Species and Varietal Differences in Scab Resistance of Pear

Differences in scab-resistance of Japanese, Chinese, and European pear cultivars were ex-amined by spraying with a conidial suspension (2 × 105 conidial•m1-1) of pear scab, Ventur-ia nashicola.The degree of scab resistance in Pyrus species or cultivars could be classified into four types: Highly Resistant (HR), no macroscopic evidence of infection on any leaves; Resistant (R), necrotic lesions on a few leaves but with no sporulation; Susceptible (S), sparsely sporulat-ing lesions on a few leaves; and Highly Susceptible (HS), abundance of sporulating lesions on several leaves.Differences in scab-resistance were observed among Pyrus species. All European pear cul-tivars (P. communis) were evaluated as HR; most Japanese pear cultivars and selected clones (P. pyrifolia) were rated as HS or S, although 'Kinchaku' and 'Okusankichi' were designat-ed as being HR and R, respectively. Pear cultivars classified as P. ussuriensis or P. pyrifo-lia which originated in China were evaluated as either HR or R. Cultivars of P. bretschneideri exhibited an entire range from HR to HS.