Developing Actinobacterial Endophytes as Biocontrol Products for Fusarium pseudograminearum in Wheat.

Cathryn A O’Sullivan,Margaret M Roper,Louise F Thatcher,Cindy A Myers

doi:10.3389/fbioe.2021.691770

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.

Highlights

Fusarium crown rot is a fungal disease of cereals which occurs when the roots and crown of susceptible cereals become infected with one of several Fusarium spp., most commonly Fusarium pseudograminearum (Backhouse et al, 2004)
Endophytic, plant-growth promoting Actinobacteria were isolated from the roots of field grown wheat plants in the wheat belt of Western Australia (WA)
Twelve of the 53 Actinobacteria isolates were selected for 16s ribosomal DNA sequencing to confirm their identity

Summary

Introduction

Fusarium crown rot is a fungal disease of cereals which occurs when the roots and crown of susceptible cereals become infected with one of several Fusarium spp., most commonly Fusarium pseudograminearum (Backhouse et al, 2004). Crown rot reduces both the yield and quality of cereals, with recent estimates showing that it costs growers ∼$80M for wheat and ∼$18M for barley annually in Australia alone (Murray and Brennan, 2009a,b). Infection occurs at the crown (base of the stem) and decreases the ability of plants to transport water and nutrients from roots to shoots. But not all, cases plants develop white-heads (heads with little or no grain) because water, photosynthate and nutrients are prevented from being translocated (Burgess et al, 2001)

Methods

Results

Discussion

Conclusion