Plant Traits and Belowground Interactions dataset

Rootstock from existing <i>R. idaeus</i> 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 <i>R. idaeus</i> were transplanted into individual pots, 40 <i>O. sulcatus </i>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 <i>O. sulcatus</i>, EPNs were added to plants, with control plants remaining untreated. Three weeks after nematodes were added, the plants were harvested and <i>O. sulcatus </i>larvae were retrieved, counted and fresh mass taken. A subset of half the plants were then freeze dried to ascertain dry mass (<b>Fig 1</b>). <i>Otiorhynchus</i><i> sulcatus</i> 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 <i>O. sulcatus. S. kraussei</i> (Becker and Underwood®, Littlehampton, UK) and <i>H. megidis</i> (Biobest®, Milton Bridge, UK). They were both added to plants as separate treatments at their recommended dosages<i>.</i> When formulated to the commercially recommended dosages this results in approximately 9000 <i>S. kraussei</i> added per pot and approximately 16000 <i>H. megidis</i> 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 <i>R. idaeus</i> cultivars (Glen Ample and Glen Rosa) were subdivided into one of four treatments. A control treatment, where neither <i>O. sulcatus</i> or EPNs were added, an <i>O. sulcatus</i> ‘only’ treatment where the herbivore was observed in the absence of EPNs and two treatments in which, in addition to <i>O. sulcatus</i>, either <i>S. kraussei</i> or <i>H. megidis</i> were added to plants. <b>References</b> 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.). <i>Biol. Control</i> 24, 42–49. doi:10.1016/S1049-9644(02)00004-X.