Soma térmica na brotação e qualidade de tubérculos de batata

Abstract

Tuber quality and sprouting are affected by the environmental conditions that the potato plants are subjected to during their developmental cycle. Despite the different environmental conditions between seasons and places, the thermal sum has been used to simulate plant developmental stages. In the case of potato, plant development also affects tuber maturity and post harvest behavior during storage. The objectives of this work were to evaluate the effect of accumulated thermal sum at different developmental phases of potato clones on sprouting and processing quality of tubers, for spring and autumn growing conditions, on central region of Rio Grande do Sul (state of Brazil), in different locations, storage temperature and size os tuber. We evaluated the emergency (EM), the tuber initiation (IT) and the onset of senescence (IS) of four potato clones (SMIJ461-1, SMINIA793101-3, SMINIA97145-2 and Macaca) produced in Santa Maria and Júlio de Castilhos during the spring and autumn seasons. We calculated the accumulated thermal sum (STa) for each phase. The tubers were stored at 10 and 20°C and evaluated for sprouting and processing quality at 0, 30, 60 and 90 days after the curing period. The percentage of sprouted tubers and the number of sprouts per tuber were assessed to evaluate dormancy and apical dominance of different sized tubers. The processing quality was assessed as the content of reducing sugars, dry matter, and starch and the percentage of fresh weight loses. The environmental conditions of spring and Júlio de Castilhos resulted in greater accumulation of STa, higher percentage of sprouted tubers, number of sprouts per tuber, percentage of fresh weight loses, dry mass and starch contents and lower content of reducing sugars than tubers produced in other environmental conditions. Despite the different environmental conditions of seasons and places that affected tuber maturity and physiological age, the accumulated thermal sum of the phases EM-IS or IT-IS can be used as indicative of sprouting and the starch and reducing sugars content. However, the physiological age and maturity at tuber harvesting is also correlated with tuber size, since tubers with diameter smaller than 35mm showed higher dormancy and apical dominance period, when compared to those with diameter larger than 35mm.