EFFECTS OF AMINOETHOXYVINYLGLYCINE AND NAPHTHALENEACETIC ACID ON ETHYLENE BIOSYNTHESIS, PRE-HARVEST FRUIT DROP AND FRUIT QUALITY OF APPLE

Cultural control of pre-harvest drop has relied upon plant growth regulators. To investigate the effects of plant growth regulators on pre-harvest drop and fruit quality, 150, 300 and 600 mg L-1 aminoethoxyvinylglycine (AVG) and 20 mg L-1 NAA were sprayed to 'Red Chief' apple trees at 4 week before anticipated harvest date. Untreated trees were kept as control. Results revealed that all AVG treatments increased the fruit removal force and significantly delayed pre-harvest drop and fruit maturity. Pre-harvest drop generally was unaffected by NAA. Internal ethylene concentration decreased with increasing AVG concentrations. Fruits treated with 150, 300 and 600 mg L-1 AVG showed increased fruit firmness and titratable acidity and reduced soluble solids content. Red colour development and starch degradation were retarded by all AVG treatments. Fruits treated with AVG (300 and 600 mg L-1) had lower fruit mass, fruit width and fruit length. The effect of NAA on all quality parameters was similar to the control treatment. AVG treatments decreased pre-harvest drop by fifty percent relatively to control.