Protocooperative Biocontrol Agents and Wheat Genotypes for Sustainable Management of Fusarium Head Blight

Abstract

Fusarium Head Blight (FHB) is an economically devastating disease that affects small-grain cereal worldwide. Traditionally, agronomic practices such as crop rotation combined with no-tillage, resistant cultivars, and synthetic fungicides have been used to treat this plague. However, none of the above methods proved desired effectiveness, while the spread of Fusarium graminearum across the globe has resulted in, i) accelerated disease epidemic rates over the last century, and ii) prolonged FHB outbreaks in wheat, barley, oats, and corn. Compounding this is also the increasing trend of mycotoxins accumulation in grains, food, and feed that has been detrimental to human and animal health. It is therefore with great urgency that alternative treatment methods are found and implemented. As a result, research into biocontrol agents (BCAs) to protect crops from phytopathogens has attracted wide-ranging attention from both the public and the agri-food industry worldwide. In this study we evaluated the effects of a plant endophyte Sphaerodes mycoparasitica- a formulated biocontrol inoculant applied on common and durum wheat affected by FHB. The parameters evaluated were agronomic traits, mycotoxin accumulation, and the profile of Fusarium communities in harvested grains. Sphaerodes mycoparasitica showed biocontrol efficacy and plant-growth-promoting traits against FHB. This BCA significantly improved agronomic traits in all cultivars assessed. The most improved traits were seed weight, spike number, and spike weight followed by plant biomass and plant height. The most overall improved crop was moderately susceptible plus (MS+) durum wheat CDC Credence with a maximum increase of 52% in spike weight, and a maximum increase of 58% in seed weight. The most improved common wheat cultivar was the moderately resistant (MR) AAC Brandon. Sphaerodes mycoparasitica also significantly reduced the commonly detected mycotoxin, deoxynivalenol (DON) concentration in all cultivars. Deoxynivalenol concentration in common wheat cultivars decreased by 99.5% compared to a 97% reduction in durum wheat cultivars. The BCA effect was more consistent in reducing mycotoxin DON, 3+15ADON, NIV, T-2, HT-2 toxins, and even Fumonisins, an atypical group of mycotoxins in wheat. However, the BCA appeared to be more effective in the resistant cultivars than the susceptible ones. The BCA was also effective in reducing the diversity of Fusarium operational taxonomic units (FUS OTUs) and Fusarium abundance, based on Fusarium (FUS) sequence reads in grain samples as revealed by Illumina platform using internal transcribed spacer (ITS) primers ITS1F and ITS4. There was a significant reduction of FUS OTUs in durum compared with common wheat cultivars. The BCA was also more effective in reducing FUS sequence reads in the susceptible cultivars compared to the resistant cultivars. This study also revealed that there was a positive association between F. graminearum OTUs and DON concentrations. The abundance of F. graminearum OTUs was associated with an increase in DON occurrence. This study's results revealed the importance of i) protocooperation between an endophytic BCA mycoparasite and different wheat host genotypes to increase the efficacy in controlling FHB and associated mycotoxins, and ii) improved response in common wheat and durum wheat with different FHB tolerance levels. It also provides information for breeders and farmers who are interested in using a more environmentally friendly approach to treat FHB, as well as to gain a better understanding of the importance of the host microbiome as another treatment strategy. The overarching aim is to use biocontrols as a part of an integrated approach to improve the bioeconomy or profitability of the global agri-food sector, reduce FHB, reduce chemical pesticide usage, minimize mycotoxins, improve yields, and provide quality, safe, and nutritious products to consumers.