell Walls, Infection Thread Walls, and Symbiosomes in Pea (Pisum sativum L.) Symbiotic Nodules.

Maxim G Vorobiev,Artemii P Gorshkov,Viktor E Tsyganov,Anna V Tsyganova

doi:10.3390/plants9111488

Abstract

In Russia, tetramethylthiuram disulfide (TMTD) is a fungicide widely used in the cultivation of legumes, including the pea (Pisum sativum). Application of TMTD can negatively affect nodulation; nevertheless, its effect on the histological and ultrastructural organization of nodules has not previously been investigated. In this study, the effect of TMTD at three concentrations (0.4, 4, and 8 g/kg) on nodule development in three pea genotypes (laboratory lines Sprint-2 and SGE, and cultivar ‘Finale’) was examined. In SGE, TMTD at 0.4 g/kg reduced the nodule number and shoot and root fresh weights. Treatment with TMTD at 8 g/kg changed the nodule color from pink to green, indicative of nodule senescence. Light and transmission electron microscopy analyses revealed negative effects of TMTD on nodule structure in each genotype. ‘Finale’ was the most sensitive cultivar to TMTD and Sprint-2 was the most tolerant. The negative effects of TMTD on nodules included the appearance of a senescence zone, starch accumulation, swelling of cell walls accompanied by a loss of electron density, thickening of the infection thread walls, symbiosome fusion, and bacteroid degradation. These results demonstrate how TMTD adversely affects nodules in the pea and will be useful for developing strategies to optimize fungicide use on legume crops.

Highlights

Legumes, including peas (Pisum sativum L.), are important food and feed crops
These results demonstrate how TMTD adversely affects nodules in the pea and will be useful for developing strategies to optimize fungicide use on legume crops
Our results show that pea symbiotic nodules are highly sensitive to the phytotoxic effect of the fungicide TMTD

Summary

Introduction

Legumes, including peas (Pisum sativum L.), are important food and feed crops. In 2018, the largest pea producers in the world were Canada (3.6 million tonnes), Russia (2.3 million tonnes), and China (1.5 million tonnes) [1]. Forecasts by Mordor Intelligence predict world pea production to grow by an average of 5.9% from 2019 to 2024 [2]. Peas are suitable for cultivation in regions with cool climates covering more than 12 million ha in more than 100 countries worldwide. Dry pea production is ranked fourth in the world among legumes, after soybeans, peanuts, and dry beans [3]. In Russia, pea crops occupy about 70% of the area under grain legume cultivation

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