Study On The Interaction Between Rice And Nilaparvate.lugens Mediated By Seed Coating Agents

Rice(Oryza sativa L.) is one of important crops in the world only second to wheat and corn, and the outbreak of plant diseases and insect pests are the major factors causingthe serious loss of production. The seed coating agents(SCAs) increasing rice yields is an effective material to control plant diseases and insect pests. in this study, five types of rice SCAs were selected and some indexes of rice were detected, such as the seed germination rate, seeding rate, leaf age, root length and so on. And then some of the five types with side effects were studied further to observe the effects on the biological characteristics and feeding behaviors of brown planthopper(BPH), Nilaparvata lugens(Stal). The results mentioned in the study will provide scientific basis for producing and selecting better types of SCAs and making full use of SCAs.Results are as follows: 1 Some parameters of rice development were detected after treatment with five common rice SCAs, such as seed germination rate, seedling qualities and adversity abilities(three principal enzyme activities for CAT, POD and SOD), the content of free praline, MDA and chlorophyll, and root activities. The results showed that Liangdun(6.25%) and Daozhe(15%) promoted seedling rate, which increased the rate by 5.56% and 4.81%, respectively. Correspondingly, the root activities were increased by 13.30% and 12.20%, activities of CAT were increased by 50.01% and 42.17%, those of POD were increased by 15.18% and 11.43%, and those of SOD were increased by 3.05% and 2.39%. All results have significant difference compared with controls(P<0.05), which showed that the effects of Liangdun(6.25%) and Daozhe(15%) were much higher than that of treatments with 2.5% fludioxonil, 2.5% prochloraz plus imidacloprid and γ-PGA. 2 Two types of SCAs possessed harmful effects on rice were selected and the rice seeds were treated with four different treatments for the two types of SCAs. Results indicated that BPHs feeding on the rice treated with the mixture treatment developed best, the controls was worst on all treatments. The survival rate of nymphs in the treatment of mixture between 2.5% fludioxonil and γ-PGA and 2.5% fludioxonil treated alone were the highest, which was almost 90%, and that of controls was the lowest, which was about 80%. In the three treatments of SCAs, the body length of adult both female and male had significant differences compared with the control(P>0.05);The development period of nymphs in the 2.5% fludioxonil treatment alone and mixture treatment were 12.59 d and 12.57 d, respectively, which was shorter than that of controls(12.82d), and there were significantly different between individual of all SCAs treatments and controls(P<0.05). In laboratory tests, different treatments had little impacts on the adult longevity of the BPHs, that is, adult longevity had no significant difference among 4 treatments(P<0.05),except that female longevity in 2.5% fludioxonil treatment is much shorter than that of control(P>0.05). The fecundities in females in 2.5% fludioxonil treated alone and mixture treatment were highest, increasing by 28.8% compared with control. In addition, the egg hatchability was also higher than that of control(P>0.05). 3 The feeding behavior of BPHs of three different treatments was monitored by EPG.. The results showed that there were not differences among the treatments of SCAs and control about feeding duration waveforms of BPHs on different tissues of rice. The EPG signals of BPH are made up of seven distinctive waveforms, which are np, N1, N2, N3, N4-a, N4-b, and N5, respectively. This duration in phloem of three SCAs treatments was longer than that in control, especially for the N4-b waveform. In the three treatments(2.5% fludioxonil treated alone, γ-PGA treated alone and mixture of the two SCAs), the total time of duration on a feeding site on rice seedling for BPHs, which means the total percentage of NC plus N4 plus N5 total percentage, was 99.75%, 99.37% and 99.17%, respectively, which had significant difference compared with that of controls(P<0.05,89.65% for controls). Considering the occurrence numbers of EPG waveform in different treatments, the occurring numbers for np in control and γ-PGA treated alone were significantly higher than that in 2.5% fludioxonil treated alone and mixture treatments. The duration for N4-b waveform in three treatments of SCAs was all significantly different from that of controls(P<0.05). Among of them, the duration for N4-b waveform in 2.5% fludioxonil treated alone took 11151.72 seconds, which was the longest, and that of controls only did 8903.27 seconds, which was the shortest.