Aboveground Feeding by Soybean Aphid, Aphis glycines, Affects Soybean Cyst Nematode, Heterodera glycines, Reproduction Belowground

Abstract

Heterodera glycines is a cyst nematode that causes significant lost soybean yield in the U.S. Recent studies observed the aphid Aphis glycines and H. glycines interacting via their shared host, soybean, Glycine max. A greenhouse experiment was conducted to discern the effect of A. glycines feeding on H. glycines reproduction. An H. glycines-susceptible cultivar, Kenwood 94, and a resistant cultivar, Dekalb 27–52, were grown in H. glycines-infested soil for 30 and 60 d. Ten days after planting, plants were infested with either zero, five, or ten aphids. At 30 and 60 d, the number of H. glycines females and cysts (dead females) and the number of eggs within were counted. In general, H. glycines were less abundant on the resistant than the susceptible cultivar, and H. glycines abundance increased from 30 to 60 d. At 30 d, 33% more H. glycines females and eggs were produced on the resistant cultivar in the ten-aphid treatment compared to the zero-aphid treatment. However, at 30 d the susceptible cultivar had 50% fewer H. glycines females and eggs when infested with ten aphids. At 60 d, numbers of H. glycines females and cysts and numbers of eggs on the resistant cultivar were unaffected by A. glycines feeding, while numbers of both were decreased by A. glycines on the susceptible cultivar. These results indicate that A. glycines feeding improves the quality of soybean as a host for H. glycines, but at higher herbivore population densities, this effect is offset by a decrease in resource quantity.

Interactions of effects of host plant resistance and seed treatments on soybean aphid (Aphis glycines Matsumura) and soybean cyst nematode (Heterodera glycines Ichinohe)

“…Another benefit of growing H. glycines‐ resistant soybean is that there is no premium for purchasing the seed compared with H. glycines ‐susceptible soybean. Suppression of H. glycines with resistant cultivars may indirectly affect A. glycines reproduction through host plant defenses or alterations to host plant quality, but further studies are needed on the interactions between these pests . Thiamethoxam seed treatment may help reduce A. glycines populations on susceptible cultivars, but HPR cultivars appear not to benefit from thiamethoxam when they have substantially reduced A. glycines populations.…”

“…measured a greater intrinsic growth rate of A. glycines on soybeans that were attacked by H. glycines , implying that feeding by H. glycines may increase host plant quality for A. glycines . Because H. glycines and A. glycines co‐occur in many soybean‐producing regions, there could be an added benefit to planting H. glycines ‐resistant soybeans if suppression of the belowground nematode pest could lead to lower populations of A. glycines and vice versa …”

“…We performed 30‐day greenhouse experiments modified from the Standard Cyst Evaluation‐2008 (SCE‐08) protocol to measure effects of treatments, used in our field study, on a single generation of H. glycines reproduction, using the H. glycines populations from our study sites . The experimental design followed McCarville et al with some slight modifications. Heterodera glycines typically completes one generation every 25 to 32 days at 27 to 30 °C, and thus the 30‐day experiment estimates the amount of H. glycines reproduction in one generation .…”

“…Integrated pest management (IPM) strategies that include growing soybean cultivars with HPR to manage both H. glycines belowground and A. glycines aboveground can protect crops with low environmental risk . The co‐occurrence of both H. glycines and A. glycines in the north‐central region of the USA also is of importance because there is evidence that A. glycines feeding may enhance the quality of soybean as a host plant for H. glycines . If feeding of both pests has a non‐additive, negative impact on soybean yield, the planting of soybean cultivars with stacked resistance genes for both pests would be a good strategy for preserving yield.…”

Below‐ground nematode herbivory of resistant soybean cultivars impairs the performances of an above‐ground caterpillar and its parasitoid

“…Many empirical studies have examined correlations between constitutive and above-ground herbivore-feeding induced defences, demonstrating varied associations including trade-offs, positive correlation, or no correlation between them (Brody & Karban, 1992;Lombardero et al, 2000;Koricheva et al, 2004;Kempel et al, 2011), as well as the relevance of these associations to other plant life-history traits (Moreira et al, 2014). For example, soybean cultivars with varying constitutive resistance have been shown to play a role in interactions between the soybean cyst nematode and the soybean aphid, Aphis glycines Matsumura (Heeren et al, 2012;McCarville et al, 2014). Our results provide support for the role of constitutive plant defences in interactions between root-feeding nematodes and above-ground chewing herbivores.…”