Genetic diversity of rhizobia associated with <Emphasis Type="Italic">Vicia faba</Emphasis> in three ecological regions of China

Great genetic diversity was revealed among 75 rhizobal isolates associated with Vicia faba grown in Chinese fields with AFLP, ARDRA, 16S rDNA sequencing, DNA–DNA hybridization, BOX-PCR and RFLP of PCR-amplified nodD and nodC. Most of the isolates were Rhizobium leguminosarum, and six isolates belonged to an unnamed Rhizobium species. In the homogeneity analysis, the isolates were grouped into three clusters corresponding to (1) autumn sowing (subtropical) region where the winter ecotype of V. faba was cultivated, (2) spring sowing (temperate) region where the spring ecotype was grown, and (3) Yunnan province where the intermediate ecotype was sown either in spring or in autumn. Nonrandom associations were found among the nod genotypes, genomic types and ecological regions, indicating an epidemic symbiotic gene transfer pattern among different genomic backgrounds within an ecological region and a relatively limited transfer pattern between different regions. Conclusively, the present results suggested an endemic population structure of V. faba rhizobia in Chinese fields and demonstrated a novel rhizobium associated with faba bean. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Relative rates of divergence of spacer and gene sequences within the rDNA region of species in the Triticeae: Implications for the maintenance of homogeneity of a repeated gene family

Summary The relative rates of divergence of 11 regions of the wheat rDNA cloned in pTA250 were estimated by measuring sequence change in 6 Triticum species. The Tm analysis of ³²P probes synthesized from the pTA250 regions and hybridized to DNA from the Triticum species provided an estimate of sequence change relative to T. aestivum. The results revealed a region of 1.2 kb preceding the 18S rRNA gene which was more conserved than the rest of the spacer. In addition the transcribed spacer between the 18S and 26S rRNA genes was shown to be poorly-conserved; the genes, as expected, were highly conserved. A model which proposes RNA as a co-factor in gene conversion is suggested to account for the observations.     

Applications of Extensions of Bivariate Rank Sum Statistics to the Crossover Design to Compare Two Treatments Through Four Sequence Groups

Summary This article describes applications of extensions of bivariate rank sum statistics to the crossover design with four sequence groups for two treatments. A randomized clinical trial in ophthalmology provides motivating background for the discussion. The bilateral design for this study has four sequence groups T:T, T:P, P:T, and P:P, respectively, for T as test treatment or P as placebo in the corresponding order for the left and right eyes. This article describes how to use the average of the separate Wilcoxon rank sum statistics for the left and right eyes for the overall comparison between T and P with the correlation between the two eyes taken into account. An extension of this criterion with better sensitivity to potential differences between T and P through reduction of the applicable variance has discussion in terms of a conceptual model with constraints for within‐side homogeneity of groups with the same treatment and between‐side homogeneity of the differences between T and P. Goodness of fit for this model can have assessment with test statistics for its corresponding constraints. Simulation studies for the conceptual model confirm better power for the extended test statistic with its full invocation than other criteria without this property. The methods summarized here are illustrated for the motivating clinical trial in ophthalmology, but they are applicable to other situations with the crossover design with four sequence groups for either two locations for two treatments at the same time for a patient or two successive periods for the assigned treatments for a recurrent disorder. This article also notes that the methods based on its conceptual model can have unsatisfactory power for departures from that model where the difference between T and P via the T:T and P:P groups is not similar to that via the T:P and P:T groups, as might occur when T has a systemic effect in a bilateral trial. For this situation, more robust test statistics have identification, but there is recognition that the parallel groups design with only the T:T and P:P groups may be more useful than the bilateral design with four sequence groups.     

阪崎肠杆菌能力验证样品均匀性和稳定性的研究

目的制备出以脱脂奶粉为基质的均匀性好、稳定性强的阪崎肠杆菌(Enterobacter sakazakii)能力验证样品。方法研究奶粉基质的粒度、奶粉和菌粉的混合比例,得到阪崎肠杆菌能力验证样品的最佳均匀性条件;研究包装形式及贮存温度对样品稳定性的影响,得到阪崎肠杆菌能力验证样品的最佳稳定性条件。结果要保证样品足够均匀,奶粉最佳粒径范围为120μmD180μm,1 g菌粉最多与300 g奶粉进行混合;贮存温度对样品稳定性有较大影响,高温明显降低样品稳定性;真空包装可以显著提高样品稳定性。结论以奶粉为基质的阪崎肠杆菌能力验证样品的制备能够更准确地考查乳品微生物检验人员的检测水平,为国内微生物能力验证水平的提高奠定了基础。     

