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Knowing a tree crop’s seasonal growth and development as a function of heat accumulation can facilitate scheduling of irrigation, pesticide applications, and harvest. Our objective was to compare the goodness of fit of applied models and determine which provides the best description of pistachio nut growth as a function of thermal unit accumulation. Three fruit growth traits of pistachio—pericarp (hull) + endocarp (shell) size, endocarp thickening and hardening, and embryo (kernel) size—exhibited clear nonlinear dependence on heat accumulation. We tested three nonlinear models—Michaelis–Menten, three-parameter logistic, and Gompertz—fitted to fruit development data to create a tool to forecast pest susceptibility and harvest timing. Observation of development began at full bloom and ended at harvest. Data were collected from six pistachio cultivars in one experimental and eight commercial orchards over 3 years. Analyses of residual distribution, parameter standard errors, coefficient of determination (R 2) and the Akaike information criterion (AIC) all demonstrated the Gompertz function was the best model. Cultivars differed significantly in all the three parameters (Asym, b, and c) for all three traits with the Gompertz model, demonstrating the Gompertz model can adjust to incorporate cultivar differences. The growth curve of the three traits together provided integrated information on nut biomass accumulation that facilitates predicting the critical timing for multiple orchard management practices.
Lu Zhang; Emilio Laca; Cara J. Allan; Narges M. Mahvelati; Louise Ferguson. Nonlinear Model Selection for Fruit and Kernel Development as a Function of Heat in Pistachio. HortScience 2021, 56, 769 -779.
AMA StyleLu Zhang, Emilio Laca, Cara J. Allan, Narges M. Mahvelati, Louise Ferguson. Nonlinear Model Selection for Fruit and Kernel Development as a Function of Heat in Pistachio. HortScience. 2021; 56 (7):769-779.
Chicago/Turabian StyleLu Zhang; Emilio Laca; Cara J. Allan; Narges M. Mahvelati; Louise Ferguson. 2021. "Nonlinear Model Selection for Fruit and Kernel Development as a Function of Heat in Pistachio." HortScience 56, no. 7: 769-779.
Pecan is native to the United States. The US is the world’s largest pecan producer with an average yearly production of 250 to 300 million pounds; 80 percent of the world’s supply. Georgia, New Mexico, Texas, Arizona, Oklahoma, California, Louisiana, and Florida are the major US pecan producing states. Pecan trees frequently suffer from spring freeze at bud break and bloom as the buds are quite sensitive to freeze damage. This leads to poor flower and nut production. This review focuses on the impact of spring freeze during bud differentiation and flower development. Spring freeze kills the primary terminal buds, the pecan tree has a second chance for growth and flowering through secondary buds. Unfortunately, secondary buds have less bloom potential than primary buds and nut yield is reduced. Spring freeze damage depends on severity of the freeze, bud growth stage, cultivar type and tree age, tree height and tree vigor. This review discusses the impact of temperature on structure and function of male and female reproductive organs. It also summarizes carbohydrate relations as another factor that may play an important role in spring growth and transition of primary and secondary buds to flowers.
Amandeep Kaur; Louise Ferguson; Niels Maness; Becky Carroll; William Reid; Lu Zhang. Spring Freeze Damage of Pecan Bloom: A Review. Horticulturae 2020, 6, 82 .
AMA StyleAmandeep Kaur, Louise Ferguson, Niels Maness, Becky Carroll, William Reid, Lu Zhang. Spring Freeze Damage of Pecan Bloom: A Review. Horticulturae. 2020; 6 (4):82.
Chicago/Turabian StyleAmandeep Kaur; Louise Ferguson; Niels Maness; Becky Carroll; William Reid; Lu Zhang. 2020. "Spring Freeze Damage of Pecan Bloom: A Review." Horticulturae 6, no. 4: 82.
Springtime flail mowing of row middles for weed control in California pistachio (Pistacia vera L.) orchards blows dust into the leafless canopy if it occurs during bloom. The effect of dust on pistachio pollination and fruit set is unknown. Rachises were bagged prebloom and hand pollinated with pollen and dust mixtures at 1:0, 1:1, 1:4, 1:16, and 0:1 volume/volume ratios on five successive days. The 2016 and 2017 trials demonstrated that the inflorescences treated with a high pollen:dust ratio (0:1, 1:4, and 1:16) had significantly lower split nut rates (commercially less profitable) compared with low dust ratio tests (1:0 and 1:1). Our results also showed that dust damaged both pollen viability and stigma quality, particularly if contaminated with herbicide residues (GlyStar® Plus and Treevix®). Decreased yield was a function of decreased fruit set; increased embryo abortion, parthenocarpy, or both; and a lower split nut percentage. The GA3 content in flowers of both the pollen and dust treatments was significantly higher than that in nonpollinated flowers, suggesting dust stimulated parthenocarpy, resulting in empty nutshells, “blanks” at harvest.
Lu Zhang; Robert Howard Beede; Gary Banuelos; Christopher M. Wallis; Louise Ferguson. Dust Interferes with Pollen–Stigma Interaction and Fruit Set in Pistachio Pistacia vera cv. Kerman. HortScience 2019, 54, 1967 -1971.
AMA StyleLu Zhang, Robert Howard Beede, Gary Banuelos, Christopher M. Wallis, Louise Ferguson. Dust Interferes with Pollen–Stigma Interaction and Fruit Set in Pistachio Pistacia vera cv. Kerman. HortScience. 2019; 54 (11):1967-1971.
Chicago/Turabian StyleLu Zhang; Robert Howard Beede; Gary Banuelos; Christopher M. Wallis; Louise Ferguson. 2019. "Dust Interferes with Pollen–Stigma Interaction and Fruit Set in Pistachio Pistacia vera cv. Kerman." HortScience 54, no. 11: 1967-1971.