Performance and adoption of submergence-tolerant TDK1-Sub1 rice in southern Lao PDR

Abstract

Under short-term submergence (7–15 days), submergence-tolerant rice genotypes (e.g. TDK1-Sub1) have been reported to be higher yielding than their intolerant equivalents without the Sub1 gene. This paper examined whether TDK1-Sub1 was superior to Other locally-preferred genotypes, with and without submergence, using 66 on-farm comparisons in southern Lao PDR. Data were examined for 2 genotype categories (TDK1-Sub1, Other) in 3 environment groups (Favourable, Drought, and Submergence), with 22 farms per group used as replicates. Farmers saved seeds of TDK1-Sub1, planted it again in flood-prone fields, and disseminated its seeds to relatives, neighbours and friends, but they did not do so in areas with lower flood risk. Grain yield was generally higher under Favourable conditions (2.42 ​t ​ha⁻¹) than under Submergence (1.94 ​t ​ha⁻¹) or Drought (1.90 ​t ​ha⁻¹). Under Submergence, the grain yield of TDK1-Sub1 (2.22 ​t ​ha⁻¹) was significantly higher than the Other genotype (1.65 ​t ​ha⁻¹; P ​< ​0.10). Conversely, under Drought, the grain yield of TDK1-Sub1 (1.58 ​t ​ha⁻¹) was significantly lower than the Other genotype (2.22 ​t ​ha⁻¹; P ​< ​0.10). Submergence-tolerant genotypes should enhance system intensification and food security in submergence-prone areas, but yields of other locally-preferred genotypes were more stable in the absence of submergence, especially under late-season drought. Current efforts to introgress additional resistances into submergence-tolerant genotypes are worthwhile, to reduce any downside risk in the absence of flooding. Nevertheless, for Lao PDR and others who prefer glutinous rice, the Sub1 gene should be introgressed into the best-adapted glutinous rice genotypes, which already possess other resistances.