Brown planthopper resistance characteristic of seven purple rice varieties

【Objective】The study aimed to preliminarily explore the resistance characteristics of purple rice varieties against brown planthopper（BPH）and the impact of BPH infestation on the anthocyanin content in purple rice，providing reference for the cultivation of new purple rice varieties resistant to BPH.【Method】Seven purple rice varieties，50-6， 54-3，NY14，NY17，NY30，WD098 and DT01，were used as test materials，with the susceptible and non-purple phenotype variety 9311 as the control，to investigate the purple leaf sheath phenotype of purple rice varieties. Resistance evaluation of the seven purple rice varieties at seedling and tillering stages was conducted according to the evaluation standard for BPH resistance of rice varieties. The resistance mechanism of the resistant purple rice varieties was explored through BPH host selection and survival tests，and anthocyanins in rice leaf sheath were extracted by hydrochloric acid-ethanol solution without light. The absorbance was measured by a spectrophotometer，and the anthocyanin optical density and content were calculated according to the Greey formula. Furthermore，a correlation analysis was conducted between the resistance score and anthocyanin relative content of purple rice varieties.【Result】Resistance identification at the seedling and tillering stages revealed that purple rice varieties 50-6 and 54-3 were highly susceptible，while NY14，NY17，NY30，and DT01 exhibited resistance or high resistance against BPH. Variety WD098 showed moderate resistance at the seedling stage and resistance at the tillering stage. The results of the insect survival rate and host selection tests suggested that，compared to the susceptible control 9311，NY14 and NY30 exhibited significant antibiosis and avoidance（P<0.05，the same below）， while the antibiosis and avoidance of varieties NY17，WD098，and DT01 were not significant. After BPH feeding at the seedling and tillering stages，the anthocyanin content in five resistant purple rice varieties NY14，NY17，NY30， DT01 and WD098 continued to increase，and still higher than baseline levels after 8 d of infestation，but it fell below baseline levels after a 4-d infestation in susceptible varieties. Correlation analysis indicated that there was an extremely significant negative correlation between the resistance grade and the changes of anthocyanin relative content in the leaf sheaths of 7 purple rice varieties at seedling and tillering stages（P<0.01）. The survival rate of BPH after feeding on the resistant purple rice varieties was significantly negatively correlated with the anthocyanin content and anthocyanin relative content.【Conclusion】In summary，there are great differences in the resistance levels and characteristics of BPH among different purple rice varieties，but the BPH resistance scores at seedling and tillering stages show extremely significant negative correlation with the anthocyanin relative content