Endophyte survival during seed storage: Endophyte–host interactions and heritability
Use of nontoxic endophytes in forage tall fescue [Schedonorus phoenix (Scop.) Holub.] is a preferred strategy to overcome fescue toxicosis. Endophytes are transmitted through the seed, but suffer mortality preferentially to the embryo during storage. Loss of viable endophyte reduces the value of the seed, so increasing storage life would be a benefit. The objectives of this study were to examine (i) viability of an endophyte AR542 in different tall fescue cultivars and endophytes AR542 and AR584 in a Jesup tall fescue seed when stored for extended periods of time, and (ii) heritability of endophyte persistence during seed storage. Seed from each population were stored at room temperatures for 18 mo. Jesup plants containing endophyte after 18 mo of seed storage were placed into polycross blocks. Seed from the selected and parent populations, Jesup with toxic endophyte, and Grasslands Flecha with AR542, were stored at 30°C for 22 mo and tested for endophyte monthly. Pairwise t tests and regression analysis were performed to describe the population responses to storage conditions. Heritability of endophyte viability during storage was calculated. Endophyte AR542 viability during storage was greatest in Flecha followed by Jesup and least in Advance, a third tall fescue cultivar studied in addition to Jesup and Flecha. Endophyte AR584 had greater viability during storage than did AR542 when in Jesup. Selection for endophyte survival increased endophyte viability in stored seed and had heritabilities of 38 and 63% for AR542 and AR584, respectively.