Category / Agriculture

by Prasad Ravindranath

Indian researcher uses novel strategy to increase wheat yield, improve resilience to drought

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Ram Sagar Misra increased the starch content of wheat by 20% by enhancing the amount of sugar-signalling molecule.

Using a novel route, an Indian researcher has been able to increase wheat grain yield by 20% and also improve the resilience of wheat to environmental stress such as drought. By using a precursor that enhances the amount of a key sugar signalling molecule (trehalose-6-phosphate (T6P)) produced in wheat plant, Dr. Ram Sagar Misra, from the Department of Chemistry, University of Oxford and currently with the Department of Chemistry, Shiv Nadar University, Greater Noida, has been able to increase the amount of starch produced and, therefore, the yield.

The T6P molecule stimulates starch synthesis, which in turn, increases the yield. Since the pathway of T6P molecule is the same in other plants, yield can potentially be increased by using suitable precursors. The results were published in the journal Nature. Dr. Misra is one of the authors of the paper.

Dr. Misra and others researchers from UK used four precursor compounds to increase the amount of T6P produced in the plant. While genetic methods can increase the T6P level by 2-3 fold, the four precursor compounds were able to achieve 100-fold increase in the sugar signalling molecule level compared with plants that did not receive the molecule.

Dr. Misra and others tested the effect of four precursors by dissolving the molecule in water and feeding to the roots of Arabidopsis thaliana plants. Compared with controls, the precursor-treated plants produced higher amount of T6P molecule and starch when exposed to sunlight.

In field trials using wheat, tiny amount of precursor given to the plant increased the yield significantly — the grains produced were bigger as the amount of starch content in the grains increased by 13-20% compared to controls that got only water. “A particular precursor molecule — ortho-nitrophenyl ethyl — showed the best results in both A. thaliana plants and wheat studies,” he says. “The uptake of this molecule by the plants was much more than the other three molecules and the precursor took less time to release T6P.”

Surviving drought

To study the resilience of wheat to drought-like condition when treated with the precursor molecules, the researchers carried out two different studies. In the first case, four-week-old wheat plants already treated with the precursor molecules were not watered for nine days to simulate a drought-like condition. “The plants were almost dying. When we watered the plants after nine days, only those that were pre-treated with the precursors were able to regrow while the control plants did not survive,” says Dr. Misra.

In another experiment, four-week-old wheat plants that were not watered for nine days were sprayed with the precursor molecules. “The regrowth of plants sprayed with the molecule was substantial when the plants were watered a day after treatment. We saw regrowth of new tissue and also survival and growth of existing tissue,” Dr. Misra says. “This also showed that the molecule could enter the plants directly when sprayed.”

“These two studies showed that wheat plants were able to survive environmental stress if treated with the precursors. The molecule 2 (dimethoxy(ortho-nitro)benzyl) was better in battling stress,” he says.

More trials on a larger scale are needed to confirm the role of the precursor molecules in increasing yield and withstanding drought-like conditions.

Published in The Hi du on March 12, 2017

by Prasad Ravindranath

Tamil Nadu researchers show chronic exposure to commonly used insecticide causes diabetes

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Degradation of organophosphate pesticide by gut bacteria causes diabetes in humans, says Ganesan Velmurugan.

A study by scientists at Madurai Kamaraj University, Tamil Nadu, India, has found evidence that long-term exposure to organophosphate insecticides induces diabetes and impaired glucose tolerance in both mice and humans. The researchers found that organophosphates-induced diabetes was mediated by gut bacteria. The results were published in the journal Genome Biology.

A survey of around 3,000 people in villages in and around the University found diabetes prevalence in people who were directly exposed to the insecticides was three-fold higher than in people who were not directly exposed to the insecticide. Serum analysis for four organophosphate insecticides revealed a direct correlation between pesticide level and HbA1c. “We saw a linear trend — for every unit increase in insecticide residue there was a corresponding increase in HbA1c level,” says Dr. Ganesan Velmurugan from the Department of Molecular Biology, School of Biological Sciences, Madurai Kamaraj University and the first author of the paper.

To ascertain if chronic exposure to organophosphates led to diabetes, the researchers treated mice (2.9 microgram per kg bodyweight) with organophosphate for 180 days, which is equivalent to 12-15 years of human life. “We saw an increase in blood sugar level from day 60 in mice treated with the insecticide,” he says. “But we didn’t see any correlation between insecticide and neurotransmitter level in mice treated with the pesticide.” The neurotransmitter is the main target of the pesticide.

So the researchers were confident that the pesticide was inducing diabetes through a new route of action. Studies have already shown that the pesticide is degraded by bacteria present in the gut. To ascertain this, the researchers collected faecal material from mice exposed to the pesticide for 180 days and transplanted it to a new set of mice. “The mice that received the faecal material developed diabetes in just one week, while the control mice did not. We repeated the experiment thrice and got the same result,” Dr. Velmurugan says. “We concluded that organophosphate-induced diabetes was mediated by gut bacteria.”

To understand the molecular mechanism, the researchers did a complete gene profiling of gut bacteria present in mice that were exposed to the pesticide for 180 days. “We found the genes linked to organophosphate degradation were highly expressed,” he says. So they focussed on finding the pathway involved in the degradation of the pesticide.

