The symbiotic endophyte of tall fescue, N. coenophialum, confers resistance to some but not to all plant-parasitic nematodes (Table 10-2). Determinations of such effects were made by comparing nematode numbers in endophyte infected tall fescue (E+) and in tall fescue without the endophyte (E-). The effect of the endophyte is often dramatic, with nematode numbers in E+ plants being less than 10% of those in E- plants for root-knot (Meloidogyne marylandi) and lesion (P. scribneri) nematodes (Elmi et al., 2000; Kimmons et al., 1990; West et al., 1988).


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Table 10-2. Nematode parasites of tall fescue.


The spiral nematode (Helicotylenchus pseudorobustus) represents the only well-documented case of a nematode that is not affected by the endophyte status of tall fescue (Davis et al., 2004; Kimmons et al., 1990). Nematodes that are found frequently in association with tall fescue (Table 10-1), such as the stubby-root and dagger nematodes (Xiphinema spp.), also are probably not affected by the endophyte. Pedersen et al. (1988) reported greater numbers of stubby-root nematode in root samples from E- than from E+ KY-31; however, Timper and Bouton (2004) observed similar numbers of this nematode in pots containing E+ and E- plants of both ‘Georgia 5' and ‘Jesup' tall fescues. They also showed that Jesup appeared to be resistant to reproduction of the stubby-root nematode, whereas Georgia 5 was susceptible (Fig. 10-4).



Fig. 10-4. Average number of lesion nematodes (Pratylenchus scribneri) per pot. Each pot contained three plants of a single cultivar either infected with the wild endophyte (E+) or endophyte free (E-).


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