| Alligator weed (Alternanthera philoxeroides) is a vicious weed spread widely in the world currently.Due to its robust clonal reproductive characteristics, biodiversity, agricultural production, the shipping industry has been jeopardised seriously in urgent need of rectification. Through this study, the biological characteristics of alligator grass, in combination with a series of research in proprietary of strain SF-193with high herbicidal activity includes the invasive features, reactive oxygen species and related defense enzyme system in time and space changes have been investigated.We initially explored the best herbicidal conditions of alligator grass and herbicidal mechanism of the SF-193, and supplied adequate theoretical basis for in-depth study of the pathogenic factors and commercialization of SF-193.(1)From April to July in2008, the local alligator grass(Alternanthera philoxeroides) has been investigated in growth cycle and other basic biological characteristics including phenology, morphology, nutrition and growth characteristics, optimal growth conditions. The results show that the local alligator grass begin to grow in early April in the growth cycle of clonal reproduction, to the main stem growth in early July to achieve the highest growth rate then began to slow down; a number of branches and leaves in mid-May to reach the first peak period of growth and then slow down; in early July to reach a second peak period of growth. Indoor pot experiment results show that the optimum growth conditions of soil moisture40%～60%for Alternanthera philoxeroides, at about40%of soil moisture the germination rate reached the maximum; the optimum soil Ph is4～6acidic soil;Optimum temperature for germination and vegetative growth is between30～35℃; either germination or vegetative growth, it is not sensitive to light intensity. Between no light and under7000LUX treatment there were no significant differences in the growth process, except loss of the green leaves off in darkness treatment,the morphology items of remaining treatments had no significant difference.(2) In this study, the process of conidial germination of SF-193and conidial infection on Alternanthera philoxeroides were observed with microscope and ultramicroscope, respectively. Different environmental factors were set to study the influence on the conidial germination of SF-193. The optimal germination rate was observed at30℃, pH6, relative humidity100%, respectively. However, light intensity didn’t affect conidial germination obviously. The conidial germination rate reached nearly100%at pH6,28℃without light. Scanning electronic micrography showed that the germination tube formed after4h of inoculation., then the appressoria were formed by swelling of the apex of germ tubes on the surface of the epidermal cells and invaded in plants after6h of inoculation, and the hyphae invaded through stomatal openings after24h of inoculation. TEM results showed that between inoculation of8and72h, the host cells, chloroplasts, mitochondria, plasma membrane ultrastructure are subject to intense damage.(3) In this study we inoculated the herbicidal bio-control fungi strain SF-193on Alternanthera philoxeroides to. The plant tissue chemistry dyeing and spectrophotometry were applied to detect changes of ROS and activity of related system of defensive enzymes The results showed that24h after inoculation Alternanthera philoxeroides blades of reactive oxygen species (H2O2, O2) produced a significant increase; SF-193treated SOD, CAT, POD activity in8h, less than the CK,24h after the rapid rise,48h After the rapid decline in SOD activity did not change significantly; MDA content of SF-193treated Alternanthera philoxeroides increased rapidly after24h. |
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