The gluconeogenesis pathway — where glucose is generated from non-carbohydrate sources such as fat and proteins — was highly expressed. “The pesticide is degraded into short-chain fatty acid, particularly acetic acid. It is well known than acetic acid produces glucose, elevated blood sugar levels and glucose intolerance,” Dr. Velmurugan says.

They ascertained the role of acetic acid in elevating blood sugar level in mice by administering sodium acetate orally and through rectal route; the rectal route led to more blood sugar increase than the oral route.

The role of gut bacteria in mediating pesticide-induced diabetes was confirmed in humans by studying the faeces of diabetics. “The acetate level was higher in people with diabetes,” he says.

“The study clearly shows the prevalence of diabetic conditions mediated by microbial degradation of the pesticide in humans,” says Subbiah Ramasamy from the Department of Molecular Biology, School of Biological Sciences, MKU and the corresponding author of the paper. “So the usage of this pesticide should be seriously reconsidered.”

Published in The Hindu on January 29, 2017

by Prasad Ravindranath

IIT Gandhinagar develops irrigation maps of India

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The maps showing estimates of irrigated areas have better accuracy than currently available ones, say Dr. Vimal Mishra (left) and Anukesh Krishnankutty Ambika.

For the first time, high-resolution maps of irrigated areas across India from 2000-2015 have been prepared using remote sensing data. The maps were validated with ground-based survey data. High-resolution irrigated water maps are essential for estimation of irrigation water demand and consumption on a spatial scale, crop productivity assessments and hydrologic modelling.

The maps were developed by a team led by Prof. Vimal Mishra from the Civil Engineering Department, Indian Institute of Technology, Gandhinagar, Gujarat. The results were published in Scientific Data, a journal from the Nature Group.

While the irrigation maps developed by the Food and Agriculture Organisation (FAO) are of low resolution, the high-resolution maps of International Water Management Institute (IWMI) are available for just one year and do not cover the entire country. “So we developed annual irrigated area maps at a resolution of 250 metres for the period 2000-2015 covering all the agroecological zones of India,” says Dr. Mishra. “We used the remote sensed vegetation index data from MODIS [Moderate Resolution Imaging Spectroradiometer] and high resolution (56 metre) land use/land cover data from the National Remote Sensing Center (NRSC) to prepare the maps.”

The irrigation maps developed is available in a repository and freely available to anyone.In the case of some States the maps tend to overestimate the irrigated areas while in others it underestimates. “Generally, humid areas lead to overestimation of the irrigated areas because of less variation in peak vegetation index, which is used as a threshold to identify irrigated and non-irrigated areas. Also, the resolution of remotely sensed vegetation index data may not be able to fully capture irrigated areas of small land holdings in India. And, a 250 metre pixel is considered fully irrigated even if there is partial irrigation in a small field within a pixel,” he says.

However, the maps have better accuracy in the case of arid and semi-arid regions as vegetation is restricted to areas that are irrigated and, therefore, the vegetation index truly reflects the vegetation health. “For most States we found our estimates of irrigated area are better in accuracy than the maps developed by IWMI,” Dr. Mishra says.

“Since a majority of agroecological zones of India fall in water-limited conditions, we assume that our method is effective for India,” they write. The developed dataset showed better accuracy against the ground-based survey than previously available datasets.

The estimation of irrigated area can be further improved if vegetation index data is available at higher spatial (to resolve small land holdings) and temporal resolution (to accurately capture crop growth cycle, which is essential to differentiate crops that are irrigated and not irrigated).

“We have plans to update the repository every year. By February 2017 we will upload the irrigated area data [in the form of maps] for 2016,” Dr. Mishra assures. The irrigation maps from 2000 to 2015 for the entire country are available in a Geotiff format in a repository and can be freely accessed by researchers and others.

Putting the maps to test

To highlight the trend and response of irrigation to rainfall variations, the authors chose the Indo-Gangetic Plain, which had witnessed severe drought in 2002 and 2015. To understand how unusual the 2015 drought was, the authors looked at the magnitude of deficit in 2015 monsoon rainfall and also looked at the long-time data from IMD.

“When we analysed the data, two regions —Indo-Gangetic Plain and Marathwada regions — were very distinct. These two regions faced very severe monsoon rainfall deficit in 2015,” he says. “We hypothesised that single monsoon deficit alone cannot result in a severe water shortage in these regions that was witnessed in the post-monsoon season of 2015 and summer of 2016.”

The GRACE satellite data showed an alarming depletion of groundwater in the post monsoon season of 2015. The combined depletion of surface and groundwater resources was caused by the two consecutive droughts over the Indo-Gangetic Plain region.

“The deficit for two consecutive years 2014 and 2015 was 51 per cent. The drought in the Indo-Gangetic plain based on two consecutive monsoon rainfall deficit was ranked one during the period of 1906-2015. Statistical analysis showed that the two-year drought was unprecedented and had a return period of more than 500 years. It means low probability of two consecutive years being drought years,” Dr. Mishra explains.

Published in The Hindu on December 25, 2016