William A. Dozier

Cold acclimation induced genes of trifoliate orange (Poncirus trifoliata)

Commercial citrus varieties are sensitive to low temperature. Poncirus trifoliata is a close relative of Citrus species and has been widely used as a cold-hardy rootstock for citrus production in low-temperature environments. mRNA differential display-reverse transcription (DDRT)-PCR and quantitative relative-RT-PCR were used to study gene expression of P. trifoliata under a gradual cold-acclimation temperature regime. Eight up-regulated cDNA fragments were isolated and sequenced. These fragments showed high similarities at the amino acid level to the following genes with known functions: betaine/proline transporter, water channel protein, aldo-keto reductase, early light-induced protein, nitrate transporter, tetratricopeptide-repeat protein, F-box protein, and ribosomal protein L15. These cold-acclimation up-regulated genes in P. trifoliata are also regulated by osmotic and photo-oxidative signals in other plants.

Cultivar Variation in Physicochemical and Antioxidant Activity of Alabama-Grown Blackberries

Abstract Blackberries are an excellent source of natural antioxidants. Fully ripened fruit of ‘Apache’, ‘Arapaho’, ‘Chester’, ‘Loch Ness’, ‘Navaho’ and ‘Triple Crown’ thornless blackberries were evaluated for their physicochemical and antioxidative activity. There were no consistent differences for variation in initial pH, titratable acidity (TA), total soluble sugar (TSS) and TSS/TA ratio values determined. Differences among cultivars with respect to reduced ascorbic acid (AA) were established, but there were no differences in either oxidized ascorbic acid (DHA) or total ascorbic acid (TAA) content. The antioxidant activity as determined by ABTS radical cation procedure for fractionated crude fruit extracts varied in response to parameters evaluated. Hydrophilic antioxidant activity (HAA) was not different among cultivars evaluated. In contrast, differences were found in lipophilic antioxidant activity (LAA) and total antioxidant activity (TAA).

Down-regulated gene expression of cold acclimated Poncirus trifoliata

Citrus sp. are important commercial fruit crops throughout the world that are occasionally devastated by subfreezing temperatures. Poncirus trifoliata (maximum freeze tolerance of -26°C) is a close relative of commercial Citrus sp. (maximum freeze tolerance of -10°C) that has been used in breeding programs to develop more cold-hardy genotypes and as a rootstock to enhance freeze tolerance of the scion. Species with greater freeze tolerance vary in gene expression during cold acclimating temperatures. mRNA differential display (DDRT-PCR) and quantitative relative RT-PCR were used to study down regulation of gene expression in intact P. trifoliata exposed to a gradual cold acclimation regime to enhance our understanding of the mechanism that makes this specie so freeze tolerant. Six down-regulated genes were isolated and sequenced. These down-regulated genes showed high homology to the following known genes: chlorophyll a/b binding protein, photosystem II OEC 23, carbonic anhydrase, tumor related protein, p...

Orchard Design Influences Fruit Quality, Canopy Temperature, and Yield of Satsuma Mandarin (Citrus unshiu ‘Owari’)

Satsuma growers in Alabama have used various orchard designs to minimize freeze damage. These designs include interplanting between pecan and pine trees, and planting behind windbreaks. Interplanting satsuma trees with pine trees resulted in warmer temperatures within the orchard, while the other orchard designs did not moderate orchard temperature during severe freeze events. Satsuma fruit harvested from plots shaded by pine tree canopies had higher soluble solids content and reduced fruit weight. Dense pine tree canopies can provide an insulating effect that reduces freeze damage and yield losses when severe freezes occur, but heavy shading can result in lower yields when damaging freezes do not occur.

Effect of nitrate concentration on hydroponially grown primocane‐fruiting red raspberries

Abstract Primocane‐fruiting red raspberry plants (Rubus idaeus L.) ‘Redwing’ were grown in six hydroponic solutions containing nitrogen (N) levels of 2.5, 5, 10, 15, 20, and 25 meq N per liter. Plant growth rates and final cane heights were similar in all treatments except for reduced growth in the 2.5 meq per liter treatment. Greatest leaf, stem, and root dry weight accumulation was found in the 10 meq per liter treatment. The greatest numbers of nodes, flowers, and inflorescences per cane were found in the 5, 20, and 10 meq per liter treatments, respectively. Solution N levels had no effect on time of flowering.