Study On The Resistance Of Solanum Nigrum L. To Pendimethalin In Xinjiang Cotton Fields

Xinjiang is a major cotton-producing region in China,and weed problems affecting cotton growth,development,yield and quality are becoming increasingly prominent,among which Solanum nigrum L.is one of the malignant weeds in the region cotton fields.In the cotton planting process,pendimethalin is commonly used as a pre-sowing soil sealing treatment and has been used continuously for decades,making a large contribution to the cotton industry.According to the related research and production actual situation,the control effect of pendimethalin to Solanum nigrum L.is gradually weakened,which leads to the continuous growth and harm of Solanum nigrum L.in cotton field and cotton seedling sealing position.Of course,the succession of weed communities in cotton fields is changing in response to changes in cropping patterns,irrigation and control techniques.In order to clarify the resistance level of weed Solanum nigrum L.to pendimethalin and metabolic resistance mechanism in Xinjiang cotton fields,56 Solanum nigrum L.populations from different cotton regions of Xinjiang were tested by the petri dish method and the whole plant method;clarification of the multiple resistance of sensitive,medium resistant and high resistant Solanum nigrum L.populations to prometryn,oxyfluorfen and flumioxazin;differences in fitness and metabolic enzyme activities between resistant and sensitive Solanum nigrum L.populations were investigated,as well as the analysis of differentially expressed genes in resistant and sensitive Solanum nigrum L.populations after pendimethalin spraying.The main findings were as follows:1.The level of resistance and multiple resistance to pendimethalin in different geographical populations of Solanum nigrum L.in cotton fields were assessed.The results of the petri dish method and the whole plant method showed that the resistance trend of Solanum nigrum L.to pendimethalin was the same,and the resistance level of Solanum nigrum L.showed northern Xinjiang>southern and eastern Xinjiang,but the resistance index measured by the petri dish method was generally lower than the whole plant method.The results of the petri dish method showed that sensitive,low resistance,medium resistance,and high resistance populations accounted for 12.5%,71.4%,12.5%,and 3.6%of the total populations,respectively.Whereas the whole plant method were 5.4%,73.2%,16.0%,and 5.4%.Compared with the sensitive population SHZ-8,the BL-1 Solanum nigrum L.population showed the highest relative resistance in both methods,the GR₅₀value was 90.30 mg/L and 4805 g/hm²,the resistance index was 20.62 and 26.20,respectively.The multiple resistance study found that the high resistance BL-1 Solanum nigrum L.population had multiple resistance to flumioxazin,while the medium resistance WJQ-2 Solanum nigrum L.population did not develop multi-resistance to prometryn,oxyfluorfen and flumioxazin.2.The difference of fitness between resistant and sensitive Solanum nigrum L.populations was determined.Under non-competitive conditions,resistant Solanum nigrum L.population had lower plant height,fruit number,stem thickness,overground biomass and whole plant biomass than sensitive Solanum nigrum L.population by 9.56%,20.69%,7.52%,12.64%and 17.15%,respectively,incurring a fitness cost,but there were no significant differences in leaf length,leaves number,leaf width,leaf area and underground biomass（P>0.05）.Resistant Solanum nigrum L.population delayed flowering by 2 day compared to sensitive Solanum nigrum L.population.3.The differences of pendimethalin on the physiological metabolism of resistant and sensitive Solanum nigrum L.populations were investigated.The results showed that the activities of GSTs and P450s of the resistant Solanum nigrum L.population were significantly higher than the sensitive Solanum nigrum L.population after being treated with pendimethalin,and both reached the highest values of 0.27 U/L and0.22 U/L at the 25th day,respectively.The soluble sugar content,MDA content and SOD activity of resistant Solanum nigrum L.population showed a trend of increased and then decreased,reaching the highest values at the 15th day and 10th day,with 3.07 mg/g,0.36 nmol/m L and 0.49 U/m L,respectively,while POD activity and soluble protein content were not significantly different（P>0.05）.It follows that resistance to pendimethalin in Solanum nigrum L.may be associated with enhanced activity of GSTs and P450s.4.The difference of transcriptome between resistant and sensitive Solanum nigrum L.populations after spraying pendimethalin was analyzed.The results showed that 210,166 transcripts and 114,582Unigene were obtained after transcriptome sequencing,and 43,537 Unigenes were annotated to 48 GO functional regions,most enriched for binding,metabolic processes,cellular processes and catalytic activities.After being treated with pendimethalin,the resistant Solanum nigrum L.population had 3853differentially expressed genes relative to the sensitive Solanum nigrum L.population,including 1694upregulated genes and 2159 downregulated genes.Through functional annotation and differential expression analysis,it was found that the differential genes were mainly enriched in the pathways related to capacity metabolism,glutathione metabolism,carbohydrate metabolism,and biosynthesis of other secondary metabolites.It can be seen that these pathways involved in metabolic resistance related pathways may be the main reason for the resistance of Solanum nigrum L.to pendimethalin.