Altered cultivar resistance of kimchi cabbage seedlings mediated by salicylic Acid, jasmonic Acid and ethylene

Abstract

Two cultivars Buram-3-ho (susceptible) and CR-Hagwang (moderate resistant) of kimchi cabbage seedlings showed differential defense responses to anthracnose (Colletotrichum higginsianum), black spot (Alternaria brassicicola) and black rot (Xanthomonas campestris pv. campestris, Xcc) diseases in our previous study. Defense-related hormones salicylic acid (SA), jasmonic acid (JA) and ethylene led to different transcriptional regulation of pathogenesis-related (PR) gene expression in both cultivars. In this study, exogenous application of SA suppressed basal defenses to C. higginsianum in the 1st leaves of the susceptible cultivar and cultivar resistance of the 2nd leaves of the resistant cultivar. SA also enhanced susceptibility of the susceptible cultivar to A. brassicicola. By contrast, SA elevated disease resistance to Xcc in the resistant cultivar, but not in the susceptible cultivar. Methyl jasmonate (MJ) treatment did not affect the disease resistance to C. higginsianum and Xcc in either cultivar, but it compromised the disease resistance to A. brassicicola in the resistant cultivar. Treatment with 1-aminocyclopropane-1-carboxylic acid (ACC) ethylene precursor did not change resistance of the either cultivar to C. higginsianum and Xcc. Effect of ACC pretreatment on the resistance to A. brassicicola was not distinguished between susceptible and resistant cultivars, because cultivar resistance of the resistant cultivar was lost by prolonged moist dark conditions. Taken together, exogenously applied SA, JA and ethylene altered defense signaling crosstalk to three diseases of anthracnose, black spot and black rot in a cultivar-dependent manner.

Keywords: cultivar resistance; defense signaling; ethylene; kimchi cabbage; methyl jasmonate; salicylic acid.

Fig. 1

Altered disease resistance of kimchi cabbage seedlings to fungal and bacterial infections in susceptible (cv. Buram-3-ho) and resistant (cv. CR-Hagwang) plants pretreated with 0.5 mM of salicylic acid (SA). (A) Lesion numbers on the inoculated leaves of both kimchi cabbage cultivars pretreated with SA were counted after C. higginsianum inoculation. 1st, 1st true leaves; 2nd, 2nd true leaves. (B) Black spot disease severity of both kimchi cabbage cultivars pretreated with SA. (C) Xcc bacterial growth in both kimchi cabbage cultivars pretreated with SA. dpi, days post-inoculation. Data points are the mean ± standard errors of four independent experiments. The means with different letter were significant at the 5% level as determined by Duncan’s multiple range test.

Fig. 2

Altered disease resistance of kimchi cabbage seedlings to fungal and bacterial infections in susceptible (cv. Buram-3-ho) and resistant (cv. CR-Hagwang) plants pretreated with 0.1 mM of methyl jasmonate (MJ). (A) Lesion numbers on the inoculated leaves of both kimchi cabbage cultivars pretreated with methyl jasmonate (MJ) were counted after C. higginsianum inoculation. 1st, 1st true leaves; 2nd, 2nd true leaves. (B) Black spot disease severity of both kimchi cabbage cultivars pretreated with MJ. (C) Xcc bacterial growth in both kimchi cabbage cultivars pretreated with MJ. dpi, days post-inoculation. Data points are the mean ± standard errors of four independent experiments. The means with different letter were significant at the 5% level as determined by Duncan’s multiple range test.

Fig. 3

Altered disease resistance of kimchi cabbage seedlings to fungal and bacterial infections in susceptible (cv. Buram-3-ho) and resistant (cv. CR-Hagwang) plants pretreated with 0.1 mM of 1-aminocyclopropane-1-carboxylic acid (ACC). (A) Anthracnose disease severity of the inoculated seedlings pretreated with ACC was evaluated. (B) Black spot disease severity of both kimchi cabbage cultivars pretreated with ACC. (C) Xcc bacterial growth in both kimchi cabbage cultivars pretreated with ACC. dpi, days post-inoculation. Data points are the mean ± standard errors of four independent experiments. The means with different letter were significant at the 5% level as determined by Duncan’s multiple range test.