Dormancy breaking of ‘Kampai’ peach trees with alternative products in subtropical regions

Peach trees initiate flowering and then dense budding when the temperatures in winter are steadily low. When temperatures during the winter are high or when the chilling accumulation needs of the cultivar are not met, it is necessary to apply chemicals that stimulate flowering and budding in a uniform manner. This study aimed to evaluate alternative products for breaking the dormancy of ‘Kampai’ peach trees in a subtropical region. The experiment was conducted with ‘Kampai’ peach trees in the 2018, 2019 and 2020 production with the following treatments: (1) negative control composed only of water (control); (2) positive control composed of hydrogen cyanamide at a dose of 1.5% (commercial product Dormex®) plus 4.5% mineral oil; (3) Erger G® organomineral fertilizer supplemented with calcium nitrate at a dose of 3%; (4) potassium nitrate at a dose of 5%; and (5) copper sulphate at a dose of 0.3%. We evaluated affected budding capacity, flowering, the production cycle, peach production, the quality of peach trees and the enzymatic activities of catalase and guaiacol peroxidase. Hydrogen cyanamide and the organomineral fertilizer Erger G® promoted earlier flowering and an earlier production cycle. On the other hand, hydrogen cyanamide and copper sulphate stimulated flower opening and peach production. The chemicals used decreased catalase activity (24 h after application) and increased guaiacol peroxidase activity (6 h after application). The application of copper sulphate may be an option to break the dormancy of peach trees in the subtropics.

Phenology and fruit set of peach trees cultivated in Dois Vizinhos, Paraná State, Brazil

Understanding the dormancy phases and dynamics of commercial cultivars in the regions where they are grown allows for the implementation of different cultural practices and aids in the understanding of the temperature requirements for collaboration with genetic improvement programs. The objective of this study was to determine the budding, flowering, and fruit set rates of peach trees cultivated in the municipality of Dois Vizinhos, Southwestern Paraná, Brazil. The present work was developed using the collection of peach trees in the fruit growing sector of the Universidade Tecnológica Federal do Paraná. Sixteen peach cultivars were evaluated: Rubimel, Leonense, Coral, Marli, Charme, Riograndense, Douradão, Chimarrita, Granada, BR-1, Bonão, and Eldorado (all planted in 2009), as well as Regalo, Kampai, Fascínio, and Zilli (planted in 2014). The experimental design was completely randomized with four replications of one plant each, in a 16 × 2 bifactorial arrangement (cultivars × year/harvest). Phenology evaluations were performed weekly by counting open (anthesis) and sprouted flower buds, and the fruit set rate was measured just before fruit thinning. Flowering (%), budding (%), and fruit set (%) rates were calculated. It was found that the year/harvest 2016 promoted the highest rates of sprouting and fruit set. The Bonão cultivar showed greater flowering intensity and regularity in the crop years evaluated (2016 and 2017). Coral and Kampai present fruit sets with greater intensities and regularities when compared to the other cultivars evaluated under the climatic condition of the municipality of Dois Vizinhos. The Riograndense cultivar showed greater irregularity in flowering and fruit production.

Water extraction pattern and transpirational losses of peach trees Under well-watered and drying cycles

Mature peach trees [Prunus Persica (L.) Batsch] grown in weighing lysimeters were subjected to soil moisture stress by shutting off irrigation. Initially transpiration (T) was at potential rate when available soil moisture in the active root zone was near field capacity. Rapid changes in soil moisture under drying cycles caused gradual decrease in transpirational rate. When 0 to 60 cm soil layer reached permanent wilting point, there was a sharp decline in water use. Mature peach trees require barest minimum of 10 mm of water for their metabolic activity. A regression model has been developed to estimate transpirational loss of peach from available soil profile water.

Effects of Siliceous Natural Nanomaterials Applied in Combination with Foliar Fertilizers on Physiology, Yield and Fruit Quality of the Apricot and Peach Trees

Siliceous natural nanomaterials (SNNMs), i.e., diatomaceous earth and natural zeolites, have a nanoporous structure with large active surfaces that adsorb cations or polarized molecules. Such nanoporous feature determines the effects related to SNNM utilization as low-risk plant protectants and soil improvers. This work used SNNMs from Romanian quarries as carriers for foliar fertilizers applied to stone-fruit trees, apricot and peach. We determined the effects of SNNMs on the physiology, yield and fruit quality of the treated stone-fruit trees. SNNM application determined impacts specific to the formation of particle films on leaves: reduced leaf temperature (up to 4.5 °C) and enhanced water use efficiency (up to 30%). Foliar fertilizers’ effects on yield are amplified by their application with SNNMs. Yield is increased up to 8.1% by the utilization of SNNMs with foliar fertilizers, compared to applying foliar fertilizer alone. Diatomaceous earth and natural zeolites promote the accumulation of polyphenols in apricot and peach fruits. The combined application of SNNMs and foliar fertilizer enhance the performance of peach and apricot trees.

