Location and rootstock affect sheepnosing in grapefruit

Field studies were conducted for 2 years, at three sites in the Lower Rio Grande Valley of Texas, to evaluate the effects of location, rootstock, and irrigation on sheepnosing (elongation of the apex) of `Rio Red' grapefruit (Citrus paradisi Macf.). Based on the ratio of equatorial to polar diameter, grapefruit budded on sour orange (Citrus aurantium L.) rootstock grown at Weslaco had a significantly higher percentage of sheepnosed fruits (63%) than did fruit grown at Mission (57%), while the grove at Bayview produced a negligible percentage of sheepnosed fruit (4%). In a second study, `Rio Red' trees grown on `Carrizo' rootstock [C. sinensis (L.) Osbeck Poncirus trifoliata (L.) Raf.] produced a significantly higher percentage of sheepnosed fruit (59%) than did those on `Swingle' (C. paradisi P. trifoliata) (48%). In a third experiment, trees irrigated by microjet had a significantly higher percentage of sheepnosed fruit (53%) than did those that were flood-irrigated (43%). Although sheepnosed fruit had significantly greater peel thickness and a lower juice content, fruit quality was better than that of normal fruit because of a higher soluble solids: titratable acidity ratio. In 1999, the significant irrigation and rootstock effects were less than that due to growing location. Effects of location, rootstock and irrigation varied between years. The interaction between factors and years was mainly due to a lack of low amount of sheepnosing in 1998.

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