Isolation And Identification Of Phytophthora Nicotianae In The Soil And Influence Of Sodium Borate To Its Growth

Black shank of tobacco is one of the most devastating disease in tobacco production, can harm all the cultivation of tobacco, such as tobacco, air-cured tobacco, burley tobacco, spices, smoke and so on, which has caused huge economic losses on the tobacco industry. Pathogen of the disease.is Phytophthora nicotianae, a parasitic fungi with high temperature and humidity, its mycelium, oospores and chlamydospores can be left lying on the soil or compost mixed in plant residual tissue in winter. As a typical soil dwelling Microorganism to cause disease, it can infect tobacco in growing season, after the harvest, transfer in the different forms to survive in the soil, reported in the literature the strain can survive for five years or longer in the tobacco-free soil. Even in air-dried soil, can also survival of 18 months. Quickly clear the viable number of P. nicotianae in the soil, can helps to understand the distribution and density of it in the soil, and then predict the dynamic occurrence in order to timely disseminate forecasting of this disease for farmer.The number of P. nicotianae in soil is in good agreement with the outbreak of Black shank of tobacco, so establishing a fast counting method for P. nicotianae does good to disaster forecast and economic loss control. Here the pour plate method, the application of selective culture medium, the mini-preparation method of fungal DNA, and the method of PCR were combined to count P. nicotianae in soil. The results showed that when cultured in selective medium with the concentration of 10-2, most of the non-P. nicotianae could be restricted form growing, which was in favor of separating the target fungi. The method of mini-preparation of fungal DNA met the requirements of qualitative PCR, and specific gene fragments of P. nicotianae could be amplified into a fragment with the length of 737 bp.6 strains of P. nicotianae were found by ITS method to be similar to the reported P. nicotianae with a degree of 99%. Thus, this method was suitable for the accounting of P. nicotianae in soil with its advantages of being accurate, low-cost and simple to implement.Boron is one of the higher plants, the normal growth of an essential trace element, the existing research, to improve the content of boron in plant tissue can enhance plant resistance to certain diseases; Other studies have found boron pathogens also have a direct impact. This paper studies the impact of sodium borate on the growth of P. nicotianae. The results show that, with the boron concentration increases, the yield of sporangia and sporangia release rate decreased significantly. One-way ANOVA analysis showed that several boron concentration reached a significant difference (0.01) between treatments and control; 0.1 mM boron can be very significant inhibition of Sporangium generation and release; its spore germination also inhibited, but inhibition is not strong, just slowing the speed of spore germination.8mM or more than the boron concentration can significantly inhibit the expansion of P. nicotianae; In liquid medium, when the boron concentration less than 12mm, mycelium dry weight increased with the boron concentration increases, when the boron concentration more than 12mm, the dry weight of mycelium reduced with the boron concentration increases.8mM, 12mM,16mM boron concentration did not significantly affect on intracellular protein expression, but there is significant effect on the expression of extracellular proteins; On 8mM, 12mM boron concentration, P. nicotianae mycelium dry weight increase may be related to the difference of the expression of extracellular proteins, suggesting that high concentrations of boron may promote the growth of P. nicotianae, the high concentration and low concentration of boron, there may be different mechanisms of influence.