Advancing Endodormancy Release in Temperate Fruit Trees Using Agrochemical Treatments

Abstract

Endodormancy in temperate fruit trees like Prunus is a protector state that allows the trees to survive in the adverse conditions of autumn and winter. During this process, plants accumulate chill hours. Flower buds require a certain number of chill hours to release from endodormancy, known as chilling requirements. This step is crucial for proper flowering and fruit set, since incomplete fulfillment of the chilling requirements produces asynchronous flowering, resulting in low quality flowers, and fruits. In recent decades, global warming has endangered this chill accumulation. Because of this fact, many agrochemicals have been used to promote endodormancy release. One of the first and most efficient agrochemicals used for this purpose was hydrogen cyanamide. The application of this agrochemical has been found to advance endodormancy release and synchronize flowering time, compressing the flowering period and increasing production in many species, including apple, grapevine, kiwi, and peach. However, some studies have pointed to the toxicity of this agrochemical. Therefore, other non-toxic agrochemicals have been used in recent years. Among them, Erger® + Activ Erger® and Syncron® + NitroActive® have been the most popular alternatives. These two treatments have been shown to efficiently advance endodormancy release in most of the species in which they have been applied. In addition, other less popular agrochemicals have also been applied, but their efficiency is still unclear. In recent years, several studies have focused on the biochemical and genetic variation produced by these treatments, and significant variations have been observed in reactive oxygen species, abscisic acid (ABA), and gibberellin (GA) levels and in the genes responsible for their biosynthesis. Given the importance of this topic, future studies should focus on the discovery and development of new environmentally friendly agrochemicals for improving the modulation of endodormancy release and look more deeply into the effects of these treatments in plants.

Male Meiosis as a Biomarker for Endo- to Ecodormancy Transition in Apricot

“…Determining endodormancy breaking in apricot through the detection of male meiosis could provide insights into whether flower buds are vulnerable to spring frosts, allowing agronomic frost protection decisions to be made. In addition, the date of male meiosis could allow the determination of the optimal application time of agrochemical treatments to advance flowering ( Guillamón et al, 2022 ).…”

Plant Biostimulants Enhance Bud Break in Vitis vinifera Crimson Seedless Using Combination Treatments

“…Additionally, SBB-01 is an amino acid-based biostimulant, and NDY-01 contains water-soluble calcium (CaO), which could enhance Ca signaling similarly to HC [26]. Indeed, the most common agrochemicals evaluated for dormancy release are amino acid and nitrite salt-based [37]. The performance of such agrochemicals has been tested in crops such as kiwi, apple, sweet cherry, grapevine, blackberry, and peach [25,30,[33][34][35][36]67,68].…”

“…However, very few reports, especially in the grapevine, exist of PBs that enhanced bud-break in a similar or superior manner to that of HC. Nevertheless, the success of PBs reported in bud-break studies may be attributed to their ability to cause major oxidative stress in plants whilst providing nutrients necessary for cellular and tissue recovery [37]. It is typical for such treatments to be amino acid-and nitrite salt-based and to be applied in combination with an adjuvant or oil-based substance as well as the additional supplementation of NO and calcium-containing biochemical agents [37].…”

“…Nevertheless, the success of PBs reported in bud-break studies may be attributed to their ability to cause major oxidative stress in plants whilst providing nutrients necessary for cellular and tissue recovery [37]. It is typical for such treatments to be amino acid-and nitrite salt-based and to be applied in combination with an adjuvant or oil-based substance as well as the additional supplementation of NO and calcium-containing biochemical agents [37]. Interestingly, all these elements have been reported in the molecular models of HC action during bud-break [26][27][28].…”

Temporal transcriptome and metabolite analyses provide insights into the biochemical and physiological processes underlying endodormancy release in pistachio (Pistacia vera L.) flower buds

“…To overcome bud endodormancy caused by the lack of winter chill, bud-break enhancing chemicals, such as horticultural oil, kaolin clays, hydrogen cyanamide, and calcium carbonate, have been applied to pistachio trees. However, the effectiveness of these bud-break enhancing chemicals can be unpredictable due to various factors, such as the concentration of the chemicals, the timing of application, genetic variability among plant species and varieties, and the influence of environmental conditions ( Guillamón et al., 2022 ). There is still much to be learned about the physiological and biochemical responses of endodormant pistachio buds to winter chill, and how bud-break enhancing chemicals function when the winter chill is inadequate.…”