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Fig. 14-36. Characteristic profusely branched hyphal growth of a p-endophyte in the outer leaf sheath of perennial ryegrass.
Tall fescue and closely related grasses [perennial ryegrass (L. perenne L.), hybrid ryegrass (L. perenne ´ L. multiflorum Lam.), and meadow fescue (Lolium pratense (Huds.) Darbysh.] also are hosts to endophytic fungi referred to as p-endophytes, endophytes with penicilliate conidiophores. These endophytes are not close kin of Neotyphodium (An et al., 1993). p-Endophytes are seed borne and are found in the intercellular spaces of the host grass. Growth of p-endophytes in leaves is not regulated in the same way as that of the Neotyphodium endophytes (Christensen et al., 2002; Philipson, 1989). Hyphae continue to grow once leaf growth ceases, giving rise to high concentrations of branched hyphae in old leaves (Fig. 14-36). Numerous conidia (asexual spores) are produced in senescent leaves. Conidia and hyphae growing from infected leaves may give rise to contagious spread of p-endophytes, although this has not been verified. No benefits to host grasses from the presence of p-endophytes have been confirmed, and their impact on persistence of host grasses is unknown. For further reading on p-endophytes see An et al. (1993), Christensen et al. (2002), Philipson (1989, 1991a,b).