The Adenine at the 4th Exon of the DRO1 Gene Provides Drought-Tolerance Capacity to Hybrid Rice Deyou4727 and Its Maintainer Line Dexiang074B

Extreme weather and global warming are drastic agricultural issues causing water scarcity. Under these conditions, it is vital to select drought-tolerant hybrid super rice breeds to enhance the rice yield in dry areas. In the current study, a dry-shed experiment was carried out in 2019-2020 to analyze the root growth, gene expression, and enzyme activity of hybrid rice Deyou4727, its parent (Dexiang074B Chenghui727), taking IR64 as a universal control. Results showed that Deyou4727 and its maintainer line Dexiang074B produced more roots (30-50 cm soil) and higher enzymatic activity than IR64 during the drought stress period, indicating a good drought-tolerant capacity for Deyou4727. The distribution and morphology of the root system in Deyou4727 were inherited by the maintainer line Dexiang074B, which was confirmed by the high upregulation of DRO1 and OsPIN1b gene expression and the sharing of the same ORF region in both the hybrid rice varieties. However, the DRO1 gene ORF study showed that, in the case of the control IR64, 'A' was missing at the 4th exon of the DRO1 gene, which may explain the shallow and weak root architecture system of IR64. The drought-tolerance capacity of Deyou4727 can be used in the future as a drought-resistant germplasm for breeding more drought-tolerant hybrid rice varieties.