Evaluation of potential prunus rootstocks for almond production – stage 2 (AL16006)
What’s it all about?
Beginning in February 2018, this project carries on from earlier industry work to evaluate a range of potential new almond rootstocks – assessing their compatibility with the common almond cultivars grown in Australia, and their performance under the country’s various growing conditions.
The earlier work saw 14 rootstocks, including Nemaguard, planted for evaluation at a trial site in Lindsay Point, Victoria. The current project is continuing these evaluations and building upon the research, including through the introduction of new technologies and the establishment of further trials.
Over the past 12 months the team completed its yearly data collection and reported its analysis.
The rootstock trial at Lindsay Point underwent its fifth harvest and evaluation, with the trees now at an age where are noticeable differences in shape, size and physiological tolerances. The data being generated will inform growers of the different characteristics that can be achieved through the selections of various rootstocks, so they receive correct advice related to orchard characteristics and objectives.
The stage two plantings at the Almond Board of Australia Almond Centre of Excellence were completed, and project activities and findings from the rootstock trials were shared with industry members at meetings and relevant events.
COVID-19 restrictions caused some challenges which were largely managed via workarounds, with the opportunity to catch up activities in the coming season.
The rootstock trial at Lindsay Point has seen its fourth harvest and the research team has been busy working on evaluating results taken this winter. This data included physiological traits such as tree dimension, yield and flowering dates. The tree dimensions and yield data were again used to calculate canopy efficiency.
Samples were also collected to produce information on tree stress with testing for nematodes, nutrient levels and canopy temperatures. The laboratory test results showed an increase in nematode levels; however it was still generally low numbers.
The data obtained to date is providing guidance to growers on the compatibility of rootstocks with scion material as an indication of the vigour of rootstocks. Evaluating the development of canopy size is a key determinant of yields in the early years of production.
Given that the 2019 harvest provided the first mature yield where industry average was achieved, there is now enough data collected to show the development to this stage through all phenological stages.
The 2020 harvest will add to the collection of mature yields and create a stronger dataset for industry growers and stakeholders. Data collected continues to add to the final rootstock evaluation document that is to be produced to achieve end of project outcomes.
Information is being monitored by the industry’s Plant Improvement Committee and conveyed to industry at grower field days. The two new trial sites due for planting in winter 2019 will extend the knowledge for additional rootstocks growing on heavy and light soil types, as well as adding to the dataset that is currently being built.
The researchers report that they have completed their yearly data collection and have ordered rootstock trees for the next stage of the project.
Winter tree measurements
Trunk circumference measures were made to track growth across the different varieties. Trends so far suggest that Carmel grows at a slower rate than the other varieties. Measurements were also made of the Nonpareil sample trees with height and width recorded and canopy area estimated from above using an unmanned aerial vehical (UAV).
Harvest yield analysis
Yield was measured showing an average 2.25 tonnes per hectare, but with variability of up to 790kg from different rootstocks. The yield and tree dimension data allowed calculation of canopy efficiency which will be updated in subsequent years.
Laboratory analysis of elements
Leaf and soil nutrition were analysed with researchers noting levels of elements from the samples.
Flowering dates were collected, showing a five-day range across the rootstocks. Tree anchorage was measured, and fungal pathogens monitored. Nematode sampling was also conducted showing a very small number of nematodes present.
Tree habit was measured using a LIDAR to assess tree canopy and density. Canopy temperature was used to measure tree stress and was recorded with UAV infra-red technology showing a consistent relationship between the light interception results and canopy temperature. Larger canopies were also found to produce a lower canopy temperature.
The project team report that data collection is ongoing at the Lindsay Point trial site, with information being collected on rootstock/scion compatibility, tree vigour, yields and susceptibility to nematodes.
Flowering phenology observations, which involve closely monitoring flowering across the site for a six-week period during August and early September, will soon begin. The researchers note that assessing the impact of different rootstock/scion combinations on bloom dates is critical in the choice of the mix of varieties to plant. As almonds are totally pollination dependent, the synchronicity of flowering times with Nonpareil, the major industry variety, is critical in designing orchard plantings.
Information from the trial is being conveyed to growers at field days conducted on site – look for future events to be advertised in industry channels.
In addition to the Lindsay Point work, the project has another trial at Loxton to evaluate prunus rootstocks in heavier soil types, as well as a further site within the experimental orchard at the National Almond Centre of Excellence, also in Loxton, to evaluate a host of rootstocks and their performance in lighter soils.
This project is a strategic levy investment in the Hort Innovation Almond Fund