| Apple replant disease (ARD), distributed in all over the apple producing areas around the world, is the main problem that affect the replacement of the different apple varieties. It is also a serious threat to the sustainable development of apple industry.The objective of this paper is to summarize the occurring situation of the ARD, analyze the mechanism and the main control measures, propose the research direction of the ARD. In this paper we took the survey, field visit and on-site interview on the name of apple varieties, age structure and the incidence of various diseases and pests in more than 200 orchards in the 10 cities of Hebei province in 2007-2009. In this paper, we studied the preliminary etiology of the ARD. The fungi were trapped, separated and identified from the soil with ARD. The plant height, biomass, morbidity and the number of pathogenic fungi was explored with the help of the flat top Begonia seedlings that treated by the soil of different ages. The community structures of bacteria and fungi were explored in the different ages of apple rhizosphere soils by DGGE. The results of the above aspects could be as follows:1,Fuji apple is the main variety in Hebei province, and the area of this variety occupied 58%of the surveyed orchards, followed by delicious apple. For the age structure, the orchards with apple trees of over 15 years old account for 69%. It showed that the phenomenon of Aged apple trees is quite serious in Hebei Province.2,The mortality of the Begonia seedlings that treated by the high-temperature sunlight, methyl bromide fumigation and formalin disinfection was significantly reduced. But the mortality of the Begonia seedlings that without any treatment can account for 67%in 8 weeks after the transplantation, however, it was just 11%when it comes to the control, thus, the corrected mortality of the Begonia seedling treated by the 16-year old apple orchard soil was 62.5%. So we are certain that the main reason that causes the ARD is the biological factors.3,Two hundred ninty three isolates from the soil were purified to inoculate the plant. The results showed that the apple orchards in different areas had different types and quantities of pathogens, but the Fusarium and Rhizoctonia were the main pathogens, Alternaria or Pythium also had a certain isolation frequency in some areas.4,The results indicated that the seedling that planted in 3,8,15,24 year-old soils decreased by an average of 31.22%,46.38%,57.66%63.10%in height; 31.7%,56.2%, 78.2%,80.5%in shoot fresh weight; and 30.57%,57.59%,78.10%,79.42%in shoot dry weight. The number of the fungi that isolated from the soil were 53,69,95,97 respectively, it is found that the differences of the height, biomass, incidence, and the number of pathogenic fungi in seedlings are more and more obviously as the years increase of the soils. The lengths of PCR products that is amplified by ITS1/ITS4-GC for fungi and F338-GC/R518 for bacteria were approximately 250 bp and 230 bp respectively. The composition of soil fungal species changed greatly, it can be reflected by the number and the intensity of the bands. The band numbers of the control and 3 year-old soil were significant less than those of 8,15, and 24 years'. It was the same in band intensity for fungi, but it was opposite when it came to bacteria.
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