Resistance-inducing chemicals against Colletotrichum gloeosporioides in mango.
Santiago J. A., Rivera-Vargas L. I., Rodríguez R. del P., Macchiavelli R.
Author Affiliation: Department of Crop Protection, P.O. Box 9030, University of Puerto Rico-Mayagüez Campus, Mayagüez, 00681-9030, Puerto Rico.
Journal of Agriculture of the University of Puerto Rico 90 : 221-235
Abstract : Various resistance-inducing chemicals were assessed in the interaction between mango (Mangifera indica) and the anthracnose pathogen Colletotrichum gloeosporioides [Glomerella cingulata]. These were salicylic acid, isonicotinic acid, benzo (1,2,3) thiadiazole-7-carbothionic acid S-methyl ester (Actigard®)7, and other chemical compounds structurally similar, such as nicotinic acid, nicotinic acid adenine dinucleotide, isonicotinic acid ethyl ester, N-oxide isonicotinic acid, benzoic acid and sodium benzoate. No significant differences (P>0.05) in C. gloeosporioides colony growth were detected on culture media amended with the different resistance-inducing chemicals evaluated. At laboratory conditions, these compounds were sprayed to runoff on mango leaves and fruit pieces prior to inoculation. Lesion size was significantly reduced (P>0.10) by concentrations ranging from 10-12 to 10-6 M of salicylic acid (SA), 10-18 and 10-14 M of isonicotinic acid (INA), 10-17 to 10-2 M of Actigard®, and 10-10 M benzoic acid (BA). Salicylic acid, INA and BA caused toxicity on leaves at concentrations ranging from 10-1 to 10-3 M. Chemical compounds that induced resistance at laboratory conditions were further evaluated on six-month-old mango seedlings in a shade house. None of the chemicals tested significantly (P>0.05) reduced lesion size caused by C. gloeosporioides. Other resistance-inducing chemicals not tested during these studies, such as probenazole, cyclopropane carboxylic acid derivatives, non-protein amino acids [?-aminobutyric acid (BABA) and ?-aminobutyric acid (GABA)] and Phytoguard®, should be evaluated individually and in combinations to clarify this lack of induced resistance in mango tissues.