Study On Seed Dormancy Of Eriochloa Villosa And Resistance To Nicosulfuron

With the change of planting structure in Heilongjiang Province,cultivation a large area of soybean cultivation became a large area of corn cultivation.The target enzyme of nicosulfuron is acetolactate synthase（ALS）,a broad spectrum herbicide.Nicosulfuron is the only herbicide in the sulfonylurea herbicide that has special effects on the grass weeds.Nicosulfuron has the advantages of low dosage,good effect and high safety.Therefore,nicosulfuron is mainly used to the control of gramineous weeds in maize of Heilongjiang.In recent years,it has been found that the control effect of nicosulfuron on the annual weeds Eriochloa villosa of maize field has been decreasede in the local areas,so that Eriochloa villosa became the main weed and had damaged seriously year by year.In this study,we used the method of indoor bioassay to study the dormancy characteristics of wild millet.At the same time,Using seeds of Eriochloa villosa in maize fields as materials,we studied the susceptibility of Eriochloa villosa to nicosulfuron and we also studied the changes of photosynthesis,target enzyme and metabolic detoxification enzyme after application of nicosulfuron on Eriochloa villosa with different resistance levels by measuring physiological and biochemical indexs in order to clarify the resistance mechanism of Eriochloa villosa to nicosulfuron.It provides theoretical and practical basis for the control of Eriochloa villosa.The main findings are as follows:1.Eriochloa villosa seeds are dormant.2.5cm at room temperature under the wet soil,5cm at room temperature under the dry soil and-20℃dry storage conditions can break Eriochloa villosa seed dormancy.3.Physical method of warm water immersion can break Eriochloa villosa seed dormancy.4.Chemical agents H₂SO₄,NaOH,KNO₃ and GA₃ are not ideal for breaking Eriochloa villosa seed dormancy.5.There were differences in the resistance level of Eriochloa villosa to nicosulfuron in 8areas of Heilongjiang province.M-3（RI=1）,M-9（RI=1.19）and M-5（RI=1.57）are Sensitive Eriochloa villosa.M-6（RI=2.05）,X-1（RI=2.08）and M-2（RI=2.11）are medium-resistant Eriochloa villosa.M-16（RI=3.23）,M-1（RI=4.51）,X-3（RI=6.48）and X-2（RI=8.30）are high-resistant Eriochloa villosa.6.X-2 as high-resistant Eriochloa villosa.X-1 as medium-resistant Eriochloa villosa.M-3as sensitive Eriochloa villosa.Eriochloa villosa of resistance to nicosulfuron was studied by using the above three kinds of biotypes as materials.The results showed that there were differences in photosynthetic indexes,target enzymes and metabolic detoxification enzymes in different levels of resistance before and after spraying nicosulfuron.Before spraying,leaf photosynthetic index（Photosynthetic rate,stomatal conductance and chlorophyll content）,target enzyme（ALS）,protective enzyme（SOD,POD）,metabolic detoxification enzyme（GST,GSH）content and activity.Above index high-resistant Eriochloa villosa（X-2）higher than that of medium-resistant and sensitive type.After spraying nicosulfuron,leaf photosynthetic index（Photosynthetic rate,stomatal conductance and chlorophyll content）,target enzyme（ALS）,protective enzyme（SOD,POD）,metabolic detoxification enzyme（GST,GSH）content and activity.The decline of above index high-resistant Eriochloa villosa（X-2）was lower than that of medium-resistant and sensitive type.From the above can be seen chlorophyll content,photosynthetic rate,stomatal conductance faster recovery,metabolism and removal of reactive oxygen species,free radicals,nicosulfuron and other substances in the strong ability to make high-resistant Eriochloa villosa（X-2）rapid return to normal metabolism.These differences are important reasons for the high level of high-resistant Eriochloa villosa（X-2）.