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Natalie Anderson and David H. Byrne

Poor germination in Rosa spp. has hindered breeding programs for years. Several methods exist to increase germination of rose seed. Unfortunately no consensus exists on the best method, or if any one method is best for all rose types. Rose seeds from a R. wichuraiana × Old Blush hybrid were broken into 3 replications with an average of 400 seeds per replication. Seeds were leached at room temperature with tap water for a period of 0, 3, 7, or 14 days. Constant filtration and aeration were supplied. After leaching, seeds were placed on either moist milled sphagnum moss or agar. Seeds were then placed in a cold stratification (≈2.8 °C) treatment for 8 to 12 weeks. Individual seedlings were planted when a root was visible. The combination of no leaching plus the moist milled sphagnum moss treatment significantly increased germination over leaching for 3 or more days and agar.

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David H. Byrne and Unaroj Boonprakob

The Thai Tiger series of low-chill peaches are being released for use in subtropical or tropical highland regions and particularly for use in the northern highlands of Thailand to expand the harvest season of the present low-chill variety grown, ‘EarliGrande’. The Thai Tiger series are yellow-fleshed acid-sweet peach varieties that produce excellent yields of firm peaches and will allow a continuous harvest from early April until early May in the northern highlands of Thailand.

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Yan Ma, David H. Byrne, Jing Chen and Amanda Byrne

Several rose species (Rosa rugosa, R. wichuraiana, R. setigera, R. laevigata, R. banksiae, R. roxburghii, R. odorata and hybrids) were employed to establish the appropriate nutrient media for shoot multiplication and root initiation of cultured shoots and to describe a procedure for the successful transfer to soil of plants obtained in vitro. Cultured shoot tips and lateral buds from different genotypes proliferated multiple shoots on a basal medium (MS salt, vitamins, glycine, sucrose and agar) supplemented with 0mg/l to 6mg/l 6-benzylamino purine (BA) and 0mg/l to 0.5 mg/l naphthalene acetic acid (NAA). Most rose species cultured in a modified MS medium supplemented with 2mg/l BA showed good growth and shoot proliferation. The buds nearest the apex exhibited the slowest rate of bud development. Root development was enhanced and shoot development inhibited by lowering the concentration of MS salts to quarter- and half-strength. With difficult-to-root species, rooting was improved by supplementing the media with auxin or giving them 3-7days of dark treatment.

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Young-ju Kim and David H. Byrne

The hybrid origin of 23 rose (Rosa spp.) accessions was examined with three isozymes: acid phosphatase (E.C.3.1.3.2), malate dehydrogenase (E.C.1.1.1.37), and phosphoglucose isomerase (E.C.5.3.1.9). All three isozymes were useful for interspecific hybrid verification. This procedure was effective if the putative parents were known and differed in isozyme phenotype. To verify the origin of hybrid species or cultivars with hybrid origins, isozymes were useful but limited by the number of generations since the original hybridization and the number of accessions of the putative parental species assayed.

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Jonathan W. Sinclair and David H. Byrne

Carbohydrate source of peach [Prunus persica (L.) Batsch] embryo culture media affects embryo growth and survival. The first objective of this study was to determine the effect of five carbohydrates (fructose, glucose, maltose, sorbitol, and sucrose) in Woody Plant Medium (WPM) on the germination and survival of peach embryos in vitro. Fructose, glucose, maltose, and sucrose in WPM resulted in better embryo germination and survival than sorbitol. Fructose (2% and 3%) produced greater survival than all other carbohydrates tested in smaller embryos (<10% ovule dry weight). However, sucrose was better than all other carbohydrates tested in the larger embryos (≥10% ovule dry weight). In addition, large embryos (>10% ovule dry weight) on fructose at 1% combined with glucose, maltose, sorbitol, or sucrose at 1% had equivalent or higher survival than did those on either 1% or 2% sucrose in conjunction with the same carbohydrates. Embryo survival on different carbohydrates varied with genotype. The second objective of this study was to determine the effect of three levels of MES buffer (0.0 mm, 4.5 mm, and 9.0 mm) on medium pH stability and embryo survival. MES buffer at 0.0 mm and 4.5 mm concentration produced significantly better embryo survival than 9.0 mm. The pH stability was better at MES 9.0 mm, however survival decreased significantly. Chemical name used: [2-(N-morpholino)-ethane sulphonic acid] (MES)

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David H. Byrne and Terry A. Bacon

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David H. Byrne and Terry A. Bacon

`TexPrince' is being released by Texas A&M University to provide a medium chilling, commercially acceptable peach that ripens after `Texstar' and with or a few days after `Juneprince' and `TexRoyal'. This large, freestone, attractive, yellow-flesh peach ripens early June in the medium chill zones of the United States. `TexPrince' is a replacement for `Juneprince' where `Juneprince' fruit inconsistently due to problems with insufficient chilling.

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David H. Byrne and Terry A. Bacon