Fruit and leaf incidence of pear scab (Venturia pirina Aderh.) in mixed European and Asian pear progenies.

摘要

In New Zealand, pear scab is caused by the fungus Venturia pirina. The scab fungus, Venturia nashicola, of Asian pear (Pyrus pyrifolia and P. bretschneideri) 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) is more limited. The results are reported of an experiment conducted in 2000-03 in New Zealand to assess the incidence of scab in breeding populations of 13 families with variable degrees of Asian/Chinese and European pear in their pedigrees. In particular, the distinction between lesions on the leaf and those on the fruit was considered. Infection of fruits (44%) was generally more common than that of the leaves (35%). 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..