Scientists find a way to precisely identify pests to minimize agricultural losses

DNA barcoding is a technique that uses gene sequence information for identifying organisms. Now scientists have deployed this technique to identify thrips insect species in India and found that this technique is effective.

The study is important for the agricultural sector as thrips cause huge losses to crops such as onion, chilli, brinjal, capsicum, watermelon and tomato. Identifying thrips correctly can help design relevant pest management strategies to prevent these losses. 

Thrips also leave white streaky trails after feeding on fruits that makes them unfit for exports. In the long run, using DNA barcoding for identifying thrips could help increase income from exports, believes Dr. Vikas Kumar, who is a lead author on this study. 

Thrips are minute plant sucking insects, one to three millimeters in length that cause damage to crops by direct feeding and by transmitting plant viruses. To date, these insects are identified based on their physical features like color and body architecture. The major obstacle in correct identification is their small size and high degree of similarity at some stages of their life cycle. Identifying these insects correctly is important for designing appropriate pest management strategies.

Researchers at the Centre for DNA Taxonomy, Zoological Survey of India in Kolkata tested DNA barcoding technique for precise identification of thrips insects. They collected 336 insect samples from 78 locations in India. The sample collection was done for 4 years between 2011 and 2015. In 3 years time, they have made a library of 370 DNA sequences that can be used for precisely identifying these plant pests. The results were published in a recent issue of the journal Scientific Reports.  

Kaomud Tyagi, who is the first author on the study, classified the collected samples into 89 species based on their physical features. “But information of physical features is not enough to identify species”, she says.

So they did a further DNA analysis to analyze the sequence of the mitochondrial cytochrome oxidase gene. 

“We have standardized and confirmed DNA barcoding method to be used for identifying thrips species correctly. Our study has also revealed that similar looking insects can belong to different species. Identifying species of thrips is now possible at the larval stage or even from a small portion of the body”, Dr. Kumar told India Science Wire. 

It will help design appropriate intervention for pest management as different species respond to different pesticides and doses. Most of the species included in this study are serious pests on a wide variety of agricultural and horticultural crops, he adds.

Sharad Mohan, Scientist at the Indian Agricultural Research Institute, New Delhi, who is not connected to the study agrees that, “bar coding is of immense value in validating the diversity of pests in different agro-climatic zone of India. Instead of using conventional taxonomic ways that may take months, barcoding helps in identifying pests that helps recommend and implement specific management protocols without wasting much time”, he says. 

The study was done by Kaomud Tyagi, Vikas Kumar, Devkant Singha, Kailash Chandra, Boni Amin Laskar, Shantanu Kundu, Rajasree Chakraborty, and Sumantika Chatterjee. It was funded by the Zoological Survey of India (ZSI), Kolkata. 

The samples were collected from different parts of India indicated in red.

The different species of Thrips classified based on physical features. 

Kailash Chandra, who is the Director of ZSI and an author on the paper said, “We are starting a new project on large scale barcoding insect pests and vectors of agricultural and veterinary importance soon”.

Reference: Scientific Reports | 7: 4898 | DOI: 10.1038/s41598-017-05112-7

This story was published by IndiaBioScience, India Science Wire, NetIndian, The Hindu (clip below), and BioVoice.