Abstract:

Using 2 red flesh apple strains‘Hongxin 7’and‘Hongxin 9’as experimental materials，we investigated volatile components，firmness，cell wall-modifying enzyme activities and gene expression related to aroma and firmness. The results showed that during fruit storage，the firmness in‘Hongxin 9’was significantly lower than in‘Hongxin 7’while the ethylene production rate in‘Hongxin 9’was significantly higher than in‘Hongxin 7’. The contents of ester and total aroma as well as the expression of AAT1，AAT2，LOX in‘Hongxin 9’were significantly higher than in‘Hongxin 7’during fruit storage，however，in the later period of storage（90–120 d），the contents of alcohols and aldehydes and the expression of HPL and ADH in‘Hongxin 9’were significantly lower than in‘Hongxin 7’. The cell wall-modifying enzyme activities and related-gene expression of PG，XET，PME，AM，α-L-Af and β-Gal in‘Hongxin 9’were significantly higher than in‘Hongxin 7’during fruit storage. All results indicated that the main reason causing the firmness in‘Hongxin 9’was lower than in‘Hongxin 7’during fruit storage was of a high level in the ethylene production rate and ester content and the up-regulated expression of ester biosynthesis related genes and cell wall related genes. Meanwhile，the change，types，content of aroma compounds can be used as one of the evaluation indicators of fruit quality during storage.

Key words: apple, red flesh, volatile component, firmness, gene expression, enzyme activity