β– amino butyric acid mediated changes in cellular redox homeostasis confers tomato resistance to early blight

Abstract

Foliar application of β-aminobutyric acid (BABA) restricted the colonization of Alternaria solani in tomato leaves. The activities of antioxidative enzymes were studied in defence response to oxidative stress generated upon A. solani infection. At 1 dpi (days post inoculation) and 2 dpi, these defence responses are found to be prominent in BABA- primed plants as compared to untreated plants after A. solani infection. Elevated antioxidant enzyme capacity in BABA- primed plants was coupled with less lipid peroxidation. Generation of superoxide radical (O2._) and hydrogen peroxide (H2O2) was efficiently modulated in BABA- primed plants in response to pathogen inoculation suggesting there role in restricting fungal growth whereas, in BABA untreated plants increased accumulation of H2O2 at late stage of infection (36 and 48 h post inoculation) resulted in failed defence response. A positive correlation was observed in levels O2._, H2O2, and SOD activity. In addition, the activity of phenylalanine ammonia-lyase (PAL) and deposition of callose was studied as a biochemical marker of induced resistance and marker for PAMP-triggered immunity respectively. BABA- primed plants showed an elevated PAL activity over untreated infected plants at all studied time points (1, 2, 3, 5 dpi). Contradictory to previous studies, we found that in BABA- primed plants level of callose deposition is not as much of untreated plants upon A. solani infection. Overall the results indicate that BABA priming triggers changes in oxidative status suitable for the expression of resistance against A. solani.