Endophytes enhance Asia minor bluegrass ( Polypogon fugax ) resistance to quizalofop-p-ethyl

Aims The mechanisms of weed resistance to herbicides are generally thought to include alteration of the target site, enhanced detoxification, and sequestration. Endophytes can promote plant growth and enhance tolerance to abiotic stress. To date, how endophytes affect weed resistance to herbicides has not been reported. Methods The dose-response tests performed on the derived seed batches in our study were used to test the toxicity of Polypogon fugax to quizalofop-p-ethyl. The endophytes were isolated, and the degradation rate of endophytes to quizalofop-p-ethyl was measured. The endophyte was inoculated onto the susceptible P. fugax using inoculation techniques. The effect of germicide on the toxicity of quizalofop-p-ethyl to the resistant P. fugax plants was observed. Results Resistance was confirmed in several tested P. fugax populations. Among them, the population collected from Qingshen County, Sichuan Province (QCSP) had the highest resistance index. The number and degradation rate of quizalofop-p-ethyl degrading endophytes was lower in the susceptible population than in the QCSP resistant population. The isolated KT4 strain from the QCSP population had the highest degradation rate. The 16S rDNA sequence of KT4 was identical to that of Sphingomonas sp. The treatments that contain inoculating endophytes KT4 enhanced the resistance to quizalofop-p-ethyl in the susceptible population. Treatments containing a combination of quizalofop-p-ethyl with either kasugamycin or jinggangmycin, which can kill or inhibit endophytes growth, reduced the resistance level of the QCSP population to quizalofop-p-ethyl. Conclusions This is the first report that endophytes can degrade quizalofop-p-ethyl to enhance resistance in P. fugax .