Impact of <I>Rag1</I> Aphid Resistant Soybeans on <I>Binodoxys communis</I> (Hymenoptera: Braconidae), a Parasitoid of Soybean Aphid (Hemiptera: Aphididae)

Abstract

Multiple strategies are being developed for pest management of the soybean aphid, Aphis glycines Matsumura; however, there has been little published research thus far to determine how such strategies may influence each other, thereby complicating their potential effectiveness. A susceptible soybean (Glycine max L.) variety without the Rag1 gene and a near isogenic resistant soybean variety with the Rag1 gene were evaluated in the laboratory for their effects on the fitness of the soybean aphid parasitoid, Binodoxys communis (Gahan). The presence or absence of the Rag1 gene was verified by quantifying soybean aphid growth. To test for fitness effects, parasitoids were allowed to attack soybean aphids on either a susceptible or resistant plant for 24 h and then aphids were kept on the same plant throughout parasitoid development. Parasitoid fitness was measured by mummy and adult parasitoid production, adult parasitoid emergence, development time, and adult size. Parasitoids that attacked soybean aphids on susceptible plants produced more mummies, more adult parasitoids, and had a higher emergence rate compared with those on resistant plants. Adult parasitoids that emerged from resistant plants took 1 d longer and were smaller compared with those from susceptible plants. This study suggests that biological control by B. communis may be compromised when host plant resistance is widely used for pest management of soybean aphids.

<I>Rag1</I> Aphid Resistant Soybeans Alter the Movement and Distribution of Soybean Aphid (Hemiptera: Aphididae)

“…Soybean aphids were originally collected from multiple soybean plots on North Dakota Agricultural Experiment Station Þelds near Prosper, ND (47.00, Ϫ97.12) during the summer of 2008, and were refreshed with aphids from soybean Þelds in the same location in the summer of 2010. Experiments on individuals and groups of individuals from this colony (including Ghising et al 2012) indicate that the colony is predominately or entirely aphids that perform relatively poorly on soybean varieties with Rag1 resistance (biotype 1). The aphids were maintained on the susceptible soybean line RG607RR in a wood and wire mesh cage 26 Ϯ 4ЊC, 60 Ð 80% relative humidity (RH) under a photoperiod of 16:8 (L:D) h. To maintain aphid colonies, older soybean plants (vegetative stage V3-V4: three or four fully expanded Þrst trifoliates; soybean growth stages are described according to Fehr and Caviness 1977) were replaced with young soybean plants (vegetative stage V1: fully expanded Þrst trifoliate) every 4 Ð5 d depending on plant quality.…”

“…A soybean variety resistant to soybean aphids in the United States was Þrst reported in 2004 , and it contains a single dominant gene, Rag1 (resistance to Aphis glycines gene 1) that is known to impart resistance to soybean aphid (Hill et al 2006a,b,;Kim et al 2010). Most soybean aphids restricted to Rag1 resistant plants have a shorter lifespan, lower fecundity and longer development time ) that leads to much smaller aphid populations than those kept on susceptible plants (e.g., Ghising 2011, Ghising et al 2012; though see Hill et al 2010). In addition, tantalizing results from an open environment with multiple varieties suggest that the distribution of soybean aphids between and within plants may be inßuenced by the presence of resistant varieties Dashiell 2007, 2008).…”

Temperature alters the interaction between a herbivore and a resistant host plant

“…Multiple experiments with this colony (including Ballman et al 2012;Ghising et al 2012) indicate that the colony is mostly or completely aphids that perform poorly on soybean varieties with the Rag1 gene (biotype 1). The aphids were maintained on susceptible soybeans in a wire and mesh cage, 26 ± 4°C, 60-80 % RH under a L16:D8 photoperiod.…”

Emerging issues in Integrated Pest Management Implementation and Adoption in the North Central USA

“…The downside is the possibility of affecting phylogeneticallyrelated species that are not pests. Though so far such effects have been nonexistent or negligible (Marvier et al 2007;Lövei et al 2009), the possibility still requires extensive testing of each new toxin before registration, something that has seldom been a concern for varieties with conventionally-derived host plant resistance (but see Dogramaci et al 2005;Ballmann et al 2012;Ghising et al 2012). …”