Resistance to the Russian wheat aphid, commonly known as Diuraphis noxia, was studied in wheat cultivars. The aim of the study was to explore the interaction between Reactive oxygen species (ROS) and the Russian wheat aphid during infestation. It is crucial to consider the distribution and diversity of the biotypes before conducting an experiment as the Russian wheat aphid control might not be effective in areas where the biotype exists.

The study found that resistant cultivars of wheat were able to induce defense mechanisms such as ROS and hydrogen peroxide that are controlled by NADPH oxidase when infested by the Russian wheat aphid. This response was more prominent in resistant cultivars than susceptible cultivars. However, a decrease in protein concentration was observed in the infested plants.

Reactive oxygen species (ROS) are reactive molecules and free radicals produced by molecular oxygen. These molecules play a critical role in regulating growth and development in cultivars, especially in response to biotic and abiotic environmental stressors. ROS can cause severe damage to cellular components such as DNA and mutations, leading to metabolic dysfunction and cell death.

Wheat (Triticum) is a commonly consumed cereal grain belonging to the Poaceae grass family. It is rich in antioxidants, nutrients, minerals, and fiber. However, it contains gluten, a protein that triggers adverse reactions in individuals with celiac disease. Since resistant cultivars induce effective defense responses, they are less susceptible to damage from the Russian wheat aphid than susceptible cultivars.

The study materials and methods involved pre-cooling a mortar and pestle on ice, grinding frozen leaf material into a fine powder in liquid nitrogen, adding extraction buffer, centrifuging the mixture, measuring NADPH oxidase activity and protein concentration, and measuring hydrogen peroxide content. The results showed that the activity of NADPH oxidase decreased over time when measured at 340 nm, and the hydrogen peroxide content was measured by incubating the samples for 20 minutes at 25°C.

In conclusion, resistance to the Russian wheat aphid is more effective in cultivars that can induce defense mechanisms such as ROS and hydrogen peroxide. These cultivars have a better chance of inhibiting and destroying the growth of the pathogen, preventing it from multiplying.

The graph depicted in Figure 2 displays the impact of Russian Wheat Aphid (RWA) infestation on the concentration of protein in wheat, with the error bars indicating the standard deviation in NADPH oxidase activity. Figure 3 illustrates the effect of RWA infestation on hydrogen peroxide levels in wheat, with the same error bars showing the standard deviation in NADPH oxidase activity.

During the experiment, Reactive Oxygen Species (ROS) and hydrogen peroxide were found to be defence responses against RWA infestation. As the level of NADPH oxidase activity and hydrogen peroxide content increased, it was observed that defence responses were induced more rapidly. The control was used to monitor the effect of RWA infestation, while the blank helped to calibrate the spectrophotometer before measuring the unknown absorbance values of wheat cultivars. Buffer solution was used to create an acidic environment for the experiment, and the reaction was centrifuged to separate the solutions based on their masses, with the aim of removing the supernatant. NADPH oxidase, one of the enzymes that induces ROS, was found to be mediated by the ROS and hydrogen peroxide, and its activity increased in wheat cultivars at 9 hours of infestation, as shown in Figure 1. In other cultivars, there was a slight increase in NADPH oxidase induction.

It can be concluded that plants build up a defence structure that inhibits the growth of RWA, and that when induced, the defence response successfully blocks the RWA from penetrating the plant. If left uncontrolled, RWA infestation can lead to decreased wheat yield production, stunted growth, and yellowing of the leaves, scientifically called chlorosis. Resistant cultivars survive and produce well compared to susceptible cultivars, which eventually die.

References:

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Moloi, M.J.'s doctoral dissertation from the University of the Free State in 2010 examined the relationship between reactive nitrogen species and the resistance of wheat to aphids, particularly in Russian wheat. The study was conducted over a span of 28 to 75 pages and yielded useful insights into this important area of research.