Adaptability And Heredity Variation Of Diamondback Moth Populations Under Host Plants Stress

The Diamondback moth (DBM) [Plutella xylostella (L.)] is an important pest widely distributed in cruciferous vegetables crops, and cause huge losses worldwide. With the extensive use of chemical pesticides, DBM resistance to chemical pesticides has been increasingly serious, which make it outbreak frequently in the world. Herein, finding more eco-friendly methods to controlling DBM is extremely urgent. This paper researched the effects of the six host plants on the development and reproduction of DBM, and revealed differences of DBM`s effects among different host plants. The purpose was to provide the basis for integrated pest management of DBM.In this paper, the six cruciferous vegetables, Raphanus sativus L., Brassica parachinensis Bailey, B. juncea L., B. chinensis L., B. alboglabra Bailey, B. oleracea L., were selected as host plants for testing. DBMs were raised under the same conditions of isolation and hermetization, and the biological characteristics such as developmental duration, oviposition duration, pupal weight and fecundity were recorded during the fourth, sixth, and thirteenth generations, as well as the eleventh generation on the changing host plant. DBM`s DNA was extracted from the fourth-instar larvae at the fourth, ninth, and fifth generations, which were used to study the genetic variation of DBM populations feeding on the six host plants with RAPD-PCR technology. Genetic distance map of DBM populations from the six host plants was constructed. Coevolution between DBM and host plants and the phenomenon of population differentiation was analyzed. The results were as follows.1. Effects of the six host plants on the development duration of DBMThe developmental duration of DBM had significant difference among the six host plants. At the same generation, DBMs feeding on B. alboglabra had the longest developmental duration. For the same host plant, the developmental duration of DBM decreased with the reared generations increasing. After changing host plants, the control group feeding on B. juncea had significantly shorter developmental duration than those feeding on the other host plants.2. Effects of the six host plants on the fecundity of DBMThe fecundity of DBM had significant difference among the six host plants. At the same generation, DBMs feeding on B. alboglabra had the most fecundity. With the generations increasing, the extence of fecundity reduction was the most. For the same host plant, the fecundity of six DBM`s generations had a reduction except DBM on R. sativus. After changing host plants, the control group feeding on B. juncea had less fecundity than those feeding on the other five host plants.3. Effects of the six host plants on the spawning duration of DBMThe spawning duration of DBM had significant difference among the six host plants. At the same generation, DBMs feeding on B. alboglabra had the shortest spawning duration. But after changing host plant, it had the longest extence of the spawning duration than those feeding on the other host plants. For the same host plant, each group`s spawning duration had a reduction at sixth generation then had an increase except DBM feeding on B. alboglabra. After changing host plants, each group`s spawning duration had an increase except the control group feeding on B. juncea, but the extence of the spawning duration increase was different.4. Effects of the six host plants on the pupal weight of DBMThe pupal weight of DBM had significant difference among the six host plants. At the same generation, The pupal weight of DBM feeding on six host plants had some differences. For the same host plant, the pupal weight of DBM feeding on R. sativus and B. alboglabra had a reduction with the generations increaing. After changing host plants, each group`s pupal weight had an increase, and the control group feeding on B. juncea had a smaller increasing extence than those feeding on other five host plants.5. The study of DBM`s population differention dynamic trend on six different host plants.DNA polymorphism of the fourth, ninth, and fifteen generations` diamondback moth (DBM) [Plutella xylostella (L.)], population feeding on six different cruciferous host plants were studied with RAPD-PCR technique. After PCR amplicated experiments with 17 primers repeatedly, electrophoretic bands were statistically analyzed with NTsys software, genetic distance matrix and genetic dendrogram were constructed. The result indicated that, the genetic distance between DBM feeding on Brassica alboglabra and other five host plants was the largest (0.6523～0.8246), and clustered independently into one branch. The genetic distance between DBM feeding on Raphanus sativus L. and B. oleracea was close (0.3443), and clustered into one branch. The genetic distance among DBM feeding on B. chinensis, B. juncea and B. parachinensis was also closed. Each successively clustered into one branch. With DBM generations of the feeding on B. juncea, R. sativus and B. oleracea increased, the regularity of population differentiation become stable. As the generations increased, the average value, range of genetic distance between each host population and the proportion of polymorphic bands in the total number of bands enlarged. It showed that the level of population differentiation enhance as the generations increased.