With annual ryegrass costing Australian grain growers more than $360 million a year in control measures, PhD student Joe Moore has joined the effort to look for alternatives to manage the weed’s invasive spread
Charles Sturt University PhD student Joe Moore
watering his annual ryegrass plants in the glasshouse.
He spends much of his time looking at annual ryegrass
seeds under the microscope (below) to check for the
presence or absence of the fungal endophyte Neotyphodium
occultans. The stained seed cells (aleurone) look like
dark blue ‘blobs’ whereas the fungal hyphae resemble
a mass of ‘two-minute noodles’.
A tiny fungus invisible to the naked eye is being investigated as a possible aid to reducing the devastating impact of annual ryegrass on Australian grain crops. The fungus Neotyphodium occultans is known as an endophyte because it lives its entire life cycle inside annual ryegrass (Lolium rigidum) plants in what is thought to be a symbiotic (mutually beneficial) relationship. However, little is known about the advantages it offers its host.
In perennial ryegrass (L. perenne) a different endophyte (N. lolii) produces alkaloids (toxic chemicals) that protect its host against predation by pests, while also making it unpalatable to grazing livestock.
Joe Moore, a Charles Sturt University PhD student working at the EH Graham Centre in Wagga Wagga, New South Wales, received an Australian Postgraduate Award with additional support from the GRDC in 2010 to study how N. occultans interacts with annual ryegrass and whether this endophyte confers similar protection to its host.
“If we can establish that the endophyte is contributing to making annual ryegrass more of an invasive weed, it may be that elimination of the endophyte is a viable option for controlling the weed,” Mr Moore says.
After growing up on a farm, attending an agricultural secondary school and completing undergraduate studies in agronomy, Mr Moore became interested in studying fungal endophytes following conversations with Charles Sturt University researcher Professor Jim Pratley, who now oversees his work.
“Jim encouraged me to go into this area because I like to figure out how agricultural systems relate with each other,” Mr Moore says. “I find research really interesting because I like to look at the ‘big picture’ plus the practical applications of agricultural research.”
Previous research by Dr Karen Kirkby on 299 annual ryegrass seed lots sent to Charles Sturt University’s herbicide resistance testing service confirmed that N. occultans is not confined to a particular area or state but is present in all annual ryegrass populations so far tested from across southern Australia.
To test if endophytes contribute to making the plant more competitive as a weed, Mr Moore removes the endophytes from annual ryegrass seeds, without damaging the seeds, so they can be grown and used for further experiments.
Infected seed is separated from the non-infected seed and both groups are germinated before being planted in pots to be grown into mature annual ryegrass plants, which can then be harvested and planted for further tests in the laboratory, greenhouse and paddock.
“Many commercially available fungicides don’t kill the endophyte or do a very poor job,” he says. “To date, most of my experiments indicate that N. occultans does not offer any growth benefits to annual ryegrass plants.”
Mr Moore has looked for a link between herbicide resistance and N. occultans infection but, so far, has found none.
Nonetheless, further research will be conducted this year to confirm these findings. He also plans to look at the genetic diversity of N. occultans within international annual ryegrass samples.
Another aspect of Mr Moore’s work will involve detailed analysis of the chemicals produced by N. occultans when he visits Dr Wade Mace based at AgResearch in Palmerston North, New Zealand, who has extensive experience working with endophytes and their alkaloids.
Mr Moore hopes the collaboration will provide a clearer insight into the alkaloids produced by N. occultans endophytes and their role in assisting annual ryegrass plants to survive as weeds.
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