Responses of 'Shih Huo Chuan' pitaya (Hylocereus polyrhizus (Weber) Britt. & Rose) to different degrees of shading nets

This study was to investigate the effects of three shading nets (25% shading with a white net, 50% shading with a black net, and 75% shading with a black net) on the growth and fruiting of red-fleshed 'Shih Huo Chuan' pitaya (Hylocereus polyrhizus (Weber) Britt. & Rose). All shading nets reduced sunburn occurrence and improved cladodes color by decreasing lightness (L*) and chroma (C*), but increasing hue angle (h°). Shading resulted in more chlorophyll a, chlorophyll b, and total chlorophyll content in cladodes than seen in control. Fruit length significantly increased but there were no effects on fruit width under 50% and 75% black shading nets. Shading treatments reduced total soluble solids content, but did not influence on total titratable acidity and TSS/TA ratio. The highest fresh weight and the lowest fruit splitting percentage were found with a 50% black shading net. In addition, the peel and pulp of fruit turned red and total betacyanins were accumulated one and two days earlier than seen with the control when plants were grown under 50% and 75% black shading nets, respectively.