Abstract:

In this study， bulk segregant analysis using simple sequence repeat markers （BSA-SSR） was used to screen and identify DNA fragments linked to low hydrocyanic acid content of sorghum-sudangrass hybrids. By PCR amplification using nine pairs of suitable SSR primers screened， 26 SSR target fragments related to low cyanide traits in sorghum-sudangrass hybrids were discovered. After PCR product recovery， partial purification， and sequence analysis， the base sequences of these DNA fragments linked to low cyanide content were obtained. Sequence comparison using the BLASTn database showed that two ‘low cyanide’ target fragments， TF8 （101 bp） and TF16 （586 bp） had， respectively， 95.4% and 97.0% homology with sorghum phosphoribulokinase chloroplastic gene XM_021458168.1 and sorghum clone BAC 88M4 gene AY661656.1， but there was no mention of hydrocyanic acid regulation in the functional annotation of these two genes. However， there are a number of variations in the DNA base sequences. The TF8 fragment has three base substitutions and one insertion， resulting in the replacement of an alanine and a glycine with cysteine， a threonine with alanine， and deletion of a glycine. Fragment TF16 has one base A missing， resulting in alanine deletion. Based on these results it is inferred that TF8 and TF16， two low cyanide target fragments， regulate the expression of a low hydrocyanic acid content trait. These results lay a foundation for further research on the detailed mapping and marker-assisted breeding of the major QTLs for low hydrocyanic acid content of sorghum-sudangrass hybrids.

Key words: sorghum-sudangrass hybrid, the trait of low hydrocyanic acid content, BSA-SSR, target fragment screening, sequence alignment identification