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Physiological studies from thinning to bitter pit at the EUFRIN thinning group meeting in Porto

Blanke, M.
Erwerbs-Obstbau 2016 v.58 no.4 pp. 281-283
1-aminocyclopropane-1-carboxylic acid, abscisic acid, abscission, alternate bearing, apples, bitter pit, calcium, climate, ethylene, flowering, leaves, pears, photosynthesis, stone fruits, Europe, New York, South Africa
This contribution summarises the outcome of the annual meeting of the EUFRIN WG thinning group in 2016 in Porto.1) Among the new future thinning products, the emphasis was on Brevisᵀᴹ, the new fruitlet thinning agent for pome fruit in Europe, based on inhibition of leaf photosynthesis at the 8–10 mm fruitlet stage for apple (and pear).2) ACC (1-aminocyclopropane-1-carboxylic-acid), the ethylene precursor, was trialed on both pome and stone fruit in South Africa, Geneva (US) and Europe. ACC stimulated fruitlet abscission at the late 18–20 mm stage in apple, with occasional leaf fall depending on concentration mimicking photosynthesis inhibition, and with a direct positive effect on preventing alternate bearing as known from ethylene releasing compounds.3) First experiments at the Cornell University in Geneva, USA investigated the potential of S-ABA (abscisic acid) for bitter pit control using 5 applications after full bloom at 10 days interval on ’Honeycrisp’ apple with an increase in fruit calcium from 3 to 5 mg Ca/100 g FM, but 10–15 % smaller fruit size and slight leaf yellowing under New York climate conditions.Future research will show, which of these compounds show persistently positive results to make them suitable for our varieties, region and climate and legal approval.