Study On Infection Process To Potato And Crude Toxin Characteristics Of Alternaria Solani

This paper comprehensively studied the host to Alternaria solani of inoculation method, bioassay methods of toxic , the culture conditions of toxin production, phytotoxin-producing capacity and the pathogen of infection process and disease mechanism. The results were as follows:1. This inoculation method was carried out indoor wound detached leaflets method, non-wound detached leaflets, wound whole leaflets and non-wound whole leaflets to Dongnong 303 to resistance identification. The result showed that the host could quickly and accurately respond to the pathogen of wound inoculation of detached leaflets method. Using wound inoculation of detached leaflets was carried out 8 potato main varieties (Dongnong 303, Kexin1, Kexin12, Kexin16, Kexin18, LT-5 and Youjin) for rom the main production areas of Heilongjiang Province. The result showed that Dongnong 303 was the most susceptive variety and Kexin1 was the most resistant variety.2. The optimal condition for the growth of A. solani was a still culture in 25℃, pH 7.0, dark and static culture on PS medium, and the optimal condition for the producing phytotoxin was a still culture in 25℃, pH 6.0, dark and static culture 21d in modified Fries medium.3. Potato excised leaves stinging with needle, seedlings dipping in the toxin, leaf discs and tomato radicle growth inhabited by the toxin were screened. The results showed that the toxin was easy to be tested by using potato excised leaves stinging with needle and seedlings dipping in the toxin. There was difference markedness in phytotoxin producing ability in four kinds of strains (SH0806、NH0807、JS0801、KS0823) of A. solani. The virulence of phytotoxin of SH0806 was the most powerful.4. The infection process and ultrastructural of A. solani on leaves of potato was observed by using of microscope, scannning and transmission electron microscope. The results showed that conidia began to germinate by 2 h postinoculation. The top of hypha formed appressorium by 6 h postinoculation. The germ tubes penetrated the host epidermal cells junctions directly and formed infection hypha for susceptive variety by 8 h postinoculation, but that was 10 h postinoculation for resistant variety. The hypha expanded to the adjacent host cells penetrated by 24 h postinoculation. Inclusions inside epidermal cells, all organelles have the solution in susceptible host by 24 h postinoculation. There was dissolution rate of cell inclusion in the resistant variety epidermal cells by 72 h postinoculation. The dissolution rate of cell inclusion in susceptive variety was faster than that in resistant variety. The amount of infection hypha had significant difference between susceptive variety and resistant variety .That was more in susceptive variety than in resistant variety.