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sur le développement des zones arides et semi-arides

Titre : Ruptura de dormición, brotación y floración en nogal (Juglans regia L.) en el valle inferior del río Negro : necesidades de frío invernal y requerimientos de calor en un contexto de cambio climático

Auteur : del Barrio, Ricardo Alfredo

Université de soutenance : Universidad Nacional del Sur

Grade : Doctor en Agronomia 2020

Résumé partiel
In the lower valley of the Negro river, Argentina, nut production, e.g. walnut (Juglans regia L.) is one of the fastest growing and most dynamic fruit activities since the beginning of the current century, a situation extended overall the North Patagonian valleys historically dedicated to pomaceous fruits. The main aim of this thesis was to study the effect of winter chill and spring heat accumulation on breaking of bud dormancy, budburst and flowering in walnut cultivars ‘Chandler‘ and ‘Franquette‘ in the said region, laying to their ecophysiological and bioclimatic characterization in a climate change context. Winter chill (CR) and spring heat (HR) requirements were defined for breaking of dormancy, assessing its variability according to : type of bud (vegetative-mixed- or catkin), type of twig (with and without apical bud), by cultivar and year (Chapter II). The anatomical and morphological characteristics that distinguish the states of endo and ecodormancy in buds were detailed by light microscopy (Chapter III), and the sugars progress in them was analyzed and quantified by near-infrared spectrometry (NIRs) and high-performance liquid chromatography (HPLC) (Chapter IV). A negative correlation (―parallel‖ influence) was verified between CR incremental treatments to break dormancy and HR for sprouting, requiring a higher incidence of HR than CR as main factors in the said processes. The forced chill tests indicated some overestimation of CR against chill field determinations. An advance was observed in budburst of twigs extracted without apical bud with respect to those that maintained it ; aspect also visualized by light microscopy, as a print of paradormancy processes in the studied species. Non-uniform sugars dynamics in buds were determined by HPLC during the endo-ecodormancy-pre-sprouting progression. The sucrose concentration, in its cryoprotection role was similar to that of fructose and glucose only during endodormancy, then increasing until reaching its maximum, 15-30 days after the dormancy break, and then falling abruptly as the spring pre-sprouting approached. The monosaccharides (fructose and glucose) maintained, during this period, similar concentrations to those of endormancy, to increase just in pre-sprouting as a feasible source of cellulosic carbon. The results obtained by applying NIRs techniques, although preliminary, constitute an advance in its adjustment to evaluate sugars dynamics in these processes. The earlier spring phenology in ‗Chandler‘ than ‘Franquette‘ cultivars was found to be a consequence of somewhat lower CR for dormancy disruption, along with lower HR for budburst / flowering. In winter chill overexposure conditions like the regional ones, the HRs were more determining than the CRs in the phenological prospective of the studied species.

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