Maize can be primed for self-defence against leafhoppers

28th Jul 2013

It is well documented that leafhoppers which can transmit the maize streak virus (MSV) can have devastating effects upon maize production and therefore significant economic loses for farmers. Plants respond to insect attacks by the release of blends of volatile organic compounds (VOCs) that are attractive to the natural enemies of the plant – eating (herbivore) pests, thus activating a defence mechanism. cis -Jasmone (CJ) is a natural plant product that researchers at Rothamsted have previously identified as capable of activating indirect and direct plant defence. In the present study Rothamsted Research scientists, who receive strategic funding by BBSRC, have shown for the first time that using CJ-exposed maize plants can be predisposed to enhance their defence against the leafhopper. The study has been published in PLOS One journal.

In sub-Saharan Africa maize is major source of food and supplies 50% of the calories that the population needs. An attack by leafhoppers that transmit the MSV can result in 100% loses of the crop for some farmers. The search for control methods is currently pertinent and urgent.

Plants communicate with insects using semiochemicals (naturally-occurring behavior or development-modifying chemicals). Researchers study this type of communication in order to identify potential sustainable pest-management tools. In order to achieve this scientists exploit the fact that when plants are infested with pests release a blend of VOCs that can repel the pests or that may attract the natural enemies of the pests. Several compounds that can activate the generation of such "smells" upon pest infestation have been identified and one of those is (CJ).

Rothamsted researchers tested systematically the potential of CJ to induce a defence response in maize plants. When young maize plants were pre-treated with CJ and then infested with leafhoppers they released VOCs that repelled the pest insects. The effect of this response was strongest within the first few hours of infestation. In this time window the pests have not yet affected the smell that plant can release. When the "blend of smells" i.e VOCs was analysed for its chemical composition it was indeed found that the CJ pre-treated plants emitted increased amounts of chemicals that are natural insect pest repellents.

Dr Mike Birkett, lead scientist of this study and Principal Investigator in Chemical Ecology at Rothamsted, said "This an exciting discovery which shows that maize be primed to protect itself against a major insect pest that can devastate maize crop yields in sub-Saharan Africa". Dr Birkett further explained that "Our study provides further evidence that cis-jasmone, which is released naturally by insect-damaged plants is able to induce defence mechanisms in nearby undamaged plants. We have also shown this for other crops, including wheat, soybean and cotton."

Professor John Pickett, Scientific Leader of Chemical Ecology at Rothamsted, said: "These findings are really very promising and encouraging and they come at a time that here is increasing need for novel targeted biological control of pests in agriculture. Our future field experiments based on this study will bring closer these findings to the hands of the farmers in sub-Saharan Africa countries that are indeed in great need of leafhopper infestation control in maize plantations."



Priming of Production in Maize of Volatile Organic Defence Compounds by the Natural Plant Activator cis-Jasmone (10.1371/journal.pone.0062299)

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