Peroxidase activity in common bean (Phaseolus vulgaris L.) cv. Aporé in the presence of salicylic acid and Thanatephorus cucumeris

Abstract

The common bean is cultivated in all regions of the country, presenting great economic and social importance, and is one of the basic food elements, being one of the main suppliers of proteins, iron and carbohydrates. The objective of this study was to evaluate the induction of pathogenesis related proteins, specifically the peroxidase enzyme, in common bean plants challenged with biotic and abiotic inducers. For this, 1 mL of 10 mM salicylic acid solution was sprinkled on bean primary leaves, and then collected in four times: 0, 24, 48 and 72 hai (hours after inoculation) and stored in a freezer at -20 ºC to carry out the biochemical analyzes. The cultivar presented levels of proteins varying from 0.046 to 0.076 mg/mL in the plants tested with water and inoculated with the fungus, with protein peak at 72 hai. In the plants tested with 10 mM salicylic acid (SA) and subsequently inoculated with the fungus, the values ​​ranged from 0.052 to 0.086 mg/mL, with protein peak 24 hai. The levels of peroxidase activity (POX) ranged from 5.31 to 29.37 UA/mgP in plants inoculated with water and fungus and from 1.17 to 22.83 UA/mgP in plants treated with salicylic acid and fungus. Plants treated with 10 mM SA and then inoculated with the fungus showed POX activity peak 24 hours after inoculation of the pathogen, whereas in plants treated with water the POX activity peak occurred 72 hours after inoculation of the pathogen. The results obtained to date suggest a potential of salicylic acid as an inducer of the defense response of the common bean against the fungus T. cucumeris.