| In recent years, breeding resistant cultivars has gradually become a major trend in prevention and treatment of potato late blight. In our country, thousands of potato germplasm were collected and introduced, screening resistant late blight varieties from these potato germplasm can help breeding for disease resistance. In order to improve and enhance disease resistance breeding, we found 63 potato germplasm from Potato Engineering Technology Research Center of Hunan Province; hope to find a broad-spectrum potato germplasm which can resistance to potato late blightand and help us fully understand their resistance mechanism. After screenning, we selected two broad-spectrum resistance species:Jiaxiang 1, 2-2, and primry studied the resistance mechanisms to late blight. The main findings are as follows:1?In order to understand the disease resistance of potato germplasm to phytophthora infestans, and to get a broad spectrum resistance germplasm to potato late blight. We taked Favorita (susceptible) as a control, by inoculated phytophthora infestans on leaves in vitro, to judge the resistances of 63 potato germplasm. The results are as follows:under indoor inoculation condition, potato leaf started to infect after 48h, the disease resistance can be evaluatedafter 5d. Inoculation of 63 species, most varieties showed moderate infection and only nine showed moderate resistanc, three of which Jiaxiang 1,2-2 and GS393 showed immunity. By inoculation tubers in vitro, Jiaxiang 1 and 2-2 still have good resistance.2?To understand the interaction between late blight and potato, to study the mechanism of disease resistant varieties. We inoculated the Phytophthora infestans CN152 with Favorita (Susceptible), Jiaxiang 1 (Resistance) and 2-2 (Resistance), and then observed wax layer of leaf surface and stomata density by scanning electron microscopy. The results are showed that susceptible varieties Favorita leaf surface wax layer was thinner than the other two resistant potato varieties, the stomata of leaf surface of Favorita also less than others.3?Flavine 7GFE as fluorescent staining method was selected in this paper to better viewing the plant infected by pathogen. The results show that spore germination were observed after inoculation 12h on leaves of Jiaxiang 1,2-2 and Favorita. But the speed of germ tubes and spread of mycelial growth have great differences. Favorita with the blade spreading of resistant varieties Jiaxiang 1 and 2-2 began a slow germ tube invade potato leaves; after inoculation 72h, Favorita formed mycelial net. Jiaxiang 1 and 2-2 observed only a small amount of mycelial growth. After inoculation 96h, extending hyphae and zoosporangium can be observed from Favorita's stomata.2-2 mycelium formed, Jiaxiang 1 still only a small amount of mycelial growth. That should be the resistant varieties can inhibit the growth of mycelial and producing of zoosporangium.4?To understand the molecular mechanisms of resistance, we taked susceptible varieties as a control, detected the expression of pathogenesis-related proteins (PRs) and heat shock proteins (HSPs) by qPCR. The results showed PR2 ((3-1,3-glucanase) and PRS (Osmotin) in Jiaxiang 1 expression reached a high level in disease process. PR1 (PR-1b), PR2 ((3-1,3-glucanase), PRS (acidic chitinase), PR5 (Osmotin) and PR9 (lignin peroxidase) expression in a large number in 2-2. This showed that pathogenesis-related proteins play an important role in the potato late blight, which PR2 and PR5 involved in Jiaxiang 1, and PR1, PR2, PR3, PR5 and PR9 involved in 2-2. After inoculation 24h, heat shock protein gene in the resistant and susceptible materials are declining after the phenomenon increases, indicating that the pathogen invaded into host could inhibit the defensive of host resistance proteins. |
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