Induction of systemic acquired resistance in cotton by BTH has a negligible effect on phytophagous insects

Abstract

Whether or not chemical changes in plants in response to pests (insects and pathogens) are general or specific remains unclear. Some evidence indicates that an induced response (IR) to arthropods via the octadecanoid pathway represents a distinct mechanism from the salicylic acid-based pathway of systemic acquired resistance (SAR) to pathogens. To further test this hypothesis, young cotton seedlings were activated with benzo (1,2,3) thiadiazole-7carbothioic acid (S) methyl ester (BTH), an elicitor of SAR. The enzymatic activities of a number of pathogenesisrelated (PR) proteins in young and old leaves of control and BTH treated plants were measured. BTH applications elicited marked increases in the activity levels of chitinase, peroxidase, and β-1,3-glucanase both locally and systemically. The highest levels of induction were detected systemically in young leaves. Except for some local effects on whitefly oviposition, the induction of SAR by BTH had no effect on either host preference of whiteflies Bemisia tabaci (Gennadius) or on feeding efficiency of cotton bollworms Helicoverpa armigera (Hübner). We conclude that SAR induction via the salicylic acid pathway in 'Acala' cotton has negligible effect on the tested insect herbivores.

Silicon and acibenzolar-S-methyl as resistance inducers in cucumber, against the whitefly Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) biotype B

“…in sorghum and wheat plants (Carvalho et al 1999, Basagli et al 2003. Inbar et al (2001) did not observe a reduction in whitefly oviposition in young cotton leaves treated with BTH, similarly to the results obtained in the no-choice test.…”

“…The mean number of whitefly nymphs was similar to that for oviposition; survival rate for the egg to fourth-instar nymph period, however, was lower in plants treated with silicon, BTH, or both (Table 1). In the field, the whitefly did not show oviposition non-preference on cotton plants with BTH (Inbar et al 2001), contrary to what was observed in cucumber plants treated with silicon, BTH, or both. When given a choice, the whitefly preferred to oviposit on the most suitable substrates for the development of nymphs (Villas Bôas et al 2002).…”

“…Activation of the enzymes chitinase, peroxidase, 1,3-glucanase, polyphenoloxidase and phenylalanine ammonia-lyase proteinase and lipoxygenases, related to the synthesis of secondary compounds, increased with silicon and BTH application in cotton, tomato, and wheat (Stout et al1994, Inbar et al 2001, imparting an antibiosis-type mechanism of resistance to the treated plants.…”

“…In sorghum, accumulation of phytoalexins in plant tissues occurred as the concentration of BTH increased, indicating plant systemic response to the resistance inducer (Oswald et al 1998). In cotton, the application of BTH induced increases in activity levels of the enzymes chitinase, peroxidase, and 1,3-glucanase in young and old cotton leaves, indicating some local resistance effect (Inbar et al 2001). To date, the interaction among cucumber, whitefly, and silicon-induced resistance has not been investigated.…”

Efeito de indutores da resistência e cultivares de algodão no comportamento de Aphis gossypii

“…Em sorgo e em trigo foi possível observar que a aplicação de silício reduziu a preferência e a reprodução de Schizaphis graminum (Rondani) (Hemiptera: Aphididae) (BASAGLI et al, 2003;CARVALHO et al, 1999). A eficiência do ASM na redução da oviposição e no desenvolvimento da mosca-branca Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) foi observada por Inbar et al (2001) e Correa et al (2005). O ASM também reduziu a preferência de S. graminum por plantas de trigo tratadas com esse produto (COSTA; MORAES, 2006).…”