Arun Kumar Joshi is Principal Scientist, Global Wheat Program, CIMMYT and CSISA Objective 4 Leader. Based in Kathmandu, Nepal, he is a Fellow of the Indian National Science Academy (INSA) and also of DAAD Germany. He has facilitated development of around three dozen wheat varieties and made numerous contributions to disease resistance, heat and drought tolerance and biofortification in South Asia. He has been awarded the Jeanie Borlaug Laube Women in Triticum Mentor Award 2014 from Borlaug Global Rust Initiative, Cornell, USA.
In this article, he offers his personal insights on some of the most pressing issues concerning wheat breeding today:
How does wheat breeding help ensure food security in South Asia?
South Asia faces multiple challenges in future wheat production, including heat stress, dwindling water supplies for irrigation, changes in urbanization patterns and a growing threat of increased virulent diseases such as wheat rusts (yellow, brown and black) and leaf blight.
Wheat breeding has played a major role in ensuring food security and combating these challenges by developing agronomically superior cultivars with good quality traits and genetic resistance to biotic and abiotic stresses. The Green Revolution came about due to the release of dwarf, photo-insensitive, nitrogen-responsive varieties and some of the most important gains have been sustained by the continued release of improved varieties and the associated support of agronomy, policy and socio-economic factors.
While many smallholders throughout South Asia benefited from the introduction of first-generation Green Revolution cultivars that replaced lower-yielding landraces, the adoption of second and third-generation cultivars has led to ongoing improvements in wheat production. Wheat production in India in the last five years (2009-14) increased from 80 to 96 million tons, in Pakistan from 21 to 25 million tons, in Nepal from 1.3 to 1.9 million tons and in Bangladesh from 0.84 to 1.37 million tons.
What is Ug99? Can you put into perspective the magnitude of the challenge stem rust diseases pose for food security?
Ug99 is a race of stem or black rust caused by Puccinia graminis f. sp. Tritici. It was first identified in Uganda in 1999 and has since spread to other countries in East Africa and to Sudan, Yemen and Iran. At the time of discovery, nearly 80-90 percent of wheat cultivars in the world were susceptible to this race. Thanks to strong collaborative work with the Borlaug Global Rust Initiative, the International Wheat and Maize Improvement Center (CIMMYT) and various national agricultural research systems (NARS), wheat breeders and other relevant stakeholders managed to develop and disseminate Ug99-resistant wheat varieties, keeping the disease in check.
However, there is no scope for complacency. Given certain conditions, Ug99 threatens to spread to other wheat-producing regions of Africa and Asia and potentially the entire world. The threat is particularly acute in South Asia, which produces 20 percent of the world’s wheat. Other rusts are also equally potent. Recently, for example, yellow rust has become extremely threatening for India, Pakistan and Nepal.
Stem rust has been known to be a constant threat causing severe losses to wheat production worldwide. It has remained in control for the last three decades only through the use of genetic resistance in semidwarf cultivars. This is a significant reason why resistance-breeding programs must continue.
How can wheat breeding help smallholder farmers in South Asia mitigate the effects of problems such as scanty rainfall, increasing temperatures, salt-affected soils and increasing incidence of diseases?
A critical factor in the Green Revolution’s success was that new varieties were broadly adapted to the resource-poor environments prevalent in South Asia and they performed well under abiotic stresses such as heat, drought (exacerbated by limited irrigation) and variable fertilizer doses. An aggressive strategy to develop and disseminate stress-tolerant cultivars in farmers’ fields is an important response to abiotic stress in South Asia as resource-poor farmers cannot afford to use many other control measures. Stress-tolerant varieties combat multiple problems and hence can be very useful for farmers.
Disease-resistant varieties are one of the most effective control strategies for most diseases of wheat grown by resource-poor farmers in the developing world and are often considered by commercial producers as the most environment-friendly and profitable responses to disease as well. For a farmer, the cost of protecting 1 hectare of wheat against disease through the application of modern chemicals is estimated to be US$ 10-80 per hectare. With the use of disease-resistant varieties, farmer can save this cost as the rust resistance in wheat is embedded in the seed.
How can new improved varieties reach farmers more quickly?
Two systems of germplasm dissemination and adoption are found in South Asia – formal (organized) and informal (unorganized). Modern crop varieties are the backbone of the formal seed industry, which is almost equally shared by public and private sectors. The private sector takes more interest in cross-pollinated and low-bulk crops, in which hybrids are common. NARS plays a major role in germplasm conservation, variety development and in generating appropriate technologies to utilize the yield potential of new varieties. New varieties are passed through a series of evaluation and release tests before farmers can access them.
Although new improved varieties developed by NARS should be multiplied and made available to farmers in the shortest possible time so they can realize the benefits, in practice, weak extension and seed distribution systems often slow the distribution of new varieties to farmers. As a result, more than 80 percent of all seed in South Asia is saved by farmers and it can be even higher for self-pollinating crops such as wheat. In some regions such as the eastern Indo-Gangetic Plains of India, the availability of experienced seed growers, supported by either the public or private sector, is far lower than in the north-western plains.
The options for improving germplasm dissemination and adoption in India include: strengthening the public and private sectors through vigorous policy planning and implementation and promoting participatory research. Indian research centers already work on this model with partners (including CIMMYT) and it has so far proven quite successful. Anticipating the advantages of working in a participatory mode, the Indian Council of Agricultural Research made it mandatory for all research centers receiving support under the National Seeds Project to actively engage in participatory seed production since 2003. This path can be used effectively for quick dissemination of superior varieties in areas characterized by weaker linkages.
Another approach being used for rapid multiplication and distribution include pre-release seed multiplication whilst candidate resistant lines are being tested in national evaluation trials and farmers’ participatory selection approaches. This pre-release multiplication was successfully used in Nepal, Bangladesh, Afghanistan and Pakistan for faster dissemination of Ug99-resistant varieties as part of a US Agency for International Development seed project from 2009-2012.
Can you tell us more about CSISA’s work on wheat breeding?
One of CSISA’s objectives is to develop high-yielding, heat and water-stress-tolerant and disease-resistant wheat varieties for current and future cereal and mixed crop-livestock systems. To this end, we have produced a series of new varieties and ensure their multiplication and dissemination. For instance, in the last year alone, 12 wheat varieties were released for different environments and management conditions of South Asia. In addition, 10 varieties were identified for release in different environments of South Asia. Seed growers and farmers’ groups continued seed dissemination of superior lines produced by CSISA over the last five years and as a result, according to breeder seed indent and production figures, CSISA-bred lines now cover 18 percent of the wheat production area in India, 24 percent in Nepal and 34 percent in Bangladesh.
Can you highlight additional impacts of CSISA’s wheat breeding work?
Considerable spillover effects have also been achieved on account of CSISA’s work on wheat breeding. One of the most tangible spillover output of our wheat breeding work occurred on August 13 this year, when the Government of Bhutan officially released two new improved wheat varieties (Bajosokhaka and Gumasokhaka) from CIMMYT. This is the first release of any wheat variety in Bhutan in two decades. On average, both varieties yielded 50 percent higher than the most popular variety (Sonalika) in three years of multi-location testing in Bhutan. Both varieties are believed to have water-stress-tolerance and good resistance to yellow rust.
Further, two wheat varieties from Punjab (PBW 621, PBW 644) that were released for the northwestern plains zone have been widely adopted Bihar. Also, CSISA-bred wheat varieties in Bangladesh have spread to new areas in southern Bangladesh, benefitting nearly 10,000 farm families.