LIGHT-INDUCED COLOUR CHANGE IN TWO WINTER-GROWN PEPPER CULTIVARS (CAPSICUM ANNUUM L.)

C.M. Alcock , I. Bertling
Coloured peppers generally fetch much higher market prices than green fruit, particularly in winter, when demand exceeds supply. However, peppers grown in winter take longer to change colour than those produced in summer, and may not change colour at all under winter conditions. This study was conducted to investigate the viability of eliciting preharvest colour change in dark green ‘Sondela’ and pale green ‘Menta’ pepper fruit, grown in winter under plastic, by illuminating fruit at the green mature stage with white LED lamps at 400 μmol m-2 s-1. Ripe fruit of ‘Sondela’ are typically red, while ‘Menta’ fruit are scarlet when ripe and red when overripe. Colour was assessed visually and also expressed in terms of the CIELAB tristimulus model. Illuminated ‘Sondela’ fruit had turned 80% black after seven days of treatment. This black colour gradually faded when fruit started turning brownish from day 24. By day 35, illuminated ‘Sondela’ fruit were red. Control ‘Sondela’ fruit remained dark green until colour break, first observed on day 29, and had reached final ripe colour (red with traces of green) by day 46, 11 days after illuminated fruit. Some illuminated ‘Menta’ fruit immediately showed traces of purple, but this colouration gradually faded as fruit ripened. Illuminated ‘Menta’ fruit had turned from pale green to yellow by day 11, and from day 16 gradually changed from yellow to orange. These fruit were scarlet by day 33 and red by day 40. Control fruit of ‘Menta’ remained pale green until day 27, when they changed from pale green to pale yellow-orange with traces of green. These control fruit were scarlet by day 40, seven days after illuminated fruit, and red by day 48, eight days after illuminated fruit. Accelerating colour change in green pepper fruit by illumination with LEDs could improve profitability by enabling producers to exploit early season prices, particularly with cultivars with pale green unripe fruit, and possibly with peppers that are yellow when ripe, rather than red.
Alcock , C.M. and Bertling, I. 2012. LIGHT-INDUCED COLOUR CHANGE IN TWO WINTER-GROWN PEPPER CULTIVARS (CAPSICUM ANNUUM L.). Acta Hort. (ISHS) 956:275-281
http://www.actahort.org/books/956/956_31.htm
CIELAB tristimulus model, LED, 'Menta', 'Sondela'
English

Acta Horticulturae