Swiss Federal Research Station for Plant Production of Changins, PO Box 254, CH-1260 Nyon, Switzerland

Background and objectives
The grass endophyte Neotyphodium uncinatum was discovered in meadow fescue (Festuca pratensis) genotypes of the forage grass improvement programme of Changins [1]. Positive interactions of Neotyphodium-endophytes with grass species were reported for insect and drought tolerance, but their effect on disease resistance appeared to be marginal [2]. After 27 ;years of continuous screening for disease resistance, the majority of the meadow fescue genotypes at Changins are naturally infected with N> ;uncinatum, thereby indicating a possible positive effect of the endophyte on their host's disease resistance. The objective of this study was to verify if such an effect of N. ;uncinatum on meadow fescue resistance to three major diseases exists.

Materials and methods
Three endophyte-infected (E+) meadow fescue genotypes were cloned and endophyte-free (E-) clones were produced using a fungicide sanitation method. The three pairs of E+ and E- clones were arranged as a polycross to produce E+ and E- meadow fescue populations. The populations were tested for resistance to bacterial wilt (causal agent Xanthomonas campestris pv. graminis), leaf blight (causal agent Bipolaris sorokiniana) and seedling blight (causal agent Fusarium culmorum). Disease incidence of each blight was measured as a percentage of wilted plants, dead plants and mortality, respectively. The screening was conducted in a growth chamber, each test was repeated twice. Arcsin-transformed disease incidence data were analysed using ANOVA and linear contrasts.

Results and conclusions
Across all three populations, the endophyte significantly (P<5%) increased the resistance of meadow fescue to bacterial wilt, but had no effect on resistance to leaf blight and seedling blight. However, the effect of N. ;uncinatum on individual populations was restricted to three out of nine possible combinations (three populations X three diseases). The general increase of bacterial wilt resistance was due to the significant (P<5%) effect of the endophyte in one population, no effect occurred in the two other populations. In two populations, the endophyte significantly (P<5%) increased or decreased seedling blight resistance, resulting in no general endophyte effect. The results suggest that infection with the endophyte is of little importance to the increase of disease resistance of meadow fescue. Therefore, the high ratio of E+ meadow fescue genotypes at Changins is most likely caused by other endophyte-related effects, such as improved drought or insect tolerance.

1. Gams W, Petrini 0, Schmidt D, 1990. Mycotaxon 37, 67-71.
2. West CP, Gwinn KD, 1993. Proceedings of the Second International Symposium on Acremonium/Grass Interactions: Plenary Papers, pp. 131-140.