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  • Author or Editor: David Bedford x
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`Honeycrisp', a relatively new apple cultivar, is susceptible to bitter pit, a physiological disorder that develops mainly during storage. Although the cause of bitter pit is unknown, calcium (Ca) content of the fruit is known to be involved. A field experiment was conducted in Chanhassen, Minn. to refine recommendations for use of Ca sprays for reduction of bitter pit in `Honeycrisp' apple. Specific objectives were to determine: 1) Ca concentration and content throughout the fruit growing season; and 2) the association of bitter pit incidence with Ca concentration, crop load, vegetative growth and fruit size. Six treatments tested included: control; Ca(NO3)2 sprays all season; Ca(NO3)2 sprays early in the season; Ca(NO3)2 sprays late in the season; hand-thinning combined with Ca(NO3)2 sprays all season and hand-thinning. Ca concentration in fruits was measured bi-weekly using three different sampling methods: segments, cores and plugs. A randomized block design with four trees as experimental unit and five replications was used. Results suggest lower crop loads increase bitter pit incidence. While fruit from the thinned treatments was larger in size by the end of the experiment, no bitter pit was present at harvest. After 4 months of storage, the hand thinning treatment had 7.4% bitter pit, while thinning plus Ca reduced bitter pit to 2.4%. The other treatments had less than 1% bitter pit. Fruit analyses at the end of the growing season indicate that early and full season sprays resulted in the highest Ca concentration in fruit segments and cores. The lowest values were found for the thinning treatment. No association was found between vegetative growth and bitter pit incidence.

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High levels of sphagnum peat in the growing medium promoted growth of asparagus (Asparagus officinalis L. cv. Viking 2K) in a greenhouse study. Application of NH4NO3 > 1 g/pot (84 kg·ha-1 equivalent) was detrimental to root growth. High N rates and high organic matter levels decreased fibrous root development. Shoot dry weight was highly correlated with fleshy root number, root dry weight, and shoot vigor.

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During storage, many apple (Malus ×domestica Borkh.) genotypes lose their desirable textural qualities, but some like `Honeycrisp', maintain their sensory Crispness and Firmness. To understand this differential response of genotypes to postharvest changes in texture, reliable and quantifiable methods of texture measurement are needed. This study integrated data from a snapping test, confocal laser scanning microscopy (CLSM), and sensory panels to study postharvest textural changes and to predict sensory textural attributes of Firmness, Crispness, Mealiness, and Juiciness. Three separate analyses on fresh, stored, and combined fresh and stored fruit data yielded different predictors for the same sensory attributes. Change in Crispness during storage was successfully predicted by change in Work during storage. Cell number and size were related to fresh fruit texture and its maintenance during storage. Unique textural properties of `Honeycrisp' were found to be inherited by its progeny.

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Abstract

Selection criteria to identify primocane-fruiting red raspberry seedlings (Rubus idaeus L.) with high, early yield are desirable in regions with short growing seasons. To identify possible parents contributing these desirable characteristics, ‘Heritage’, ‘Redwing’, and two genotypes from the Minnesota breeding program were subjected to yield component analysis. In all genotypes, yield was determined by canes/meter of row, fruit per node, and fruit weight. Over the 3-year period, ‘Heritage’ had the highest yield/meter of row, yield per cane, fruit per cane, and number of fruit per fruiting node among all genotypes. Component compensation was highest for ‘Redwing’, while MN 652 had the greatest degree of independence among components. In selecting seedlings for early fruiting and high yield, high cane densities and/or large fruit size will be needed.

Open Access

We used microsatellite loci to investigate the parentage of the apple cultivar `Honeycrisp', a patented University of Minnesota introduction. In an attempt to find the correct parents, we also examined other apple varieties associated with the University of Minnesota apple breeding program. Based on written records from the 1960s, the presumed parents of `Honeycrisp' were `Honeygold' and `Macoun'. We were able to exclude both of these as parents, but found that `Keepsake' was consistent as one of the parents. A second potential parent could not be discovered. `Haralson', another commercially important cultivar from the University of Minnesota, is likely from a cross between `Malinda' and `Wealthy'.

