New Options for Soybean Aphid Host Plant Resistance

Host plant resistance for soybean aphid is the newest management tool for yield protection. In 2010, a single gene expression, called Rag1, was commercially released in the north central region. Aphids feeding on Rag1 plants do not live as long or produce as many offspring compared to when they feed on susceptible plants. In small plot evaluations of the Rag1 gene, there is a dramatic decrease in the seasonal accumulation of soybean aphid compared to aphids developing on susceptible varieties

Biopsy-based calibration of T2* magnetic resonance for estimation of liver iron concentration and comparison with R2 Ferriscan.

BACKGROUND: There is a need to standardise non-invasive measurements of liver iron concentrations (LIC) so clear inferences can be drawn about body iron levels that are associated with hepatic and extra-hepatic complications of iron overload. Since the first demonstration of an inverse relationship between biopsy LIC and liver magnetic resonance (MR) using a proof-of-concept T2* sequence, MR technology has advanced dramatically with a shorter minimum echo-time, closer inter-echo spacing and constant repetition time. These important advances allow more accurate calculation of liver T2* especially in patients with high LIC. METHODS: Here, we used an optimised liver T2* sequence calibrated against 50 liver biopsy samples on 25 patients with transfusional haemosiderosis using ordinary least squares linear regression, and assessed the method reproducibility in 96 scans over an LIC range up to 42 mg/g dry weight (dw) using Bland-Altman plots. Using mixed model linear regression we compared the new T2*-LIC with R2-LIC (Ferriscan) on 92 scans in 54 patients with transfusional haemosiderosis and examined method agreement using Bland-Altman approach. RESULTS: Strong linear correlation between ln(T2*) and ln(LIC) led to the calibration equation LIC = 31.94(T2*)-1.014. This yielded LIC values approximately 2.2 times higher than the proof-of-concept T2* method. Comparing this new T2*-LIC with the R2-LIC (Ferriscan) technique in 92 scans, we observed a close relationship between the two methods for values up to 10 mg/g dw, however the method agreement was poor. CONCLUSIONS: New calibration of T2* against liver biopsy estimates LIC in a reproducible way, correcting the proof-of-concept calibration by 2.2 times. Due to poor agreement, both methods should be used separately to diagnose or rule out liver iron overload in patients with increased ferritin

Aboveground feeding by soybean aphid, Aphis glycines, affects soybean cyst nematode, Heterodera glycines, reproduction belowground.

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

Biotype-2 and biotype-3 <i>A</i>. <i>glycines</i> reproduction reduced on a susceptible soybean compared to aphid resistant cultivars.

<p>Note that biotype 1 is avirulent to both aphid-resistant cultivars, but virulent to the susceptible cultivar. The susceptible soybean cultivar was IA3027, the <i>Rag1</i> cultivar was IA3027RA1, and the <i>Rag2</i> cultivar was IA3027RA2. Data were analyzed by soybean cultivar, and capital letters indicate significance differences across biotypes (<i>P <</i> 0.05).</p

Simulated effect of induced susceptibility and fitness costs on virulence development.

<p>^a Default simulations were run with the inclusion of induced susceptibility effects but not fitness costs or negative cross-resistance effects.</p><p>^b Inheritance of virulence and fitness costs.</p><p>^c Years until the frequency of the allele conferring virulence to <i>Rag1</i> exceeded 0.50.</p><p>^d If the frequency of the virulence allele failed to surpass 0.50 within 25 years, its frequency after 25 years is provided in parentheses</p><p>Simulated effect of induced susceptibility and fitness costs on virulence development.</p

Biotype-4 <i>A</i>. <i>glycines</i> reproduction reduced on a susceptible soybean compared to an aphid resistant cultivar.

<p>Note that biotype 1 is avirulent to both aphid-resistant cultivars, but virulent to the susceptible cultivar. For this experiment the susceptible soybean cultivar was IA3027, the <i>Rag1</i> cultivar was IA3027RA1, the <i>Rag2</i> cultivar was IA3027RA2, and the <i>Rag1</i>+<i>Rag2</i> cultivar was IA3027RA12. Data were analyzed by soybean cultivar, and capital letters indicate significance differences between biotype populations (<i>P <</i> 0.05).</p

A Bacillus thuringiensis Cry protein controls soybean cyst nematode in transgenic soybean plants

Genetic resistance to soybean cyst nematode (SCN) is beginning to decline. Here, the authors report that soybean lines expressing the Bacillus thuringiensis protein Cy14Ab have significant levels of protection from SCN in both greenhouse and field trials

Effect of <i>Aphis glycines</i> feeding on numbers of <i>Heterodera glycines</i> (a) females and cysts plant⁻¹ and (b) eggs plant⁻¹ as affected by <i>H. glycines</i> population density.

<p>The effect of <i>A. glycines</i> on <i>H. glycines</i> reproduction was calculated as the ratio of the mean of the ten-aphid treatment divided by the zero-aphid treatment. The average number of <i>H. glycines</i> females and cysts plant⁻¹ and eggs plant⁻¹ was calculated as the average of the ten-, five-, and zero-aphid treatment means. <i>Aphis glycines</i> increased <i>H. glycines</i> reproduction at the lowest <i>H. glycines</i> population density, with competition occurring at higher population densities. Asterisks denote data points in which the effect of aphid density was significant at <i>P</i> = 0.10 (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0086415#pone-0086415-g001" target="_blank">figures 1</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0086415#pone-0086415-g002" target="_blank">2</a>).</p

Numbers of <i>Heterodera glycines</i> females and cysts and eggs plant⁻¹ on the <i>H. glycines</i>-susceptible soybean cultivar Kenwood 94 and resistant cultivar Dekalb 27–52 after 60 d.

<p>Numbers of females and cysts are represented by bars and numbers of eggs represented by boxes above the bars. Note the different scales used for the two graphs. Three aphid density treatments were established by artificially infesting plants with zero, five, or ten <i>Aphis glycines</i> plant⁻¹ 10 d after seed was planted. For the susceptible cultivar, aphid density significantly affected the number of <i>H. glycines</i> females and cysts plant⁻¹ and had a marginally significant effect on numbers of eggs plant⁻¹. Letters represent significant differences among aphid densities (<i>P</i><0.10), with capital letters assigned to eggs plant⁻¹ and lower case letters assigned to females and cysts plant⁻¹.</p