In the face of extreme, fluctuating weather, developing climate-resilient wheat a daunting challenge

The year 2022 saw the hottest March in India since observed record-keeping started in 1901, with temperatures exceeding the normal by 4 degrees celsius to 6 degrees celsius in many parts.

In the plains of the north, the heatwave adversely affected human as well as plant life – like the standing wheat crop. Parvinder Singh, a seed farmer in Rambha, a village in Haryana’s Karnal, told IndiaSpend that farmers in his village lost 20%-40% of the average wheat yield of 25 quintal per acre.

Wheat, a winter (rabi) crop usually planted in November and harvested in April, grows best in temperatures below 30 degrees celsius. Higher temperatures towards the end of the growing season causes what is called terminal heat stress, which manifests as wilting and results in lower yields.

High temperatures not only affect plants directly but also increase evaporation rates, thus aggravating drought-like conditions and reducing agricultural and potable water supplies at a time when water is needed more than usual, said Mangi Lal Jat, Global Research Programme Director-Resilient Farm and Food Systems, ICRISAT. “Extra irrigation is vital to increase soil moisture and mitigate the heat stress on crops.”

India’s 2022 heatwave curtailed the country’s wheat production to 107 million tonnes, below the government’s initial forecast of 111 million tonnes. This triggered an inflationary trend and a ban on wheat exports.

Wheat is the government’s primary choice of cereal for free supply of rations to 810 million people across the country. Producing and storing sufficient wheat is vital for the country’s food security. But climate vagaries in recent years cut wheat stocks to 75.02 million tonnes by April 2024, the lowest level since 2008.

With India’s population expected to touch 1.5 billion by 2030, the projected demand for wheat for that population would increase to about 140 million tonnes. There is no visible path for domestic wheat production to increase to the optimal level when climate vagaries have kept the output fluctuating and more or less stagnant over the last five years.

To protect a staple of millions, in laboratories across India and experimental farms such as Singh’s, efforts are underway to develop and test drought- and heat-resilient varieties of wheat, a daunting task in the face of an ever-evolving climate.

“Prepare for one problem and the next season you face a new challenge,” Achla Sharma, a principal wheat breeder at Punjab Agricultural University, told IndiaSpend.

Wheat hit hard

The most devastating effect of a heat wave on wheat productivity was observed in 2010, when an abrupt rise in temperature during the grain filling stage in wheat (March 2010) adversely affected the crop productivity in north-west India, said Sharma.

“Surveys showed that the terminal heat stress in the granary of Punjab led to an average yield penalty of 5.8% as compared to the previous year. However, the yield penalty was as high as 20% in the south-western districts of Punjab, especially in Bathinda and Sri Muktsar Sahib.”

“We found that PBW343, the historic wheat variety released in 1994, can tolerate terminal heat stress,” said Sharma. “However, since it succumbs to foliar rusts, we started to focus on its improvement as well as on developing new adaptive varieties which could minimise losses even under stresses like heat and drought.”

Wheat rust is a fungal disease occurring globally that can cause major crop loss.

Research indicates that India is likely to see more frequent early season heat. India’s north and west are showing the fastest warming during March, according to a study by Climate Central, an independent group of scientists and communicators who research and report on climate change.

“We found that climate change made the 2022 heatwave 30 times more likely and 1 degrees celsius hotter,” said Mariam Zachariah, Researcher at the Grantham Institute - Climate Change and the Environment, Imperial College London, and lead author of a separate World Weather Attribution study.

“The below average [monsoon] rainfall that occurred before the rainfall [in winter] caused the heatwave to be a dry, rather than humid, heatwave,” Zachariah said. “The timing of monsoon rains determines whether heatwaves in India are dry or humid. Dry heatwaves tend to have greater impacts on crops, while humid heatwaves are more dangerous for vulnerable communities.”

“Unless the world rapidly moves away from fossil fuels, climate change will continue to bring extreme temperatures to India, threatening food production and agricultural livelihoods,” Zachariah added.

“Summers are getting longer and hotter while winters [are getting] shorter and warmer due to global warming,” said Yuping Guan, the lead author of a study by the South China Sea Institute of Oceanology. By 2100, Guan concluded, summers could last six months while winters may be curtailed to only two months.

Heat stress is not the only climatic challenge to have emerged in the last few years.

Unseasonal rain and hail storms in March 2023 dented wheat yields, curtailing the total produce in the 2022-’23 season to 110 million tonnes against the government’s expectation of a bumper 112 million tonnes.

“Just one or two episodes of hailstorms at critical grain development stages are enough to destroy standing wheat,” observed Sharma.

