Phenological growth stages of tree tomato (Solanum betaceum Cav.), an emerging fruit crop, according to the basic and extended BBCH scales

Abstract

The tree tomato (Solanum betaceum Cav.) is a small tree native to the Andean region cultivated for its juicy fruits, which are having an increasing demand. Tree tomato is morphologically and phenologically different from other Solanum crops and tools for the phenological description of the developmental stages are needed for the enhancement of this emerging crop. We developed a basic and an extended numerical BBCH (Biologische Bundesanstalt, Bundessortenamnt, Chemische Industrie) scales which allow the precise identification of the phenological stages of tree tomato. Eight principal stages are described for germination, leaf development, formation of side shoots, stem elongation, inflorescence emergence, flowering, development of fruit, and ripening of fruit and seed. The basic (two-digit) scale is sufficiently precise for germination, stem elongation, and ripening of fruit and seed. However, for leaf development, formation of side shoots, inflorescence emergence, flowering, and development of fruit the extended (three-digit) scale is considered necessary for an adequate description. The description of the phenological stages is combined with illustrations for clarification. The tree tomato BBCH scale has been validated by characterizing 24 accessions of different varietal groups for traits of agronomic interest and evaluating the differences observed among accessions at specific BBCH developmental stages. The basic and extended BBCH scales represent a useful tool for the description and identification of phenological scales of tree tomato. These scales will be useful for the enhancement of this emerging fruit crop.