Ethephon-Mediated Bloom Delay in Peach Is Associated With Alterations in Reactive Oxygen Species, Antioxidants, and Carbohydrate Metabolism During Dormancy

Ethephon (ET) is an ethylene-based plant growth regulator (PGR) that has demonstrated greater efficacy in delaying bloom in deciduous fruit species. However, the underlying mechanisms by which ET modulates dormancy and flowering time remain obscure. This study aimed to delineate the ET-mediated modulations of reactive oxygen species (ROS), antioxidants, and carbohydrate metabolism in relation to chilling and heat requirements of “Redhaven” peach trees during dormancy. Peach trees were treated with ethephon (500ppm) in the fall (at 50% leaf fall), and floral buds were collected at regular intervals of chilling hours (CH) and growing degree hours (GDH). In the control trees, hydrogen peroxide (H2O2) levels peaked at the endodormancy release and declined thereafter; a pattern that has been ascertained in other deciduous fruit trees. However, H2O2 levels were higher and sustained for a more extended period than control in the ET-treated trees. ET also increased the activity of ROS generating (e.g., NADPH-oxidase; superoxide dismutase) and scavenging (e.g., catalase, CAT; glutathione peroxidase) enzymes during endodormancy. However, CAT activity dropped significantly just before the bud burst in the ET-treated trees. In addition, ET affected the accumulation profiles of starch and soluble sugars (hexose and sucrose); significantly reducing the sucrose and glucose levels and increasing starch levels during endodormancy. However, our study concluded that variations in ROS levels and antioxidation pathways, rather than carbohydrate metabolism, could explain the differences in bloom time between ET-treated and -untreated trees. The present study also revealed several important bud dormancy controlling factors that are subject to modulation by ethephon. These factors can serve as potential targets for developing PGRs to manipulate bloom dates in stone fruits to avoid the ever-increasing threat of spring frosts.

Genetic and phenotypic characterization of the fungal pathogen Cytospora plurivora from western Colorado peach orchards and the development of a ddPCR assay for detection and quantification

Cytospora canker is one of the most important diseases affecting peach production in Colorado, yet previous efforts to characterize Cytospora species diversity in Colorado have relied exclusively on morphological traits. Recently, several new Cytospora species were described from peach orchards within the United States using molecular and morphological data, prompting the need to reexamine Cytospora spp. present on peach trees in Colorado. A total of 137 isolates of Cytospora spp. were collected from eight orchards in western Colorado. Isolates were sequenced at the ITS (internal transcribed spacer) region and EF1a (elongation factor 1 alpha) and assessed with reference sequences in phylogenetic analyses. All isolates from western Colorado peach trees resolved with the newly described Cytospora plurivora. In addition to molecular characterization, temperature growth and virulence assays were conducted to assess phenotypic variation among the isolates from western Colorado. Variation across isolates was found both in growth at different temperatures and in virulence. Ancestral state reconstruction analyses resolved the most virulent (and most often collected) haplotypes together in a well-supported clade from which a single monophyletic origin of high virulence can be inferred. Finally, a droplet digital PCR assay was developed for use in ongoing and future studies to detect and quantify C. plurivora from field and laboratory samples.

A modification in an open centre training system for increasing the crotch angles of peach scaffold branches

One-year-old ‘Florida Prince’ cultivar (cv) peach trees grafted on a ‘Nemaguard’ rootstock were planted in the early spring of 2018 at the Centre of Agricultural Research and Experiments, Minia University, located in southwest Egypt. The trees were planted 5 × 5 m in a randomised complete block design with four replicates, with ten trees in each replicate. In the late spring, two different pruning systems were applied; traditional open centre (OC) and de-branched top trees (DBT). The OC trees were headed at 80 cm above the ground. DBT is a modification of the OC, but no heading was undertaken and the new shoot growth arising from the 20 cm at the top of the plant were removed. Before the winter pruning took place, measurements were taken on the upper two opposite branches. The average length and diameter values of the upper two opposite branches at the top of the trees trained to the OC were higher than those trained with the DBT. In contrast, the distance between the upper two branches (25 cm) at the top of the DBT trees was significantly higher. Likewise, the values of the crotch angles (48°) and the number of branches (81 of 100 branches) that showed desired crotch angles (more than 40°) were remarkably higher in the trees trained with the DBT. After the winter pruning took place, the DBT trees were higher than the OC trees. Additionally, the trees trained with the DBT had low pruning costs and took less time. Moreover, the pruning wood weight of the DBT trees was about half of the pruning wood weight of the OC trees. In conclusion, the DBT training system showed the desired impact on the crotch angles and the tested pruning characteristics.

Orchard Level Assessment of Irrigation Performance and Water Productivity of an Irrigation Community in Eastern Spain

Over the last three decades, a great investment effort has been made in the modernization of irrigation in the Valencian Community (Spain). The initial change from distribution networks to pressurized ones and the shift towards drip irrigation systems was followed by improvements in irrigation scheduling, based on agrometeorological data, soil water content sensors, and remote sensing. These improvements are considered adequate for increasing irrigation water use efficiency, but it is difficult to find systematic measurements to assess its impacts on irrigation adequacy along with irrigation productivity in fruit orchards. This work presents the results of a four year assessment of irrigation water and energy use efficiency along with water productivity of a recently established irrigation community in the province of Valencia (Spain). The study was carried out at the orchard level and focused on two fruit crops: persimmon and peach trees. Six irrigation performance indicators, relative water supply (RWS), relative irrigation supply (RIS), yield performance (Yp), global water productivity (WPoverall), output per unit irrigation water (OUI), and the percent of nitrogen fertilization obtained by irrigation water, were defined and calculated for years 2017 to 2020 in 104 persimmon and peach orchards. The results showed that most of the farmers irrigated below the crop water requirements, showing RWS and RIS values less than 1, and there was great variability among farmers, especially in WPoverall and OUI indicators.