Abstract

CAICEDO O, OBRADITH  and  HIGUERA, BLANCA L. Polyphenol Oxidase Induction in Lulo Fruits (Solanum quitoense) Infected by Colletotrichum acutatum. Acta biol.Colomb. [online]. 2007, vol.12, suppl.1, pp.41-54. ISSN 0120-548X.

Polyphenol oxidase (PFO) activity induction was evaluated in lulo fruits to determine the role of this enzyme in resistance responses towards the pathogen Colletotrichum acutatum which causes anthracnose disease. We studied the experimental conditions to obtain the enzyme, using lulo peel, and found that extraction with phosphates buffer 100 mM pH 7, 1% SDS y 1% PVPP showed higher activities. The adequate parameters for activity measurement was also evaluated and established as cathecol 40 mM, pH 7,0, 23 °C and 30 µL of extract. Then, we performed an in vivo assay using lulo fruits in three maturity stages, green, semimature and mature, which were inoculated with the fungus or with sterile water. Enzymatic induction of this protein was studied at nine postinoculation times, and it was found that the induction was differential according to the time, the maturity stage, and as consequence of pathogen presence. The PFO activity increased in green fruits at 48, 96 y 144 (hours postinoculation (hpi), and in mature lulos for the majority of times studied, with the most significant induction response at this stage. In semimature lulo, the induction was observed only at 72 and 144 hpi. The highest nominal value of activity was found in green fruits. Fruits responded to incision with enzyme activation. The increase in the activity of the enzyme was faster in the fruits with the minor anthracnose symptoms than the ones that were more affected. Therefore, it is possible to postulate a positive relation between PFO induction and tolerance to anthracnose symptoms.

Keywords : Colletotrichum acutatum; polyphenoloxidase; anthracnose; Solanum quitoense.

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