Effect of Candidatus <i>Phytoplasma pyri</i> infection on fruit quality, total phenolic content and antioxidant capacity of ‘Deveci’ pear, <I<Pyrus communis</i> L.

Abstract

Pear decline is an important threat for Turkish pear production. In this study, we attempt to compare several pomological characteristics, total phenolic content and total antioxidant capacities in Candidatus Phytoplasma pyri infected and noninfected ‘Deveci’ pear from Bursa, Turkey. Based on pear decline symptoms, the fruit samples were taken in October 2008 on harvest maturity from four infected and non-infected trees. Presence of Candidatus P. pyri was later confirmed by nested PCR tests. The result indicated that infection significantly reduced fruit size, width, length; and increased pH, color values of a, b and hue. Abortive and healthy seed numbers and weights, soluble solids and acidity did not change significantly. Similarly, the infection did not affect the flesh color. To investigate a possible differential response on skin and flesh of fruits, total phenolic (TP) and total antioxidant capacity (TAC) analyses were conducted on skin and flesh tissues separately. The results indicated that, infected skin tissue had higher total phenolic and total antioxidant capacity for both methods analyzed (TEAC and FRAP). TP content of skin increased from 806 to 923 μg gallic acid equivalents (GAE)/g fresh weight (fw) while TP content of flesh increased from 195 to 249 μg GAE/g fw. TAC also found to be enhanced on infected fruits. On average, non-infected trees had 32.4 and 28.3 μmol TE/g fw for TEAC and FRAP, respectively. Infection increased these averages to 35.4 and 32.3 μmol TE/g fw tabulating 18 and 12% increase in flesh tissue. Similarly, the TEAC and FRAP averages increased from 4.0 to 5.8 and 3.3 to 4.9 μmol TE/g fw, respectively.

Keywords: Abiotic stress, FRAP, pear decline, phytoplasma, TEAC