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Heidi Bouws Maria R. Finckh 《European journal of plant pathology / European Foundation for Plant Pathology》2007,117(4):313-327
The effects of origin of seed potatoes and the cropping history on the phenotypic structure of Phytophthora infestans populations was studied in northern Hessia, central Germany, from 2000 to 2002. Populations originating from fields with
a history of potato cropping with only short or no rotation (old fields) were compared with populations from new fields, i.e.,
where no potatoes had been grown for at least 30 years and seed potatoes were either imported from breeders or produced on-farm
(certified). The main goal was to determine the importance of seed potato infection in the establishment of new P. infestans populations. Isolates were characterized for mating type, virulences and rep- (repetitive extragenic palindromic) PCR fingerprints.
Among a total of 639 isolates sampled from 31 sites, mating types A1 and A2 co-existed in all three years in 60–92% of the
sites. Over all three years, 53 pathotypes were detected in a subsample of 272 isolates. Isolates originating from the new
fields had significantly higher frequencies of the virulences v1, v2, v3, v6 and v7, indicating general effects of seed introduction
into a new region. Thirty-six fingerprints were detected in a subsample of 281 isolates of which 22 were unique while four
occurred in all three years and in many sites. Pathogen populations from potato fields that were grown from seed tubers of
geographically different origin differed significantly based on χ
2 tests. While the Nei genetic distances were less than .1 among the local populations, distances to the US lineages US-1,
US-6, US-7 and US-8 ranged from .22 to .47; however, the bootstrap values were not significant. Populations from old fields
were more diverse and 14 of the 22 rep-PCR types occurred there among 132 isolates tested in comparison to six in the new
fields (n = 140 isolates) and two among six isolates from volunteers. The results also suggest that both sexual and asexual reproduction
play a role. 相似文献
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Two cases of Rhodococcus equl infection in foals are described, in which osteomyelitis was a feature. Because rhodococcal infection is usually low grade and chronic, and because the signs of early metaphysitis can be subtle, any articular or periarticular swelling in a foal from a farm with a history of rhodococcosis should be strongly suspected to be associated with R equl until proven otherwise. 相似文献
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Retracted: Effect of Post‐Thaw Storage Time on Motility and Fertility of Cryopreserved Beluga Sturgeon (Huso huso) Sperm 下载免费PDF全文
The aim of this study was to test the influence of post ‐ thaw storage time on the duration of sperm motility, percentage of motile sperm, and fertilization and hatching rates of fresh sperm and sperm stored for 0, 30 and 60 min at 4°C post‐thawing. After being frozen in liquid nitrogen and then thawed, the percentage of motile sperm and duration of motility were not affected by 30 min of storage at 4°C, whereas a significant decline in these parameters was observed after 60 min of storage. Similarly, fertilization and hatching rates were significantly affected within 60 min of storage at 4°C, and the fertility of frozen‐thawed sperm was significantly lower than that of fresh sperm. We conclude that cryopreserved sperm of beluga sturgeon could be stored for 30 min without the loss of sperm quality. This described procedure for beluga sturgeon cryopreservation is reliable and efficient and therefore can be recommended for hatchery practice after scaling up this technique. 相似文献
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