The precipitation change in Eastern Forest Regions of China in recent 50 years

The Eastern Forest Region is of importance for its economic timber forest and water and soil conservation in China. It provides basic information and response to climate change by analysis on the precipitation change of the Eastern Forest Region. In this study, the missing daily precipitation data was interpolated by spatial correlation and stepwise regression methods, and the Standard Normal Homogeneity Test (SNHT) was used to examine the homogeneity of the data serial with the interpolated value(s) on all individual discontinuous points among the entire annual data serial, to obtain the interpolated value of any missed data by passing the STHT test. Finally, the full precipitation data set with a full annual series of 853 Observation Stations in the Region was completely obtained. Based upon that precipitation data set from 1961 to 2010, the long-term change trend of the annual precipitation, numbers of precipitation days, seasonal precipitation and extreme precipitation were analyzed. The results revealed that the annual precipitation increased insignificantly with a tendency of 5.58 mm/10a, but with an obvious decadal fluctuation; however, the spatial distribution of precipitation is not uniform, with decreasing trends in northern part, but increasing trends in the southern part of the Eastern Forest Region. Annual number of precipitation days had a significance reduce; showing a consistent decreasing trend in many stations in the Eastern Forest Region. The proportion of the annual amount of light rain (0.1–9.9 mm/d) and moderate rain (10.0–24.9 mm/d) to the annual precipitation and the annual number of the light rain and moderate rain days were significantly decreasing in recent 50 years. Both the percentage of annual extreme precipitation and percentage of annual extreme precipitation days had a significant tendency of increase, both intensity and frequency of extreme precipitation events have contributed to the rising of the extreme precipitation amount, extreme precipitation events which were tending to become frequencies and intensified, it might have increased the risk of severe floods in the Eastern Forest Region. In the recent 50 years, the trends of amount and days of the rainstorms (50.0–99.9 mm/d) and the heavy rainstorms (?100 mm/d) in the region increased significantly, with the values 5.59 mm/10a, 0.07d/10a and 4.27 mm/10a, 0.03d/10a respectively. The Mann-Kendall abrupt change test was conducted on the two different intensity rains, and the results showed the amount and days of both rainstorms and heavy rainstorms exhibited an abrupt change, the amount and days had significant increasing shift. While the remarkable increase of both the amount and days of the rainstorms presented since the middle 1980s, the heavy rainstorms since 1990s. The basic characteristics of seasonal precipitation in the Eastern Forest Region during the recent 50 years are investigated. For the seasonal precipitation in June to August and December to next February had an increasing tendency, with linear trends of 11.22 mm/10a and 5.91 mm/10a, respectively; while the decreasing tendencies in March to May and September to November in the Region, with linear trends of ?2.59 mm/10a and ?8.96 mm/10a, respectively.     

Structural Changes in the Relationships of Body Dimensions of Four Species of Pulmonate Slugs (Mollusca : Gastropoda : Pulmonata)

Four species of pulmonate slugs viz. Milax rusticus, Milax sowerbyi, Milax gagates and Limax tenellus are colonised along the north eastern region of Libya. These slugs are homogeneous in character since they belong to the same class and order. However, their body dimensions were significantly different. Significant positive relationships existed on most of the body dimensions of each species and these relationships were found to be heterogeneous among the four species studied.     

Various X2-Tests of Homogeneity: Some Comments

Methodological issues in the analysis of incidence rates or prevalence proportions for count data, presented in a form of a sequence of 2×2 tables, corresponding to levels (strata) of a specified variable (risk factor) X, are discussed. Suppose λ_1i and λ_2i are the incidence rates of an event D in the ith stratum for populations 1 and 2, respectively. The homogeneity (null) hypothesis is formulated in the form: H_0:λ1i=λ_2i for all i (i = 1, 2, …, I). Three X²-tests for H₀ and their theoretical bases are discussed: X_Total² which is sensitive to alternatives HA :λ1i± λ2i for at least some i; X_Comb² which is sensitive to alternatives H A : λ1iλ2i² or < λ_2i but not both for all i; and X_Diff² which is sensitive to alternatives H_A:λ1i>λ2i³ for some i and λ_1i′ < λ_2i′ for some i′ (i≠i′). These statistics satisfy the relation X_Total² = X_Comb² + X_Diff². Also, X′²-statistic for pooled data is calculated, which in conjunction with X_Comb² can serve for detecting confounding. Although most of these techniques are known, they are rather scattered in the literature, and not always considered jointly, as it is emphasized in the present paper. It is hoped that these comments will be helpful to biostatisticians as well as to epidemiologists and medical researchers in the analysis of mortality and morbidity data. For illustration, two examples with large sets of epidemiological data are given.