Effect of salicylic acid and structurally related compounds in the accumulation of phytoalexins in cotyledons of common bean (Phaseolus vulgaris L.) cultivars

Abstract

In the present work, isoflavonoid phytoalexin production in response to the application of salicylic acid in cotyledons of four common bean (Phaseolus vulgaris) cultivars (SA) was evaluated. The time-course and dose-response profiles of the induction process were established by quantifying the isoflavonoids by HPLC. Cotyledons of anthracnose-resistant cultivars induced by SA produced substantially higher phytoalexin contents as compared to the susceptible ones. In addition, maximum levels of phytoalexins (50-100 fold increases) were reached between 96 and 144 h, and when a concentration of SA from 3.62 to 14.50 mM was used. The observations also indicate that there was a relatively good correlation between the phytoalexin contents and the inhibitory effect against C. lindemuthianum; the higher antifungal activity was observed during the first 48 hours for extracts from cotyledons treated with SA at 1.45 and 3.62 mM, and between 96 and 144 h after induction. Finally, compounds structurally related to SA (dihydro-quinazolinones and some imines) showed a strong elicitor effect. Moreover, induced extracts from cotyledons treated with these potential elicitors, besides the properly elicitors, displayed a weak to moderated antifungal activity. These compounds may be considered good candidates for developing of new phytoprotectants. Furthermore, phytoalexin-eliciting substances may contribute for selecting disease resistant cultivars.

Figure 1

Chemical structures of some phytoalexins in common bean.

Figure 2

Time-course accumulation of phytoalexins in common bean cotyledons treated with SA. , genistein; , dalbergioidin; , phaseollinisoflavan; , phaseollidin; , daidzein; , 2’-hydroxygenistein; , kievitone; , coumestrol; , phaseollin. Bars represent the mean concentrations of the isoflavonoids ± standard deviation (n = 3). Cultivars: CM, Cargamanto Mocho; CR, Cargamanto Rojo; IQ, ICA Quimbaya; CI, CORPOICA 106. For each compound, bars with different letters are significantly different (p = 0.05; Fisher’s LSD test).

Figure 2

Time-course accumulation of phytoalexins in common bean cotyledons treated with SA. , genistein; , dalbergioidin; , phaseollinisoflavan; , phaseollidin; , daidzein; , 2’-hydroxygenistein; , kievitone; , coumestrol; , phaseollin. Bars represent the mean concentrations of the isoflavonoids ± standard deviation (n = 3). Cultivars: CM, Cargamanto Mocho; CR, Cargamanto Rojo; IQ, ICA Quimbaya; CI, CORPOICA 106. For each compound, bars with different letters are significantly different (p = 0.05; Fisher’s LSD test).

Figure 3

Accumulation of isoflavonoid phytoalexins on cotyledons of Phaseolus vulgaris by SA at different concentrations. , genistein; , dalbergioidin; , phaseollinisoflavan; , phaseollidin; , daidzein; , 2’-hydroxygenistein; , kievitone; , coumestrol; , phaseollin. Bars represent the mean concentrations of the isoflavonoids ± standard deviation (n = 3). Cultivars: CM, Cargamanto Mocho; CR, Cargamanto Rojo; IQ, ICA Quimbaya; CI, CORPOICA 106. For each compound, bars with different letters are significantly different (p = 0.05; Fisher’s LSD test).

Figure 3

Accumulation of isoflavonoid phytoalexins on cotyledons of Phaseolus vulgaris by SA at different concentrations. , genistein; , dalbergioidin; , phaseollinisoflavan; , phaseollidin; , daidzein; , 2’-hydroxygenistein; , kievitone; , coumestrol; , phaseollin. Bars represent the mean concentrations of the isoflavonoids ± standard deviation (n = 3). Cultivars: CM, Cargamanto Mocho; CR, Cargamanto Rojo; IQ, ICA Quimbaya; CI, CORPOICA 106. For each compound, bars with different letters are significantly different (p = 0.05; Fisher’s LSD test).

Figure 4

Antifungal activity against C. lindemuthianum of extracts from common bean cotyledons induced by SA at different concentration (up) and post-induction time (down). Cultivars: CR, Cargamanto Rojo; IQ, ICA Quimbaya. Figure 4a: , solvent control; , CR-untreated cotyledons; , CR-0.72 mM SA; , CR-1.45 mM SA; , CR-3.62 mM SA; , IQ-untreated cotyledons; , IQ-0.72 mM SA; , IQ-1.45 mM SA; , IQ-3.62 mM SA. Figure 4b: , solvent control; , CR-untreated cotyledons; , CR-48 h post-induction; , CR-96 h post-induction; , CR-144 h post-induction; , IQ-untreated cotyledons; , IQ-48 h post-induction; , IQ-96 h post-induction; , IQ-144 h post-induction. For each time point, the bars headed by the same letter do not differ at p = 0.05 (Fisher’s LSD test).

Figure 5

Chemical structures of compounds evaluated as elicitors.