Salicylic acid treatments induce resistance to Tuta absoluta and Tetranychus urticae on tomato plants

ABSTRACT This study was performed to evaluate the effect of exogenous application of salicylic acid as a resistance inducer to two-spotted spider mite and tomato pinworm on tomato genotypes. Bioassays were carried out in three commercial genotypes (‘Redenção’, ‘Giuliana’, and ‘Alambra’) and one wild genotype (Solanum habrochaites var. hirsutum, accession PI-127826). Average distance travelled by the two-spotted spider mite and number of eggs deposited over the leaflets of the genotypes were investigated. Concerning pinworm bioassay, number of eggs, leafminers on leaflet surface and percentage of leaf area consumed by leafminers were evaluated using a scanner. Furthermore, severity of attack to plants was evaluated by score scale for damages, types of lesions and attacked leaflets. Salicylic acid application induced resistance in the commercial genotypes against both pests, reducing the two-spotted spider mite and pinworm oviposition. The spider mites travelled shorter distance on leaflets of genotypes treated with salicylic acid at intermediate concentrations, indicating a positive effect of substance as inducing resistance. Attack severity by pinworm was also reduced when intermediate doses of salicylic acid were applied. Also, higher resistance was observed on accession PI-127826 as compared to other genotypes. The obtained results indicate that the resistance of PI-127826 was due to constitutive defense, whereas on commercial genotypes defense was dependent on responses mediated by salicylic acid. Hence, salicylic acid treatment, as resistance inducer, seems to be efficient against two-spotted spider mite and pinworm, being a promising tool within an integrated pest management on tomato plants. RESUMO Objetivou-se avaliar os efeitos da aplicação exógena de ácido salicílico como indutor de resistência ao ácaro-rajado e à traça em genótipos de tomateiro. Para isso, realizaram-se bioensaios com três genótipos comerciais (‘Redenção’, ‘Giuliana’ e ‘Alambra’) e um silvestre (Solanum habrochaites var. hirsutum acesso PI-127826). Determinou-se a distância média percorrida pelo ácaro-rajado e o número de ovos depositados sobre os folíolos dos genótipos. Com relação ao bioensaio da traça-do-tomateiro, foram avaliados o número de ovos e lagartas na superfície do folíolo e a porcentagem de área foliar consumida pelas lagartas por meio de digitalização dos folíolos. Além disso, avaliou-se a severidade do ataque na planta utilizando uma escala de notas referente a da