Evaluation and GWAS of radicle gravitropic response in a core rice germplasms population
Abstract Aims: Gravitropism is one of the primary determinants of root development, facilitating root penetration into soil and subsequent absorption of water and nutrients. To study the gravitropism of the radicle roots, we conducted this research.Methods: The gravitropism of 226 Chinese rice micro-core accessions and drought-resistant core accessions were assessed through the modified gravity-bending experiment and genome-wide association analysis (GWAS) was used to map the associated QTLs.Results: The average value of gravitropic response speed of radicle roots was 41.05°/h from 16.77°/h to 62.83°/h. Significant difference (p < 0.002) in gravity response speed between Indica (42.49°/h) and Japonica (39.71°/h) subspecies was found. The gravitational response speed of radicle roots was significantly positively correlated with the number of deep roots (r =0.16), the growth speed of radicle roots (r =0.21) and the drought resistance coefficient (r=0.14).Conclusions: In total, 3 QTLs (quantitative traits) associated with gravitropic response speed were identified on chromosome 4,11 and 12. There are some known QTLs relating to roots traits and drought resistance located nearby the QTLs identified here, which confirms the close relationship between radicle gravitropism and the drought resistance. From within these intervals, 5 candidate genes were screened for qPCR in 6 extreme rice varieties, demonstrating that gene LOC_Os12g29350 may regulate gravitropism negatively and confirming its candidacy for further study.