Viability ofLoliumendophyte fungus in seed stored at different moisture contents and temperatures

Abstract

The effect of storage on viability of the Lolium endophyte fungus (Acremonium loliae Latch, Christensen and Samuels) in seed of perennial ryegrass was studied. Treatments included four initial seed moistures (13.8, 12.1, 10.0, and 8.6%); different storage bags (calico, polyethylene film (9, 35, or 70 /lm thickness), and laminated aluminium foil-polyethylene); and four storage conditions (ambient 5-2YC, 5°Cj70% RH; 0°C/30% RH; -1 YC/90% RH). After 12 months of ambient temperature storage, seeds with final moisture contents > 11.3% had a rapid linear decline in endophyte viability from an initial 84% to < 15% at 13.0% seed moisture. Samples in 70 /lm thick polyethylene and aluminium foil laminated packets had the highest endophyte viability (70-78%) at ambient temperatures. Seed stored at 5, 0, or -15°C had high endophyte viability with no effect of seed moisture. Seed germination was not affected by any treatments. Cool or low humidity environments ( < 60% RH) are required to maintain viability of Lolium endophyte fungus in stored seed.

Neotyphodiumendophyte infection frequency in annual grass populations: relative importance of mutualism and transmission efficiency

“…For postzygotic transmission failure, the patterns associated with environmental conditions are well documented. The temperature and humidity to which infected seeds are exposed affect the survival of the endophyte mycelia and, therefore, depending on these environmental factors, variable proportions of viable endophyte-infected seeds produce non-infected seedlings (Siegel et al 1984b;Rolston et al 1986;Welty et al 1987). In addition, it has been observed that infected seeds that passed through the digestive tract of steer produce substantially larger proportions of non-infected seedlings that control infected seeds (Siegel et al 1984a).…”

“…Transmission efficiency fluctuations might occur, for example, as a result of year-to-year changes in summer weather conditions. Because high temperatures and humidity increase the mortality of the endophyte in seeds, transmission efficiency would decrease when the summer is wet and hot (see Rolston et al 1986;Welty et al 1987). Fluctuations in reproductive advantage of infected individuals might result, for example, from year-to-year oscillations in the activity of seed predators consuming preferentially non-infected seed, and therefore transiently increasing the relative fitness of infected individuals (Bush et al 1997;Clay & Schardl 2002).…”

“…Pre-zygotic failure occurs when the endophyte fails to infect seedlings or colonize tillers, spikes or panicles, spikelets and ovaries during flowering ( Welty et al 1994;Ravel et al 1997;Schulthess & Faeth 1998). Post-zygotic failure occurs when the endophyte dies in mature seeds (Rolston et al 1986;Welty et al 1987). Both types of failure would be affected by environmental variation (Do Valle Ribeiro 1993;Hill et al 2005;Ju et al 2006).…”

Agronomic performance and water-soluble carbohydrate expression of selected ryegrasses at two locations in New Zealand

“…Undoubtedly a major factor driving these differences was the infection of New Zealand cultivars by the fungal endophyte Neotyphodium lolii, which improves yields and persistence, most commonly through improved pest protection (Popay et al 1999). Most northern hemisphere cultivars lacked this infection (Latch et al 1987), or at least any endophyte may have died by the time seed was sown in New Zealand (Rolston et al 1986). Prior to the 1980s, the critical role endophyte has in determining plant performance in New Zealand was unknown and therefore not quantified in trials.…”

Ceres Progrow Westerwolds ryegrass (Lolium multiflorumLam.)

“…This is designed to maintain both germination and endophyte presence (Rolston et al 1986). Each year sufficient seed is released for the production of breeders' grade seed.…”