Effect of β-aminobutyric acid on resistance of tomato against Pectobacterium carotovorum subsp. carotovorum

Abstract

Stem rot of tomato caused by Pectobacterium carotovorum subsp. carotovorum (Pcc) results in economic yield loss worldwide. Previous studies have demonstrated the role of β-aminobutyric acid (BABA) in control of numerous plant diseases. To extend our understanding for the efficacy of BABA as an inducer agent against plant diseases, we evaluated the effect of BABA on disease severity of stem rot during infection of tomato by Pcc. BABA at concentration of 200 µM reduced the disease severity and offered protection against Pcc. On the other hand, BABA did not have direct antibacterial effect in vitro. Furthermore, we examined the effects of BABA on expression of pathogenesis-related gene 1 (PR-1), pathogenesis-related gene 2 (PR-2), phenylalanine ammonia-lyase (PAL) and catalase (CAT). Pretreatment with BABA led to more expression of PR-1 and PR-2 after Pcc infection when compared with their counterparts pretreated with water (control). PR-1 expression in BABA/Pcc treatment increased 2.83-, 4.31-, 2.46- and 1.88-fold at 24, 48, 72 and 96 h postpathogen inoculation (hpi), respectively, compared to water/Pcc treatment. Moreover, PR-2 expression in BABA/Pcc treatment increased 2.66-, 3.43-, 2.19- and 1.91-fold at 24, 48, 72 and 96 hpi, respectively, compared to water/Pcc treatment. On the other hand, PAL expression was transient during enhanced resistance by BABA. In comparison with water/Pcc treatment, PAL expression enhanced 2.42-fold at 24 hpi in BABA/Pcc treatment, whereas PAL expression was remained unchanged at 48, 72 and 96 hpi. CAT expression increased in early stages of the resistance induced by BABA. In BABA/Pcc treatment, CAT expression enhanced 4.6- and 3.1-fold at 24 and 48 hpi, respectively, compared to water/Pcc treatment. Our data confirmed the role of BABA as an effective resistance inducer against Pcc that might be considered in integrated diseases management programs.