|Authors: ||V. Bus, L. Brewer, C. Morgan|
|Keywords: ||Venturia pirina, Venturia nashicola, Pyrus spp., non-host resistance|
Scab is a major disease of pear worldwide.
The disease is caused by two species: Venturia pirina, which infects European pear, and V. nashicola, which infects Asian pear species.
The host types are mutually exclusive to the Venturia species and this phenomenon is heavily exploited in the Plant & Food Research pear breeding programme for the breeding of scab-resistant pear cultivars.
In 2008 and 2009, 18 seedling families with a range of 0 to 100% Asian pear pedigree were screened in the glasshouse following artificial inoculation with V. pirina, the scab species present in New Zealand.
The progenies showed a range of resistance reactions, mostly in the classes 0 (no symptoms) and 2 (necrotic reaction without sporulation). Some seedlings showed a hypersensitive response (class 1) or chlorotic reactions with limited sporulation (class 3). As expected, the seedling progenies of low Asian pear descent showed high proportions (78-91%) of susceptible seedlings.
Ten families showed 100% resistant seedlings, with a further two families showing 98 and 94% resistance.
We show that the average proportion of Asian ancestry of a progeny estimated from their parents is not necessarily a good predictor for the expected resistance segregations of that progeny.
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