Lack of Specificity in Plant Extracts and Chemicals as Inducers of Systemic Resistance in Cucumber Plants to Anthracnose

Abstract

Canoia, lettuce, green bean, dwarf pea, tobacco, tomato, poplar, corn, wheat, and cucumber leaves were extracted by boiling with 95% ethanol. The ethanol was removed from the ethanol‐water extract, and the water‐soluble fraction was centrifuged and filtered to remove compounds with a molecular weight > 1 000 D. The undersides of the first true leaf of a cucumber plant (leaf 1) and the leaf above (leaf 2) were sprayed with each plant extract (induction), and 7 days later leaf 3 was inoculated with a conidial suspension of Colletotrichym lagenarium (challenge). Extracts from all plants tested induced systemic resistance in leaf 3 to C. lagenarium. Commercially available compounds were screened to determine structural similarities among the compounds which can induce systemic resistance. All compounds which induced resistance in leaf 3 caused some damage to leaves 1 and 2. but not all compounds which damaged leaves 1 and 2 induced resistance in leaf 3. Galacturonic acid, glucuronic acid, salicyhc acid, m‐hydroxybenzoic acid, p‐hydroxybenzoic acid, y‐resorcylic acid, protocatecbuic acid, gallic acid, hemimelletic acid, trimelletic acid, trimesic acid, phloroglucinol, and glycine induced systemic resistance, whereas catechol, resorcinol, hydroquinone, pyrogaLol, hydroxyhydroquinone, benzoic acid, phthalic acid, α‐resorcylic acid, β‐resorcylic acid, gentisic acid. 2, 3‐dihydroxybenzoic acid, benzaldehyde, 2,3‐dihydroxybenzaldehyde, β‐resorcaldehyde, protocatechuic aldehyde, benzyl alcohol, salicyl alcohol, myo‐inositol, phytic acid, pinitol, and quebrachitol did not. Structural similarities were not evident among either compounds which induced systemic resistance or those that did not.

Induction of plant defense responses by Ocimum gratissimum L. (Lamiaceae) leaf extracts

“…For other plant extracts, including cucumber, a dose response study indicated that increasing concentrations generally produce increasing levels of systemic resistance in cucumber to Colletotrichum lagenarium and that some are phytotoxic at higher concentrations (14). We did not observe a dose response, but there were no signs of phytotoxicity in response to the concentration tested of the extract either.…”

“…Preliminary anatomical observations have shown the accumulation of granules of phenolic nature in treated, inoculated cucumber hypocotyls (10), which suggests that penetration and/or initial development of the pathogen might be affected. Many different substances seem to trigger responses in cucumber, with no apparent common structural features among a compound that does or does not induce systemic resistance (14). Not surprisingly, in most in previous studies plants parts, of O. gratissimum including the leaves, showed a very complex chemical composition.…”

Inductores de resistencia vegetal en el control de Candidatus Liberibacter asiaticus en árboles de limón (Citrus aurantifolia) mexicano

“…In our experiment, some of the pest control products that were applied, when necessary, to all the lemon trees during the first four months before starting the experiment could have contributed to the induction of resistance. Previous studies have demonstrated that some of the components of those products are able to induce resistance, for example, imidacloprid (Francis et al, 2009), some essential oils (Banani et al, 2018) and plant extracts (Fought and Kuć, 1996;Khoa et al, 2017). Despite the above, in our experiment the treatment with no inductor (T4) did not have a significant effect on the reduction of CLas after eight months during which these products were not applied.…”

“…En nuestro experimento, algunos productos utilizados para el control de plagas aplicados a todos los árboles de limón durante los primeros cuatro meses cuando fue necesario, previo al inicio del experimento, podrían haber contribuido a la inducción de resistencia. Estudios previos han demostrado que algunos componentes de estos productos son capaces de inducir resistencia como el imidacloprid (Francis et al, 2009), algunos aceites esenciales (Banani et al, 2018) y extractos vegetales (Fought y Kuć, 1996;Khoa et al, 2017). A pesar de lo anterior, en nuestro experimento el tratamiento sin inductor (T4) no mostró un efecto significativo en la disminución de CLas después de 8 meses de no haberse aplicado estos productos.…”

"Aspectos bioquímicos e moleculares da resistência sistêmica adquirida em cafeeiro contra Hemileia vastatrix"

“…Existem vários relatos na literatura de diversas substâncias de origem biológica que agem como indutores de resistência (Kuć, 2001), como por exemplo, frações de parede celular de plantas, de fungos (Doke et al, 1987) e de bactérias, como lipopolissacarídeos de rizobactérias promotoras de crescimento de plantas (Pieterse et al, 2001be Van Loon et al, 1998; fluído intercelular de plantas; extratos vegetais (Fought & Kuć, 1996) e de microrganismos não patogênicos, como S. cerevisiae (Pascholati, 1998) e substâncias provenientes de fitopatógenos, como Phytophthora spp.,…”