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Apple (Malus ×domestica Borkh.) breeding at the University of Minnesota (UMN) has been ongoing continuously since 1908 when staff originally planted thousands of seedlings from open-pollinated (OP) seeds collected from regional orchards. The first cultivar from the program, ‘Minnehaha’, was introduced in 1920 and several others from these OP seeds followed over the next 3 decades. Controlled crosses were initiated in 1916, and until the time of this publication, 28 cultivars have been introduced. Historical records of parentage, as recorded by staff in notebooks and in 20th-century publications, have been used to inform breeding decisions but might be incorrect as indicated by earlier explorations of parentage using simple sequence repeat (SSR) markers. Our objective was to elucidate parentage and extended pedigrees of all available cultivars introduced from the UMN apple breeding program using evaluations of Mendelian errors and shared haplotype length information based on data from single nucleotide polymorphism (SNP) arrays. Sixteen of the 21 cultivars introduced before ‘Honeycrisp’ (1991) had incorrect or incomplete pedigrees that are now at least partially elucidated. These include the two most important regional cultivars in the 20th century: ‘Haralson’ (parents: ‘Malinda’ and ‘Wealthy’) and ‘Fireside’ (parents: ‘Wealthy’ and ‘Northwest Greening’). ‘Wealthy’, a widely grown cultivar in the United States in the late 19th and early 20th centuries, was a frequent parent of older UMN cultivars. ‘Malinda’ was a less frequent parent than indicated by breeding records. ‘Duchess of Oldenburg’ (synonym ‘Borowitsky’) was revealed as an ancestor of overwhelming importance in the UMN breeding program. It was an ancestor of 27 of the 28 UMN cultivars, including as a parent of two cultivars, and a grandparent of 15 cultivars, including ‘Honeycrisp’.

Open Access

Incorporating DNA-informed breeding techniques can improve selection efficiency for desired traits as compared with conventional breeding methods that do not use DNA-informed techniques. Incorporation of DNA technologies requires additional costs associated with reagents, equipment, and labor. To elucidate the cost-effectiveness of DNA-informed breeding in perennial crops with multiple years per generation, we conducted a cost–benefit analysis examining incorporation of marker-assisted selection (MAS), a type of DNA-informed breeding, applied to an apple breeding program. Annual operational costs for a midwest apple breeding program were used to develop a simulation with inputs including itemized costs and per unit costs for procedures at each breeding program stage. Simulations compared costs of MAS breeding techniques to conventional breeding methods to identify the break-even point (BEP) where cost-savings associated with MAS equals the accrued additional costs. Additional sensitivity analyses were conducted to examine changes in laboratory costs, seedling maintenance costs, and seedling evaluation costs. We found the BEP for this program occurs when MAS results in a removal rate of 13.18%, and changes to other costs (i.e., maintenance costs) result in a smaller percent decrease to the overall program budget. Our findings are useful to perennial crop breeding programs in which managers are considering incorporating DNA-informed breeding techniques.

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Many studies of apple (Malus ×domestica Borkh.) softening have been done using cultivars that eventually become mealy. We wanted to determine whether observations in these studies would be seen in a cultivar that maintains its crispness. In this paper, we compared the texture, ultrastructure, and some physiological parameters of Honeycrisp, an apple cultivar introduced in 1991 by the Minnesota Agricultural Experiment Station, with its parents and Delicious. Sensory evaluations and instrumental texture measurements showed that `Honeycrisp' maintained a crisp texture from harvest through 6 months of cold storage, whereas its parents, `Macoun' and `Honeygold', softened over the same time period. Turgor potential, cell wall composition, and ultrastructural comparisons of the fruit were made. Cell turgor potentials of `Honeycrisp' and `Delicious' were similar and greater than those of `Macoun' and `Honeygold', and clearly correlated with firmness. There were no differences in cell wall neutral sugar composition, except for arabinose, which was not highly correlated with crispness. `Honeycrisp' fruit maintained cell wall integrity after 6 months of storage, while cell walls of `Macoun' and `Honeygold' deteriorated. These data show that it is important to compare more than one cultivar when studying crispness. Honeycrisp is a cultivar that maintains its crispness through long storage without controlled atmosphere conditions. After 6 months of storage, this crispness can be attributed to a maintenance of high turgor potential and cell wall integrity.

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MN55 is an apple (Malus ×domestica Borkh.) cultivar recently released by the University of Minnesota apple breeding program, with fruit marketed in the U.S. as Rave®. When stored for 4 months at 0 to 4 °C, MN55 fruit can develop several storage disorders, including skin dimpling. Skin dimpling incidence was greater for fruit harvested 1 week later than those harvested earlier. Dimpling was not alleviated by prestorage treatments of 1-methylcyclopropene or diphenylamine or by holding fruit at room temperature for 1 day before long-term cold storage. However, dimpling incidence was very low when fruit were stored at 6 to 7 °C. Because viruses have been implicated in other fruit dimpling disorders, the presence of viruses in MN55 leaves and fruit was studied. Apple stem pitting virus (ASPV) was detected by microscopy, reverse transcriptase polymerase chain reaction (RT-PCR) methodology, and high throughput sequencing (HTS) in peel of fruit from MN55 trees that exhibited skin dimpling after 4 months of storage at 0 to 1 °C. ASPV was also detected in supermarket-purchased fruit of other cultivars with noticeable skin dimpling. Although ASPV was not conclusively demonstrated to cause skin dimpling in our work, its prevalence indicates that further investigations are warranted to determine the relationship between viruses and skin deformities in stored apples.

Open Access