Abstract
The presence of the fungal endophyte Neotyphodium coenophialum in tall fescue
(Festuca arundinacea) confers resistance to some plant-parasitic nematodes
but also results in the production of ergot alkaloids. Recently, new strains
of N. coenophialum have been isolated from wild tall fescue and artificially
inoculated into elite tall fescue cultivars. These strains produce low to
nil levels of ergot alkaloids and are referred to as non-ergot strains. Our
objective was to determine whether non-ergot strains of the endophyte confer
the same level of resistance to Pratylenchus spp. as the endemic strain in
tall fescue. In a glasshouse experiment, nematode resistance was compared in
two fescue cultivars (Jesup and Georgia 5) infected with either the endemic
strain (E+), or two non-ergot strains, AR542 and AR584. An additional
non-ergot strain, AR514, was tested only in cv. Jesup. Cultivars Georgia 5
and Jesup without endophytes (E−) were used as controls. The endophtye
status of the plants was confirmed and then three plants per
cultivar/endophyte combination were transplanted into 10 cm square pots. The
pots were inoculated with a mixed culture of Pratylenchus zeae and P.
scribneri in the first trial and a pure culture of P. scribneri in the
second trial of the experiment. After 8 weeks, the number of nematodes
within the roots from each pot was determined. Numbers of Pratylenchus spp.
in either cv. Georgia 5 or cv. Jesup containing the non-ergot strain AR542
were not different from numbers in E− plants. AR514 also did not confer
resistance to the nematodes in cv. Jesup. By contrast, the non-ergot strain
AR584 appears to confer resistance to Pratylenchus spp. in cv. Georgia 5,
but not in cv. Jesup; however, the level of resistance in cv. Georgia 5 was
less than the resistance conferred by the endemic endophyte. Genetic
differences between the two tall fescue cultivars may affect growth of the
endophyte or production of a nematode toxin or deterrent by the endophyte.
As only a small subset of endophyte strains has been tested, we are
screening additional non-ergot strains for resistance to P. scribneri.
Direct Evidence of Endophyte (Neotyphodium coenophialum) Genotype Effect on Growth and Vertical Transmission of Endophyte in Tall Fescue (Schedonorus phoenix Scop.) Under Water Stress