Ascorbic acid content and enzyme activities during maturation of the mango fruit and their association with bacterial black spot.
Lelyveld L. J. Van
Author Affiliation: Citrus and Subtrop. Fruit Res. Inst., Nelspruit, South Africa.
Agroplantae 7 : 51-54
Abstract : Mango cvs. Sensation, Zill, Kent and Haden were examined and compared for intensity of hypersensitive reaction to [Erwinia mangiferae] infection. Ascorbic acid decreased with maturation in all cvs. but was consistently higher in sensation. The critical min. conc. of ascorbic acid required to prevent lesion formation is probably between 40 and 50 mg/ 100 g fruit tissue. Ascorbic acid oxidase and polyphenol oxidase activities for Sensation were lower during Oct. and Nov. (active fruit growing and susceptible period) than for Zill, Kent and Haden. The destruction of ascorbic acid by these enzymes is discussed. It is concluded that the more intense hypersensitive lesion formation in Haden and Kent may be due to the low ascorbic acid content, possibly associated with higher polyphenol oxidase activity. Peroxidase activity has no apparent connection with the intensity of lesion formation, although all cvs. showed no increase with maturation.ADDITIONAL ABSTRACT:Ascorbic acid oxidase and polyphenol oxidase activities in Sensation, which is normally resistant to Erwinia mangiferae, were reduced during active fruit growth, which was also the period of maximum susceptibility. In Haden and Kent intense hypersensitivity appeared to be caused by a low ascorbic acid content which in turn could be due to higher polyphenol oxidase activity.