With annual production of about 315 million tonnes in Asia ( FAO, 2016 ), wheat is second only to rice in importance. Since the start of the 'Green Revolution' around 1970, wheat production has seen an average annual growth rate of over 3% ( Figure 1 ), whilst wheat yield has grown at an annual average rate of 2.1% ( FAO, 2016 ). However, yields vary signifi cantly between developed and developing countries. Lopes et al. (2012) studied 26 wheat genotypes released between 1977 and 2008 and estimated annual increases in yields of between 0.5% and 0.9% in Asia and Africa. Other recent estimates of genetic gain are less than or around 1% per annum ( Sharma et al., 2012 ; Manes et al., 2012 ). Wheat yield stagnation is currently being faced in everal parts of the world ( Knight et al., 2012 ). It has been estimated that wheat production in South Asia needs to grow at the rate of 2-2.5% annually until the middle of twenty-fi rst century to feed its population ( Chatrath et al., 2007 ). Singh et al. (2007) also reported that world wheat production needed to grow at 2% annually to meet future demands, half of which could come from breeding better varieties and half from improvements in cultivation techniques. China exemplifi es both the successes and the continuing challenges of improving wheat yields.

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