Comparison of two methods to evaluate quantitative resistance to eastern filbert blight in European hazelnut

A rapid and reliable assay for screening European hazelnut (Corylus avellan a L,) genotypes for quantitative resistance to eastern filbert blight [Anis ogramma anomala (Peck) E. Muller] was tested by comparing two methods using the same clones. in the first assay, disease spread was followed for five consecutive years (1992-96) in a field plot planted in 1990, Measured respo nses included disease incidence (the presence or absence of cankers) and to tal canker length, quantified as the length of perennially expanding canker s. The second assay consisted of annually exposing replicated sets of 2-yea r-old, potted trees to artificially high doses of pathogen inoculum and mea suring incidence and canker lengths at the end of the nest growing season, The potted trees were exposed to inoculum in 1990, 1992, 1993, and 1994, Co mpared to the field plot, disease incidence and total canker length were hi gher in all the potted-tree experiments. Nonetheless, disease responses of individual clones in the two screening methods were significantly correlate d in some contrasts (r(s) = 0.97 between 1996 field and 1995 potted trees). However, for a few clones ('Camponica', 'Tombul Ghiaghli', and 'Tonda di G iffoni'), disease developed slowly in the field plot, but disease incidence on these clones averaged >30% in most of the potted-tree studies. Disease responses also were significantly correlated among some of the potted-tree experiments (r(s) = 0.72 for the comparison of 1993 to 1995), Highly suscep tible and highly resistant hazelnut clones were identified by both methods. However, the field plot method was superior to the potted-tree method for distinguishing among moderately resistant clones, 'BulgariaXI-8', 'Gem','Ca mponica', 'Tombul Ghiaghli', and 'Tonda di Giffoni' were identified as prom ising sources of quantitative resistance to eastern filbert blight.