FRUIT AND LEAF INCIDENCE OF PEAR SCAB (VENTURIA PIRINA ADERH.) IN MIXED EUROPEAN AND ASIAN PEAR PROGENIES

In New Zealand, pear scab is caused by the fungus Venturia pirina Aderh. The scab fungus, Venturia nashicola Tanaka et Yamamoto, of Asian pear in Asia, has not yet been recorded here. Most Asian species are reported to be moderately resistant to V. pirina, but resistance in European pears (P. communis L.) is more limited. We report on the results of a scab assessment of a breeding population consisting of 13 families with variable degrees of Asian/Chinese and European pear in their pedigrees. In particular, we consider the distinction between lesions on the leaf and those on the fruit. Infection of fruit was generally more common than that of the leaves, with 35% of seedlings trees showing leaf infection, but 44% showing fruit infection. Trees from families with at least 75% Asian ancestry rarely exceeded a mean leaf score of 1 (scale: 0 (immune) - 9 (highly susceptible)), but frequently had severe (rating 7-9) fruit infection. Many of the trees from families with all seedlings resistant to leaf scab exhibited some fruit scab. Most trees from families with nearly all seedlings susceptible to leaf scab were also susceptible to fruit scab. Thus, seedling leaf resistance alone is not an accurate indicator of pear scab resistance in populations derived from Asian parents.