| Using 3 transgenic insect resistant cotton varieties Center 94,Shanxi94-24,R19, 2 bivalent Bt+CpTI transgenic insect resistant cotton varieties Bi-resistant-1 , Bi-resistant-2 and 3 transgenic insect resistant cotton F1 hybrids Nankang 3 hao, Nankang 6 hao, Nankang 7 hao as experimental materials, a series of researches involving the characteristics of the spacial and temporal expression of the resistance against bollworm (Helicoverpa armigera) of the transgenic cotton varieties, the genetic regulation of the resistance , the influences to the dynamic situation of the non-target harmful insects and the native predator race groups in cotton fields as well as the breeding of the insect resistance varieties etc. were conducted.1. Resistance of transgenic insect-resistant cotton lines to bollwormDuring the reproductive processes of cotton plants, the resistance of the main stem leaves on the 4th-21st node site of the main stem of the different kinds of the resistance cotton varieties were tested respectively. The insect resistance of the bivalent resistant varieties and the univalent resistant varieties such as Shanxi94-24 , R19 and Center 94 were mutually approximate and all reduced downward while the leave sites raised upward. Which indicated likewise the resistance at the earlier growing stage was strong whereas weak at the late stage. Five days after bollworms were fed with young leaves on the plant at the early growing stage ,the mortality rate of the neonate larvae amounted to 100%;whereas while fed with young leaves on the plant at later growing stage ,the mortality rate of the neonate larvae were generally 40%-80%,the survival larvae were mainly 1st and 2nd instar larvae ,one instar later than the survival larvae on the check cultivar plants. If an insect resistant variety was planted at the different dates, the cotton plants different in sizes were tested for the insect resistance simultaneously, the result was that insect resistance of theplants decreased in terms of the increase of the plants ages, which indicated that the resistance against bollworm was mainly affected by the growing stage while no distinct relationship with the external conditions was discovered. The spatial site distribution of the plant leaves didn't influence the expression of the resistance to bollworm.At the boll setting stage(July 20th) while 2-3 instar larvae were fed with the young leaves of the resistant cotton varieties continuously, the results indicated that though the resistance of the resistant cotton varieties decreased at late growing stage of cotton plant yet it was still able to retard the growth and development of the 2-3 instar larvae and cause their death, wheras the 2-3 instar larvae on the check variety Sumian No. 12 plant could still realize the symphosis and eclosion .The insecticidal test executed inside the room indicated that the leaves on the main stem of the insect resistant variety expressed low insect resistance at late growing stage whereas still showed high resistance in the test executed in the field , which indicated that the insect resistance test executed inside the room or in the field showed not completely similar results. The insect resistance tested in the field is better than that tested in the room.At Yangtze River Valley cotton region,the insect resistant cotton varieties still show strong resistance to the 3rd and 4th generation bollworm.Insect resistant variety of 3-4 different generations were used to evaluate the resistance against bollworm at seedling , budding , flowering and boll setting stages . The results indicated that resistant varieties at different generations all showed resistance against bollworm and that the resistance at different generations were fundamentally uniform, which indicated that the resistance against bollworm can be inherited steadily among these generations. Transgenic Bt and transgenic Bt+CpTl bivalent insect resistant cotton varieties showed resistance against bollworm at the uniform level.2. Inheritance of resistance to bollworm by trans...
|
PDF Full Text Request