Atividades de enzimas do metabolismo de carboidratos em pessegueiros 'BRS Kampai' autoenraizados ou enxertados

Abstract

Peach cultivation in subtropical regions faces critical challenges related to excessive vegetative growth, low winter chilling accumulation, and susceptibility to late frosts. The use of appropriate rootstocks is a fundamental strategy to mitigate these problems, although the physiological mechanisms involved in vigor control and assimilate partitioning still require further investigation. This study aimed to determine the influence of five clonal rootstocks and the own-rooted scion cultivar (without rootstock) on the dynamics of the source–sink relationship and the seasonal partitioning of carbohydrates in ‘BRS Kampai’ peach trees. The central hypothesis tested was that differences in vigor and genetic constitution of the rootstocks modulate vegetative and productive growth through the regulation of carbohydrate metabolism and the source–sink dynamics of the ‘BRS Kampai’ cultivar. Phenological analyses were performed, including shoot growth (SG), shoot growth rate (SGR), number of leaves (NL), and fruit diameter (FD); and physiological analyses through quantification of the enzymatic activity of sorbitol oxidase (SOX) and acid invertase (AI), as well as the concentration of reducing sugars (RS). The results demonstrated that the high-vigor group (own-rooted ‘BRS Kampai’ and the ‘Okinawa’ rootstock) prioritized the allocation of assimilates toward vegetative growth, resulting in smaller fruit size. In contrast, low-vigor rootstocks [‘Cadaman®’ (P. persica × P. davidiana) and ‘Clone 15’ (P. mume)], although facilitating high-density orchard management, exhibited delayed shoot growth that induced direct competition with the initial fruit development phase (cell division). The most efficient physiological balance was observed in medium-vigor rootstocks [‘Tsukuba-2’ and ‘Tsukuba-3’ (P. persica)], which showed the highest enzymatic activity (SOX and AI) in fruits, indicating greater sink strength in economically important organs.It is concluded that medium vigor optimizes carbon partitioning toward fruits, consolidating the activity of both evaluated enzymes as reliable markers of sink strength in peach under subtropical conditions.