UV-B and protection against pest attack
Attack by insect pests can be very damaging to plants and may greatly reduce crop yield. Although insecticide application reduces pest attack, these chemicals are expensive and environmentally damaging. Hence it is important to develop crop varieties with increased resistance to herbivorous pests.
When plants are attacked by pests genes are expressed that promote a defence response, including (depending on the species) changes in the levels of various phenolics, alkaloids and defence proteins, such as proteinase inhibitors, in leaf tissue. These biochemical changes deter herbivory. Interestingly, exposure of plants to UV-B can also promote resistance to a variety of insect pests. Thus, pre-exposure of plants to UV-B reduces subsequent feeding by insects and, conversely, filtering of UV-B from light sources makes leaf tissue more palatable to insects. The extent of resistance is dependent on both the plant and pest species. In several studies the protective effects of UV-B were correlated with changes in biochemical composition of leaf tissue that resembled the plant’s defence responses to insect attack. Hence there is overlap in the molecular responses activated by UV-B exposure and those triggered by wounding and insect herbivory.
We are examining gene expression responses to UV-B in the major crop, oilseed rape to try to gain a better understanding of the molecular and biochemical changes that promote resistance to pest attack. We hope, in the longer term, that this knowledge will facilitate breeding of plants with increased pest resistance.