Variable effect of
Trichoderma Bio-inoculants
on Ectomycorrhizal
colonisation of Pinus radiata
seedlings.
Rhys Minchin1,
2
Robert Hill ,
Hayley Ridgway1,
Leo Condron1,
1
Eirian Jones
1
Lincoln University, PO Box 84, New
Zealand
2
Biodiscovery New Zealand Ltd,
Auckland,
New Zealand
METHODS
INTRODUCTION
Trichoderma bio-inoculants, applied to Pinus radiata seedlings in the nursery, provide
protection from infection by Armillaria spp. during their establishment in forestry
plantations. Trichoderma spp. suppress plant pathogens through mycoparasitism,
antibiosis and their highly competitive saprophytic ability. These mechanisms could
affect ectomycorrhizal (ECM) colonisation of P. radiata seedlings. The effect of
Trichoderma inoculation on ECM growth and colonisation was investigated in both a
pot experiment and in a dual plate bioassay.
Pot trial
Eight treatments were tested for their effect of ECM colonisation
of P. radiata seedlings. These were six individual Trichoderma
isolates (LU655, LU659, LU663, LU686, LU688 and LU695), one
mix of all six isolates and an untreated control.
Potting media (Yates composted bark plus Osmocote (28 Kg m3 )) was inoculated with Trichoderma strain(s), to give an
inoculum concentration of approximately 2x108 cfu ml -1 .
Container trays (12 x 8 cell/tray) were filled with inoculated
media before planting Radiata pine seed. Trays were set out on
raised nursery beds in a randomized block design. Twenty trays
were used for each treatment and 45 seeds were planted in each
tray. Each treatment contained five replicates of four trays per
replicate. Percentage ECM colonisation was assessed after 3
months growth.
Dual plate Bioassays
Dual plate bioassays were conducted to assess the individual
interaction between five ECM species (Suillus granulatus, S.
luteus, Rhizopogon spp., R. parksii, and R. luteolus) and six
Trichoderma isolates.
Fig. 1 Armillaria infection in Pinus radiata plantation.
RESULTS
Pot trial
Dual plate Bioassays
A Trichoderma isolate specific effect on the overall percentage ECM colonisation was
observed. Two Trichoderma isolates (LU659 and LU686) increased the percentage
ECM colonisation while the other isolates, including a mix of all isolates, had no
effect over the untreated control (Fig. 2).
In dual plate bioassays, isolate specific interactions were seen.
Suillus granulatus was not mycoparasitised or out-competed by
any of the six Trichoderma isolates (Fig. 3). Rhizopogon parksii
was out-competed by all Trichoderma isolates and, although not
mycoparasitised, was extensively overgrown by Trichoderma
hyphae (Fig. 4).
Fig. 2. Percentage ECM colonisation of Pinus radiata seedlings after
treatment with six different Trichoderma isolates or a mix of six isolates,
after 3 months growth. Treatments significantly different (P 0.05)
from the control denoted by *
(a)
(b)
Fig. 3. Dual plate bioassay with Trichoderma
(c)
Fig. 4 Rhizopogon parksii dual plate bioassay (a) control; (b) against
Trichoderma isolate LU659, showing overgrowth of R. parksii colony by
Trichoderma; (c) against Trichoderma isolate LU663, showing inhibition of
R. parksii mycelial growth.
CONCUSIONS
While two Trichoderma isolate individually increased ECM colonisation, these isolates
in a composite mix had no effect on ECM colonisation. Changes in the diversity of
ECM species colonising the roots could have occurred, as indicated by the dual plate
bioassays where differential isolate specific interactions between the two classes
of fungal symbionts occurred. The effect of Trichoderma application on colonisation
of P. radiata seedlings by the five ECM species is currently being investigated.
ACKNOWLEDGEMENTS
This research is funded by New Zealand Foundation for Research
Science and Technology (LINX0304) and PF Olsen and Co Ltd.