Mechanical scarification speeds up the study of wild oats
Australia
December 16, 2021
It turns out that wild oats wear raincoats.
Anyone who has researched wild oats knows that getting them to germinate involves picking up each seed and puncturing it with a needle, enabling water to penetrate the seed coat. One powerball!
Now there’s an easier way, thanks to AHRI researcher Roberto Lujan Rocha and others. The research team studied a range of techniques to physically damage the seed coat, discovering that a mechanical seed thresher at 1500 rpm for 5 seconds is enough to achieve 65% germination. Un-treated seed achieved 0% germination.
To be fair, this edition of AHRI Insight is likely to appeal more to weeds researchers than growers and agronomists. However, there is some interesting information about wild oat dormancy if you’re prepared to take a risk and keep on reading.
AHRI Researcher Roberto Lujan (right) and Technician Shane Baxter (left) examine wild oat samples in a controlled environment cabinet. This cabinet is used to simulate ideal germination conditions.
Two types of seed dormancy
Wild oats can exhibit a combination of the two main types of dormancy.
Physical dormancy – in this case, a seed coat stops water from reaching the seed.
Physiological dormancy – this one is a bit harder to understand. In fact, a recent paper was titled “Dormancy, still a mystery”! This refers to a set of conditions that the seed must be exposed to before it will germinate such as time, temperature and light. In other words, in wild oats, the seed coat may be damaged and water able to reach the seed, but if the seed is in a state of physiological dormancy, it still won’t germinate.
This AHRI research is focused on physical dormancy.
AHRI Research Technician Shane Baxter uses the mechanical thresher to scarify wild oat seed and trigger germination.
Enter the Haldrup seed thresher
While spending hours on end picking up wild oat seeds and poking them with a needle, the researchers and technicians had plenty of time to think! There must be a better way. This is not dissimilar to the thoughts going through the heads of farmers sewing and carrying bags of grain in the early days, but that’s another story.
Manual puncturing of individual wild oat seeds to trigger germination. A time-consuming exercise that researchers working on this species must do.
The Haldrup LT-15 laboratory benchtop thresher, made in Germany*, is a common piece of research laboratory kit. Eight populations of wild oats were grown in plots and the seed hand harvested for this research. The Haldrup thresher was tested at a range of speeds and times, along with a suite of other common lab techniques used to break physical dormancy, including sulphuric acid, sandpaper, exposure to sodium nitroprusside (NO donor SNP), and partial endosperm removal (by hand).
*The AHRI team conducted this research using a Haldrup LT-15 laboratory benchtop thresher, but other similar research threshing machines are likely to achieve a similar result.
And the winner is…
Manual extraction of the caryopsis plus needle puncture.
But that is way too hard and time-consuming, so the people’s choice award goes to the Haldrup LT-15 laboratory benchtop thresher from Germany.
Wild oat germination (%) from a range of treatments to remove physical dormancy
The Haldrup benchtop thresher didn’t achieve the highest germination percentage in this research, but it is the quickest and most practical.
Germination of wild oat after the mechanical thresher treatment was applied. The smaller white grains are the caryopsis which are contained within what we see as darker seeds (husk). When the treatment is applied, some caryopses remain inside the husk, but the treatment is so effective that germination is still possible.
Wild oat growth
Seeds treated with the Haldrup thresher at 1500 rpm for 5 seconds, as well as seeds treated with the standard practice of needle puncture, were germinated and wild oat plants were grown. The growth of both populations was the same, demonstrating that the Haldrup thresher is an acceptable means of germinating seeds for research purposes.
A leaf area meter was used to determine whether mechanical scarification affected plant growth. The results indicated that wild oat growth is not affected.
Summary
There’s nothing like a boring job such as puncturing individual wild oat seeds with a needle to get the creative juices going in the search for a better way. Perhaps the saying should go “Boredom is the mother of invention”! This research is a win for wild oat research technicians the world over. A niche group of people but I’m sure they’re very appreciative nonetheless!
The AHRI team wishes you a safe and happy holiday season.
Wild oat is a herbicide resistance-prone global weed species that causes significant economic losses in dryland and horticultural agriculture. As a result, there has been a significant research effort in controlling this species.
Species
Australian Herbicide Resistance Initiative (AHRI)
