Use of Endophytic Fungi in Turf Grasses; Difficulties in Delivering to the Market

Stewart, Alan & Barcellos, Guilherme & Brilman, Leah. (2022). Use of endophytic fungi in turf grasses; difficulties in delivering to the market. International Turfgrass Society Research Journal. 14. 10.1002/its2.131.

Seedborne fungal endophytes of the genus Epichloë infects many species of turfgrasses, including ryegrass (Lolium spp.), tall fescue (Festuca arundinacea Schreb.), and fine fescue.

These are generally mutualistic associations, where the endophyte protects the host grass plant from biotic (e.g., insects) and abiotic stresses, while the host grass provides nutrition to the endophyte and transmits the endophyte via seed to the next generation.

Beneficial responses in plant performance to endophyte infection largely occur in summer and autumn when the seasonal maximum of alkaloid production (Fletcher et al., 2001) coincides with the summer stresses of heat, drought and insects. Winter hardiness appears to be unaffected by endophytes (Casler & van Santen, 2008). The effect can be dramatic when insect numbers are high, particularly when combined with conditions that are favorable for insects and unfavorable for grass growth.

Figure 1- Photo shows a Vancouver area endophyte trial testing a new endophyte that prevents damage to chafer grub feeding and damage.  Trial Seed supplied by DLF and Premier Pacific Seeds, image credit Nik Wall

Endophyte infection has been shown to enhance the summer performance of ryegrass throughout much of New Zealand in both forage and turf, and the impact of this can carry over to improve autumn recovery and winter wear tolerance on winter sports fields (Stewart,1987, 2005; Davies et al., 1990). In addition, endophyte strains that are able to produce particularly high levels of ergot alkaloids have been developed for turf purposes to control not only insects but also birds and small mammals grazing on the turf.

The accepted commercial standard in the forage and turf industry is 70% live infection. However, little research has been carried out on the levels of endophytic grasses needed in turf systems to provide the benefits of insect resistance, except for the work of Richmond et al. (2000), who suggested that a least 50% is crucial (Richmond et al., 2000). However, delivering seed with over 70% live endophytes to the turf requires a concerted effort through all stages of the breeding and supply chain, as well as reliable methods to test for endophyte infection and appropriate quality control practices in seed production and delivery.

It is crucial that the cultivar is maintained with a very high level of endophyte in the stock seeds. This can usually be achieved by storage of stock seed with over 90% viable endophytes in cool, low-humidity (4˚ C, 30% relative humidity) environments over all generations. It is essential to undertake grow-out tests before sowing and after harvest. It must also be recognized that endophyte viability can drop during storage, usually over several years; when this occurs, reselection for 100% endophytes is recommended prior to sowing further seed crops. To date, few fine fescue endophytes appear to store well in cool store conditions, making reliable commercial delivery of these species extremely difficult.

NOTE: Seed companies are now testing new endophytes in turfgrass with new characteristics. One example is an ‘hot’ endophyte that occurs in the roots of the turfgrass and discourages feeding by insects such as Chafer grubs - Nikolas Wall, Premier Pacific Seeds