The action of aminoethoxyvinylglycine (AVG) on apple (‘Maxi Gala’) leaf abscission in plants infected by Glomerella leaf spot (Colletotrichum gloesporioides)

Abstract

Abstract In Brazil, leaf abscission in apple trees can occur prematurely due to infection by Glomerella leaf spot (Colletotrichum gloeosporioides). The extent of leaf fall is correlated with ethylene production resulting from the reaction by the host to prevent the dissemination of the pathogen. The aim of this study was to verify the impact of the aminoethoxyivinylglycine (AVG) on the process of leaf abscission in plants exhibiting Glomerella leaf spot symptoms. The experiment was conducted in the spring of 2011 in ?Maxi Gala?/M9 young apple trees (2 years old) in pots under greenhouse conditions at 22±2°C, with 80±5% relative humidity, (28°30?52?S and 50°52?58?W, 950 m). Plants without disease symptoms were artificially inoculated with C. gloeosporioides, and treatments were applied when the leaves had symptoms of infection. The experiment included 7 treatments with AVG and/or the fungicide Folpet (mg L-1 active ingredient ? a.i.) as follows: AVG 60, AVG 150, AVG 30 + Folpet 120, AVG 45 + Folpet 120, AVG 60 + Folpet 120, AVG 150 + Folpet 120, Folpet 120 alone and the untreated control. Assessments of percentage defoliation were made weekly until 68 days after spraying (das). The results indicated that AVG in doses 60 and 150 mg L-1 resulted in a reduced level of defoliation, compared with the fungicide treated trees, and abscission was equivalent to control at 21 das. After the disease is established and is not controlled by fungicide there was an increase in leaf abscission compared to the control.