Revista Brasileira de Fruticultura (Mar 2010)
Identificação pré-colheita do risco de ocorrência de "bitter pit" em maçãs 'gala' por meio de infiltração com magnésio e análise dos teores de cálcio e nitrogênio nos frutos Preharvest identification of bitter pit risk in 'gala' apples by fruit infiltration with magnesium and analysis of fruit contents of calcium and nitrogen
Abstract
O "bitter pit" é um distúrbio fisiológico pós-colheita em maçãs, ocasionado pela deficiência de Ca e agravado pela presença de elevados níveis de Mg, N e K nos frutos. O objetivo deste trabalho foi avaliar a viabilidade prática da infiltração de maçãs 'Gala' com Mg, visando a avaliar, em pré-colheita, o risco de ocorrência de "bitter pit" durante o armazenamento refrigerado, bem como a identificar os atributos minerais do fruto associados à ocorrência do distúrbio. Em 50 talhões de pomares localizados no município de Fraiburgo-SC, foram coletadas amostras de 25 frutos / talhão, cerca de 20 dias antes do início da colheita comercial, sendo os mesmos infiltrados a vácuo com Mg e avaliados quanto à incidência (%) e severidade (manchas / fruto) de "bitter pit". Nos mesmos talhões, na maturação comercial, foram coletadas amostras de 120 frutos / talhão, sendo que 100 frutos foram armazenados em câmara fria convencional durante quatro meses (0 ± 0,5ºC e 90-95% UR), e 20 frutos foram utilizados para a análise mineral (teores de Ca, Mg, K e N). Cinco dias após a remoção da câmara fria, os frutos foram avaliados quanto à incidência (%) e severidade (manchas / fruto) de "bitter pit". Houve correlação linear altamente significativa (r² = 0,69; pBitter pit is a postharvest physiological disorder in apples, related to Ca deficiency, and aggravated by high levels of Mg, N, and K in the fruits. This work was carried out to assess the practical viability of 'Gala' apples infiltration with Mg, for preharvest identification of bitter pit risk during cold storage, as well as, to identify the mineral attributes associated with the occurrence of the disorder. Fruits were sampled in 50 plots of apple orchards located in Fraiburgo, SC (Southern Brazil). Samples of 25 fruits / plot were harvested about 20 days before commercial harvesting, and then vacuum infiltrated with Mg and assessed for incidence (%) and severity (pits / fruit) of bitter pit. Samples of 120 fruits were harvested in the same plots, at the commercial maturity. One hundred fruits were stored in conventional cold storage for four months (0 ± 0.5ºC and 90-95% RH) and 20 fruits were analyzed for mineral content (Ca, Mg, K, and N). Cold stored fruit were assessed for incidence (%) and severity (pits / fruit) of bitter pit five days after removal from storage. There was a highly significant linear correlation (r² = 0.69; p<0.001) between the incidence of bitter pit assessed in fruits infiltrated with Mg and in fruits left in cold storage. In both, fruits infiltrated with Mg and fruits left in cold storage, there was a decrease in Ca and an increase in N contents with increases of incidence and severity of bitter pit. Results show that preharvest infiltration of 'Gala' apples with Mg is a viable method to identified plots in a commercial orchard with risk to manifest bitter pit during cold storage.
