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Dennis J. Werner and Layne K. Snelling

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Dennis J. Werner and Michael A. Creller

Inheritance of the sweet kernel trait was studied in F1 and F2 families generated by crossing `Summer Beaut' nectarine (sweet kernel) with `Ellerbe' and `Biscoe' peach. F1 plants showed bitter kernel. Segregation in the F2 fit a 3 bitter : 1 sweet phenotypic ratio, suggesting that sweet kernel is controlled by a single recessive gene, for which the symbol sk is proposed. Sweet kernel (sk) was linked to nectarine (g) at a map distance of 12 cM. Seed bitterness phenotype is controlled by the genotype of the maternal tree and not the genotype of the individual embryo. Inheritance of male sterility derived from plant introduction (PI) 240928 and allelism of male sterile genes found in `Chinese Cling' and `White Glory' were investigated. Analysis of F1, F1 open-pollinated, and BC1 families derived from crossing PI 240928 with six different wild-type cultivars showed that male sterility in PI 240928 is controlled by cytoplasmic factors. Allelism studies showed that the male-sterile gene found in `White Glory' is not allelic to ps found in `Chinese Cling', and hence is designated ps2.

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Bruce D. Mowrey and Dennis J. Werner

To determine the earliest developmental stage at which isozyme screening could be accomplished, 10 isozyme systems were examined in peach [Prunus persica (L.) Batsch] for differential expression during development. Differences in isozyme expression based on stage of development were detected in nine systems. The earliest stage for complete screening of most isozymes examined is in l-month-old seedlings. The significance of these results relative to genetic mapping is discussed.

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Dennis J. Werner and Dana F. Moxley

The relationship between malate dehydrogenase (MDH) isozyme genotype and plant vigor in peach [Prunus persica (L.) Batsch] was examined in two F2 populations (selfed `Belle of Georgia' and `Cresthaven') segregating at the Mdh1 locus. Total progeny examined were 1610 and 998 in the `Belle of Georgia' and `Cresthaven' populations, respectively. In both populations, plant vigor (as defined by total height and trunk caliper after 1 year of growth) was significantly less in Mdh1-1/Mdh1-1 homozygotes. Homozygous Mdh1-2/Mdh1-2 individuals showed the greatest vigor, and were significantly different in vigor from Mdh1-1/Mdh1-1 homozygotes in both populations and from Mdh1-1/Mdh1-2 heterozygotes in the `Belle of Georgia' population. A significant deviation from the expected 1 Mdh1-1/Mdh1-1: 2 Mdh1-1/Mdh1-1: 1 Mdh1-2/Mdh1-2 ratio was observed in the `Belle of Georgia' population, suggesting moderate lethality of homozygous Mdh1-1/Mdh1-1 genotypes.

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Dennis J. Werner and Dana F. Moxley

The relationship between malate dehydrogenase (MDH) genotype and plant vigor in peach [Prunus persica (L.) Batsch] was examined in two F2 populations (selfed `Belle of Georgia' and `Cresthaven') segregating at the Mdhl locus. Total numbers of progeny examined were 1610 and 998 in the `Belle of Georgia' and `Cresthaven' populations, respectively. In both populations, plant vigor (as defined by total height and trunk caliper after 1 year of growth) was significantly less in homozygous F/F (Mdh1-1/Mdh1-1) individuals. Homozygous S/S (Mdh1-2/Mdh1-2) individuals showed the greatest vigor, and were significantly different in vigor from homozygous F/F (Mdh1-1/Mdh1-1) individuals in both populations and from heterozygous F/S (Mdh1-1/Mdh1-2) individuals in the `Belle of Georgia' population. A significant deviation from the expected 1 F/F:2 F/S:1 S/S ratio was observed in the `Belle of Georgia' population, suggesting moderate lethality of homozygous F/F genotypes.

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Dennis J. Werner and Michael A. Creller

Inheritance of male sterility in peach [Prunus persica (L.) Batsch] Plant Introduction (PI) 240928 was investigated. Crosses of PI 240928 with five wild-type clones yielded all male-sterile offspring, indicating dominant gene action. Inheritance of the sweet kernel trait in peach was studied in F1 and F2 progeny of `Summer Beaut' nectarine (sweet kernel) × `Biscoe' peach (bitter kernel). All four F1 progeny were bitter. Segregation in an F2 of 80 progeny fit a ratio of 3 bitter: 1 sweet. We propose that the gene controlling the sweet kernel trait be designated sk. Sweet kernel (sk) was linked to nectarine (g) at a map distance of 17 cM. Evaluation of the peach PI collection showed that PI 129678 (`Stanwick' nectarine) and PI 34685 (`Quetta' nectarine) were the only clones with a sweet kernel. Crosses between `Davie II' and `Honeyglo' nectarine (dwdw) confirmed that the gene conferring the dwarf phenotype in progeny of `Davie II' is non-allelic to dw.

