Effect of dark treatment of the eggplant on fruit skin color and its anthocyanin component

Abstract

Eggplant (Solanum melongena L.) fruit of six Japanese cultivars and eight cultivars/lines from Bangladesh were covered with a dark, cloth, 3-5 or 10-20 days after anthesis, depending on the cultivar and kept covered until harvest. The purpose of the experiment was to study the effect of darkening on the production of anthocyanins in the skin. The composition of the anthocyanin was determined for the 14 cultivars. The fruit color of all Japanese cultivars and 'Shinghnath' is purplish black, whereas those of 'KL purple' and 'Bork' is dark reddish purple; that of 'Uttara' is moderately reddish purple. The fruits of 'SL 28', 'SL 32', and 'SL 50' have a yellowish green stripe on green and partly red purple, whereas that of 'SL 65' is yellowish green and partly red purple. The major anthocyanin in fruit skin of all the cultivars/lines, except 'Wase-Beikokuoomaru', was identified as delphinidin 3-pcoumarylrhamnosylglucoside -5-glucoside(Nasunin); the ratio of this anthocyanin to the total ranged from 69.1 to 87.7% in these cultivars/line. The major anthocyanin of 'Wase-Beikokuoomaru', delphinidin 3-glucosylrhamnoside, made up 79.5% of the total. The fruit color of 'Wase-Beikokuoomaru' changed into dark purplish red in the dark, however, the anthocyanin component was the same as that of control treatment. The fruit color of 'Senryou-2gou', 'Syoyaoonaga', 'Borka' changed into yellowish white and partly moderate reddish purple, and that of 'SL 50' changed into yellowish white and partly pale yellowish pink in the dark but the percentage of major anthocyanin in fruit skin of these four cultivars/line remained unchanged. In the other seven cultivars/lines; 'Kurumenaga', 'Toochi', 'Miyukisennari', 'KL purple', 'SL 28', 'SL 32', and 'SL 65', the epidermal cells failed to produce anthocyanin in the dark.