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  • Author or Editor: Dennis Werner x
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Catalase isozymes were examined in a wide range of peach [Prunus persica (L.) Batsch] cultivars representing historical U.S. cultivars, commercial cultivars from numerous North American breeding programs, and the peach plant introduction (PI) collection. All historical peach cultivars from the United States and those released from commercial breeding programs were fixed for the slow (Cat l-2) allele, with the exception of `Belle of Georgia', `Honeyglo' nectarine, and various cultivars from the Univ. of Florida breeding program, which possessed a fast-migrating (Cat 1-l) allele in homozygous or heterozygous state. Polymorphism was revealed in the 51 peach PI clones examined, with allelic frequencies of 0.69 and 0.31 for the Cat l-2 and Cat l-1 alleles, respectively. Most PIs that originated directly from China were homozygous Cat l-l/Cat l-l, while most PI clones introduced from Europe were homozygous Cat l-2/Cat l-2. Examination of the catalase genotype of cultivars previously proposed as the possible male parent of `Belle of Georgia' (`Champion', `Early Crawford', `Late Crawford', `Oldmixion Free', and `Stump-the-World') revealed that none of these cultivars could have been the male parent of `Belle of Georgia'. Segregation data from various peach crosses was consistent with the hypothesis that catalase polymorphism could be explained by the presence of two alleles at a single locus.

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Genetic interaction of the pillar (PI) and weeping (WE) growth habit genotypes was investigated in peach [Prunus persica (L.) Batsch]. Data from F2, BC1P1, and BC1P2 families showed that PI (brbr) was epistatic to the expression of WE (plpl). A unique growth habit not previously described in peach, and referred to as arching (AR), was recovered in the F2 family. Arching trees showed an upright phenotype similar to Brbr heterozygotes, but had a distinct curvature in the developing shoots. Progeny testing of AR trees revealed their genotype is Brbrplpl.

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Stokes aster is a herbaceous perennial native to the southeastern United States. Stokesia is a monotypic genus belonging to the tribe Vernonieae Cass. (family Asteraceae Dumont). The level of genetic diversity within the genus is unknown. The goal of this study was to determine the level of genetic diversity and relatedness among cultivars of stokes aster. The genetic relatedness among 10 cultivars of stokes aster, one accession of Vernonia crinita Raf. (syn. V. arkansana DC.), and one accession of Rudbeckia fulgida Ait. var. sullivantii (Beadle et Boynton) Cronq. `Goldsturm' was estimated using 74 randomly amplified polymorphic DNA (RAPD) primers. Similarity indices suggest that cultivars of stokes aster are very closely related, with values for all pairwise comparisons of cultivars of stokes aster ranging from 0.92 to 0.68. One cultivar, `Omega Skyrocket', had markedly lower similarity indices from the other cultivars, ranging from 0.72 to 0.68. Similarity indices between stokes aster and Vernonia and between stokes aster and Rudbeckia were 0.44 and 0.50, respectively.

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Segregation analysis of two different F2 families of stokes aster created by hybridizing two blue-flowered cultivars [`Peaches Pick' (PE) and `Omega Skyrocket' (OSR)] with the yellow-flowered cultivar `Mary Gregory' (MG) gave disparate results. The F2 progeny of PE × MG segregated in the expected 3:1 (blue:yellow) ratio. In contrast, all 782 progeny from the MG × OSR F2 family were blue-flowered. Flow cytometric analysis of the parents and F1 hybrids was conducted to determine if ploidy differences existed among the parents, as such differences could account for aberrant segregation behavior in the MG × OSR F2 family. Peak ratios suggested that MG and PE were diploid, OSR was tetraploid, and F1 hybrids of MG × OSR were triploid. Chromosome counts from root tip squashes confirmed that MG and PE were diploid (2n= 2x= 14), OSR was tetraploid (2n= 4x= 28), and F1 hybrid progeny of MG × OSR were triploid (2n= 3x= 21). Karyotype analysis also confirmed these results. We propose that the lack of recovery of yellow-flowered progeny in the MG × OSR F2 family is due to differences in parental chromosome number. These results document the first report of polyploidy in stokes aster, and suggest the absence of a triploid block in this species.

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Abstract

Flower bud respiration of ‘Redhaven’ peach [Prunus persica (L.) Batsch] remained relatively constant during rest and increased rapidly after rest termination, but stem tissue respiration remained relatively constant. Three seedling rootstocks (Lovell, Nemaguard, Siberian C) had no significant effect on respiration of flower buds. Stem tissue respiration was significantly higher on seedling rootstocks of Siberian C on most dates, as compared to Nemaguard, with Lovell generally intermediate.

Open Access

Abstract

A technique is described for obtaining nondestructive estimates of shoot and root fresh weight using Archimedes’ principle that the buoyancy of an object is equal to its volume times the density of the submersion fluid. Apple and peach seedlings grown in solution and sand cultures for 14 weeks were measured periodically using this technique. Destructive measurements also were taken for comparison. Estimated and actual shoot weights were not significantly different for seedlings grown in a solution culture; however, they were significantly different in sand culture. Coefficient of determination (r 2) values of estimated shoot weight regressed on actual shoot weight were over 0.99 for all groups of seedlings.

Open Access

Abstract

Cytokinin (6-BA) was applied to the dormant shoots of young apple (Malus domestica Borkh.) and peach [Prunus persica (L.) Batsch.] trees after applying all combinations of shoot and root chilling during rest. After greenhouse forcing, bud-break, new shoot dry weight, and new root growth were greatest in apple trees with both shoot and root chilling. In contrast, only shoot chilling was necessary for maximum response in peach. Applied 6-BA substituted for root chilling in apple trees that had only the shoot chilled, resulting in budbreak equal to trees that had both the shoot and root chilled. Applied 6-BA had no significant effect on peach budbreak or new shoot and root growth. Chemical name used: 6-benzyladenine (6-BA).

Open Access

Abstract

In the article “6-BA Applied After Shoot and/or Root Chilling and Its Effect on Growth Resumption in Apple and Peach” by Eric Young and Dennis J. Werner (HortScience 21:280-281, Apr. 1986), “0.5% Silaid” in the 20th line, 3rd column, p. 280 should read “0.5% Silwet (Union Carbide).”

Open Access