Selection of mycorrhizal inoculum for California Native Plants

Selection of mycorrhizal inoculum forCalifornia Native Plants• Tree of Life Nursery?• What is a mycorrhizal fungi?• Why and how do we inoculate our plants withmycorrhizal fungi?• Why selection?

We GrowCalifornia native plantsTree of Life Nursery

Tree of Life Nursery• Most of the plants of theTree of Life nursery areinoculated with VAM 80.• VAM 80: Mycorrhizalinoculum propagated atthe nursery.

What is a mycorrhizal fungi?In the rhizosphere there are certain kind of fungi which arespecialized to colonize the roots of most plants and formwith them a symbiotic organ called

Where do we find mycorrhizal fungi?• Under naturalconditions mycorrhizalfungi are ubiquitousThey are everywhere• We find them in the soilin the rhizosphere.

“The majority of plants strictly speaking do not haveroots, they have mycorrhizas”http://www.kent.ac.uk/bio/beg

What is a mycorrhiza?Mykes (greek) = fungusRhiza (latin) = rootBoth partners benefit from the association

Mycorrhizal fungi:A bridge between plants and soil resources• The fungi produce fine thread-like filaments that grow inand around the roots and develop an underground networkthat helps the plant to acquire mineral nutrients from thesoil.• The plant provides a “home” for the fungus and a supplyof Carbon.Their association enables them to survive, grow and reproduce more effectivelyhttp://www.ffp.csiro.au/research/mycorrhiza

Mycorrhizal networksHyphae grow out into the soil, enlarging the absorbingcapacity of the root system, and acquire phosphate andother nutrients that often are too distant to be available tothe relatively coarse root system.Zhu, Y. et al. 2001. Backseat driving? Accessing phosphate beyond therhizosphere-depletion zone. Trends in Plant Science 6:194.

Value of mycorrhizal colonization in nurseryconditions• Increases plant growth• Increases planttolerance to water andsalt stress-VAM80+VAM80Dichelostemma capitatum0.04• Increases resistanceagainst pathogensBulb weight (g)0.030.020.01-AM+AM0

Types of mycorrhizal associationsEctomycorrhizasForest treesArbuscular mycorrhizasHerbaceous plants, shrubs, ornamentals,Fruit trees, vegetable crops, turf grassesEricoid mycorrhizasEricaceaeOrchidaceous mycorrhizasOrchids

Arbuscular mycorrhizal inoculumHyphaeColonized root fragmentsSpores

*Bever et al. 2001. Bioscience 51(11):923-929.Arbuscular mycorrhizal fungi: More diverse than meets the eye,and the ecological tale of why*• Spores are swollen structures• 160 species form mycorrhizaswith 300,000 plants• AM fungi are not functionallyequivalent• Different geographic isolateshave different effects in plantgrowth and protection

ProductCommercial Mycorrhizal Inoculum1Glomus intraradices, G. mosseae, G. brasilianum, G. clarum,G. deserticola, G. monosporus and Gigaspora margarita2 Endo/Ecto mycorrhizal inoculum3 Glomus intraradices4 Glomus intraradices5 Glomus intraradices6 Glomus intraradices7 Glomus intraradices, Glomus aggregatum and Glomusmosseae8 Glomus intraradices9 Glomus intraradices, Glomus aggregatum and Glomusmosseae10 Glomus intraradicesGianinazzi, S., Vosatka, M. 2004. Inoculum of arbuscular mycorrhizal fungi for production systems: Science

Propagation of arbuscular mycorrhizal fungiAm fungi are obligate symbiontsPot culturesSoil and root tissue are collected from a site to start “trap cultures”and boost the number of propagules for isolation and further multiplication

Beyond the big plant - little plant• Benefits for plant growth and protection• Benefits in soil structure• Benefits for nursery• Benefits for environmentMultifunctional mycorrhizas

Top soil removalSoil compactionRestoration and revegetationDisturbed sites/constructionEliminates or severly reduces the mycorrhizalinoculum potential of the soil

Arbuscular mycorrhizal fungi:The soil’s superglue• Fungal hyphae linksoil particles• AM fungi produce theglycoprotein glomalinMycorrhizal fungi influence soil structure

Mycorrhizal fungi: An environmentallyfriendly alternative• Valuable tool to minimize the use offertilizers and pesticides

How do we incorporate mycorrhizal fungi at theTree of Life Nursery?1. AM fungiPlants in nurseries are grownin soilles mixes that do notcontain mycorrhizal fungi• Mycorrhizal associations arethree way interactionsbetween plants, growingmedium and soilPlantSoilFungi

PlantMycorrhizasCOST/BENEFITNutrient uptake - CarbonSoilSoilAM fungiAM fungiThe combination of these three factors will determine the successful applicationof mycorrhizas at the nursery

Mycorrhizal colonization is not always beneficialAre mycorrhizas always mutualisms?• The infectivity and effectiveness of aparticular AM fungi vary with the plant andgrowing medium• The choice and preparation of pottingmixes, fertilizers and pesticides is crucial.

Different products had different percentages ofmycorrhizal colonization in different mixesProduct 2504540Product 1aaaAM %50403020100aba35soilAM %302520151050Nursery mixSunshineAM %50403020Product 3baa100Corkidi, L. et al. 2004. Assessing the infectivity of commercial mycorrhizalInoculants in plant nursery conditions. J. Env. Hort. 22(3):149-154.

Selection of compatible mycorrhizal fungus/hostandgrowing media combinationsmycorrhizalnonmycorrhizalCorkidi et al. 2005. Effectiveness of commercial mycorrhizal inoculants on the growth of Liquidambarstyraciflua. J. Env. Hort. 23(2):72-76.

Sources of mycorrhizal inoculumVAM 80Spores, hyphae androot fragments colonized by Glomus intraradicesNative AM fungi

Highly infective species of woody and herbaceous plantsin a wide range of conditions.

Nursery versus environmental conditionsMycorrhizal fungi needed to sustain seedlings at the nurserymay differ from those that will help establishment in a harsh site

What’s the best approach for the selection ofmycorrhizal inoculum?• Effects of mycorrhizal colonization on the growth ofCalochortus weedii var. intermedius

What’s the best approach for the selection of mycorrhizalinoculum?Are native populations of AM fungi appropriate for thepropagation of intermediate • mariposa \ lily?orIs the inoculation of the more aggressive fungi present inmost commercial inoculants, Glomus intraradices,more effective to promote survival, growthand reproduction?

Effects of mycorrhizal colonization on the growth ofCalochortus weedii var. intermedius• Bulbs of intermediatemariposa lily wereinoculated with• Top Soil• VAM 80• Sterile soil

Inoculum treatment Number of flowersNonmycorrhizal 7VAM 80 9Top Soil 18Bulbs inoculated with top soil had significantly more side branches and flowersthan those inoculated with VAM80, or than the non-mycorrhizal controls.

Successful application of mycorrhizas inhorticulture is a four way interaction

Ramiro (“Ramo”), Salvador, Sinfo, Toño,Chris Meloni, Jim Harrison,Becky Bohn and Daniel Evans