“Rain and humidity have been adversely affecting the quality of wheat in our village,” Prahlad Singh, the sarpanch of Ajdawada in Madhya Pradesh’s Ujjain district, told IndiaSpend. “We’ve been getting yields of only 13-14 quintal per bigha (22 quintal per acre) of late, as against 33 quintal per acre a few years ago.”

Another challenge is early heat stress, manifesting in temperatures significantly exceeding the normal in October and November when wheat is sown.

“Until about five years ago, early heat used to be a concern only in Madhya Pradesh,” Sandeep Sharma, assistant professor, Department of Genetics and Plant Breeding, Banaras Hindu University, told IndiaSpend. “In the north west plains, we only had concerns for terminal heat stress, but now these areas have also started to face early heat stress. High temperature at the time of sowing affects the germination and early growth of the crop. Also, some parts of Karnataka, the Dharwad region, are seeing higher temperatures round the year.”

“If we cannot halt climate change and the consequential increasing scarcity of water, it will become very challenging to grow wheat in India after 40 years,” said Sandeep Sharma.

Can science beat climate change?

This year, 80% of the area under wheat in Haryana and Punjab, and around 70% of the area under wheat in other states, was covered by climate-resilient varieties better adapted to varying weather conditions.

But Punjab saw a new climate phenomenon this year.

“We saw almost four successive weeks without sunlight, just fog,” said Achla Sharma. “The absence of sunlight completely changed the wheat phenology, that is, the look of the plant based on the interaction of its genes with the environment.”

“Weather has a huge impact on the expression of a plant’s genetic material,” explained Sandeep Sharma. “Each variety behaves differently in a different environment. Essentially, genotypes are impacted by day and night temperatures, wind velocity, humidity, the soil and other environmental factors. So a variety that grows well in, say, Ludhiana, might not grow well in Jabalpur. That’s why developing a one-size-fits-all-geographies variety is challenging. There is no way to predict how a genotype will interact with the environment, and hence, how a new cross will behave in a certain area.”

At about 112.9 million tonnes, India’s overall wheat harvest in the 2023-’24 season was lower than the government’s target – 114 million tonnes – for the third consecutive season.

It’s not as if the new varieties of wheat didn’t perform.

“Punjab saw the highest yield and production of the last decade,” said Achla Sharma. “Our high-yielding variety PBW826 having the components of heat tolerance performed well.”

Singh from Rambha, Karnal affirmed that the yield in his village touched 28 quintal per acre this year. “But the climate vagaries kept the high-yielding strain from achieving its full potential,” added Achla Sharma.

Poor soil moisture due to insufficient rain has also been cited for this year’s lower than expected wheat yield. Rainfall across India during the 2023 monsoon season was 94% of the long-period average, while winter rains in January and February 2024 in the major wheat-growing states of Uttar Pradesh, Madhya Pradesh, Punjab, Rajasthan and Haryana were also below average.

Other newish wheat strains that have been very successful are PBW826, PBW 1 Chapati, DBW371 and DBW372, which help protect wheat from excessive cold during winter.

“DBW327 is the only strain that can be sown late, towards the end of December, and still delivers high yields,” said Singh, while Achla Sharma indicated that PBW757 would deliver too. “If other strains are sown late, the yield is adversely impacted by about 30%. We need more strains that can be sown late so that farmers get to harvest one more (vegetable) crop before sowing wheat.”

PBW826 by Punjab Agricultural University was the first strain to be recommended for a wide geographical area, from Jammu to Kolkata, essentially because it was so adaptive.

“To be used over a wide geographical area, a new strain has to be adaptive to different environmental conditions as well as different agronomic conditions of more than two agro-climatic zones,” said Ratan Tiwari, Director, ICAR-Indian Institute of Wheat and Barley Research, Karnal. “DBW187 (Karan Vandana) is a popular and widely adapted variety that has been recommended for the whole of north and central India.”

Apart from genetic potential of the variety, agronomic practices and protection practices impact the yield. Agronomy covers production practices such as the time of sowing, fertiliser application and irrigation.

Ancient strains

Developing new varieties necessitates new genetic material. The quality of a new variety depends a lot on the parents from which the genetic material is taken.

In that sense, Sandeep Sharma points out that access to a wider gene pool helps identify novel genes that haven’t been used in any existing breed programme, and hence will give a new cross more durable resistance to a stressor. Access to more lines also helps rule out biased conclusions about the usefulness of a gene.

While genetic improvement is a continuous process, Singh of Rambha feels that new varieties used to perform better until a decade ago. Of late, he said, “the performance of new varieties dwindles after just a few seasons”.

