In May 2022 QDAF hosted a virtual field walk showcasing the macadamia rootstock trial and phase II of the macadamia planting systems trial which are part of the new 'national tree crop intensification program - AS18000'. This is what was covered by the event (and by whom):
Performance of cultivar 741 grafted on 24 different rootstocks at the Maroochy Research Facility. See what impact these seedlings and cutting rootstocks can have on vigour, early bearing and yield efficiency. - Queensland Alliance for Agriculture and Food Innovation breeding team
Performance evaluation of scions P, A203 and A16 along with two canopy management strategies: vase and complex. The macadamia planting systems trial, now in year 2, was planted at a density of 667 trees per hectare, 5 m between rows and 3 m between trees. - Department of Agriculture and Fisheries macadamia team in Bundaberg
New progeny blocks producing the next generation of macadamia varieties and the exciting traits being developed to increase the profitability and sustainability of the Australian macadamia industry. - Professor Bruce Topp and Dr Mobashwer Alam
How orchard design and management practices are being influenced by collaboration with macadamia researchers and affecting the growth and yield of macadamia trees. - Queensland Alliance for Agriculture and Food Innovation modelling team
QUESTION RESPONSES POST EVENT
There were two questions Prof Bruce Topp responded to following the tour, his responses are below:
Are you keeping microclimate in mind on SKR?This is an important point to consider. Microclimate can certainly influence SKR. We are selecting all these seedling genotypes under the one environment and so they are competing on an even playing field. The caveat here is that if there is a genotype x environment interaction (i.e. the performance ranking of the genotypes alters in other environments) then selection can be skewed. Testing of the selections in multiple environments prior to release is essential in this regard.
Microclimate in high density (more decoupled) and microclimate in young trees (more coupled to the atmosphere) will swing SKR. Root volume may also play a role? Microclimate can be influenced by tree planting density and so this needs to be considered. Russ Stephenson conducted experiments that showed kernel recovery (and oil accumulation) can be reduced if temperature is too high or too low. Relative humidity and other climatic factors would also be influenced by planting density. I have not read any reports on root volume but this is an interesting aspect to consider.
Further details on each of the projects can be found in the Summer 2021 AMS News Bulletin stories (the News Bulletin can be downloaded from the AMS website):
Planting systems trials to improve orchard systems
Growers have their say on new selections from the breeding trials
In addition, Dr Mobwasher Alam recently gave a seminar titled “Routes of Rootstocks, in which he presented early years data on the effect of rootstocks on scion traits, explained if rootstock traits can be translated to scions, and discussed future opportunities for rootstock breeding. You can watch it here.