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 'Redchief Delicious' Mercier strain fruits were sampled 0, 2, 4, and 6 days after cutting. Thin-layer-plate assays were developed and used to identify hydrolytic enzymes active in the abscission zone (AZ) after induction. Increased activity of cellulase, but not polygalacturonase, was detected in the AZ following cutting. Cellulase activity was consistently high in AZs 4 days after cutting. Both AVG (652 mg·L^-1) and NAA (10 mg·L^-1) applied 2 or 4 days after 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); naphthaleneacetic acid (NAA).