Persian Walnut (Juglans regia L.) Bud Dormancy Dynamics in Northern Patagonia, Argentina

DEL BARRIO, RICARDO; ORIOLI GUSTAVO; BRENDEL ANDREA SOLEDAD; LINDSTRÖM LILIA IVONE; PELLEGRINI CECILIA; CAMPOY, JOSÉ ANTONIO

Frontiers in Plant Science

Frontiers Media

Año: 2022 vol. 12 p. 1 - 20

Temperate deciduous fruit trees survive winter temperatures by entering a dormantphase in their aerial meristematic organs. Release from bud dormancy occurs afterchill requirements (CR) have been satisfied, whereas bud burst/flowering follows heatrequirement (HR) fulfillment. The physiological basis behind these metrics remainselusive. In this study, we are presenting the first multidisciplinary dormancy progressionanalysis in northern Patagonia, linking (1) forcing/field phenology, (2) bud anatomicaldevelopment, and (3) soluble sugar (sucrose, glucose, and fructose) dynamics inJuglans regia L. CR and HR were determined for ?Chandler? and ?Franquette,? twowalnut cultivars with markedly different CR, in artificial chill/forced heat trials (threeseasons) and in-field chill/forced heat tests (five seasons) using excised twigs eitherwith or without apical buds (non-decapitated and decapitated). The soluble sugardynamics of ?Chandler? (high-performance liquid chromatography) and the anatomicalchanges of the buds (light microscopy) of the two cultivars were analyzed during endoecodormancy progression in one and two seasons, respectively. The CR defined byartificial chill tests proved to be an overestimation compared to the field determinations.Moreover, HR was the main driver in the phenology dynamics, as expected for ahigh-chill region. ?Chandler? showed an average of 10.3 field chill portions (CP) and2,163 Growing Degree Hours (GDHC) less than ?Franquette? for dormancy release andbud burst, respectively. These results were consistent with the transition of the shootapex from the vegetative to the reproductive phase and the soluble sugar profile. Thedecrease in sucrose between 15 and 30 days after CR fulfillment could be a reliablebiological marker for endodormancy release in walnut, while the increase in fructoseand glucose is likely an osmolyte and cellulosic carbon source in pre-sprouting. Inaddition, we discuss the effect of paradormancy thanks to our apical bud experiment(with or without). Our results improve the current understanding of endo-ecodormancyprogression in walnut and provide insightful results for walnut production (i.e., cultivationpractices such as pruning) as well as for further application in dormancy modeling, toinfer the ideotypes that should be bred for future climate conditions.