Lisa.Wood@grasslanz.com

wayne.simpson@agresearch.co.nz

Richard.Johnson@agresearch.co.nz

stuart.roy@adelaide.edu.au

rainer.hofmann@lincoln.ac.nz

john.caradus@grasslanz.com

Epichloë endophytic fungi are used in commercial grass pasture throughout the world offering protection from insect herbivory and other biotic and abiotic stresses (these benefits are being discussed in Caradus et al. 2024 - BENEFITS OF AN OBLIGATE MUTUALIST ENDOPHYTE, EPICHLOË, IN WHEAT). Epichloë endophytes are mutualistic fungi that grow intercellularly within host grasses.

Visible growth is observed in sexual species where reproductive structures are formed. Asexual Epichloë show no visible external growth and it is these Epichloë that are commonly exploited in pastures. They are strictly vertically transmitted (maternally inherited), through seed to the next generation.

The success of this bio protection technology in temperate grasses, where in some cases Epichloë infection has increased dry matter production three times more than nil endophyte grasses, could have applicability to modern cereals, reducing the reliance on synthetic chemistry for controlling biotic stress.

However, modern wheat does not naturally host Epichloë endophytes and the genetic compatibility between host plant and endophyte has been a challenge. The most successful inoculation of Epichloë in wheat involved Chinese Spring with a Leymus racemosus H chromosome substitution (TACBOW0011).

Plants established a successful symbiosis with Epichloë and vertically transmitted the endophyte to the next generation. However, the initial Epichloë infected plants displayed undesirable phenotypes, a combination of the effect of the endophyte and the alien chromosome substitution from an ancient wheat species.

Endophyte positive plants show delayed maturity, have a stunted height and shrivelled seed. They also exhibit low germination and low endophyte transmission to the next generation. Here we describe the progress of improving the compatibility of Epichloë and modern wheat varieties to improve the plant phenotype.

Progress to date has resulted in maturity delay reducing to one week, a more acceptable plant height for commercial harvesting and increased seed size compared with the original inoculated TACBOW0011 material.

Germination and endophyte retention have also been improved. The future opportunities and challenges of using this endophyte technology in modern wheat is discussed.