Avocado is a very nutritious and tasty fruit, characteristics that have caused a high global demand for this fruit. Increasing evidence of health benefits of the avocado is both driving increased consumption and stimulating research. The results of this study are expected not only to provide more foundation into the agronomic, biochemical and molecular aspects associated to waterlogging of ‘Hass’ avocados grafted on different rootstocks but also provide potential biomarkers and genes involved in stress tolerance and select the best suited rootstocks for the current and the upcoming extreme climate change events, which may help to implement new Hass avocado production protocols that will reduce this predicted climate change problem in practice.

Avocado is a very nutritious and tasty fruit, characteristics that have caused a high global demand for this fruit. Increasing evidence of health benefits of the avocado is both driving increased consumption and stimulating research. Over the next few decades, a number of climate-related factors are expected to undergo significant change, leading to increases in CO2 and, depending on the region, temperature, humidity, salinity, flooding, and drought. Chile is expected to experience more frequent and severe flooding in the future due to climate change and sea level rise. By 2050, flooding in Chile could increase by an order of magnitude compared to the previous decade, while by the end of the century, Chile could experience more than 100 days of flooding each year. The frequency and severity of flooding will increase as sea levels rise. Under such predicted conditions, avocado orchards will suffer significant harm from waterlogging, which significantly will affect the growth, physiological performance and a general avocado production.
The majority of avocado orchards are currently vulnerable to sporadic waterlogging as a result of climate change, either because of poor soil qualities or occasionally rising water tables. Waterlogging detrimentally affects avocado orchards at various levels. Reduced root and shoot growth due to soil oxygen depletion (plant-soil system), decreased transpiration rate, changes in the soil’s oxidation-reduction status, decreased redox potential and ultimately decreased avocado production are the main effects of waterlogging on avocado. Climate change is increasing the frequency and severity of extreme weather events with flooding being the largest concern for Chile. Investigating how climate change factors combine with waterlogging stress, novel genes, and signaling components can provide useful insights into plant responses to waterlogging stress and future agricultural difficulties

The species and occasionally the cultivar determine how long a plant may survive in a waterlogged condition. The rootstock (clonal or seedling rootstocks) used in the orchard may have an impact on the sensitivity to waterlogging. In this Project, it was hypothesized that: (1) Hass avocado grafted to different rootstocks (clonal or from seedling) may have a differential performance under waterlogging conditions and that the tolerance is driven by rootstock cultivar, stress severity, balance of oxidative stress and defense system at morpho-physiological, biochemical and molecular level and (2): Clonal o seedling rootstock influence Hass avocado responses to waterlogging by affecting root microbial community, carbon, nitrogen cycling and reduced soil components. Thus, the main objective of this proposal is to evaluate the effects of waterlogging on grafted Hass avocado to 04 different rootstocks (Dusa, Duke 7, Mexicola and Zutano) mainly used in the Central and South-Central region of Chile.

A systematic fingerprinting analysis will be used in this project by integrating different tools for deep analysis (Chemo-Metabolomics, transcriptomics and metagenomics) and for monitoring changes in morpho-physiological and gas-exchange parameters, changes in plant-soil system by evaluating the composition and function of microbial communities within the pot soil in each treatment, the antioxidant defense system and reactive oxygen species, for better understanding the regulatory mechanisms of tolerance to waterlogging, identification of the potential genes regulating tolerance to waterlogging in Hass avocado and finally the selection of the rootstock with better agronomic performance. Four (4) different rootstocks will be used in this research (two hybrids from Mexican and Guatemalan races – Zutano and Dusa, two Mexican races – Mexicola and Duke 7) which will be grafted with the scion material collected from Hass avocado cultivar. Mexicola and Zutano Will be propagated by seeds; Duke 7 clonally propagated and clonal Dusa plantlets acquired in the national plant propagation nurseries due to protection of intellectual property. One year grafted Hass avocado on different rootstocks will be subjected to a waterlogging greenhouse experiment by submerging them in a plastic water tank with water level 5 cm above the soil Surface (140% field capacity) for 3, 6, 9, and 15 days against the control treatment (no waterlogging stress). Morphological, physio-biochemical and gas-exchange parameters, soil nutrient dinamics, function and composition of microbial community within the pot soil and sampling for transcriptomic analysis will then be performed.

The results of this study are expected not only to provide more foundation into the agronomic, biochemical and molecular aspects associated to waterlogging of ‘Hass’ avocados grafted on different rootstocks but also provide potential biomarkers and genes involved in stress tolerance and select the best suited rootstocks for the current and the upcoming extreme climate change events, which may help to implement new Hass avocado production protocols that will reduce this predicted climate change problem in practice. This project will generate scientific and academic publications, extension and training of young researchers and will strengthen the network with national and international key partners. The findings will be also valuable for agronomists, plant physiologists, microbiologists and plant breeders to develop new avocado production protocols useful for waterlogging conditions that are predicted in Chile.