Project Overview
Commodities
Practices
Proposal summary:
Porcini mushrooms (Boletus spp.) are culturally and economically significant edible ectomycorrhizal fungi (EMF), commonly harvested in natural and cultivated chestnut forests spanning Europe1 and Asia2. Prior to the devastation of chestnut blight3, Boletus spp. were closely associated with American chestnut4,5, though porcini-chestnut mutualism has not yet been pursued in North American agroforestry6. To develop this practice here, more research is needed into the basic biology of porcini as it relates to the inoculation of Chinese chestnut seedlings1,6–9. Confounding this challenge, “mycorrhiza helper bacteria (MHB)” appear necessary for porcini fruiting in chestnut-porcini orchards overseas11, highlighting the importance of a healthy soil microbiome to successful inoculation. A related barrier to establishing chestnuts in the region is a general lack of ectomycorrhizal species and microbial diversity in legacy agricultural soils12. Encouragingly, there is a significant, positive relationship between low-tech EMF inoculation and chestnut seedling performance on former hay ground13. If porcini inoculation proves successful, future research could assess porcini inoculation effects on chestnut growth, as well as porcini harvest and farmer income. To our knowledge, no chestnut grower in North America has yet derived additional income by selling the fruiting bodies of EMF from their orchard.
Project objectives from proposal:
Solution:
Our study examines the viability of porcini-chestnut agroforestry by: 1. Evaluating three inoculation techniques (mother tree, liquid culture, spore solution) for mycorrhizing chestnut seedlings; and 2. Establishing a commercially available culture for porcini that is native to the SARE NC region.
Porcini are a group of closely related species16. Porcini have successfully colonized chestnut seedlings from liquid mycelial culture, enhancing growth and nutrient uptake rates under laboratory conditions9. Another inoculation technique, the “mother-plant method,” uses mature myccorhized trees to inoculate seedlings 18. Both liquid mycelial culture19 and the mother-plant method6 have been used to commercially produce the culinary “saffron milkcap” EMF in pine plantations and are intuitive, cost-effective strategies for EMF inoculation. We will test these techniques in a North American setting with porcini and Chinese chestnut.
If these techniques are successfully implemented in North American orchards, they offer long-term co-benefits to farmers. EMF form mutualistic relationships with their host trees, increasing nutrient uptake, growth rates, and drought resistance 2,14,15. After inoculation with EMF, chestnut seedlings planted in former hay fields exhibit improved growth rates and drought resistance13, which is desirable within a context of climate change. Inoculating chestnuts with porcini may improve the growth rates and survival of chestnut seedlings during the critical establishment period. Additionally, porcini mushrooms themselves could be a valuable secondary crop. Research using spore solutions and existing porcini sites to inoculate chestnut seedlings found that the spore-inoculated seedlings produced porcini mushrooms after 10 years17. Inoculated plantations can yield 36 lbs/acre/year of dried porcini20,21, which if sold at $15.10-$148.52/lb16 could generate $544 - $5,346/acre/year, making porcini more valuable than the chestnuts depending on price realization.
Methods:
400 chestnut seedlings will be grown at the nursery, in pots and in air pruning beds at the Camp Washington Perennial Farm in Cincinnati. These will be assigned a treatment randomly and introduced to their respective treatment conditions in Summer 2025. All 400 seedlings will be watered as needed for the remainder of the grant cycle. 6 months after inoculation, 10 seedlings from each treatment will be destructively sampled and sent to Cosmos ID, a contract laboratory, for sequencing following protocols described in Epp Schmidt et al 24,25. Outplanting of all seedlings is planned for early summer 2027, after this grant cycle is completed.
Mother Tree Treatment
A known porcini host tree location will be selected from 26 candidate locations in Ohio where porcini have been collected in the past. 100 seedlings will be planted in mother tree root zones in July 2025. Seedlings will be mulched and protected from deer with cages.
Liquid Culture Treatment
100 seedlings will be removed from their pots, submerged in an aliquot of the liquid mycelial culture and repotted in freshly prepared potting mix in July 2025.
Spore Solution Treatment
100 seedlings will have an aliquot of fresh spore solution applied in summer 2025. The solution will be prepared using the sporocarps of fresh, wild-harvested porcini from oak forests in the region. It will also contain 4 oz of soil from underneath the volva of each harvested sporocarp.
Control
100 seedlings will be grown from seed in nursery beds, not pots, and will not receive inoculation, yet will receive the same sterilized soil media. Testing the soil microbiome of these seedlings will allow us to control for two (2) potential effects: an increase in mortality due to transplant shock in the two treatments; and a relationship between soil microbiome in potting medium and seedling mycorrhization. We do not expect porcini to be present in the potting medium.
ATTACHED: Works_cited