Sub1 Rice: Engineering Rice for Climate Change

Abstract

By the year 2100, the number of people on Earth is expected to increase by ∼50%, placing increasing demands on food production in a time when a changing climate is predicted to compromise crop yields. Feeding this future world requires scientifically informed innovations in agriculture. Here, we describe how a rice gene conferring tolerance to prolonged submergence has helped farmers in South and Southeast Asia mitigate rice crop failure during floods. We discuss how planting of this new variety benefited socially disadvantaged groups. This example indicates that investment in agricultural improvement can protect farmers from risks associated with a changing climate.

Figure 1.

Expression of the Sub1A transgene (right) confers robust tolerance to submergence compared with the control rice (left). Plants were grown for 2 weeks, submerged for 2 weeks, and then allowed to recover for 2 weeks before photography (Ronald laboratory). This work was significant because it represented the first isolation of a quantitative trait locus (QTL) with an important agronomic effect. Isolation of Sub1A and the 180 kb of genetic sequence surrounding the gene set the stage for advanced marker-assisted breeding at the International Rice Research Institute (IRRI) (Neeraja et al. 2007; Septiningsih et al. 2009; Mackill et al. 2012).

Figure 2.

Yield of Swarna and Swarna-Sub1 under variable durations of submergence in farmers’ fields. Data are from 24 farmers in Uttar Pradesh, India, during the wet season of 2007 who cultivated both varieties (n = 24). (From Ismail et al. 2013; reproduced, with permission, from Elsevier © 2013.)

Figure 3.

Map of the 128 villages where the Swarna-Sub1 randomized controlled trial was performed in the 2011 and 2012 Kharif rainy seasons. (From Emerick et al. 2016; reproduced, with permission, from the authors.)

Figure 4.

Experimental evidence on the flood tolerance of Swarna-Sub1. The horizontal axis shows the duration the plot was submerged during the season (in days). The vertical axis shows the yield in kilograms per hectare. The blue and black lines show nonparametric Fan regressions of yield on flooding duration. The blue line is for the Swarna-Sub1 treatment group, whereas the black line is for the control group. The dots show the average yields for different flood durations for Swarna-Sub1 (blue) and Swarna (black). (Image created with data from Dar et al. 2013.)

Figure 5.

Percentage impact of introducing Swarna-Sub1 on the listed outcomes (dots). The black bands show the 95% confidence intervals. The figure shows that Swarna-Sub1 farmers obtained higher yields, increased cultivated area, used more fertilizer (conditional on area), and were more likely to transplant their fields. All these effects occurred in a year without flooding. (Image based on authors’ calculations using the replication data in Emerick et al. 2016.)