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Lyn A. Gettys and Dennis J. Werner

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Jessica G. Barb, Dennis J. Werner, and Robert J. Griesbach

Stokes aster [Stokesia laevis (J. Hill) Greene] is a herbaceous perennial endemic to the coastal plains of the southeastern United States. Anthocyanin and copigment aglycones from flowers were characterized using high-performance liquid chromatography. Blue, lavender, violet, and albescent flowers each contained the anthocyanidin petunidin, although albescent flowers contained a substantially smaller amount. Pale pink flowers were found to contain only cyanidin. Anthocyanins and carotenoids were not present in pale yellow flowers of this species. All flowers contained the flavone luteolin. Genetic analysis of F1, F2, and BC1 populations suggested that flower color in stokes aster is controlled by at least three loci. F2 populations of blue × albescent and blue × pale yellow flowering plants segregated in a 3:1 ratio of blue to albescent or pale yellow flowered progeny, indicating that albescent and pale yellow flower colors were recessive and each controlled by a single locus with two alleles. BC1 populations supported these results. We propose the symbols A and Y: AA and YY plants synthesize a normal amount of anthocyanins, aa plants synthesize a reduced amount of anthocyanins, and yy plants do not synthesize anthocyanins. When the two mutant phenotypes (i.e., albescent [aa] and pale yellow [yy]) were crossed, the F1s were blue, and the F2 segregated in a 9 blue:3 albescent:4 yellow ratio, indicating that the recessive locus (y), when homozygous, was epistatic to other loci involved in anthocyanin production (e.g., A), and that the genotypes of the parents used in these crosses were aaYY (albescent) and AAyy (pale yellow). F1, F2, and BC1 populations of blue (petunidin) × pale pink (cyanidin) flowering plants revealed that cyanidin production was recessive and controlled by a single locus, P, with two alleles, whereby PP plants synthesize petunidin and pp plants synthesize cyanidin. It was difficult to distinguish albescent- and pale pink-flowered progeny in segregating generations, therefore three genetic models were proposed and tested to determine the genotype(s) (i.e., AApp, Aapp, or aapp) of the pale pink-flowered plants. Based on these analyses, we propose a theoretical biochemical pathway for flavonoid biosynthesis in stokes aster.

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Richard T. Olsen, Thomas G. Ranney, and Dennis J. Werner

Inheritance of two mutant foliage types, variegated and purple, was investigated for diploid, triploid, and tetraploid tutsan (Hypericum androsaemum). The fertility of progeny was evaluated by pollen viability tests and reciprocal crosses with diploids, triploids, and tetraploids and germinative capacity of seeds from successful crosses. Segregation ratios were determined for diploid crosses in reciprocal di-hybrid F1, F2, BCP1, and BCP2 families and selfed F2s with the parental phenotypes. F2 tetraploids were derived from induced autotetraploid F1s. Triploid segregation ratios were determined for crosses between tetraploid F2s and diploid F1s. Diploid di-hybrid crosses fit the expected 9: 3: 3: 1 ratio for a single, simple recessive gene for both traits, with no evidence of linkage. A novel phenotype representing a combination of parental phenotypes was recovered. Data from backcrosses and selfing support the recessive model. Both traits behaved as expected at the triploid level; however, at the tetraploid level the number of variegated progeny increased, with segregation ratios falling between random chromosome and random chromatid assortment models. We propose the gene symbol var (variegated) and pl (purple leaf) for the variegated and purple genes, respectively. Triploid pollen stained moderately well (41%), but pollen germination was low (6%). Triploid plants were highly infertile, demonstrating extremely low male fertility and no measurable female fertility (no viable seed production). The present research demonstrates the feasibility of breeding simultaneously for ornamental traits and non-invasiveness.

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Dennis J. Werner, Michael A. Creller, and José X. Chaparro

Inheritance of the blood-flesh (red-violet mesocarp) trait in peach [Prunus persica (L.) Batsch.] was investigated in S1, S2, F1, F2, F3, BC1P1, and BC1P2 families derived from `Harrow Blood', a clone showing anthocyanin accumulation in fruit about 45-50 days after anthesis. This trait invariably was associated with the red midrib leaf phenotype in `Harrow Blood', an S1 family from `Harrow Blood', and in green leaf F2 progeny derived from `Harrow Blood' × `Rutgers Red Leaf 2n'. A segregation ratio of about 3 blood-flesh : 1 wild-type was observed in the S1 family, but F1 progeny produced only wild-type fruit. Examination of F2 progeny segregating for the blood-flesh and red leaf traits revealed no evidence of epistasis. Based on segregation ratios in F1, F2, F3, BC1P1, and BC1P2 families from this cross, the F1 family from `Contender × (`Harrow Blood' × `Rutgers Red Leaf 2n'), and six additional F1 families from crosses between `Harrow Blood' and green leaf clones with wild-type fruit, we propose that blood-flesh is controlled by one gene, designated bf (blood-flesh). The blood-flesh phenotype was associated with reduced tree height in S1 and F2 progeny derived from `Harrow Blood'. Segregation for leaf blade color deviated significantly (P = 0.05) from the expected 3 red : 1 green ratio in six of the F2 families derived from selfing seven F1 trees from `Harrow Blood' × `Rutgers Red Leaf 2n'.