Retrospective study in US commercial sorghum breeding: I. Genetic gain in relation to relative maturity

Sorghum [Sorghum bicolor (L.) Moench] is an important staple food for human consumption and a source of animal feed in the semiarid regions of the world. Sustained positive rates of crop improvement are necessary to supply food and feed to a growing population. However, land allocated to sorghum and its inclusion in production systems has been in constant decline. Here we report the rate of sorghum genetic gain in a commercial breeding program in the United States and provide evidence that a modest yield improvement is an important factor limiting land allocation to this crop. A 6-year study that evaluated 50 sorghum genotypes commercialized between the decades of 1960 and 2010 was conducted in 19 environments within the US Sorghum Belt region. Yield varied between 500 and 850 g m(-2). Here we show a positive rate of genetic gain of 2.63 g m(-2) y(-1) on average across three different maturity groups grown in the United States. Rates ranged from 2.1 to 4.3 g m(-2) y(-1) across maturity groups. This result contrasts with a stagnant rate of crop improvement for many regions of the world, yet the rates are insufficient to reverse the negative trend in planted area. Breeding technologies are proposed to hasten genetic gain in sorghum to reverse the loss of on-farm agricultural biodiversity.