Plant Traits and Belowground Interactions dataset

Rootstock from existing R. idaeus plants of two cultivars; Glen Ample and Glen Rosa was
sourced from The James Hutton Institute’s (Dundee, UK) breeding stock. The
rootstock was washed with a 4% sodium hypochlorite solution, rinsed with water
then planted in twice autoclaved (with a 12hr gap between autoclave runs) compost
(Keith Singleton sterilized loam, Nethertown, UK) and grown on under-heated
benches in a controlled greenhouse environment (16:8 days at 18˚C). Four weeks
after this, plants were transplanted into 1.8L pots containing 1.6L of a homogenized,
twice autoclaved 1:1 soil (Keith Singleton sterilized loam, Nethertown, UK) and
sand mix. Compost was autoclaved in batches to control for the possibility of
there being any nematodes living in the compost which could interact with added
treatments (Jagdale
et al., 2002). Plants from each cultivar were
equally and randomly distributed between the 4 treatments giving a replication
of 26 plants for each treatment. To account for any possible environmental
heterogeneity within the glasshouse the plants were then incorporated into
blocks each equally representing individuals from each treatment in a randomized
order to adhere to a randomized block design. Two weeks after the plants were
transplanted, and before any herbivore or EPN treatments were added, plant
height was recorded in order to be used later as a random effect in statistical
models to account for the initial variation in height between plants.

Five weeks after R.
idaeus were transplanted into individual pots, 40 O. sulcatus eggs were added into a 10mm indent in the soil surface,
20mm away from the stem of each plant. This egg density was selected to
simulate arrival of a gravid adult feeding on plants for several weeks (Clark et al. 2012). Four weeks after plants were
infested with O. sulcatus, EPNs were
added to plants, with control plants remaining untreated. Three weeks after
nematodes were added, the plants were harvested and O. sulcatus larvae were retrieved, counted and fresh mass taken. A
subset of half the plants were then freeze dried to ascertain dry mass (Fig 1). Otiorhynchus sulcatus eggs were taken from a culture of
adults maintained at 18˚C with a 16:8 light: dark cycle at The James Hutton
Institute, Dundee. The EPNs used in the experiment were purchased from
commercial suppliers and were advertised as being a specific line to control
for O. sulcatus. S. kraussei (Becker
and Underwood®, Littlehampton, UK) and H.
megidis (Biobest®, Milton Bridge, UK). They were both added to plants as
separate treatments at their recommended dosages. When formulated to the commercially recommended dosages this
results in approximately 9000 S. kraussei
added per pot and approximately 16000 H.
megidis added to each pot according to the product formulation guidelines.

This created a 2 × 4 factorial
experiment which was conducted under controlled conditions (16:8 days at 18˚C).
Two R. idaeus cultivars (Glen Ample
and Glen Rosa) were subdivided into one of four treatments. A control
treatment, where neither O. sulcatus
or EPNs were added, an O. sulcatus
‘only’ treatment where the herbivore was observed in the absence of EPNs and
two treatments in which, in addition to O.
sulcatus, either S. kraussei or H. megidis were added to plants.

References

Jagdale, G. B., Somasekhar, N., Grewal, P. S., and Klein, M.
G. (2002). Suppression of plant-parasitic nematodes by application of live and
dead infective juveniles of an entomopathogenic nematode, Steinernema
carpocapsae, on boxwood (Buxus spp.). Biol. Control 24, 42–49.
doi:10.1016/S1049-9644(02)00004-X.