Sulfhydryl‐reagent alteration of soybean resistance to the cabbage looper, Trichoplusia ni

Abstract

The hypothesis that the sulfhydryl reagent, N‐ethylmaleimide, would function as an elicitor of alterable resistance in soybean (Glycine max) plants to Trichoplusia ni herbivory was tested experimentally under greenhouse conditions. This elicitory chemical, which allows receptor thiols to add across its carbon‐carbon double bond, altered the resistance in one or more leaves of plants at one or more intervals after treatment; and thus yielded results supporting the hypothesis. Leaf dipping and soil application were both effective methods of treatment. Results support the interpretation that an elicitor may function in intact plants by altering the integrity of sulfhydryl groups in receptor macromolecules which are also involved in signaling a change in the plant's biosynthesis of characteristic defensive compounds such as phenyl‐propanoids including antifeedant and antibiotic flavonoids. Induced feeding non‐preference by T. ni was highly correlated positively with the amount of glyceollins in the leaf.

Antioxidant alteration ofGlycine max (Fabaceae) defensive chemistry: Analogy to herbivory elicitation

“…An elicitor apparently just The elicitory effects of vitamin C were influenced by dosage, time after treatment and space in the plant. Comparable influences on the systemic dimensions of elicitation were noted previously in G. max (Neupane & Norris 1990, 1991a. Regarding the effects of dosage, the only significant alterations by 10 -» to 10 -3 M L-ascorbic acid were increases in anti-herbivory.…”

“…6 cork borer. Two leaf discs, one from the appropriate leaf on a treated (elicited) plant and the other from the same leaf on a control plant, were each secured with its abaxial surface up in an opposed position, 3 cm apart, in the center of a 9 cm diam plastic petridish arena (Neupane & Norris 1990, 1991a. Each arena contained a 3 mm-deep bed of paraffin covered by a Whatman No.…”

“…The diverse natures of such biotic and abiotic elicitors of plants may infer that a common mechanism of action is unlikely, but Sequeira (1983) suggested that sulfhydryl (--SH) groups may be involved in elicitation related to phytopathology. Neupane & Norris (1990, 1991a have since shown that both iodoacetic acid (IAA) and N-ethylmaleimide (NEM), classical sulfhydryl reagents, elicit Glycine max (L.) Merrill plants to alter their defensive chemistry against Trichoplusia ni larval herbivory. A thiol (--SH)-protein receptor for such sulfhydryl-reagent elicitors has been demonstrated in G. max plasma membrane (Liu & Norris 1992).…”

Inducible Phytoalexins in Juvenile Soybean Genotypes Predict Soybean Looper Resistance in the Fully Developed Plants

“…The levels of induced glyceollin and coumestrol in a given soybean hypocotyl depended on seedling age, the chemical The efficiency of chemicals as elicitors differs significantly even among the tested sulfhydryl-binding reagents, IAA, PMBS, and AgNO3, which are confirmed inducers of phytoalexins, especially glyceollin, in soybean (15,16,25). The order of efficiency of these chemicals as elicitors of glyceollin and coumestrol in Davis hypocotyls was AgNO3 > PMBS >> IAA, but in PI 227687 hypocotyls the order was AgNO3 2 PMBS >> IAA.…”

“…Regarding chemical elicitors, some classical sulfhydryl-binding reagents mimic insects in the induction of phytoalexin (e.g. glyceollin) accumulation in fully developed soybean plants (15,16). Stossel (24,25) also showed that sulfhydrylbinding reagents could induce glyceollin accumulation in soybean hypocotyls.…”