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Radish (Raphanus sativus L.) is a biennial herb native to China's important vegetable crops for cruciferous radish. Downy mildew infection by the parasitic downy mildew (Hyalonosporan parasitica) is an important disease on the cruciferous vegetables. In recent years, spring radish downy mildew occurred, especially in a suitable temperature, humid environment more susceptible to this disease are prone to growth in radish cotyledon stage, seedling stage and adult stage, seriously affecting the radish yield and quality. Therefore, radish breeding for disease resistance is an important breeding objective one. The cruciferous vegetables downy mildew focused on Brassica vegetables such as cabbage, broccoli, cauliflower and broccoli crops. Radish downy mildew resistance infancy, radish downy mildew identification evaluation system has not been established, physiological indicators, inheritance of resistance and resistance genes has not been reported at home and abroad, limiting radish downy mildew resistance breeding in progress and the breeding of new varieties. Therefore, this study from the Resistance evaluation system, the the physiological indicators resistance reaction, inheritance of resistance mechanisms and disease resistance gene was more systematic study four aspects of the physiological basis and the genetic basis of radish downy mildew, as Evaluation of resistance and resistance to downy mildew of radish germplasm resources cultivar selection provides a theoretical basis and technical reference. Field the natural incidence indoor Inoculation combination radish germplasm resources of the laboratory downy mildew resistance screening radish plants cotyledon stage, seedling stage and adult stage downy mildew disease evaluation system. 500 field of radish germplasm identified downy mildew, foliage spreading, skin color is red or cyan, plant type collapse-of radish plants more susceptible to downy mildew. Select the the 20 radishes material for indoor artificial inoculation, the results show high resistance varieties have better performance in the whole process of its growth resistance, high sense of material the cotyledon stage disease, especially serious, and the results of this identification with the field under natural conditions disease manifestations consistent. Resistant plants were correlation analysis showed that the cotyledons and seedling resistance and adult stage was a significant positive relationship (correlation coefficient R2 = 0.9778 R2 = 0.8519). Therefore, the the radish cotyledon stage or seedling stage of disease manifestations may reflect the resistance of the adult stage. Polyphenol oxidase enzyme (PPO), peroxidase enzyme (POD), hydrogen peroxide enzyme (CAT), superoxide dismutase (SOD) activity and radish downy mildew resistance relationship. The results showed that the disease-resistant materials in different hours after inoculation pathogens, plants were PPO activities of POD, CAT, SOD and radish resistance was significantly positively related, and different processing time peak; analysis of variance showed each activity peak compared with other vaccination period, the difference reached a significant level. Defense Enzyme Activity and Plant disease resistance in susceptible inbred lines no correlation, analysis of variance was not a significant difference. Defense enzyme activity for plants that can be used as auxiliary evaluation radish downy mildew identification. The preparation of turnip anti-susceptible material to NAU,-XBY06 x to NAU,-SH08 of NAU-DHP07 × NAU-BJQ09, P1, P2, F1, F2, BC1, BC2 VI behalf Materials radish the downy mildew genetic analysis. The analysis showed that F1 two crosses all show high resistance to disease; F2 population of resistant and susceptible segregation ratio close to 3:1; resistant parent backcross BC groups are resistant and susceptible groups back cross the BC population presents a separation of 1:1. The resulting radish seedling stage downy mildew resistance in single gene dominant inheritance pattern, F2 and BC groups reciprocal cross differences, indicating that the resistance without maternal genetic effects. Primers were designed based on the conserved domain of the Arabidopsis downy mildew resistance gene, radish high disease-resistant inbred lines the NAU-XBY06 of genomic DNA as a template for PCR-specific amplification. Result, the length of 2372bp, 924bp, 636bp and 607bp resistance gene fragment, were named as the Rs-dml the Rs-dm2 Rs-dm3 Rs-dm4. Analysis of the nucleotide and protein structure showed that the the Rs the-dml Arabidopsis downy mildew resistance genes RPP8 homology of 61%; speculate its amino acid sequence has a conserved region of the NBS-LRR type. Rs-dm2, Rs-dm3, dm4 NCBI and homologous Rs-tree analysis showed that with Arabidopsis downy mildew resistance gene RPP1 RPP5 and RPP27 high homology and speculated that they protein structure each having a TIR-NBS-LRR conserved domains and protein receiving device (RLP). In this study, the cloned in-depth study of the radish after radish downy mildew resistance gene for resistance to downy mildew molecular mechanisms to provide technical reference and theoretical basis.
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