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Horticultural crops are economically valuable for sustainable agricultural production. Plant diseases caused by Pathogens including virus, phytoplasma and bacterium have been a great threat to production of horticultural crops. The efficient use of pathogen-free plant materials has overcome the menace of plant diseases and has sustained crop production. Cryotherapy of shoot tips, a novel application of cryopreservation technique, has become a new plant biotechnology tool for plant pathogen eradication. When compared with the traditional methods, cryotherapy of shoot tips produces high frequency of pathogen-free plants, which is independent of shoot tip size and cryogenic methods. Cryotherapy of shoot tips has six major steps to produce pathogen-free plants: (1) introduction of infected plant materials into in vitro cultures; (2) excision of shoot tips; (3) cryotherapy; (4) post-culture for plant regeneration; (5) indexing of pathogens in regenerated plants after cryotherapy; and (6) establishment of pathogen-free nuclear stock plants. The key steps 2, 3, and 4 are similar to cryopreservation, and play a major role in obtaining high pathogen eradication frequency.

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Turnip mosaic virus (TuMV) is one of the most devastating threats to oilseed rape by causing serious crop losses. A total of 86 leaf samples of oilseed rape from eight different locations in Shaanxi, China, were tested by RT‐PCR for TuMV; the results revealed an infection level of 43% by TuMV. The complete coat protein (CP) gene of 32 TuMV isolates was cloned and sequenced. Analysis of the CP gene with sequences from the database allowed the genetic classification of 170 TuMV isolates or sequences. Four genetic clusters were obtained: MB (mostly Brassica isolates), MR (mostly Radish isolates), IBR (mostly Intermediate between Brassica and Radish clusters) and OBR (mostly outside Brassica and Radish clusters). All subgroups were slightly related to the hosts, but unrelated to geographical origins. Most of Shaanxi TuMV isolates were on separate branches, compared with the 138 known isolates originating from other parts of the world. Our results help provide a better understanding of the genetic diversity of TuMV isolates infecting oilseed rape in Shaanxi, China.

WWII dealt a heavy blow to British cities, especially to urban housing provision. The purpose of this research paper is to compare the differences in urban housing supply data and policies in the UK before and after the WWII and draw out some successful experiences and housing policies. With reference to the changes in housing provision in London and Manchester before and after WWII, this essay firstly focuses on an overall development process of housing provision before and after WWII in British industrial cities represented by the two cities through a comparative and analytical data research method. Then, through comparative analysis, the article compares what effective government policies were put in place to stabilise housing supply before and after the WWII. Before WWII, the government met the large demand for working-class housing by clearing slums and increasing housing construction, while after WWII, the government encouraged the development of counter-urbanisation and dealt some conflicts in the urban-rural fringe to ensure effective urban housing provision.