Gibberellic Acid, Rootstocks, and Post-freeze Fruit Quality of ‘Rohde Red’ Valencia Oranges

Abstract

<jats:p>The authors’ objectives were to determine whether gibberellic acid (GA<jats:sub>3</jats:sub>) initially increases juice content of ‘Rohde Red’ valencia oranges and prevents or delays decreases in juice content after a freeze, and to determine whether there is an interaction between GA<jats:sub>3</jats:sub>, rootstock, and juice content. The experiment consisted of a 2 (+, –GA<jats:sub>3</jats:sub>) × 3 (rootstock) factorial using a completely randomized design with 10 replications per treatment. Gibberellic acid was applied to mature ‘Rohde Red’ valencia [<jats:italic>Citrus sinensis</jats:italic> (L.) Osb.] orange trees on three rootstocks—<jats:italic>Citrus volkameriana</jats:italic> Ten. &amp; Pasq.(Volk), Swingle citumelo [<jats:italic>C. paradisi</jats:italic> Macf. ×<jats:italic>Poncirus trifoliata</jats:italic> (L.) Raf.], and Carrizo citrange [<jats:italic>C. sinensis</jats:italic> ×<jats:italic>P. trifoliata</jats:italic>]—at color break in Fall 2002, 2003, and 2004. Juice content, soluble solids content (SSC), titratable acidity (TA), ratio of SSC to TA, and kilogram solids per box were determined at about 2-week intervals after several freezes. In 2002–03 and 2004–05, juice content in the fall was greater and the rate of decrease in juice content lower for GA<jats:sub>3</jats:sub>-treated fruit than nontreated fruit for about 8 weeks after a freeze. In contrast, in 2003–04, juice content and rate of decrease in juice content were not different between treatments. Juice content was lower for fruit from ‘Rohde Red’ trees on Volk compared with those on Carrizo and Swingle, and more important, the rate of decrease in juice content after a freeze was greatest for trees on Volk in all three seasons. Soluble solids content, TA, SSC-to-TA ratio, and kilogram solids generally were not effected by GA<jats:sub>3</jats:sub> treatment. Therefore, GA<jats:sub>3</jats:sub> application at color break in the fall generally increased juice content and slowed the rate of decrease in juice content after a freeze compared with nontreated fruit. In addition, juice content differed significantly with rootstock, but there was no GA<jats:sub>3</jats:sub> × rootstock interaction.</jats:p>

Effect of Different Inorganic, Organic and Bio-Fertilizers on Plant Growth of Sweet Orange (Citrus sinensis Osbeck.)

“…The Sweet orange (Citrus sinensis Osbeck) is the members of family Rutaceae sub-family Aurantoideae (Davies and Zalman, 2006) and a single genus contains the most important species, sweet orange, mandarin, lemon, lime, citrus, grape fruit and the shaddock. All these are excellent source of vitamin ‛C' and fruit acids and are appreciated all over the world for their -fruity‖ fruit taste and refreshing qualities (Helail et al, 2012).…”