The relative merits of tetraploid and diploid perennial ryegrass

Perennial ryegrass remains the preferred choice due to its rapid establishment and resilience, with two distinct ploidy types: diploid and tetraploid.

The key genetic difference is that diploids have two sets of chromosomes (2n), while tetraploids have four (4n), influencing turf characteristics such as leaf structure, cell size, root development, and disease resistance.

Both ploidy types bring unique strengths, and their performance can vary depending on management practices and environmental conditions.

Understanding these differences is critical when selecting seed mixtures for sports pitches that require wear tolerance, fast recovery, and strong year-round visual quality.

Live ground cover & recovery

For sports pitches that endure heavy play, maintaining live ground cover and ensuring fast recovery are critical factors.

The BSPB 2025 Seed Guide measures these attributes to assess how well a variety maintains density under wear conditions and how quickly it regenerates after stress.

Diploid Performance:

• The top five diploid varieties average 8.1/10 for live ground cover.
• Their recovery score averages 7.5/10, meaning they consistently restore density after wear.

Tetraploid Performance:

• The top five tetraploid varieties average 5.6/10 for both live ground cover and recovery.
• This suggests slower regeneration, which may require additional management input in high-use situations.

Practical Takeaway:
For pitches that experience frequent wear and need rapid surface regeneration, the data indicates that top-performing diploids provide a notable advantage. However, tetraploids may still have a role where other factors, such as colour retention or stress tolerance, are prioritised.

Visual Merit

The visual quality of a sports pitch plays a major role in both playability and presentation. The BSPB 2025 Seed Guide scores visual merit based on factors such as sward density, leaf fineness, colour, and disease resistance.

Diploid Performance:

• The top five diploid varieties average 8.1/10, reflecting their ability to create a dense, uniform, and visually refined sward.

Tetraploid Performance:

• The top five tetraploid varieties average 5.3/10, often due to coarser leaf blades and lower shoot density.

Practical Takeaway:
For stadiums and elite sports facilities where a fine-textured, uniform playing surface is essential, the BSPB data indicates that diploids remain the preferred option. However, in lower-maintenance settings, where absolute visual quality is less of a priority, tetraploids could still be considered.

Fineness of Leaf

Leaf fineness contributes to turf uniformity, impacting both aesthetics and ball roll. Finer leaves create a smoother, more professional playing surface.

Diploid Performance:

• The top five diploid varieties score an average of 7.4/10 for leaf fineness, reinforcing their ability to produce a high-quality, dense sward.

Tetraploid Performance:

• The top five tetraploid varieties average 4.8/10, reflecting their broader, coarser leaf blades.

Practical Takeaway:
While tetraploids may offer other benefits, for premium sports pitches where surface consistency is critical, the finer leaf structure of diploids gives them an edge.

Red Thread Resistance

With limited fungicide options, disease resistance is increasingly important in turf management. The BSPB 2025 Seed Guide measures resistance to Red Thread, a common turf disease—though this is less relevant in stadia settings where intensive management minimises its impact.

Diploid Performance:

• The top five diploid varieties average 4.9/10, indicating moderate susceptibility.

Tetraploid Performance:

• The top five tetraploid varieties average 7.3/10, suggesting higher resistance.

Practical Takeaway:
For high-input stadium pitches, Red Thread resistance is unlikely to be a decisive factor. However, for lower-input facilities where disease control options are limited, selecting tetraploids with strong Red Thread resistance may be advantageous.

Winter and Summer Colour Retention

Maintaining consistent colour throughout the year is important, especially where nutritional inputs are restricted. The BSPB 2025 Seed Guide provides ratings for winter greenness and summer greenness, with higher scores indicating darker green shades.

Winter Greenness:

• Tetraploids: 7.1/10 (stronger winter colour retention).
• Diploids: 5.2/10 (reduced winter colour).

 Summer Greenness:

• Tetraploids: 7.2/10 (better retention in hot, dry conditions).
• Diploids: 5.6/10 (more prone to fading under drought stress).

Practical Takeaway:
For locations where maintaining turf colour is a priority—especially in cold winters or prolonged dry summers—tetraploids have an advantage. However, in stadium environments where colour is managed through nutrition and irrigation, this factor may be less significant.

Choosing the right varieties for your pitch

The best choice between diploid and tetraploid perennial ryegrass depends on the specific needs of each site.

Where Diploids Excel:
✔️ High-wear sports pitches requiring strong ground cover and fast recovery.
✔️ Stadium pitches demanding fine leaf texture and high visual quality.
✔️ Premium turf surfaces where density and uniformity matter most.

Where Tetraploids Excel:
✔️ Lower-input facilities needing better Red Thread resistance.
✔️ Sites prioritising year-round colour in cold winters or dry summers.
✔️ Blends where improved stress tolerance is desired.

Final consideration: A balanced approach?

While diploids dominate in key areas like wear tolerance and aesthetics, tetraploids bring useful traits for specific conditions. Some turf managers may incorporate tetraploids into mixtures to benefit from their colour retention and disease resistance, while still relying on diploids for core performance attributes.

By focusing on independent BSPB data, turf managers can make informed decisions tailored to their pitch conditions, balancing wear tolerance, recovery speed, seasonal appearance, and disease resilience.