“A resistant variety may develop susceptibility to a pathogen when there are drastic changes in the weather like when it becomes hotter, or more humid, and so on, and it may no longer be able to photosynthesise as earlier, which adversely affects the yield,” explained Sandeep Sharma.

Since most of the new varieties developed in India have been based on nursery material received from CIMMYT, a nonprofit working on futuristic agricultural solutions, in 2020 the Union government, supported through the Department of Biotechnology, launched “Germplasm characterisation and trait discovery in wheat using genomic approaches and its integration for improving climate-resilience, protectivity and nutritional quality”, a five-year mega mission mode programme aiming at evaluating germplasm (a collection of gene resources) lines in material repatriated from Australia, UK and USA.

Some of this material is native to India, some comes from other Indian-origin wheat germplasm lines, and yet others from exotic germplasm lines procured from the CIMMYT, Mexico, and the Borlaug Institute for South Asia, India. Evaluation will help identify useful genetic material that is resistant to various stresses and quality traits, and resistant genes associated with those traits.

“This germplasm material has not been characterised earlier for economically important traits, and hence, has not been used in the breeding programme till date,” said Sandeep Sharma, a key investigator.

“We found that some of India’s native wheat lines were very resilient, which is important because so far scientists have not found wheat plants that are naturally very good at resisting all the things that can harm them, like diseases, pests, or harsh weather,” said Sandeep Sharma. “Without these naturally resistant plants to start with, it’s harder to breed new varieties that can withstand these challenges.”

However, the native wheat lines weren’t high-yielding, he added. “You don’t find every desirable trait in every line. Crossing lines that are known to be commercially high-yielding with lines with resilient traits creates desirable new varieties.”

Another challenge that the wheat initiative seeks to address is the development of robust markers for their use in Indian wheat breeding programmes for developing new varieties/lines, said Sandeep Sharma.

A genetic marker is a nucleotide sequence with a known location on a chromosome. Markers show exactly where useful genes are located. When the marker gets transferred to a cross, it helps to identify the parents of the new variety/germplasm lines.

“Using markers identified overseas to evaluate genetic material available in India often leads to incorrect outcomes because varying genetic compositions have different gene orientations,” explained Sandeep Sharma. For example, “sometimes, a marker that should have been present in a resistant line was absent while a marker that shouldn’t have been present in a susceptible line was present. We would be more confident about markers we have identified in our germplasm.”

Engineering healthier wheat

Globally, wheat alone contributes 18% of the per capita total dietary calories and 19% of the protein intake.

With the awareness that any improvement to the nutritional profile of wheat could help improve health, India’s wheat breeding programme not only aims to develop climate-resilient but also bio-fortified varieties. Climate-resilient varieties may not necessarily be bio-fortified.

About 30%-35% of the seeds indented by different agencies are bio-fortified, according to the ICAR-IIWBR. These varieties have a higher (>40 ppm) iron and zinc content than varieties cultivated previously.

Iron and zinc deficiencies are associated with anaemia, stunting and impaired development, and are widely prevalent in India.

“India’s ancient wheat lines have been found to have a high protein content, 18% as opposed to between 9% and 14% in most of the cultivated varieties,” said Sandeep Sharma.

“Breeding lines with this genetic material could make a huge difference to the problem of protein malnutrition in the population,” he said. “Poor people cannot afford to eat legumes every day but imagine if they could get equivalent protein in their chapati.”

The challenge is that breeding new varieties is time-consuming.

“It takes eight-10 years to develop a new variety: four-five years to identify genes that can bequeath resilience to the plant, and after that many more years to test the new breed,” said Sandeep Sharma.

Nor is switching to an ancient variety an option because those aren’t high-yielding. Sandeep Sharma hoped that the wider cultivation of ancient varieties is taken up. Blending that flour with normal flour could create more nutritious wheat mixes, he believes.

Efforts are also underway to develop wheat lines containing less fructan, a non-digestible carbohydrate found in various plant foods, particularly wheat, said Sandeep Sharma. Fructan intolerance causes digestive discomfort.

Punjab Agricultural University’s PBW1 Chapati was the first variety with a premium baking quality, and a demonstrated tolerance to terminal heat stress and the availability of moisture. Further, Punjab Agricultural University’s PBW RS1 variety has an altered starch ratio.

“Wheat usually has 10% resistant starch and 90% non-resistant starch, the former is metabolised slowly and mimics fibre in the colon whereas the latter increases blood sugar very quickly,” said Achla Sharma. PBW RS1 has higher resistant starch. “This is recommended to diabetics and those who are obese.”

Without both healthier varieties and climate-resilient varieties of wheat, the threat to India’s food security looms large.

This article first appeared on IndiaSpend, a data-driven and public-interest journalism non-profit.