Articles
FOLIAR-APPLIED TRYPTOPHAN INCREASES TOTAL YIELD AND FRUIT SIZE OF NAVEL ORANGE AND CLEMENTINE MANDARIN
Article number
884_99
Pages
729 – 736
Language
English
Abstract
The United States Department of Environmental Protection recently received a petition to revoke all tolerances and cancel all registrations for the pesticide 2,4-dichlorophenoxyacetic acid (2,4-D) (Federal Register 2008). The significant use of 2,4-D in commercial citrus production in California and its potential loss prompted the investigation of the capacity of the naturally-occurring amino acid L-tryptophan (TRP), a precursor of IAA, to increase fruit set and size of citrus.
Leaves, flowers and fruit of the Washington navel orange take up, translocate and convert TRP to IAA. Metabolism of TRP to IAA is independent of microorganisms.
In addition, consistent with a positive effect of L-TRP on fruit set and size, foliar application of DL-TRP (10-7 M) to commercially bearing Frost nucellar navel orange trees when fruit were at maximum peel thickness (July), end of the cell division stage of fruit development, significantly increased the 4-year cumulative total yield and yield of commercially valuable large size fruit (6.9-8.8 cm) (P<0.05) with no negative effect on fruit quality compared to untreated control trees.
Recently, the yield benefit of foliar-applied DL-TRP (10-7 M) at maximum peel thickness was demonstrated with Fina Sodea Clementine mandarin.
The TRP treatment significantly increased the 3-year average and 3-year cumulative total yield per tree (P<0.05) and the 3-year average and 3-year cumulative yield of commercially valuable size fruit (5.1-7.6 cm transverse diameter) (P<0.05) compared to untreated control trees.
The treatment had no negative effect on fruit quality.
DL-tryptophan might be a safe, cost-effective alternative to 2,4-D, and other synthetic auxins, for use in commercial citrus production.
Leaves, flowers and fruit of the Washington navel orange take up, translocate and convert TRP to IAA. Metabolism of TRP to IAA is independent of microorganisms.
In addition, consistent with a positive effect of L-TRP on fruit set and size, foliar application of DL-TRP (10-7 M) to commercially bearing Frost nucellar navel orange trees when fruit were at maximum peel thickness (July), end of the cell division stage of fruit development, significantly increased the 4-year cumulative total yield and yield of commercially valuable large size fruit (6.9-8.8 cm) (P<0.05) with no negative effect on fruit quality compared to untreated control trees.
Recently, the yield benefit of foliar-applied DL-TRP (10-7 M) at maximum peel thickness was demonstrated with Fina Sodea Clementine mandarin.
The TRP treatment significantly increased the 3-year average and 3-year cumulative total yield per tree (P<0.05) and the 3-year average and 3-year cumulative yield of commercially valuable size fruit (5.1-7.6 cm transverse diameter) (P<0.05) compared to untreated control trees.
The treatment had no negative effect on fruit quality.
DL-tryptophan might be a safe, cost-effective alternative to 2,4-D, and other synthetic auxins, for use in commercial citrus production.
Authors
L.J. Pillitteri, I. Bertling, T. Khuong, C.T. Chao, C.J. Lovatt
Keywords
Citrus sinensis L. (Osbeck) ‘Washington’ navel and ‘Frost’ nucellar, C. reticulate (Blanco) ‘Fina Sodea’ Clementine, 2,4-dichlorophenoxyacetic acid (2,4-D), maximum peel thickness
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