Seleção de porta-enxertos de videira tolerantes ao déficit hídrico

Abstract

In the semi-arid region, the predominant climate is characterized by long periods without precipitation, promoting water deficit, which is one of the abiotic factors that has contributed the most to the reduction of production in the field, sometimes resulting in a decrease in grapevine productivity. Plant breeding has been one of the main strategies to mitigate the damage caused by abiotic stress such as water deficit, through various studies to obtain rootstocks with tolerance to water stress. Thus, this study aimed to select grapevine rootstocks tolerant to water deficit based on above and belowground biomass, primary metabolite content, ecophysiological variables, and leaf pigments. Rootstock seedlings of Paulsen 1103, SO4, IAC 313, IAC 572, IAC 766, Ramsey, and 101-14 MgT were transplanted into 25-liter pots filled with soil from an area cultivated with grapevine at the Experimental Field of Bebedouro, belonging to Embrapa Semiárido, in Petrolina, PE. Each rootstock was subjected to three irrigation depths (100, 50, and 20% ETo) in a randomized block design with four replications, and the experimental unit consisted of two pots with one plant each, in a split-plot scheme, with the main plot being the irrigation depth and the subplot the rootstocks. During the experiment period (08/25 to 12/31/2021), the following ecophysiological variables were obtained: net photosynthesis (A), stomatal conductance (gs), transpiration rate (E), the ratio of internal to external CO2 concentration (Ci/Ca), intrinsic water-use efficiency (A/gs), instantaneous water-use efficiency (A/E), and leaf temperature (Tf). After 128 days, leaves and roots were collected for analysis of the following variables: aerial and root biomass, total chlorophyll (a and b), carotenoids, total soluble carbohydrate content, sucrose, and proline. Biochemical, biomass and gas exchange characteristics were used to select the best rootstocks for drought tolerance through PCA and analysis of variance. The reduction of soil water availability to 20% and 50% ETo led to a reduction in assimilates and gas exchange during the experiment period, and all grapevine rootstocks studied responded differently to changes in photosynthetic pigments, sucrose and proline production, both in leaves and roots, especially in the IAC rootstock group. 'IAC 313' and 'IAC 766' stood out for their higher proline synthesis in the roots, 'IAC 766' showed the best result for leaf sucrose synthesis, while 'Paulsen' stood out in foliar proline and carotenoids and the total chlorophyll/carotenoids ratio. Regarding A and E values, the rootstocks '101-14 MgT', 'Paulsen 1103', and 'Ramsey' showed good results and stood out, especially under conditions of lower water availability, thus demonstrating greater tolerance. It can be concluded that the rootstocks 'IAC 313', 'IAC 766', and 'Paulsen 1103' showed better performance in terms of primary metabolites, aboveground biomass, pigments, and gas exchange, which are important adaptation strategies to water deficit. The results obtained provide important contributions for the choice and use of rootstocks in the Submédio do Vale do São Francisco, especially under conditions of water deficit.