马哈利樱桃PGIP cDNA克隆序列分析

以马哈利樱桃（Prunus mahaleb L.）为材料,通过RT－PCR获得了1045bp的目的段,经克隆测序,证实该片段包含1个完整的开放阅读框架,该阅读框架由990碱基组成,编码330个氨基酸。该序列与杏、梨、苹果的PGIP cDNA序列同源性分别达97.2%、83.4%和83.6%,可能编码的氨基酸与杏、梨、苹果的PGIP cDNA所编码的氨基酸的同源性分别达到96.7%、85.2%和85.2%。与已经克隆的PGIP DNA序列的对比分析表明,PGIP DNA序列中包含2个外显子和1个内含子,内含子全长147 ,符合TG－AG规律,2个外显子长度分别为581bp、464bp。     

Chloroplast DNA study in wild populations and some cultivars of Prunus avium L.

The PCR-RFLP technique was used to detect chloroplast DNA diversity in wild populations of Prunus avium from five European deciduous forests and some cultivars. A study of 10.8% of the total chloroplast genome detected eight insertion-deletion (indel) mutations, distributed over 12 haplotypes. Six haplotypes (H1, H2, H3, H4, H5 and H6) were found in wild populations and eight (H2, H6, H7, H8, H9, H10, H11 and H12) in the cultivars. Only two haplotypes (H2 and H6) are shared by the wild populations and the cultivars. The most-abundant and frequent haplotype in wild populations is H2 (frequency=78%). The wider geographical distribution along with the high frequency reflects its ancient origin. Of the five populations, three are polymorphic. Populations GA (Scotland) and KE (Germany) have unique haplotypes. The total cpDNA diversity in wild populations is h_T=0.40, and a major portion of it is within populations (h_S=0.37). The genetic differentiation among populations was low (G_STC=0.08) and no genetic structure among wild populations was observed. A minimum-length spanning tree, demonstrating relationships among the haplotypes in wild populations, indicated two possible chloroplast lineages. The ten identified cultivars were represented by seven haplotypes; this result proposes the possible utilisation of the PCR-RFLP technique for the characterisation of sweet cherry cultivars. The cpDNA diversity in P. avium should be considered carefully for phylogenetic studies involving this species. Received: 10 July 2000 / Accepted: 19 October 2000     

好气与淹水条件下水稻土各粒级团聚体有机碳矿化量

采用室内恒温培养法观测了好气和淹水处理下水稻土不同粒级团聚体中有机碳矿化的动态变化.结果表明：两种处理下,各粒级团聚体中有机碳矿化量都表现为培养前期快速下降,培养后期保持相对稳定的趋势.不同粒级团聚体之间有机碳矿化速率存在明显差异,在整个培养过程中,均以1～2 mm粒级团聚体最高,以＜0.053 mm粒级团聚体最低.统计分析表明,不同粒级团聚体中有机碳矿化量变化与有机碳和微生物生物量碳含量呈显著线性相关.好气和淹水处理下对土壤总有机碳累计矿化量贡献最大的是0.25～1 mm粒级团聚体,分别达41.77%和34.11%;好气处理下贡献最小的是0.053 mm粒级团聚体,淹水处理下贡献最小的是1~2 mm粒级团聚体,分别仅为7.8%和6.6%.     

Differential response of four tree species to ozone-induced acceleration of foliar senescence

Ozone (O₃)-induced accelerated senescence of leaves was measured in four tree species: black cherry ( Prunus serotina ), hybrid poplar ( Populus maximowizii x trichocarpa , clone 245), northern red oak ( Quercus rubra ) and sugar maple ( Acer saccharum ). Seedlings or ramets of the four species were subjected to chronic O₃ exposures and designated leaves harvested periodically from emergence to senescence. Gas exchange was analysed, and concentrations of total soluble protein and ribulose-1,5-bisphosphate carboxylase/oxygenase were measured as indicators of leaf senescence. Total antioxidant potential and ascorbate peroxidase and glutathione reductase activities also were determined. Black cherry and hybrid poplar exhibited O₃-induced accelerated leaf senescence, whereas sugar maple and northern red oak did not. When the O₃ effects were related to cumulative uptake of the gas, black cherry was the most sensitive of the four species. Although hybrid poplar exhibited similar symptoms of O₃-induced accelerated senescence after the same exposure period as did black cherry, this species took up much greater quantities of O₃ to achieve the same response. The O₃-induced increase in glutathione reductase activity in hybrid poplar was consistent with the capacity of this species to take up high concentrations of the gas. Relative tolerance of northern red oak and sugar maple could be explained only in part by lower cumulative O₃ uptake and lower rate of uptake. Sugar maple had the highest antioxidant potential of all four species, which may have contributed to O₃ tolerance of this species. Ascorbate peroxidase activity, when expressed on a fresh weight basis, could not account for differential sensitivity among the four species.     

