Cutting apple fruits induces cellulase activity in the abscission zone

Preharvest abscission of apple [Malus xdomestica (L.) Borkh.] fruits causes significant crop loss in many years. In this study, fruit cutting was used to induce abscission in August and September. Abscission zones of 'Redchie f Delicious' Mercier strain fruits were sampled 0, 2, 4, and 6 days after c utting. Thin-layer-plate assays were developed and used to identify hydroly tic enzymes active in the abscission zone (AZ) after induction. Increased a ctivity of cellulase, but not polygalacturonase, was detected in the AZ fol lowing cutting. Cellulase activity was consistently high in AZs 4 days afte r cutting. Both AVG (652 mg.L-1) and NAA (10 mg.L-1) applied 2 or 4 days af ter cutting delayed drop, but NAA delayed drop 1.6 days longer than did AVG , Fruits treated with AVG dropped over a longer period than did control or NAA-treated fruits. Chemical names used: aminoethoxyvinylglycine (AVG); nap hthaleneacetic acid (NAA).