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AgResearch scientists internationally recognised

AgResearch scientists internationally recognised for challenging fungi growth model

20 December, 2007

A team of AgResearch scientists has been recognised by world renowned magazine ‘Science’ for challenging the centuries’ old model of how fungi grow in grasses.

Fungal endophytes of the genera Epichloë and Neotyphodium form symbiotic associations with temperate forage grasses such as perennial ryegrass and tall fescue. The endophyte synthesises compounds, which provide the forage grass with protection from insect pests but can also adversely affect the health of grazing livestock.

The Editor’s Choice section of the 7 December edition of ‘Science’ highlights a discovery by AgResearch Scientists Mike Christensen, Dr Christine Voisey and colleagues from AgResearch’s Forage Improvement and Forage Biotechnology Sections. Citing an article authored by the researchers that will be published in the February 2008 issue of internationally renowned journal Fungal Genetics and Biology, it describes how endophyte hyphae, which are long filaments that grow inside the grasses, infect the leaves of their hosts. This occurs through a novel mechanism of fungal growth, known as intercalary division and extension.

“This is the first evidence of intercalary growth in fungi, and directly challenges the long held belief that fungi grow exclusively at hyphal tips,” says Dr Voisey.

“Having worked with endophytes for many years we believed that the conventional wisdom of how the fungi grew was inaccurate. It is very satisfying to have brought the evidence together and have this published in such a prestigious international journal and recognised by such an authoritative magazine,” says Mike Christensen.

The mode of growth described by the researchers is an adaptation that enables the fungi to extend as fast as leaves are growing, through their attachment to developing leaf cells.

The research explains how endophytes are able to colonise host grasses from seed as if they were a host tissue, and also explains other puzzling aspects of the endophyte-grass lifestyle, say the researchers.

“These findings have profound implications for the way in which we view hyphal growth processes in fungi. In the long term this research may offer new insights into key constraints around using novel beneficial endophytes in commercial seed production.”

The AgResearch Designer Endophyte programme has identified a number of novel, non-toxic endophyte strains that can protect plants from insects and have little or no ill effects on the health of livestock. For ryegrass these include the commercially available, AR1 and the recently released strain AR37, and for tall fescue, MaxP and MaxQ.

The article, Epichloë endophytes grow by intercalary hyphal extension in elongating grass leaves, will appear in the February 2008 issue of Fungal Genetics and Biology (volume 45, issue 2, pp. 84-93). A photograph of the endophyte in the anthers of a ryegrass host is on the front cover of the same issue. The article also features in the Editor’s Choice column of Science, Volume 318, 7 December 2007, pg 1525.


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