Ascophyllum nodosum Extract and Mycorrhizal Colonization Synergistically Trigger Immune Responses in Pea Plants against Rhizoctonia Root Rot, and Enhance Plant Growth and Productivity.

Younes M Rashad,Hany H A El-Sharkawy,Nahla T Elazab

doi:10.3390/jof8030268

Abstract

Rhizoctonia root rot is one of the most destructive diseases affecting pea crops, resulting in up to 75% loss. In this study, the biocontrol activity of seaweed (Ascophyllum nodosum) extract at 1, 2, and 3% and/or mycorrhization of pea roots was investigated against Rhizoctonia root rot under greenhouse conditions. In addition, their effects on the transcriptional, physiological, ultrastructural, and growth status of pea plants were also studied. The results showed that the mycorrhizal colonization of pea roots and the application of the seaweed extract at 3% synergistically overexpressed the responsive factor (JERF3) recording 18.2-fold, and the defense-related genes peroxidase (23.2-fold) and chitinase II (31.8-fold). In addition, this treatment improved the activity of the antioxidant enzymes POD and PPO, increased the phenolic content in pea roots, and triggered multiple hypersensitivity reactions at the ultrastructural level of the cell, leading to a 73.1% reduction in disease severity. Moreover, a synergistic growth-promoting effect on pea plants was also observed. The photosynthetic pigments in pea leaves were enhanced in response to this dual treatment, which significantly improved their yield (24 g/plant). The inducing effect of mycorrhizal colonization on plant resistance and growth has been extensively studied. However, developing improved and synergistically acting biological agents for plant disease control and growth promotion as alternatives to the chemical fungicides is crucial for safety and food security. Based on these results, it can be concluded that the mycorrhizal colonization of pea roots and soaking their seeds in the A. nodosum extract at 3% have a promising and improved biocontrol activity against R. solani, and a growth-promoting effect on pea plants. However, field applications should be evaluated prior to any use recommendations.

Highlights

Pea (Pisum sativum L.), a herbaceous legume that belongs to the family Fabaceae, is widely grown all over the world, mainly in the cold climate areas, as it can withstand freezing temperatures down to −13 ◦ C [1]
The highest expression was recorded for the infected pea roots, which were treated with the seaweed extract at 3%, and colonized with Arbuscular mycorrhizal fungi (AMF)
The mycorrhizal-infected roots showed gene expression higher than the infected-nonmycorrhizal roots and the infected-nonmycorrhizal roots which were treated with the seaweed extract at 3%

Summary

Introduction

Pea (Pisum sativum L.), a herbaceous legume that belongs to the family Fabaceae, is widely grown all over the world, mainly in the cold climate areas, as it can withstand freezing temperatures down to −13 ◦ C [1]. It has a rich nutritional value with high amounts of protein, carbohydrates, vitamins, minerals, and fibers. Disease control using chemical fungicides may be undesirable, owing to their adverse effects on human and animal health, the diversity and composition of soil microbial communities, and environment [10]. Biological control represents an eco-friendly alternative to the chemical fungicides and a promising strategy for plant diseases management [11]

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