Ecological Characteristic Of Polypogon Fugax And Resistance To Quizalofop-p-ethyl In Rape(Brassica Campestris) Field

Asia minor bluegrass (Polypogon fugax) is an annual weed which has caused great damage to rape (Brassica campestris) in Hunan province. In this study, Experiments were conducted to determine the influence of environmental factors on seed germination and emergence of Polypogon fugax, monitor the resistance level of the population collected from rape fields in Hunan Province to quizalofop-p-ethyl, and explore the resistance mechanism. The results were as follows:Tests were conducted to determine the effect of temperature, light, pH, osmotic and salt stress, and depth of burial on seed germination and emergence of Polypogon fugax. The optimum temperature for seed germination was20C for constant temperature and22/15C for alternating temperature regime, respectively. Seeds could germinate under dark condition, but light exposure would significantly enhance germination percentage. More than50%of seeds germinated over a pH range from4to10. Seeds were highly sensitive to osmotic stress and completely inhibited at an osmotic potential of-0.4MPa, indicating its germination was favor of a moist environment. However, it was tolerant to salinity, with germination rates over30%at salinity stress ranging between0and40mM. The highest seedling emergence (62%) was observed when seeds were placed on the soil surface, and no seedling emerged from seeds placed at a depth of5cm.The resistant level of Thirteen Polypogon fugax biotypes to quizalofop-p-ethyl were tested by wholeplant and seed bioassay experiments. Seeds in this test were collected from the main canola planting areas in Hunan Province. The results of wholeplant experiments showed that Taoyuan biotype (TY) was the most sensitive with the IC50value as2.414ai gha-1.Eight biotypes showed different resistant level to quizalofop-p-ethyl. The highest relative resistant index was found in Anxiang biotype(AX1) which was9.4folds with IC50value as1.290mg/L. In bioassay experiments, results also showed that TY biotype was the most sensitive while AX1biotype was the most resistant one with the IC50value as0.148mg/L and1.290-mg/L separately.Physiological and biochemical methods were used to test the activity of glutathione- S-transferase (GSTs) in resistant (AX1) and sensitive (TY) Polypogon fugax biotypes. Results showed that the GSTs activity in resistant biotype is higher than that in sensitive biotype, indicating this may be the factor causing the resistance to quizalofop-p-ethyl.By molecular biology methods, ACCase-resistant gene (GenBank:KF158414.1) of Polypogon fugax was amplificated. The results showed that sequence of ACCase gene from resistant and susceptible biotypes in Hunan province had no difference.