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introductory pomology class provided a sound pedagogical approach to teach horticultural techniques while also meeting broader university learning objectives, including fostering critical thinking, communication, teamwork, and community involvement. Materials

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Dr. Steve A. Pieniazek, retired director of the Institute of Pomology in Skierniewice, Poland, tells us he would be interested in coming to the United States and teaching pomology on a temporary basis. There is an increasing need for teachers in pomology. It is possible he could fill an opening caused by retirement while the department is looking for a replacement.

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Abstract

Historians tend to find what they are looking for. My bias in developing historical aspects of Growth Regulators (GR) in Pomology has been positive, as I believe that control of plant growth will eventually be possible. The thought processes and actions taken by individuals who led the way to eventual use of GR are difficult to access. Perhaps the beginnings were initiated by those who had the time to observe plant growth and write down what they saw. To credit any one individual would be of doubtful accuracy. Historically, the one who accumulates fame for a breakthrough put the finishing touches on an idea which had evolved over a long period of time.

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Seventy-five years ago U.S. pomology was caught up in a ferment which marks the ebb and flow of any great agricultural industry. The beginnings of great things to come were in sight, though perhaps unrecognized as such, while the end of other eras was at hand. San Jose scale was being conquered, while peach yellows had destroyed the vast peach industry which bordered the Chesapeake Bay, an industry which made Maryland the leading peach state for a while. The demise of the peach industry was followed shortly by runaway plantings of apples from the mountains of Appalachia westward to Ohio; curiously a similar overexpansion developed in Washington and Oregon as well at that time. South Carolina was just beginning to plant peaches, and it would be 20 years before Michigan would commence peach breeding at South Haven. New Jersey had supported orchard fertilization experiments for 20 years, other Northeastern states for nearly as long. Cultivars were called varieties, and there were great numbers of them in all commercial deciduous fruit orchards. The leading apple cultivar by far was ‘Ben Davis’, but Stark Bros. Nursery had owned Jesse Hiatt's apple for 10 years, and was well under way toward making the 20th century, the ‘Delicious’ century in American apple production. The first high density apple orchard was already 8 years old, this a planting of ‘Wealthy’ trees on seedling rootstocks, spaced 10 × 10 feet, at the Central Experimental Farm in Ottawa, Ontario. But this planting was an idea well ahead of its time, for more than 60 years would pass before the term “high density” would have any meaning in American or Canadian pomology.

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varying success. The present workshop, History of Hawaiian Pomology, sponsored by the History of Horticultural Science and Pomology Working Groups, explored three famous fruit and nut crops of Hawaii: pineapple (oral presentation by Johnny Lopez), papaya

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has had an enormous influence on pomology and horticulture. Trait improvements have been associated with characters that are beneficial to consumers such as the improvement of edible quality and appearance and to growers, packers, and processors such

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Chemical thinning, the most common and cost-effective thinning method, is conducted during early apple fruit development over a 3- to 4-week period using multiple applications of plant growth regulators. It is critical to provide apple growers with tools to assess the efficacy of chemical thinners quickly and accurately because visible responses are not apparent for up to 2 weeks after application. The objective of this study was to build a model to predict apple fruitlet abscission following a chemical thinner application with in situ reflectance data obtained with a portable visible and near infrared (Vis/NIR) spectrophotometer. Developed models were compared with the currently available fruitlet growth model (FGM). ‘Honeycrisp’ fruitlet diameter and reflectance were measured on dates around a chemical thinner application across a 2-year period. After June drop, measured fruitlets were determined to have either persisted or abscised. Random forest, partial least squares regression, and XGBoost classification models were used to predict fruitlet abscission from reflectance data. Each classification model was developed with 2021, 2022, and combined 2021 + 2022 data. For each dataset, 5-fold cross validation was used to assess three model performance metrics: 1) overall accuracy, 2) recall, and 3) specificity. Datasets tested were either unbalanced, majority class down-sampled, or minority class up-sampled with synthetic minority oversampling technique. In both years, the FGM reliably estimated chemical thinner efficacy 9 days after application. Before this time point, the FGM had low prediction accuracy of the minority class in both years—persisting fruitlets in 2021 and abscising fruitlets in 2022. For reflectance spectroscopy, the developed random forest models that were balanced with synthetic minority over-sampling technique were found to be the best combination in predicting chemical thinner efficacy. The combined 2021 + 2022 dataset overall model accuracy ranged from 84% the day before to 93% at 9 days after thinner application. These results show that Vis/NIR is a promising tool to predict chemical thinner efficacy. This technology had high prediction accuracies over a range of fruitlet abscission potential and two growing seasons. Further development and testing of the model over cultivars, chemical thinner timings, and growing regions would facilitate commercialization of the technology.

Open Access

Apple (Malus ×domestica L. Borkh.) growers need tools to predict the efficacy of chemical thinners that are applied to induce fruitlet abscission to aid in crop load management decisions. Recently, reflectance spectroscopy-based models to predict fruitlet abscission rates were developed. Using spectroscopy, persisting fruitlets had lower reflectance in the red-light (∼600 nm) and near infrared (∼950 nm) regions than abscising fruitlets. The goal of this study was to better understand how reflectance models distinguished between fruitlets that ultimately persisted or abscised. Individual models for the difference and ratio of each combination of wavelengths were developed to identify key wavelengths for abscission prediction from reflectance models. Accuracy for wavelength difference and ratio models was improved for all model prediction dates when reflectance (R) from R640–675 was subtracted from or divided by R675–696. This spectra region indicates differences in chlorophyll content between persisting and abscising fruitlets. Calculation of the chlorophyll concentration index (R522–579:R640–700) from nondestructively measured spectra supported this result. Chlorophyll concentration index was higher for fruitlets that ultimately persisted than abscised fruitlets (P < 0.01) for all measurement dates –1 to 9 days after thinner (DAT) in both years, except –1 DAT in 2021 (P = 0.468). Plant water index (R950–970:R890–900) was lower for persisting than abscising fruitlets for 3 to 9 DAT in 2021 (P < 0.001) and on –1 (P < 0.01) and 9 DAT (P < 0.001) in 2022. The relationship of fruit size and plant pigment (anthocyanins or chlorophyll) content in fruitlets to reflectance spectra between persisting and abscising fruitlets was also followed. Fruitlet persistence or abscission was predicted from developed models for destructively sampled fruitlets using measured reflectance spectra. Whole-fruit chlorophyll content was numerically higher in fruitlets predicted to persist than abscise for all collection dates. Higher total chlorophyll was correlated to a larger fruit size in persisting than abscising fruitlets. This higher chlorophyll content led to a lower reflectance of red light and was a key factor in model development. These results indicate that chlorophyll and water content can distinguish physiological parameters between persisting and abscising fruitlets.

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Abstract

A microcomputer program is used to calculate the production and profitability of student-created apple orchard designs. The program accumulates productivity for each year following planting and uses economic parameters to determine the net present value of total orchard profits for each design. Students can alter not only design inputs and economic predictors but are encouraged to change production cost parameters to demonstrate their effects on orchard profitability over the life of the orchard.

Open Access