LAUSR

Abstract The State of Rio Grande do Sul is used to produce the largest volume of peaches in Brazil. However, productivity in the state is lower than elsewhere in the country. One of the challenges faced by producers in the area is the occurrence soil drainage problems. These problems are observed mainly in Pelotas and its surroundings, and depending on the time of year, may produce flooding issues that hamper both the development and productivity of cultures. In situations in which soil is flooded, oxygen levels are insufficient for root growth, can hinder cellular respiration and may lead to a cellular energy crisis. In addition, global climate change is affecting the climate, and such changes are expected to increase the frequency and severity of flood events in many the agricultural regions. In order to design studies that aim to enhance the selection of flood tolerant genotypes, it is essential to understand the physiological and molecular changes that occur in plants under conditions of oxygen deprivation. Since the production of peach trees in the region is accomplished using rootstocks, the aim of this study was to evaluate gas exchange parameters and gene expression changes involved in glycolytic, fermentative and ethylene metabolism in the peach cultivar NR0170401 and plum cultivars Marianna 2624 and Myrobalan 29C under flooded soil conditions. To this end, gas exchange parameters [net photosynthetic rate (A), and stomatal conductance (gs)] and the expression of nine genes [ACO1 (1-aminocyclopropane-1-carboxylic acid oxidase), ACS5 (1-aminoacyclopropane 1-carboxylic acid synthase), ADH1 (alcohol dehydrogenase 1), G6P (glucose-6-phosphate plastidic transporter), GAPDH (glyceraldehyde 3-phosphate dehydrogenase), LDH1 (lactate dehydrogenase 1), PDC (Pyruvate decarboxylase), SAMs (SAM synthase), and UDPg (UDP-glucose pyrophosphorylase] were evaluated under conditions of flooding relative to controls. An evaluation of gas exchange showed that the plum cultivars are more tolerant to flooding than the peach cultivar studied. RT-qPCR results showed that the three evaluated rootstocks activated fermentative metabolism in roots in the first six hours post-flooding period, and root tissues were more highly affected than leaves. 'Marianna 2426' appears to have a more efficient gene response system compared to the other cultivars studied under conditions of oxygen deprivation. Although more studies are needed, such information has the potential to facilitate the selection of rootstocks used for peach production, for orchard management and for plant breeding programs aiming to produce new cultivars with increased flood tolerance.