Pest’s spit ‘doubles spud production’

WASHINGTON - A little spit may be more than enough to double the output of the world’s fourth largest food crop, spud, claim researchers.

The saliva of the Guatemalan potato moth larvae (Tecia solanivora), a major pest, which forces many farmers to spray plants with pesticides in South America, contains compounds in its foregut that elicits a system-wide response in the Colombian Andes commercial potato plant (Solanum tuberosum), researchers have found.

Researchers at Cornell University, as well as the University of Goettingen and National University of Colombia, have found that when the spit of the tuber moth caterpillar gets into a tuber, all the other tubers of the plant grow bigger.

Co-author Andri Kessler, Cornell assistant professor of ecology and evolutionary biology believes that compounds from the insect’s saliva somehow increases the rate of the plant’s photosynthesis to compensate for the tubers lost to the caterpillar damage. As a result of more photosynthesis, more carbon is drawn into the plant and used to create starch, which makes for bigger tubers.

Plants have a number of responses to insects and other animals that eat them, including changing metabolism or producing toxins, said Kessler. In turn, the herbivores may develop strategies to counter the plant’s defenses and influence its signaling pathways.

Kessler said: “This could be an example where the co-evolutionary arms race led to a beneficial outcome for both.”

Another key seems to be getting the right mix of potato and pest.

When the larvae infested fewer than 10 percent of the tubers, the plant produced marketable yields (after infested tubers were removed) that weighed 2.5 times more than undamaged plants, according to the study. When up to 20 percent of the potatoes were damaged, marketable yields still doubled. When as many as half of the potatoes were infested, yields equaled those of plants with no infestation.

The findings have implications for potato farmers. Once isolated, the compound could lead to considerably higher yields in some varieties.

Initially, researchers wanted to show how these pests reduced potato yields, but they actually they found yield increases, said Katja Poveda, the study’s principal investigator, at the Agroecology Institute of the University of Goettingen, Germany, and the Cornell entomology department.

“The moth eats all varieties of potatoes, but so far only this one variety responded” with increased yields among seven varieties that were tested as part of a larger project, said Poveda. Future experiments will test more commercial varieties, as well as wild potatoes, she added.

The study has been published in the journal Ecological Applications. (ANI)