Abstract:In order to intensify QTL fine mapping, mapbased gene cloning, functional analysis and molecular marker assisted breeding of the low hydrocyanic acid content trait of sorghumsudangrass, we used 500 isolated individual clone plants and their parents of diploid hybrid sorghumsudangrass F2 generation population as materials, which was constructed in the early stage of the research group. The QTL mapping of hydrocyanic acid content trait of the highdensity molecular linkage map of sorghumsudangrass was determined by interval mapping method. The results showed that: (1) the generalized heritability of the hydrocyanic acid traits in the four different environments was 61.70%, 72.05%, 40.16% and 69.25%, respectively, indicating that the hydrocyanic acid content is both environmentally affected and controlled by microeffects. The frequency of population measurements showed a characteristic of singlepeak normal distribution, which met the QTL mapping requirements. (2) Under the condition of LOD>2.5, 16 QTLs related to hydrocyanic acid traits were detected, which were distributed on LG1, LG2, LG4, LG6, LG7, LG8 and LG10 linkage groups. (3) There are 9 stable QTLs that can be repeatedly detected in 16 QTLs, and the genetic contribution rate ranges from 1.17% to 39.9%. Among them, the main QTLs with contribution rate >20% are Qcn22, Qcn41, Qcn6 and Qcn61, a total of four. The experiment identified the genetic effects and molecular marker sites of each QTL.