An extended interspecific gene pool available to peach and almond breeding as characterized using simple sequence repeat (SSR) markers

Genetic diversity, as revealed by eighteenSimple Sequence Repeat (SSR) markers inthirty almond [P. dulcis (Mill.) D.A.Webb], twenty fresh-market peach [Prunus persica (L.), Basch], fifteenprocessing clingstone peach cultivars, andten rootstocks, established the geneticrelatedness among cultivars andcharacterized the variation within andbetween species. One accession each of thewild Prunus species, P.davidiana [(Carriere) Franch] and P.webbii [(Spach.) Vieh.], was included inthe analysis. The number of presumedalleles revealed by the SSR analysis rangedfrom one to six in peach whereas almondcultivars showed a range of three to nine.Peach cultivars clustered into ten groups,which are in general agreement withdocumented origin. Most processingclingstone peach cultivars clusteredseparately from fresh-market freestonecultivars supporting a distinct origin. Twomajor clusters were observed in almond withone containing California cultivars and theother containing European cultivars and theimportant California cultivar Mission.Results establish the value of SSR markersfor distinguishing different geneticlineages and characterize an extensive andlargely unexploited inter-species gene poolavailable to peach and almond breedingprograms.     

The extent of similarity between near-isogenic lines of the Australian spring wheat variety Triple Dirk with their recurrent parent

Summary The near-isogenic lines of the wheat variety Triple Dirk supposed to differ only for Vrn genes have been investigated for their similarity to Triple Dirk and for purity. The NILs were found to differ from Triple Dirk. It was also discovered that Triple Dirk and the NILs each exist of more than one genotype. It is recommended that each NIL is tested for its Vrn-genotype and purified. New sets of Vrn NILs can only be made with these checked NILs and with one-plant progeny of the newly used recurrent parents.     

Molecular marker analysis of genetic variation characterizing a grasspea (Lathyrus sativus) collection from central Italy

Levels of genetic similarity characterizing 20 grasspea (Lathyrus sativus L.) populations collected in central Italy (17 populations in the Marche region and three populations in the Abruzzo region) were analysed with amplified fragment length polymorphism (AFLP) molecular markers. Two main clusters were found: one included large‐seeded populations from farms that were not market‐oriented (named Household populations) and the second, small‐seeded populations, cultivated in market‐oriented farms (named Commercial populations). Relationships among populations collected in different regions were found, although one population of the Abruzzo region was placed between the two main clusters, suggesting a possible further genetic differentiation within this grasspea germplasm collection. Principal component analysis based on AFLP marker frequency was effective in identifying polymorphic markers showing high discriminating ability between clusters H and C. In particular, seven markers showing high positive and three markers with low negative PC1 scores showed an almost cluster‐specific distribution. These results will be useful for enhancing Italian grasspea germplasm use in plant‐breeding programmes and for extending grasspea cultivation within the sustainable agricultural systems of central Italy.     

Random amplified polymorphic DNA analyses of cytoplasmic male sterile and male fertile Pigeonpea (Cajanus cajan (L.) Millsp.)

Randomly amplified polymorphic DNA (RAPD) markers were used for the identification of two pigeonpea cytoplasmic genic male sterile (CMS) lines derived from crosses between the wild (Cajanus scarabaeoides & C. sericeus) and the cultivated species of Cajanus cajan. The male sterile (A) line and its maintainer (B) line could be easily differentiated with certain random primers. The two male sterile (288 A and 67 A)systems are based on C. scarabaeoidesand the other is based on C. sericeus could also be differentiated. Amplification product of 600bp amplified by primer OPC-11 was observed in both the cytoplasmic male sterile lines (288 A and 67A), which was absent in the maintainer lines (288 B and 67 B) and the putative R-line (TRR 5 and TRR 6). CMS lines, putative R lines, other cultivars and wild species under the study could be easily distinguished with the help of different primers. Dendrogram constructed based on the similarity index showed that considerable genetic variation exist sbetween CMS lines, two putative R line and wild species studied. This revised version was published online in July 2006 with corrections to the Cover Date.     

