Developing Actinobacterial Endophytes as Biocontrol Products for Fusarium pseudograminearum in Wheat

Abstract

Crown rot of wheat, caused by Fusarium pseudograminearum, results in millions of dollars of yield losses globally each year. Management strategies to control crown rot are limited and there are concerns about development of fungicide resistance so novel treatment strategies are desirable. A collection of endophytic Actinobacteria was screened for their ability to suppress the growth of F. pseudograminearum and the development of crown rot symptoms in wheat with the aim of identifying candidates that can be developed into biocontrol products. The ability of the Actinobacteria isolates to suppress the growth of three different F. pseudograminearum strains in vitro was assessed using agar-plate competition assays. Soil-free seedling assays were used to screen for suppression of development of early disease symptoms in the susceptible wheat (Triticum aestivum) cv. Tamaroi. Four of the isolates were tested in a glasshouse pot experiment to assess their ability to decrease disease symptoms and prevent yield losses in wheat cv. Tamaroi grown to maturity in an unsterilized soil. The screening of 53 isolates identified two Streptomyces isolates, MH71 and MH243, with very strong antifungal activity against F. pseudograminearum strains in agar-plate competition and seedling assays. In the glasshouse pot trial, plants treated with seed coatings of either MH71 or MH243 had > 24% lower disease severity than control plants infected with F. pseudograminearum. These two cultures show potential for development as biocontrol products because they are easy to culture, grow on relatively inexpensive media, produce highly durable spores and can be delivered to plants as a seed coat.

Phylogenetic affiliation of endophytic actinobacteria associated with selected orchid species and their role in growth promotion and suppression of phytopathogens

“…Streptomyces , have a unique and well-documented ability to create novel antibiotics, and these species have enormous practical significance. Some well-known antibiotics derived from Streptomyces have served as fungicides ( O’Sullivan et al., 2021 ). Wang et al., 2013 reported strong biocontrol action of Streptomyces against a wide range of phytopathogens.…”

A Plant Stress-Responsive Bioreporter Coupled With Transcriptomic Analysis Allows Rapid Screening for Biocontrols of Necrotrophic Fungal Pathogens

“…This was consistent with elevated endogenous GSTF7 expression and expression of stress-related genes after incubation of Actinobacteria with Arabidopsis seedlings and particularly following Sclerotinia infection. The KB001 isolate was identified as a Streptomyces (O'Sullivan et al, 2021) and consistently induced high expression of stress marker genes and, furthermore, increased resistance in Arabidopsis plants against Sclerotinia and Rhizoctonia infection but not against the bacterium Pseudomonas. Pseudomonas syringae is also a hemibiotrophic pathogen in that it spends some of its lifecycle feeding off living plant tissues and, in later stages, off dead tissues (Xin et al, 2018).…”

“…GSTF7:luc plants were grown in the presence of Actinobacteria strains sourced from two unique collections (O'Sullivan et al, 2021;Roper 2004;Roper et al, 2016) to identify strains that could induce or enhance H 2 O 2 -dependent plant responses. As a positive control, H 2 O 2 treatment was also included, and a water-only treatment was used as a negative control.…”

Bambara Groundnut Rhizobacteria Antimicrobial and Biofertilization Potential

“…Phylogenetic analyses were conducted using softwares in MEGA version 5.2.2. Evolutionary distance matrices were generated, and a phylogenetic tree was inferred by the neighbor-joining method ( O’Sullivan et al, 2021 ). Tree topologies were evaluated by bootstrap analysis ( Tekdal et al, 2022 ) based on 1,000 resamplings of the neighbor-joining data set.…”