Variety blend tool for winter wheat

Varietal mixtures increase genetic diversity within a field and may help slow the spread of some diseases and reduce the risk of resistance breakdown. Based on Recommended Lists (RL) data and parental diversity information, use the variety blend tool to select three-way or four-way mixes for on-farm testing.

The use of mixtures has increased. For example, in France it is estimated that the area of bread-making wheat varieties grown in mixtures has more than doubled recently – from around 5% in 2017 to around 12% in 2020 (source: FranceAgriMer). Although area information is unavailable for the UK, interest in blends has increased.

Although several scientific studies have shown that the technique has promise as a disease management tool, it is a complex area – involving numerous genetic and environmental interactions. As a result, it is best to test the approach on the farm, before adopting a mix more widely.

More complex mixtures – with several disease resistance profiles – are more likely to result in a greater disease reduction. A mixture of at least three varieties is best. Crude mixtures are considered to work better than homogeneous mixing.

It is important to consider the quality implications of each mix and the requirements of grain buyers. Differing maturity dates between the varieties in the mix does not tend to be an issue. Both wheat and barley mixtures for feed and wheat for distilling are generally acceptable to markets. However, maltsters do not currently accept mixtures.

The dashboard has three tabs:

Tab 1 – Metric 1 RL component data values for each variety, based on values published in the RL.

Here you can explore the strengths and weaknesses of each variety. This information can be used to exclude or include varieties within mixtures. To do this, use the 'Blend must contain' and/or 'Blend must NOT contain' filters in top-right corner of the tool.

Tab 2 – Calculations for three-way blends.

Tab 3 – Calculations for four-way blends.

Each tab includes an array of functionality, such as data filters and sorting tools. The best way to learn about these functions is to click around to observe what happens. Do not worry, it is not possible to break the tool and all actions can be undone.

For each mix, metric 1 is based on the values associated with selected Recommended List (RL) variety component options, which are:

• Brown rust (1–9, as published)
• Yellow rust (1–9, as published)
• Septoria tritici (1–9, as published)
• Lodging – PGR (1–9, as published)
• Hagberg Falling Number (as published or 1–9 weighted*)
• Specific weight (as published or 1–9 weighted*)
• Untreated yield (as published or 1–9 weighted*)
• Protein content (as published)

The metric 1 score is simply the total of all selected options divided by the number of varieties in the mix.

If Hagberg Falling Number, specific weight or untreated yield components are selected (from the filter above the blend table), along with another component, then the RL value is converted to a 1–9 score, where:

• ‘1’ represents the minimum value
• ‘9’ represents the maximum value
• Other values (between these points) are determined by a simple linear regression

The use of weighted components avoids the influence of large numbers, associated with these components, on the total.

Metric 1 is based on the performance of single varieties in RL trials. As such, the tool needs to be used with caution and varietal mixes not considered as a recommendation.

In particular, the tool is not able to capture the complex interactions associated with varietal mixtures or predict relative performance.

However, the tool can aid the identification of mixes for subsequent on-farm testing.

For each mix, the metric 2 score considers the influence of multiple generations in the mix*.

The score is the mean of the parental diversity scores for every variety pair in that blend.

The parental diversity score for each pair comparison is calculated using the Jaccard Index:

1 - (Shared ancestors / Unique ancestors)

• Score 1 indicates that varieties in the blend share no ancestors.
• Score 0 indicates that all varieties in the blend share the same parentage.

*Based on NIAB winter wheat parentage data and Helium software. The NIAB data considers parents, grandparents, great grandparents and great great grandparents. For Helium, seven generations of parental relationships (parents and grandparents) are analysed by the variety blend tool.

Three example pairings in the four-way blend LG Skyscraper, KWS Kerrin, Gleam, Graham.

• Share one parent (KWS Santiago)
• 15 shared and 45 unique ancestors
• Calculation: 1 - (15/45) = 0.67

• Share one grandparent (Oakley)
• 7 shared and 53 unique ancestors
• Calculation: 1 - (7/53) = 0.87

• Share no ancestors
• 60 unique ancestors
• Calculation: 1 - (0/60) = 1.00

The metric 2 score for the LG Skyscraper, KWS Kerrin, Gleam, Graham blend is the mean of these three scores plus the scores for the other three variety pairings (details not shown):

(0.67 + 0.87 + 1.00 + 0.87 + 1.00 + 1.00) / 6 = 0.90

Use the 'Minimum parental diversity per variety pair in blend' filter to set a threshold value for parental diversity between any two varieties in the mix.

• Set the value as 0 to include all combinations
• Set the value to 0.1 to exclude any blends that feature (at least) two varieties with same ancestors
• Set the value to 1.0 to ensure that varieties in the blend share no ancestors

Metric 2 is only a proxy for genetic diversity. Even varieties that share no ancestors will share genes, including resistance genes. In reality, the influence of the ancestor will reduce with each generation.

When parentage is unknown ('orphans') a dummy name – such as 'W56 (Parent 1)' is used in the calculation software.

This tool is based on current RL winter wheat varieties. It does not feature non-RL varieties because it would add large amounts of complexity to the tool. However, the tool can be used to help design mixes that contain non-RL variety components.

For example, say variety X were a non-RL variety with weaknesses in septoria tritici and lodging resistance, the tool can be used to identify RL variety mixtures to help ‘offset’ them.

In this example, simply select the ‘septoria tritici’ and ‘lodging resistance’ component data options and identify the highest ranking RL variety mixes to consider blending with variety X.

Introduced into UK law, farm-saved seed payments contribute toward plant breeding and varietal development. Made to the British Society of Plant Breeders (BPSB), payments apply to eligible varieties that have been planted on a farmer’s own land using seed harvested from their own holdings (managed as the same business). The BSPB collects royalties on FSS for oats, barley, triticale, wheat and oilseed rape, in addition to several other combinable crops. Payments are made at the point of sowing (unless already paid by a processor). Farm-saved seed must not be marketed, purchased, given or transferred to another business for re-planting.