Ratooning ability of upland rice varieties under lowland condition to mitigate global climate change

Abstract Planting upland rice in lowland conditions offers an alternative strategy to mitigate the negative impacts of alternating drought and waterlogging stress associated with global climate change. At the same time, cultivation practices such as ratoon cropping enhance the sustainability of rice production by increasing yields and reducing resource demands. The research conducted between 2022 to 2024 evaluated the ratooning performance of upland rice across four agroecosystems using 11 genotypes. The experiment used a randomized block design with three replications. A genetics study on the ratooning ability of upland rice included the planting of 277 F 2 seeds derived from the cross of Inpara 2 and Sikuning. Gene action was estimated using the skewness method, while the number of genes was determined through kurtosis analysis. The results indicated that upland rice yields were higher in lowland areas compared to upland areas. Upland rice ratoons showed productivity only in two locations that retained sufficient water following the main crop harvest. Variety factors significantly affected all ratoon characteristics (P < 0.01). Sikuning had the best ratooning ability, achieving a first ratoon yield of 4.23 t ha −1 dry milled grain (DMG), compared to a main crop yield of 4.06 t ha −1 DMG. The F 2 generation follows a two-gene inheritance pattern, with a ratooning to non-ratooning ratio of 15:1, reflecting dominant duplicate inheritance. The average yield per hill of the main crop in the F 2 population was 61.80 g, higher than that of both parental lines. The yield of the main crop is regulated by numerous genes showing additive gene action. The average grain weight of the ratoon in the F 2 population was 25.62 g, showing a skewness of 0.55 and a kurtosis of -0.63. An epistatic effect was observed in the F 2 ratoon, resulting in segregants with ratoon yields greater than those of their parents. Up to 11% of the F 2 plants produced a combined main crop and ratoon yield exceeding 125 g, with the ratoon yield constituting at least 50% of the main crop yield. The results suggest the potential to use upland rice ratoons as an alternative method for enhancing rice production in lowland areas.