Drought stress increases the expression of barley defence genes with negative consequences for infesting cereal aphids

Crops are exposed to myriad abiotic and biotic stressors with negative consequences. Two stressors that are expected to increase under climate change are drought and infestation with herbivorous insects, including important aphid species. Expanding our understanding of the impact drought has on the plant-aphid relationship will become increasingly important under future climate scenarios. Here we use a previously characterised plant-aphid system comprising a susceptible variety of barley, a wild relative of barley with partial-aphid resistance, and the bird cherry-oat aphid to examine the drought-plant-aphid relationship. We show that drought has a negative effect on plant physiology and aphid fitness and provide evidence to suggest that plant resistance influences aphid responses to drought stress, with the expression of aphid detoxification genes increasing under drought when feeding on the susceptible plant but decreasing on the partially-resistant plant. Furthermore, we show that the expression of thionin genes, plant defensive compounds that contribute aphid resistance, increase ten-fold in susceptible plants exposed to drought stress but remain at constant levels in the partially-resistant plant, suggesting they play an important role in modulating aphid populations. This study highlights the role of plant defensive processes in mediating the interactions between the environment, plants, and herbivorous insects.

Lines derived from coffee BA-10 with resistance to Pseudomonas syringae under field conditions with simultaneous natural infections of the pathovars garcae and tabaci

Bacterial-halo-blight and bacterial-leaf-spot are important coffee diseases caused by Pseudomonas syringae pv. garcae and pv. tabaci, respectively. The most suitable method to control these diseases is the use of resistant cultivars. There are no studies on resistance to Pseudomonas syringae (PS) in coffee derived from BA-10 genotypes. Therefore, the aim of this study was to evaluate the resistance to PS in lines derived from BA-10 under field conditions with simultaneous natural infections of the pathovars garcae and tabaci. 38 F4 and two F5 lines derived from BA-10 were evaluated in a field trial in Londrina, PR, Brazil. The Catuaí Vermelho IAC 81 and IAPAR 59 were the susceptible and intermediate resistant controls, respectively. Resistance to PS was evaluated in January 2017 after 45 months of planting. The grading scale varied from 1 to 5, where grade 1 was plants with more resistance and 5 plants more susceptible. Two F5 lines showed 100% of resistant plants (grades 1 and 2) and the F4 line IAPAR 12201 showed 60% of plants with a high level of resistance to PS (grade 1), while the control Catuaí showed no resistant plant. IAPAR 59 and several F4 lines showed high frequency of plants with intermediate resistance to PS

Electrical signalling on Bt and non-Bt cotton plants under stress by Aphis gossypii

Plants have developed various mechanisms to respond specifically to each biotrophic attack. It has been shown that the electrical signals emitted by plants are associated with herbivory stress responses and can lead to the activation of multiple defences. Bt cotton is a genetically modified pest-resistant plant that produces an insecticide from Bacillus thuringiensis (Bt) to control Lepidopteran species. Surprisingly, there is no study–yet, that characterizes the signalling mechanisms in transgenic cotton plants attacked by non-target insects, such as aphids. In this study, we characterized the production of electrical signals on Bt and non-Bt cotton plants infested with Aphis gossypii and, in addition, we characterized the dispersal behaviour of aphids to correlate this behaviour to plant signalling responses. Electrical signalling of the plants was recorded with an extracellular measurement technique. Impressively, our results showed that both Bt and non-Bt cotton varieties, when attacked by A. gossypii, emitted potential variation-type electrical signals and clearly showed the presence of distinct responses regarding their perception and the behaviour of aphids, with evidence of delay, in terms of signal amount, and almost twice the amount of Cry1F protein was observed on Bt cotton plants at the highest density of insects/plant. We present in our article some hypotheses that are based on plant physiology and insect behaviour to explain the responses found on Bt cotton plants under aphid stress.

Anti-resistant plant protection system against harmful arthropods

Goal. To substantiate and develop an anti-resistant system of protection of crops and perennials from harmful arthropods. Methods. The sensitivity of phytophages on natural populations collected on winter wheat, soybean, and rapeseed crops was determined by various methods of their poisoning: immersion of insects on inhabited plants, immersion of insects in gauze bags for 3 seconds. in a suitable solution of insecticide. The methods are based on the study of the pest’s response to a series of doses of the drug — from the minimum, causing mortality of 5—10% of normal-sensitive individuals, to the maximum (mortality of 90% or more). Toxicological parameters were calculated using the PROBAN program. Results. Different sensitivity of natural populations of arthropods to modern insecticides is revealed. Techniques for the rational use of insecticides populations and the use of alternative biological and immunological methods. Conclusions. An effective measure to prevent and inhibit the formation of resistant populations of harmful arthropod species to insecticides is an anti-resistant plant protection system. It includes monitoring the resistance of natural populations of harmful phytophagous species, identifying the type of resistance and the rational use of chemicals.