Organic Amendments Modulate Soil Microbiota and Reduce Virus Disease Incidence in the TSWV-Tomato Pathosystem.

Giuliano Bonanomi,Maria Minutolo,Roberta Marra,Francesco Vinale,Gaspare Cesarano,Daniela Alioto

doi:10.3390/pathogens9050379

Abstract

Application of organic amendments is considered an eco-friendly practice to promote soil fertility and suppressiveness against a wide range of soil-borne pathogens. However, limited information is available about the capabilities of organic amendments to control virus disease. In this study, the suppressiveness of different organic amendments (i.e., compost manure, biochar, alfalfa straw, and glucose) was determined against the Tomato spotted wilt virus (TSWV) on tomato plants in a 1-year-long mesocosm experiment. Organic treatments were compared to the ordinary soil management based on mineral fertilizers and fumigation. Tomato seedlings were inoculated with TSWV and the infection and symptoms were assessed three weeks later. The disease incidence was higher in soil treated with mineral fertilizers and fumigation (>80%) compared to the application of organic amendments, with alfalfa straw and biochar recording the lowest incidence (<40%). Moreover, soil microbiota structure and diversity were assessed by high-throughput sequencing of bacterial and eukaryotic rRNA gene markers. Several members belonging to the bacterial phyla of Acidobacteria, Actinobacteria, Bacteroidetes, and Proteobacteria, as well as members of the fungal genus Acremonium, were positively associated with plant health. This study showed that conventional practices, by shifting microbiome composition, may increase TSWV incidence and severity.

Highlights

Application of organic amendments (OAs), like compost, agro-industry wastes, green and animal manure, and biochar, is considered a practice of pivotal importance to sustain soil fertility, functions, and, crop production [1,2,3]
The occurrence of Tomato spotted wilt virus (TSWV) and the development of symptoms on tomato plants were evaluated at three weeks post inoculation, resulting in the plant status reported in Figure 1 and Supplementary
Our results indicated that biochar combined with alfalfa or manure were among the most effective soil treatments to control the disease caused by TSWV

Summary

Introduction

Application of organic amendments (OAs), like compost, agro-industry wastes, green and animal manure, and biochar, is considered a practice of pivotal importance to sustain soil fertility, functions, and, crop production [1,2,3]. Applications of OAs affect the biological properties of soil like the development of soil microbial biomass and metabolic activity [8], as well as the richness and diversity of the microbial community [9,10]. Several studies reported that OAs, by modifying soil microbiota, can increase soil suppressiveness against numerous plant pathogens, including oomycetes. OAs application can control soil-borne pathogens directly, through the release of fungitoxic compounds [16,17,18], or indirectly by promoting the development of a suppressive microbiome [19,20] Pathogens 2020, 9, 379; doi:10.3390/pathogens9050379 www.mdpi.com/journal/pathogens (e.g., Pythium spp., Phytophthora spp.), fungi (e.g., Botrytis cinerea, Fusarium oxysporum, Verticillium dahliae, Rhizoctonia solani), and bacteria (e.g., Ralstonia solanacearum, Pseudomonas syringae pv. tomato) [11,12,13,14,15].

Objectives

Methods

Discussion

Conclusion