What this Article is About
Being involved in numerous Technology Implementation Projects in many companies I realized that the individual pollen supply chains for a given crop are often fairly similar, and that the main challenges the production researchers are tackling are common too. With my posts I try to condense my impressions gathered over many years in many countries and provide useful ideas for experiments, practical recipes and suggestions for process optimization.
In my previous blog post on ‘How Pollen Quality Affects Seed Set’, we discussed the characterization of the pollination process, a key step in Solanaceae and Cucurbitaceae hybrid seed production. That post was focused on a deeper understanding of pollination. Now, we go a step further and make use of that knowledge.
The key questions of this post are:
- If there is a pollen quality threshold to achieve a good seed set, what does that mean for our in-house pollination routine?
- What is a pollination recipe and how does it look like?
- How can we optimize pollen consumption?
In the following sections, we will highlight the benefits of systematic pollen analysis. Based on cross-specific pollen and seed yield data we will derive practical and easy-to-read pollination recipes. Those recipes aim at ensuring sufficient pollination and preventing waste of precious pollen.
Looking at your own processes today, do you think you get the maximum out of them?
Let’s have a closer look.
Creating Pollination Recipes
Determine Pollen Viability Needed for a Full Seed Set
As we have seen in our previous article, different crops and even different crosses of the same crop show individual correlation patterns between viable pollen load and seed set.
Correlations between viable pollen load on the stigma and seed set.
How Much Pollen is Enough?
If you have missed our previous post, click here to get to the corresponding chapter.
In some cases, even with the highest load of viable pollen it is impossible to reach the maximum possible seed set (Example 1). In others, only the highest pollen quality and quantity result in the maximum output (Example 2). Some cases even show an early saturation phenomenon, for which even low or intermediate pollen qualities result in a good seed set (Example 3).
Take Home Message
This leads us to a first important conclusion: If you apply the same pollination strategy to all the examples above, you are operating far from the optimum. Only by knowing the individual pollination properties of your crosses you will be able to create specific pollination recipes.
Optimize Pollen Usage
Let’s assume you have done your homework and know the specific threshold viability to get a full seed set. What can you do now with this information?
As an example, you can generate the following color-coded chart which indicates how much seed yield would be expected for a particular cross with a given stock pollen viability (x-axis) and dilution with a diluent (y-axis). The chart is derived directly from the saturation curves obtained from correlating the relation between viable pollen load and seed yield. Therefore, it also reflects the compatibility between mother and father lines.
Dilutions can be done with dead pollen or diluents such as lycopodium spores. The dilution ratios are calculated based on
- The fact that the number of viable pollen grains on the stigma depends on the pollen viability and the quantity used for pollination
- The assumption that a change in viable pollen load can be achieved by either a change of pollen viability or quantity (e.g. increasing either pollen viability or pollen quantity by 10 % will lead to an increase in viable pollen load of 10 %)
In your daily routine, you would simply take your pollen sample from storage, measure the viability, and check on the previously established color-chart whether the quality is good enough and whether you can even dilute it.
Maybe you do not only want to make sure you obtain a good seed set, but also optimize pollen usage. Then make sure that you don’t go too far into the green area. This is the saturated area and an increase in viable pollen load will not significantly increase the seed set anymore. Try to always operate close to the saturation point to not waste precious pollen. As an example, this can be 95 % of the theoretical maximum seed set obtained from the saturation curve fit.
Confused by too many colors? The following 3 tasks help you getting started with the implementation of optimized pollination recipes.
Getting Started with Your Pollination Recipes
Task 1: Make the recipe easy to read and to follow
The color-coded charts may not be unambiguous (is light green already good enough?…). Always formulate instructions with as little space for interpretation as possible. Why not using a line plot instead? Or even a table already indicating quantity of pollen and diluent?
An illustration of a simple-to-read pollination recipe for the 3 example crosses introduced earlier is here:
Task 2: Implement Pollen Quality Monitoring of Your Pollen Stocks
Having an overview of the quantity and quality of your stock samples helps to anticipate shortages and allows you to efficiently create pollen mixtures with target viabilities, as described in Task 3.
Task 3: Enhance Your Pollen Supply Chain
Implement a new step in your pollen management workflow which aims at achieving target viabilities. This step is between storage and pollination.
What's a Pollen Supply Chain?
We have come up with the concept of the Pollen Supply Chain to better illustrate important quality gates for pollen analysis.
In this step, you make sure that the pollen samples used for pollination have the target viability. Create such pollen batches by mixing above-threshold samples with a diluent or low-quality pollen. Verify the outcome and the homogeneity using the Pollen Analyzer.
Increasing Yield and Saving Money
Carefully characterizing your pollen supply chain and scrutinizing pollen management allows you to optimize the production process on several levels:
- Monitor the pollen quality in the field and only collect pollen when the quality is well-above the target viability. Remember, after collection, the pollen quality continuously decreases throughout all the steps of the supply chain (processing, storage, transportation…), it never increases. By the way, if you do not reach the quality targets, have a look at our previous post about plant stress and aberrant pollen grains.
- Know your pollen stock. Improve the yield of low-compatibility crosses by always taking the best possible pollen sample from your stock.
- Dilute high-quality pollen according to your pollination recipe and save material.
- Optimize the timepoint of pollination to ensure the highest stigmatic receptivity.
- Make the manual pollination process more reproducible and use just the right amount of pollen. This helps you reducing the area and efforts spent on pollen production, collection and processing. It also prevents yield loss due to insufficient pollination.
- A better understanding of your process will help you making more precise and reliable yield forecasts.
Taken the findings of our previous blog articles together, I think there is a lot of potential for optimization throughout the entire pollen supply chain of many crops. Do the experiments, do the math, come up with easy-to-read and tailored recipes, and eventually increase the seed yield and save money.
Take Home Messages
- The Solanaceae pollen supply chains are very diverse and extensive, and pollen qualities can range from very poor to superb.
- The implementation of quality checkpoints in all critical steps along the supply chain helps to ensure high-quality.
- The Amphasys Pollen Analyzer detects mature viable cells, mature dead cells, aberrant cells and diluent particles.
- Aberrant cells have been associated with plant stress, and they occur in virtually every sample. In a considerable fraction of samples they are strongly contributing to a decreased pollen quality.
- There is a crop- and cross-specific correlation pattern between pollen viability and seed set. Characterizing this relationship allows you to formulate tailored pollination recipes.
- Pollination recipes aim at making the pollination process more reproducible, and prevent insufficient pollination and waste of pollen.
- Systematic pollen quality monitoring and the use of a tailored pollination recipe have the potential to result in a higher seed yield and reduced surface for pollen production.
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