日本樱花根癌病病原菌的鉴定及其防治

从浙江省的慈溪、奉化、嵊州等地的日本樱花苗圃内,采集到具有典型症状的日本樱花根癌病植株。经分离纯化及在指示植物番茄、向日葵幼苗的致病性测定,共分离到致病性病原菌株１１株,经形态学、生理生化学特征鉴定及菌体可溶性蛋白ＳＤＳ－聚丙烯酰胺凝胶电泳,确定引起日本樱花根癌病的病原细菌为根癌土壤杆菌（Ａｇｒｏｂａｃｔｅｒｉｕｍｔｕｍｅｆａｃｉｅｎｓ）生物型１,经平皿拮抗和盆栽试验表明,生防菌Ｋ８４能够明显抑制致病菌株的致癌能力。     

Genetic differentiation and gene flow between wild and cultivated Prunus avium: An analysis of molecular genetic evidence at a regional scale

The presence of conspecific wild-type and cultivar populations has been a common landscape feature for centuries. As orchards generally continue to expand towards the natural forest, two important issues are raised: the potential reduction of cultivar genetic diversity compared to wild populations and the extent of gene flow between the two population types. These questions were addressed in a study of Prunus avium in northern Greece using nine simple sequence repeat loci to analyse genetic variation in 93 wild-type individuals and 21 cultivars representing the local cultivated germplasm. Results showed a significant reduction of genetic diversity parameters in the cultivated germplasm compared to natural populations. Bayesian, frequency-based and Markov chain – Monte Carlo analyses have revealed that the wild and cultivar groups are genetically divergent and that realized between-group gene flow is almost completely absent. This result was further verified by a principal component analysis showing a clear separation of the two groups in low multivariate space after a principal coordinate analysis. The significant disjunction in flowering time and a considerable geographic distance between the two groups could primarily account for the absence of substantial gene flow. These findings indicate that local wild cherry can provide a source of genetic variation for future breeding in the genetically restricted cultivar group.     

Enzymatic degradation and β-elimination of the pectic substances in cherry fruits

Pectic substances from cherry fruits (Prunus avium) were studied after extraction and purification. They were subjected to β-elimination by heat treatment and depolymerized by endopolygalacturonase from Aspergillus niger. The degraded pectins were fractionated by gel permeation chromatography (Sephadex G-100, Bio-gel P2). The results suggest that the pectic substances largely consist of an α-d-galacturonic backbone interspersed with occasional l-rhamnosyl residues. Neutral sugars as side-chains of varying lengths appear to be concentrated along certain regions of the polymer (‘hairy$\text{)}\text{?}$ in contrast to side-chain free (4mooth’) parts.     

Xylem-transported abscisic acid: the relative importance of its mass and its concentration in the control of stomatal aperture

Abscisic acid (ABA) fed in pulses to the petioles of detached cherry leaves in enclosed leaf chambers, caused a reduction in leaf conductance. The degree of inhibition was analysed with respect to the amount of ABA fed and to concentration of ABA in the feeding solution. Regression analysis of the data showed both variables to have a significant effect on leaf conductance. A hypothetical maximum ABA concentration occurring in the leaf apoplast was calculated for each pulse from a simple model. This variable explained more of the variance within the data than either the amount or the applied concentration variable. A value for the rate at which ABA is removed from the apoplast is derived from the experimental data using the model. A second experiment attempted to evaluate this rate directly, by measuring the rate of catabolism of labelled ABA within the leaf. The results suggested a half-life of 36 min for the initial rate of decay. This figure is similar to that derived from the model, the importance of ABA-metabolism for the control of leaf conductance is discussed in the context of root-to-shoot communication by ABA in the xylem stream.