Codification and description of the phenological growth stages of red-fleshed pitaya (Hylocereus polyrhizus) using the extended BBCH scale- with special reference to spines, areole, and flesh color development under field conditions

Abstract

Pitaya (Hylocereus spp.) has become a global fruit crop, particularly in Southeast Asia, with two main species cultivated over recent decades; the white-fleshed pitaya (H. undatus) and the red-fleshed pitaya (H. polyrhizus). Although the morphological description of the phenological stages of white-fleshed pitaya (H. undatus) has been recorded using a three-digit numerical system as per the Biologische Bundesanstalt, Bundessortenamt und Chemische Industrie (BBCH) scale rule; however, the description of spine development, an important characteristic of bud burst under the areole is lacking. Additionally, the description scale for flesh color change caused by the accumulation of the betalain pigment, which is important for its nutrition value in red-fleshed pitaya, is lacking. This study investigated the phenological stages of a red-fleshed pitaya, an allied species with remarkable similarity to white-fleshed pitaya, “Da Hong” (also called “Big Red”), using the BBCH scale to provide uniform phenology-related information and develop a more suitable scale for the scientific studies and crop practices of red-fleshed pitaya. Furthermore, at each stage, the development of the spine and flesh color to address fruit developmental characteristics owing to its red flesh was simultaneously assessed and recorded. The flesh started to grow at the first stage of fruit development (code 711). The flesh color changed at the final phase of fruit development (code 719) and at the first phase of fruit peel maturity (code 811). The peel color in the flesh and mesocarp changed completely in the final phase (code 819), indicating the completion of fruit maturity. This important phenological stage scale may be used in growth, development, and physiology studies, and in orchard management, including field practice, nutrition management, and pest and disease control.