Use of accelerated aging as a surrogate phenotyping approach to improve endophyte survival during storage of tall fescue seed

Abstract

Survival of the endophyte (Neotyphodium coenophialum) during seed storage of tall fescue (Lolium arundinaceum (Schreb.) Darbysh) has commercial value. The objectives of this research were to (1) identify accelerated aging (AA) conditions that compromise endophyte viability without affecting seed germination, (2) Determine whether the response to selection for endophyte persistence is consistent in laboratory and warehouse conditions (3) determine whether selection affected agronomic characteristics of the populations. ‘Jesup’ tall fescue with non-toxic endophyte strain AR542 was incubated for 35-d in sealed food containers with different salt solutions to create varying relative humidities (RH). Seed were sampled and tested for germination and endophyte viability every 7 d to determine which treatment provided the most effective conditions to induce AA. Base populations (C0) of ‘Jesup’ AR542 (Jesup MaxQ) and Jesup AR584 had previously been selected for endophyte survival after 18 months under ambient laboratory conditions to produce C1 populations. Seed from C1 were exposed to accelerated aging conditions, and seedlings with viable endophytes were selected to produce C2AA populations. All six populations (two each of C0, C1, and C2AA) were grown in isolated blocks in the field to produce the seed used in these experiments. Seed from C0 and C1 populations was stored in cloth bags at ∼21°C in the laboratory and tested for endophyte viability monthly for 22 months. Seed from C2AA populations in addition to C0 and C1 were stored in a warehouse for 27 months and endophyte viability tested every 3 months. Heritability for endophyte survival was calculated for the C1 and C2AA populations. Seventy-five percent RH was effective in inducing accelerated aging of the endophyte without compromising seed health. Heritability estimates for endophyte survival were high in both Jesup AR542 and JesupAR584 for both C1 (0.51-0.62) and C2AA (0.54-0.64). Agronomic characteristics for all populations remained comparable to the original Jesup release (C0) after both cycles of selection (C1 and C2AA).