Title: Plants under attack send finely-tuned aromatic cry for help
[Rothamsted Research - 11 Feb, 2010] Plants under attack by insect herbivores emit repellent smells to deter insect feeding. These odours often act as distress signals, which attract natural enemies of the insect pests. A study by researchers at Rothamsted Research, an institute of BBSRC, in collaboration with the International Centre for Insect Physiology and Ecology (icipe) in Kenya, reveals that the quality of these signals in terms of blend composition and chemical identity can be more important than the total amount of odour released. This study is published in the Royal Society journal Biology Letters.
Plants under attack by insect herbivores emit repellent smells to deter insect feeding. These odours often act as distress signals, which attract natural enemies of the insect pests. A study by researchers at Rothamsted Research, an institute of BBSRC, in collaboration with the International Centre for Insect Physiology and Ecology (icipe) in Kenya, reveals that the quality of these signals in terms of blend composition and chemical identity can be more important than the total amount of odour released. This study is published in the Royal Society journal Biology Letters.
African farmer with Brachiaria plant
The researchers observed changes in odour profiles emitted from signal grass, an important livestock forage crop in Africa, when under attack by spotted stemborer moths. Typically, insect attack leads to an increase in odour emission but here an unusual phenomenon was found where suppression of the main odour emitted occurred when the moths laid eggs. This changed the ratio of compounds in the odour blend but nevertheless led to insect behavioural responses that are beneficial to the plants. The odour of plants with eggs was more attractive to parasitic wasps, the natural enemies of stemborers.
Dr Toby Bruce said “These wasps are important natural enemies of the stemborer pest studied. They have evolved chemosensory systems that are fine-tuned for recognition of plant odours that signal the presence of their prey.” “Even though overall odour emission was reduced the wasps were more attracted to the odour of plants with eggs that the odour of plants without eggs. This showed that it is Quality not Quantity that is important in these interactions”.
There is an urgent need in most of rural Africa, where farmers cannot afford chemical pesticides, for crop varieties that can naturally defend themselves against insect pests. The odour-based communication between plants and natural enemies of insects that has been revealed in this study could provide insights into selecting and breeding crop varieties with better potential for induced early defence against pests such as stemborers.
