Testing soil microbial stimulators for enhancing vine health

By Justine Vanden Heuvel and Mariam Berdeja, School of Integrative Plant Science, Cornell University

What are mycorrhizae?  

Grapevines benefit from a symbiotic relationship with arbuscular mycorrhizal fungi (AMF).  Together the vine and the AMF form mycorrhizae, which play an important role in vine health, grapevine nutrition, and water relations.  A range of products – generally referred to as soil microbial stimulators – are sold with the goal of encouraging the formation of mycorrhizae. While anecdotal reports from the grape and wine industry suggest these products can provide a benefit to the vine, none have been systematically tested in Northeast vineyards.  

Arbuscular mycorrhizae penetrates the cortical cells of roots to form arbuscules (Fig. 1) to aid nutrient exchange. The hyphal coils are long, branched portions of the fungus that act as a virtual root system for the vine.  The hyphae enter the root and create vesicles for nutrient storage structures where nutrients are transferred between fungus and plant (arbuscules).

Fig 1. Arbuscular mycorrhizal fungal structures in the fine roots of grapevine. Samples were collected 5 months after inoculation. A: Arbuscules, HC: Hyphal coils, V: Vesicles, 40x magnified.

Greenhouse experiment

In order to screen products for further testing in vineyards, we initiated a greenhouse trial in 2019 using potted vines of Cabernet Sauvignon (own-rooted) and the rootstock 3309C. We decided to use only products that contained the species Glomus, as it has been shown to improve AMF formation on other crops.  (Note that many biofertilizers are for sale that do not contain Glomus). In the experiment, five commercial biofertilizers were compared to a control (Table 1).  Five months following application, the vines were destructively harvested to determine whether the biofertilizers had resulted in the formation of AMF and whether vine growth or nutrient acquisition was improved with the treatments. 

Product numberNameContained species 
1Big Foot ConcentrateGlomus intraradicesGlomus mossaeGlomus aggregatumGlomus etunicatumN,P,KHumic acidsSoftwood biocharWorm castings 
2BioOrganicGlomus mosseaeGlomus clarumGlomus aggregatumGlomus intraradicesGlomus deserticolaGlomus etunicatumGlomus monosporusGigaspora margaritaParaglomus brasilianum 
3MycoGrow SolubleGlomus intraradicesGlomus mosseaeGlomus aggregatumGlomus etunicatumbGlomus deserticolaGlomus monosporumGlomus clarumRhizopogon villosulusRhizopogon luteoulusRhizopogon amylopogonRhizopogon fulviglebaPisolithus tinctoriusSuillus granulatusLaccaria bicolor 
4MycoApply Endo GranularGlomus mossaeGlomus intraradicesGlomus aggregatumGlomus etunicatumClay 
5MycoApply All PurposeGlomus mossaeGlomus intraradicesGlomus aggregatumGlomus etunicatumRhizopogon villosullusRhizopogon luteolusRhizopogon amylopogonRhizopogon fulviglebaPisolithus tinctorius

Biofertilizers increased colonization by AMF

All five products tested increased the proportion of roots that were colonized by AMF (Fig. 2), although the Cabernet Sauvignon roots responded more strongly to the products than the 3309C roots. 

Fig 2. Significance differences were found among the treatments for AMF structures in cv. Cabernet Sauvignon and rootstock 3309C

Biofertilizers increased dry weight of vine organs

In general, the biofertilizers increased the dry weight of shoots, roots, and trunk in the vines (Fig. 3) likely as a result of increased nutrient content in the leaves (data not shown).  Most micro and macronutrients were increased in concentration in the treated vines. 

Fig 3. AMF increased shoot trunk and root biomass for all the treatments in cv. Cabernet Sauvignon and rootstock 3309C

Summary

All five of the products tested warranted further testing in the vineyard.  In a complimentary vineyard trial funded by the New York Farm Viability Institute, the products have also demonstrated their ability to form AMF in field-grown vines as well, although whether those AMF structures are increased long-term without repeated applications is unknown.

Acknowledgements

We thank the Pennsylvania Wine Marketing & Research Board for funding this research. 

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