Led by Klára Mészáros, researchers from the ELKH Centre for Agricultural Research’s Agricultural Institute (ATK MGI) and Plant Protection Institute (ATK NÖVI) have examined the role of antioxidant enzymes, including superoxide dismutase, in response to Pyrenophora infections. Through experiments on barley varieties, ATK researchers became the first to establish that the enzyme activity induced in the early stages of infection shows a tendency to increase as the disease progresses. The results could contribute to a deeper understanding of the physiological processes taking place in plants under biotic stress. The findings from the research were published in the scientific journal Sustainability.
Pyrenophora teres f. teres (PTT) is one of the fungi that infect barley and causes significant damage to these crops both in Hungary and worldwide. The presence of the pathogen causes characteristic longitudinal and transverse necrotic lesions and dead leaf surfaces – known as net blotch – to appear on barley leaves. Due to the reduction of the assimilation surface, this leads to a significant loss in yield. A wide range of resistances to net blotch can be observed among barley varieties, which vary with different isolates of the pathogen.
As a result of the stress caused by the infection, reactive oxygen forms appear in the plant’s cells, which play an important role in the regulation of signaling pathways, various metabolic and developmental processes, but which can also cause oxidative stress in higher concentrations. The balance between the generation of reactive oxygen forms and their removal plays a key role in defending against pathogens. Superoxide dismutase (SOD) is one of the most important antioxidant enzymes involved in the fine-tuning of this process.
The young ATK MGI researcher Viola Kunos and her colleagues conducted greenhouse experiments on five varieties of barley with different resistances, during which the plants were infected with three different PTT isolates. The researchers measured SOD enzyme activity during the early phase of infection (0–3 days) and evaluated leaf symptoms caused by the fungus.
An increase in SOD activity was observed as a result of the fungal infection, the extent of which significantly depended on both the variety of barley and the isolate used to infect it. The increase in SOD activity proves the presence of reactive oxygen species formed in the early stages of infection. Increased SOD activity due to infection promotes the formation of hydrogen peroxide (H2O2), thereby protecting the plant cell from the accumulation of reactive oxygen forms. The researchers found that SOD enzyme activity increased to a greater extent in cultivars susceptible to PTT infection than they did in resistant genotypes.
The results confirm that the sensitivity of barley varieties to different isolates of the fungus varies, which was also reflected in the change in SOD activity. In several cases, a significant correlation was found between the resistance of different youthful barley genotypes and the change in SOD enzyme activity. Based on the results, the measurement of SOD activity can open new perspectives on the detection of early stress reactions induced by PTT. However, the resistance of the different varieties cannot be estimated solely on the basis of SOD enzyme activity.
In order to clarify the role of antioxidant enzymes in plants under biotic stress studying other parts of the antioxidant enzyme system is also necessary, therefore the researchers plan to expand their experiments into this direction.