| Maize which has important economic returns and social benefits is one of the four chief crops in China. Corn Sheath Blight and Corn Northern Leaf Blight are the main diseases of maize producing areas in China. In recent years, epidemic dynamics of Corn Sheath Blight and Corn Northern Leaf Blight have new changes with the increasing of Northeast corn planting area and the promotion of new cultivation model. According to the principles of plant disease epidemiology, this paper definitudes the epidemic dynamics of Corn Sheath Blight and Corn Northern Leaf Blight in the two-plant orientation cultivation mode by using field experimental design and artificial inoculation technique, on the base of which, constructs the epidemic dynamic model of Corn Sheath Blight and Corn Northern Leaf Blight. This paper simulates and analyzes the disease catastrophe mechanism, by measuring the corn canopy temperature, humidity and other environmental factors on the temporal and spatial dynamics of disease in the different model cultivation model, combining with the soil temperature, water content, and pH on Corn Sheath Blight sclerotium producing conditions. Using molecular biology technique, this essay designs the specific primer of Corn Sheath Blight which detects the Rhizoctonia solani in maize plants and soil. The main results are as follows:1. The epidemic dynamics of Corn Sheath Blight and Corn Northern Leaf Blight in the two-plant orientation cultivation mode and other new modes had been researched for the first time with Comparative Epidemic Science. Researched shows that the disease index of Corn Sheath Blight in the conventional cultivation pattern, two-one row interval cultivation mode, mulching two lines cultivation mode and the two-plant orientation cultivation mode from the beginning of being inoculated to the end of prevalence (September13,2013) are50,29.6,41.2and36.2, and there is significant difference among the above four modes, whose severity was conventional cultivation mode> mulching two lines cultivation mode> two-plant orientation cultivation mode> two-one row interval cultivation mode. It was found that the disease index of Corn Northern Leaf Blight in the conventional cultivation pattern, two-one row interval cultivation mode and mulching two lines cultivation mode from the beginning of being inoculated to the end of prevalence (September11,2012) are55.3,43.9and59.9, and there was significant difference among the above three modes, whose severity is mulching two lines cultivation mode> conventional cultivation pattern> two-one row interval cultivation mode. The disease index of Corn Northern Leaf Blight in the conventional cultivation pattern, the two-plant orientation cultivation mode and two-plant abuts cultivation mode from the beginning of being inoculated to the end of prevalence (September13,2013) are respectively43.7,35.6and36.4. The disease index in the two-plant orientation cultivation mode and two-plant abuts cultivation mode were not significantly different, the reason of which was the different seed materials in the same planting method. There was a significant difference between above two modes and conventional cultivation pattern, whose severity was conventional cultivation pattern> two-plant abuts cultivation mode> two-plant orientation cultivation mode.2. This was the first study on the catastrophe mechanism of Corn Sheath Blight and Corn Northern Leaf Blight in the two-plant orientation cultivation mode and other new cultivation modes. The two growing seasons of experimental districts in the two-plant orientation cultivation mode and other new cultivation modes was regularly monitored by the electronic temperature and humidity recorder, which shows that the average humidity in the conventional cultivation pattern, two-one row interval cultivation mode, mulching two lines cultivation mode and the two-plant orientation cultivation mode in2012were87.8%,84.4%,92.6%and82.7%, and the average temperature were23.3℃,22.5℃,24℃and22.2℃. In2013, the average humidity were respectively94.0%,87.3%,91.8%and87.8%,and the average temperature are respectively24.3℃,21.9℃,23.7℃and22.2℃. It’s showed from the monitoring data that more permeability in the new cultivation modes, effectively using light and changing the temperature and humidity in the districts have slowed the diffusion rate of Corn Sheath Blight and Corn Northern Leaf Blight and reduced the incidence degree.3. This paper studies space communication of Corn Sheath Blight in the two-plant orientation cultivation mode for the first time. The results show that the diseased plants are not all the nearest to the bacteria source center in the two-plant orientation cultivation mode, which show no temporal and spatial gradients of certain, but present random state. A single growing season of Corn Sheath Blight in the two-plant orientation cultivation mode doesn’t have space transmission, or its transmission distance is very short and the disease degree is light.4. This paper proposes a single year dynamic model of Corn Sheath Blight and Corn Northern Leaf Blight in the two-plant orientation cultivation mode and other new cultivation modes for the first time. It has confirmed that the Logistic model is the best model through field experimental design and artificial inoculation technique, which is analyzed by SPSS11.5statistical software. Every epidemic period in the single year dynamic of Corn Sheath Blight and Corn Northern Leaf Blight in the two-plant orientation cultivation mode and other new cultivation modes can be deduced from the Logistic model deformation, therefore the exponential growth phases of Corn Sheath Blight and Corn Northern Leaf Blight are also the best time of chemical control.5. The sclerotium growth and germination of Corn Sheath Blight whose soil temperature, moisture content, pH are simulated has been studied by test method of soil borne plant pathogen ecology for the first time. The results show that the soil temperature has great effect on sclerotium germination and mycelium growth of Corn Sheath Blight, which at25℃under certain moisture content and pH was fastest and at30℃was the second. Soil moisture content has great influence on sclerotium formation and germination of Corn Sheath Blight under certain pH and appropriate temperature. The mycelium growth and sclerotium germination speed more quickly with the increasing of soil moisture, which can reflect the habit of being suitable for high humidity. Under certain soil moisture and appropriate temperature, neutral or slightly acidic conditions are suitable for the growth and germination, and strong acid and strong alkali can inhibit.6. This paper establishes the molecular detection system of Corn Sheath Blight, which provides the theoretical foundation for the early diagnosis and monitoring. This system designs the specific primer LZ-F/LZ-R for Corn Sheath Blight, which was based on PCR amplification, sequencing and sequence analysis of ITS region. Only in the Rhizoctonia solani genome is amplified a band about460bp template system, and the other strains have no specific bands. Specific bands can be amplified by using the specific primers from soil DNA infected tissue and artificial inoculation of R.solani, but there is no amplification product from the health of the corn tissues, which shows that the specific primer can be used for molecular detection of Corn Sheath Blight. |
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