Fitness of three chemotypes of Fusarium graminearum species complex in major winter wheat-producing areas of China.

In China, Fusarium head blight is caused mainly by the Fusarium graminearum species complex (FGSC), which produces trichothecene toxins. The FGSC is divided into three chemotypes: 3-acetyldeoxynivalenol (3-ADON), 15-acetyldeoxynivalenol (15-ADON), and nivalenol (NIV). In order to predict the geographical changes in the distribution of these chemotype populations in major winter wheat-producing areas in China, the biological characteristics of twenty randomly selected isolates from each of the three chemotypes were studied. No significant difference was exhibited in the growth rate of 3-ADON, 15-ADON, and NIV isolates at 15°C. At 20°C and 25°C, the growth rate of 15-ADON isolates was the highest. At 30°C, the growth rate of NIV and 3-ADON isolates was significantly higher than that of 15-ADON isolates. The 15-ADON isolates produced the highest quantities of perithecia and two to three days earlier than the other two populations at each temperature, and released more ascospores at 18°C. The aggressiveness test on wheat seedlings and ears indicated there was no significant difference between the 3-ADON and 15-ADON isolates. However, the aggressiveness of NIV isolates was significantly lower than that of the 3-ADON and 15-ADON isolates. The DON content in grains from heads inoculated with the 3-ADON isolates was higher than the content of 15-ADON and NIV isolates. The results showed that 15-ADON population had the advantage in perithecia formation and ascospore release, and the 3-ADON population produced more DON in wheat grains. We suggested that distribution of these three chemotype populations may be related to these biological characteristics.

[Analysis of simple sequence repeats in genomes of Sclerotinia sclerotiorum and Botrytis cinerea].

Simple sequence repeats or microsatellites have been used as genetic markers in population genetics because of their abundance and length variation between different individuals. This study examined the SSRs in the completely sequenced Sclerotinia sclerotiorum and Botrytis cinerea genomes. The occurrences, relative abundance, relative density, most common motifs, and the longest SSRs in the two species were analyzed, and compared with other plant pathogenic fungal species, such as Fusarium graminearum, Magnaporthe grisea and Ustilago maydis. The results demonstrated that the SSRs are abundant in S. sclerotiorum and B. cinerea genomes, and 6 539 and 8 627 SSRs were obtained from these species. The types and distributions of SSRs have similarities between the two species. In the genomes of S. sclerotiorum and B. cinerea, tetra-, penta- and hexa-nucleotide repeats were more abundant than other species, indicating high mutation rates in these species. Furthermore, the abundance and relative density of SSRs were not influenced by the genome sizes and GC content. The analysis in this study provided useful information on applications of microsatellites in population genetics of S. sclerotiorum and B. cinerea.

[Study on risk factors of sporadic hepatitis E virus cases in some districts of Shanghai].

OBJECTIVE: To study the risk factors of acute sporadic hepatitis E virus (HEV) cases and to analyze its partial sequence in some districts of Shanghai. METHODS: 30 blood samples were collected from the acute sporadic HEV cases in 2003-2004 and the RT-nPCR method was applied to obtain the sequence of HEV in these cases. Meanwhile, a 1:2 case-control study was used to identify risk factors in the process of sporadic HEV infection in these regions of Shanghai. RESULTS: Data from the sequential analysis showed that HEV of the sporadic cases belonged to HEV genotype IV. Finding from the case-control study implicated that the housing condition, outside eating history, especially seafoods (OR = 7.048) played an important role in the infection of HEV. Results from multiple logistic regression showed that eating raw seafoods appeared to be one of the risk factors of HEV infection. CONCLUSION: HEV sequences isolated from the sporadic cases of HEV in some districts of Shanghai belonged to HEV genotype IV. Foods, especially seafood, were the risk factors in the infection of HEV.