Influence Of Lignin Metabolism On Effectiveness Of Bioherbicide Junkekuo

Solidago canadensis L.which originates from North American was introduced into China as ornamental flowers in the 1930s and then became a malignant weed since 1980s.S.canadensis had caused damage to ecological environment and economic losses.The manual,mechanical and chemical control of S.canadensis failed to achieve desired effect.SC64,a Sclerolium rolfsii strain,isolated from S.canadensis,was developed as bioherbicide product,Junkekuo.Junkekuo could be used to control S.canadensis and other broadleaf weeds in grain crop fields and lawns.Previous research on Junkekuo remain an urgent need to increase effectiveness.Field experiments showed that the pathogenicity of Junkekuo varied from different growth stages of S.canadensis.Through studies on lignin metabolism of S.canadensis,we found that higher lignified level of the population had stronger defense ability.In this study we had tested the lignin content,distribution and metabolism of S.canadensis of different population and different growth stage,which correlate with effectiveness of Junkekuo.Our study is dedicated to provide theoretical and technical basis for more effective biocontrol on S.canadensis.1 Correlation study of lignin content of S.canadensis among different growth stages and effectiveness of JunkekuoWe had conducted experiments for 5 times(monthly,S1-S5)in reproductive period during which plant height,stem diameter,content of lignin,lignification level in phloem and xylem were measured.Junkekuo treatment and the same measurement after treatment were also conducted for S1-S5 respectively.The results showed that the lignin accumulated a lot with the increase of plant height and stem diameter.Compared with the S1 stage,the average plant height and stem diameter in the S5 stage were 81.13 cm and 3.8 mm higher than those in the S1 stage,and the total content of lignin was 15.4%higher than the S1 stage.The biocontrol effectiveness of Junkekuo varies among different growth stages.Results show that mortality rate and fresh weight control effectiveness of S5 stage decreased 57.4%and 75.5%compared with S1 stage.The effectiveness of Junkekuo was reduced along with growth of S.canadensis.Among variables with the effectiveness of Junkekuo,lignin content had the highest correlation coefficient and significant negative correlation(p<0.01).Our studies showed that when content of lignin increased with the growth of S.canadensis,the effectiveness of the Junkekuo was reduced.2 Influence of lignin metabolism in the different population of S.canadensis on effectiveness of bioherbicide JunkekuoUsing S.canadensis as materials.Lesion size of leafs was determined after pathogen(SC64)inoculation to mark off susceptible and resistant population.Then TGA method was used to determine lignin content of leaves and the extent of ligninal was compared by fasga and malue method in different populations of S.canadensis,relative expression of lignin metabolic related genes in the phloem and xylem was determined.According to our results susceptible and resistant population was determined as lesion size of leafs greater or less than 5%of total surface of leaves.Our results indicating that the resistant population present singnificant more lignin content than susceptible population.The results of fasga and malue staining showed that the phloem of the resistant population had higher extent of ligninal;at the same time,we found that the expression of lignin metabolism-related enzyme gene was significantly higher than that of susceptible population,and there was no significant difference between the two population of xylem.The results of the above studies show that resistant populations have a stronger resistance than susceptible populations,the resistance of the resistant population was associated with higher lignin content and stronger lignin metabolism-related enzyme expression,the extent of ligninal of phloem of the resistant population was correlated with the ability to resist the infection of SC64.The results of the study explain the difference in the control effect of herbicides for different populations of S.canadensis.3 Studies on lignin metabolism of Solidago canadensis in its ability to recover after SC64 infected.The resistant and susceptible populations of S.canadensis were used as materials.Stem cross-section were made from the stem of the 24h inoculated plants at 14 day after treatment.Lignin histochemistry was examined using Fasga and Malue methods.Relative expression of lignin metabolism related enzymes in phloem and xylem of stem was also determined.The results showed 14 day after treatment resistat plants showed slight injury compared with the susceptible plants.Both populations showed an increased level of expression of lignin synthesis-related genes and increased was greater and faster in the resistant line.After 14 days of recovery,the cell wall inside the vascular tissue of S.canadensis was thickened and with highly extent of ligninal in the phloem,and phloem connected between the formation of a ring of defense barrier.Compared with the susceptible population,the cell wall thickening in the vascular tissue of the resistant population was more obvious,and the extent of ligninal was higher.The results of the study show that lignin metabolism has a great impact on the recovery ability of S.canadensis,the relative expression of lignin metabolism related enzymes of the stalk after infected was rapidly up,at the same time,a large amount of highly ligninal phloem and xylem are produced to resist the invasion of SC64.The mechanism affects the recovery ability of different populations of S.canadensis after being infected by SC64.