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  • Author or Editor: Dennis J. 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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Scanning electron microscopy (SEM) was used to compare the novel surface morphology of `Marina' peach [plant introduction (PI) 133984] to a normal peach (`Contender') and a nectarine (`Sunglo'). Samples were collected before, during, and after anthesis. Compared to `Contender', `Marina' showed different trichome structure, lower trichome density, and delayed initiation of trichomes on the gynoecium. No pubescence was observed on `Sunglo' nectarine at any sampling date. Trichomes were present on the flower bud scales of all three cultivars. Arrangement and structure of trichomes on flower bud scales of `Marina' differed from those on `Contender' and `Sunglo'.

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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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Eastern redbud (Cercis canadensis L.) is a commonly used small landscape tree. Compact growth, purple leaf color, and weeping architecture are three popular ornamental phenotypes. Inheritances of weeping architecture and purple leaves have been reported previously. Inheritance of compact growth habit and its genetic linkage with the weeping and purple leaf genes have not been reported. In the present research, the inheritance of compact growth derived from ‘Ace of Hearts’ was explored in the F1, F2, and reciprocal backcross families resulting from the controlled hybridization of ‘Ruby Falls’ (normal growth/weeping architecture/purple leaf) × ‘Ace of Hearts’ (compact growth/nonweeping architecture/green leaf). All 27 F1 individuals were nonweeping, green-leaved, and noncompact. A total of 572 F2 progeny were obtained, and subsequent analysis of segregation revealed a single recessive gene controlled compact growth habit. Analysis of reciprocal backcross families confirmed this result as well. Weeping architecture and purple leaf color were also controlled by single recessive genes, confirming findings presented in previous studies in another redbud family. No linkage between the three genes was detected. This research is the first to report the inheritance of compact growth in eastern redbud and confirms independent assortment between the compact, purple leaf, and weeping genes.

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Abstract

Fruit detachment force (FDF) in pepper (Capsicum annuum L.) was measured using mature fruit for the parental, F1, and F2 populations from the cross MSU 160 × MSU 249. Fruit detachment force was controlled by a low number of effective factors (k = 1-2) behaving mainly in an additive manner. Correlation coefficients between fruit detachment force and fruit length, width, and weight calculated from F2 data were positive and significant at the 1% level.

Open Access

Abstract

One-year-old nursery trees of ‘Starkspur Supreme Delicious’ apple (Malus domestica Borkh.) on MM 106, M 7a, and M 9 rootstocks and ‘Redhaven’ peach [Prunus persica (L.) Batsch] on Lovell and Nemaguard seedling rootstocks were subjected to all combinations of nonchilled, partly chilled, and fully chilled rootstocks and scions, followed by forcing in a greenhouse. Budbreak and new shoot growth were increased significantly in apple by increased scion and rootstock chilling with a significant interaction between treatment effects. New root growth was increased significantly by increased rootstock chilling, and decreased by scion chilling. Budbreak and new shoot growth in peach were increased significantly by increased scion chilling and decreased by rootstock chilling, also with a significant treatment interaction. Scions on M 9 apple rootstock had significantly less budbreak and new shoot growth, and M 7a had significantly more root growth over all the chilling treatments. There was no rootstock effect in the peach trees. Possible explanations are discussed for the rootstock chilling effect in apple and the differences in apple and peach responses to chilling treatments.

Open Access

Abstract

Estimates were determined for chill unit (CU) and growing degree hour (GDH) requirements for vegetative bud break in 6 apple (Malus × domestica Brokh.) rootstocks: Antonovka 313, MM 111, MM 106, M.7a, M.26, and M.9. Rooted layers were lifted in the fall, potted, and kept in a cold room at 4°C for various lengths of time. plants then were moved to a greenhouse, and the percentage of bud break was determined for various GDH intervals. Prediction equations were determined for the percentage of bud break vs. chill unit accumulation and growing degree hour accumulation. M7a had the lowest chill unit and growing degree hour requirements for 50% bud break (590 CU and 4278 GDH). MM 106 required the most chilling (1220 CU), and M.26 the highest number of growing degree hours (6138 GDH) for 50% bud break.

Open Access

Abstract

One-year-old nursery trees of ‘Redchief’ apple (Malus × domestica Borkh.) on MM106, M9, and seedling rootstocks and ‘Redhaven’ peach [Prunus persica (L.) Batsch.] on Lovell rootstock were subjected to root and shoot chilling treatments for 1500 and 1200 hr, respectively, followed by forcing in the greenhouse. Budbreak and new shoot and root growth were increased by chilling the apple root and shoot. In contrast, only shoot chilling increased these parameters in peach. When shanks of clonal apple rootstocks were treated as part of the shoot, statistical interaction between shoot and root chilling was eliminated when the shank was treated as part of the root. The root chilling effect was significant for both clonal and seedling apple rootstocks. Rootstock temperature (4° or 16°C) did not affect starch, soluble sugars, or sorbitol levels in scion, shank, or roots of apple and peach. Starch and soluble sugars generally decreased throughout the chilling and forcing phases, while sorbitol increased.

Open Access

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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Abstract

Seed germination and respiration of peach [Prunus persica (L.) Batsch] were evaluated as potential preselection indices for predicting bud chilling requirement. Low chilling lines (Ã650 hours) germinated significantly earlier than high chilling lines, with an average r of 0.91 between cultivar chilling requirement and mean days to 80% germination at 4°C in 2 experiments. Based on germination behavior, differentiation between lines exhibiting small differences in chilling requirement was not feasible but separation into low and high chilling categories was possible. Removal of the testa resulted in earlier germination among all lines, but the order of germination remained consistent. An r of 0.84 was obtained between cultivar chilling requirement and mean days to 80% germination at 4°C using seeds with the testa removed. Respiration rate of seeds from 4 lines varying in bud chilling requirement with intact testa rose gradually during stratification. Seeds with the testa removed exhibited a rapidly increasing respiration rate during stratification. Respiration rate of seeds from low chilling lines exhibited a higher mean respiration rate than seeds from high chilling lines in seeds with the testa removed.

Open Access