Updated: September 22, 2016 6:30:29 am
Even as uncertainty looms over approval for commercial cultivation of genetically modified (GM) mustard, two new sets of indigenously developed transgenic ‘events’, this time in cotton, hold out the promise of alternative suppliers for a technology largely monopolised by multinationals.
The first of these involves Bt cotton. Scientists at Delhi University’s Centre for Genetic Manipulation of Crop Plants (CGMCP) have developed two independent ‘events’ for insertion of the cry1Ac gene — isolated from a soil bacterium Bacillus thuringiensis and coding for a protein toxic to Helicoverpa armigera or American bollworm insect pest — into cotton.
The levels of cry1Ac protein expression in these events are claimed to be much higher than in the Bt cotton hybrids based on the US life sciences giant Monsanto’s proprietary Bollgard I and II technologies. In Monsanto’s cry1Ac event, also called MON 531, the protein expression drops as the plants matures and sets bolls. Further, it is high in the roots, which serves no purpose as the bollworm pests do not feed on underground plant parts.
“In our two events, Tg2E-13 and TM-2, the cry1Ac protein expression declines over the growing season, but the overall level is two to three-folds higher compared to MON 531 and also concentrated in the leaf tissues, bracts and flower buds. The protein expression level is low in the roots, which is inconsequential anyway,” said Deepak Pental, former Delhi University vice-chancellor, whose team at CGMCP has also been behind the GM hybrid mustard, DMH-11, now awaiting commercial planting clearance.
The new events will make the resultant Bt cotton plants much more resistant to bollworm attacks. Since the higher cry1Ac toxin levels are expressed in the green plant parts, the larvae cannot progress beyond the stage of feeding on the leaves, from where they would normally move to the bolls.
High protein expression can also address the increasing vulnerability of Bollgard Bt cotton to Pectinophora gossypiella or the pink bollworm. That again may have to do with the low cry1Ac protein dose in the developing bolls of the MON 531 event, enabling these insects to survive and leave progeny.
The other promising indigenous GM event is a whitefly-resistant cotton developed by the National Botanical Research Institute (NBRI), Lucknow. Scientists there have isolated and cloned a gene from an edible fern Tectaria macrodonta and transferred it to cotton. This gene, called Tma12, encodes a protein toxic to whitefly, an insect pest that sucks sap from the phloem tissues — which carry nutrients from the leaves to other plant parts — resulting in wilting, stunted growth and eventually yield loss.
“Ferns and mosses, unlike flowering plants, are rarely infested by insect pests. We screened 38 species of ferns to identify proteins responsible for toxicity towards insects. The Tma12 protein from Tectaria macrodonta was found to cause maximum mortality in whiteflies and hence suitable for incorporation into cotton plants,” explained Pradhyumna Kumar Singh, senior scientist at NBRI’s Genetics and Plant Molecular Biology Division.
The NBRI scientists — whose research findings were published in the September 5 issue of the prestigious Nature Biotechnology journal — even conducted feeding studies of the Tma12 protein in Sprague-Dawley laboratory rats, which showed no adverse biochemical changes or effects on kidney, liver and other functions. The transgenic cotton expressing the event also did not affect the ladybird beetle, a beneficial natural predator of whitefly.
Both the CGMCP and NBRI events come at a time when farmers’ confidence in cotton has been badly shaken by the susceptibility of currently grown Bt hybrids — almost entirely based on the Bollgard gene constructs — to pink bollworm and whitefly attacks. What were considered ‘secondary’ pests vis-à-vis the American bollworm have, in recent years, emerged as significant threats: the pink bollworm in Gujarat, central Maharashtra, Karnataka and Andhra Pradesh, and whitefly in Punjab, Haryana and Rajasthan.
Between 2002-03 and 2013-14, India’s cotton production nearly trebled, mainly courtesy Bt hybrids whose rate of adoption was, perhaps, surpassed only by the mobile phone. From a mere 0.4 per cent of the country’s total cotton area in 2002-03, when they first planted, the share of Bt hybrids reached 93 per cent in 2014-15. That was the year when the effects of ‘secondary’ pest infestation began to also show up in production.
Farmers have responded by sharply cutting back on acreage. This year, they have sown only 102.23 lakh hectares (lh) under cotton, as against 115.20 lh during the same period of 2015-16. Significantly, though, while the area under Bt cotton has reduced from 105.54 lh to 84.85 lh, that for non-Bt varieties and hybrids has actually gone up from 9.66 lh to 17.38 lh.
“We need a focused backcross breeding programme for transferring both the high cry1Ac protein expression as well as whitefly-resistant transgenic cotton events into our best varieties and hybrids. No time should be lost; any delay will ultimately be at the cost of the Indian farmer,” Pental pointed out. “We are willing to give our technology even to private seed companies. Now that Nature Biotechnology has published our work, it should clear all doubts about the suitability of the event for control of whitefly,” noted Singh.
Delhi University has already signed a memorandum of understanding for sharing its Tg2E-13 event with the Central Institute for Cotton Research. “This is certainly the first authentic indigenous Bt cotton event in India and the overall expression levels of the cry1Ac protein is better than in MON 531. Our idea is to incorporate it into straight varieties amenable to high-density planting, as opposed to hybrids,” KR Kranthi, director of the Nagpur-based institute, told The Indian Express.
The Bt cotton hybrids cultivated now are typically sown with 120-150 cm distance between rows and 60-90 cm from plant to plant. In high-density planting, the spacing is much closer at about 75 cm row-to-row and 10 cm plant-to-plant. As a result, the number of plants per hectare goes up from 11,000-15,000 to 1.5-1.7 lakh.
“Through high-density planting, which is not feasible with costlier hybrid hybrids, you can achieve the same or even higher yields from straight varieties. And with the new Bt events, they would be a winner,”
Punjab Agricultural University (PAU), Ludhiana , too, is in the process of making backcrosses from the Tg2E-13 line with three of its own high-yielding American cotton varieties: F-2228, F-2383 and PIL-43.
“We will soon sign an MoU with NBRI to also access the whitefly-resistant event. The ultimate objective is to stack all these indigenous GM events into our varieties, which will give an alternative to farmers,” informed R K Gumber,
director of research, PAU.
A major constraint for the results of all this work reaching the farmers’ fields is, of course, the regulatory regime for field trials and commercialisation of GM crops. Coupled with the influence wielded by NGOs opposed to the technology, it has meant that Monsanto’s Bollgard II cotton was the last transgenic event to be ‘released’ for commercial cultivation in May 2006. The fate of CGMCP’s GM hybrid mustard will be known in less than a
The present domestic dithering over allowing approvals for GM events — even those indigenously developed — also comes when, globally, a process of consolidation in the agriculture science industry is underway.
The most recent development has been the world’s largest seed and genomics company (Monsanto) being taken over by the second largest agro-chemicals concern (Bayer). Coming soon after the “merger of equals” between Dow Chemical and DuPont, and Syngenta’s acquisition by China National Chemical Corporation, it signals restricted choices for the farmers as far as sourcing of technology goes.
The lack of a clear policy on GM could narrow that down still further.
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