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James A. Schrader, Paul A. Domoto, Gail R. Nonnecke, and Diana R. Cochran

An accurate predictive model for estimating the timing of seasonal phenological stages of grape (Vitis L.) would be a valuable tool for crop management. Currently the most used index for predicting the phenological timing of fruit crops is growing degree days (GDD), but the predictive accuracy of the GDD index varies from season-to-season and is considered unsatisfactory for grapevines grown in the midwestern United States. We used the methods of multiple regression to analyze and model the effects of multiple factors on the number of days remaining until each of four phenological stages (budbreak, bloom, veraison, and harvest maturity) for five cold-climate wine grape cultivars (Frontenac, La Crescent, Marquette, Petit Ami, and St. Croix) grown in central Iowa. The factors (predictor variables) evaluated in models included cultivar, numerical day of the year (DOY), DOY of soil thaw or the previous phenological stage, photoperiod, GDD with a base temperature of 10 °C (GDD 10), soil degree days with a base temperature of 5 °C (SDD 5), and solar accumulation. Models were evaluated for predictive accuracy and goodness of fit by calculating the coefficient of determination (R 2), the corrected Akaike information criterion (AICc), and the Bayesian information criterion (BIC); testing for normal distribution of residuals; and comparing the actual number of days remaining until a phenological stage with the number of days predicted by models. The top-performing models from the training set were also tested for predictive accuracy on a validation dataset (a set of data not used to build the model), which consisted of environmental and phenological data recorded for one popular Midwest cultivar (Marquette) in 2019. At all four phenological stages, inclusion of multiple factors (cultivar and four to six additional factors) resulted in predictive models that were more accurate and consistent than models using cultivar and GDD 10 alone. Multifactor models generated from data of all five cultivars had high R 2 values of 0.996, 0.985, 0.985, and 0.869 for budbreak, bloom, veraison, and harvest, respectively, whereas R 2 values for models using only cultivar and GDD 10 were substantially lower (0.787, 0.904, 0.960, and 0.828, respectively). The average errors (differences from actual) for the top multifactor models were 0.70, 0.84, 1.77, and 3.80 days for budbreak, bloom, veraison, and harvest, respectively, and average errors for models that included only cultivar and GDD 10 were much larger (5.27, 2.24, 2.79, and 4.29 days, respectively). In the validation tests, average errors for budbreak, bloom, veraison, and harvest were 1.92, 1.31, 0.94, and 1.67 days, respectively, for the top multifactor models and 10.05, 2.54, 4.23, and 4.96 days, respectively, for models that included cultivar and GDD 10 only. Our results demonstrate the improved accuracy and utility of multifactor models for predicting the timing of phenological stages of cold-climate grape cultivars in the midwestern United States. Used together in succession, the models for budbreak, bloom, veraison, and harvest form a four-stage, multifactor calculator for improved prediction of phenological timing. Multifactor models of this type could be tailored for specific cultivars and growing regions to provide the most accurate predictions possible.

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Mariola Plazas, Santiago Vilanova, Pietro Gramazio, Adrián Rodríguez-Burruezo, Ana Fita, Francisco J. Herraiz, Rajakapasha Ranil, Ramya Fonseka, Lahiru Niran, Hemal Fonseka, Brice Kouassi, Abou Kouassi, Auguste Kouassi, and Jaime Prohens

introgression breeding as well as on the feasibility of using eggplant wild relatives for developing interspecific hybrid rootstocks. Materials and Methods Plant material. Six S. melongena accessions, of which three originated from Ivory Coast (MEL1 to MEL3

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Raul I. Cabrera, James A. Reinert, and Cynthia B. McKenney

Nursery choice feeding study. Rooted liners from 12 cultivars, all of standard size (greater than 6 m or greater than 20 ft) at maturity representing two Lagerstroemia species and their interspecific hybrids ( L. indica , L. fauriei , and L. indica

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Xinwang Wang, Deborah Dean, Phillip Wadl, Denita Hadziabdic, Brian Scheffler, Timothy Rinehart, Raul Cabrera, and Robert Trigiano

. These species, their selections, and interspecific hybrids are collectively known as crape myrtles and are popular ornamental shrubs/trees in many temperate regions of the United States. Crape myrtle cultivars have many attractive features such as bright

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Shawna L. Daley, William Patrick Wechter, and Richard L. Hassell

regrowth ( Daley and Hassell, 2014 ). We observed that over a 21-d period following fatty alcohol treatment, both bottle gourd and interspecific hybrid squash rootstock seedling cotyledons seemed to expand, becoming long and rigid. The hypocotyl also

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Zuguo Cai, Wenfang Zeng, Liang Niu, Zhenhua Lu, Guochao Cui, Yunqin Zhu, Lei Pan, Yifeng Ding, and Zhiqiang Wang

related to peach and is the core collection of such species for China and the world. Here, we describe a practical SSR-based method for discriminating species related to peach and for identifying interspecific hybrids. The aims of this study were to 1

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Joshua H. Kardos, Carol D. Robacker, Michael A. Dirr, and Timothy A. Rinehart

hybrids. A hybrid with commercial potential was produced through ovule culture from the cross H. scandens ssp. chinensis to H. macrophylla , although the hybrid was sterile ( Kudo et al., 2008 ). Unlike most of the interspecific hybrids, the

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Hsuan Chen, Lan Xue, Tong Li, and Ryan N. Contreras

parents ( Malinowski et al., 2012 ) was released. In addition to interspecific crosses within a section, H. mutabilis has been used for intersectional crosses with H. moscheutos . Three interspecific hybrid cultivars of H. mutabilis × H. moscheutos

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Margaret Pooler and Hongmei Ma

interspecific hybrids created at the U.S. National Arboretum. Materials and Methods Plant materials and hybridizations. Prunus parent taxa and hybrids used in this study are listed in Table 1 . Controlled crosses were performed in the field during the year

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Shawna L. Daley, Jeffrey Adelberg, and Richard L. Hassell

a starch increase of 100- and 200-fold in hypocotyls of bottle gourd and interspecific hybrid squash rootstocks, respectively, over 21 d after fatty alcohol treatment ( Daley et al., 2014 ). We hypothesize that this increase of stored energy in the