Wheat Varieties and Mycorrhizal Fungi

Trial evidence showing that modern wheat varieties differ significantly in their ability to form associations with arbuscular mycorrhizal fungi (AMF), with implications for variety choice in no-till systems.

Background

Approximately 74% of flowering plants form associations with AMF. Benefits of colonisation:

  • Increased plant uptake of nutrients and water
  • Increased tolerance to biotic stress (pathogen infection)
  • Increased tolerance to abiotic stress (drought)
  • Improved soil structure through release of glomalin

Problem: Many current farming practices have depleted AMF levels in soil:

  • Some pesticides and fertilisers
  • Non-mycorrhizal crops (OSR, sugar beet) breaking the fungal network
  • Cultivation practices damaging the hyphal network

No-till farming is a good environment for re-development of natural mycorrhizal populations. The Essex trial farm used for this research had very high background levels of AMF — the result of 10+ years of no-till practice.

The Trial

Conducted by: Lottie Alves, Procam Location: No-till farm, Essex (10+ years no-till; high background AMF levels confirmed by soil testing) Previous crop: Lucerne Drill: Autumn 2016 Varieties: 9 varieties + the farmer’s own Group 4 wheat blend

Assessments:

  • March: Plants at tillering stage
  • July: Just before harvest

Method: Wheat roots stained with dye that binds to AMF structures within root cells. Proportion of root segments with mycorrhizal structures assessed visually under microscope. AMF structures appear dark blue; plant cells remain white/light blue.

Results

All Varieties Can Form AMF Associations

All nine varieties tested were capable of AMF colonisation — this is not a binary yes/no trait.

Colonisation Increased March → July

Overall colonisation levels increased from March to July:

  • Likely due to AMF becoming more active as temperatures increase
  • This temperature effect also reduced variability between varieties in July (less mycorrhizal varieties “catch up”)

KWS Bassett and KWS Silverstone Outstanding

Of all varieties trialled, KWS Bassett and KWS Silverstone showed the highest mycorrhizal colonisation:

Timing Best variety Second
March KWS Silverstone KWS Bassett
July KWS Bassett KWS Silverstone

KWS Silverstone at March assessment: double to five times the proportion of root area colonised compared to other varieties — a very large difference at this early stage.

By July the gap reduced as other varieties caught up, but Bassett and Silverstone still ranked 1st and 2nd.

“These two varieties are potentially the best to grow in no-till systems.”

Implications for No-Till Variety Choice

This trial raises an additional criterion for variety selection in no-till systems beyond the conventional RL metrics (yield, disease resistance, lodging):

Mycorrhizal compatibility — varieties that can harness existing AMF populations more effectively may:

  • Access nutrients and water more efficiently
  • Benefit more from the accumulated fungal networks in established no-till soils
  • Require less artificial nutrient input

The trial was in its second year (continuing) at the time of publication. Procam presented preliminary second-year results at Groundswell 2018, Stand E5.

Caveats

  • Single-farm trial (high AMF background — results may differ on lower-AMF soils)
  • Year 1 data only (at time of publication); second year ongoing
  • Other varieties may perform differently under different soil or weather conditions
  • Colonisation levels measured, not yield benefits — yield impact not yet quantified

Sources

  • [[sources/dd-issue-02]] — “Arbuscular Mycorrhizal Fungi and Modern Wheat Varieties”, Lottie Alves (Procam), Direct Driller Issue 2 (June 2018)

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