Isozyme Banding Pattern and Estimation of Genetic Diversity among Guinea Grass Germplasm

Isozyme banding pattern was studied in Guinea grass (Panicum maximum Jacq.), a widely cultivated grass having good fodder value. Similarity among 63 accessions collected from diverse sources was worked out using five enzyme systems (SOD, GOT, ACP, Esterase and Peroxidase) following horizontal starch gel electrophoresis. Biochemical markers such as isozymes are useful supplements in identifying the genetic variation present in any crop. A total of 35 clear and unambiguous bands were used for analysis of which 8 bands were monomorphic. Polymorphism exhibited by 27 bands from all five enzyme systems indicate presence of considerable diversity in this species. The dendrogram generated after UPGMA and SAHN cluster analysis using Jaccard genetic distance showed that 63 accessions from diverse geographical locations could be grouped in three main clusters, of which two could further be divided into sub-clusters. Although the clusters comprised members from different locations, most of the accessions from similar geographical locations tended to cluster in same group.     

Species compositional similarity and ecoregions: Do ecoregion boundaries represent zones of high species turnover?

The concept of an ecoregion, a discrete spatial area where species composition is presumed to be relatively homogeneous compared to that between areas, has become an increasingly common conservation tool. We test the effectiveness of one ecoregion delineation (World Wildlife Fund) in capturing patterns of change in species composition of birds, mammals, and trees across the United States (excluding Hawaii) and Canada, and describe the extent to which each ecoregion boundary is concurrent with relatively large changes in species composition. Digitized range maps were used to record presence/absence in 50 × 50 km equal-area grid cells covering the study area. Jaccard’s index of similarity was calculated for all pairs of cells in the same or adjacent ecoregions. The average rate at which similarity declined with geographic distance was calculated using pairs of cells within the same ecoregion (intra-ecoregion turnover) or using pairs of cells in adjacent ecoregions (inter-ecoregion turnover). The intra-ecoregion rate varies widely among ecoregions and between taxa, with trees having a faster rate of similarity decline than mammals or birds. For all three species groups, most ecoregion boundaries have similar rates across them (inter-ecoregion) than that within each adjacent ecoregion (intra-ecoregion), with the exception of zones of transition between biomes and major geographical features. Although the ecoregion concept is useful for many other conservation applications, the lack of systematic, high turnover rates along ecoregion boundaries suggests that ecoregions should not be used as a quantitative basis for delineating geographic areas of a particular taxonomic group.     

京郊风景游憩林侧柏-刺槐群落林下植被生态位研究

对北京市郊区风景游憩林侧柏-刺槐群落林下植被的主要植物种群的生态位宽度、生态位相似比例和生态位重叠分析表明,求米草、荆条、孩儿拳头和细叶苔草生态位宽度值较大,上层林分主要树种侧柏和刺槐的林下更新苗生态位宽度比其他植物种林下更新苗的生态位宽度低;林下植物种群的生态位相似性比例值和生态位重叠值相对较小,不同种群间对资源的竞争相对不剧烈,可采取人工措施改善树种的配置,促进生态位分化。     

哈萨克羊、阿勒泰羊、巴什拜羊遗传多样性的AFLP分析

利用11对AFLP引物组合,检测了哈萨克羊、阿勒泰羊、巴什拜羊池DNA遗传变异,构建了各品种的AFLP DNA 指纹图谱,根据AFLP分析结果,统计了每个引物组合在各品种中检测到的多态性条带,计算了3个品种的遗传相似系数,并据此构建了UPGMA聚类关系图,分析了它们的遗传关系.结果表明:11对AFLP引物组合在3个地方绵羊品种中共检测到310条带,平均每个引物组合产生28.18条带,变化范围在25～34条,其中多态性条带32条,占扩增总带教的10.32%,每对引物平均扩增多态性带2.909条.品种间的遗传相似系数以哈萨克绵羊与阿勒泰绵羊的最高(O.699),哈萨克绵羊与巴什拜绵羊最小(0.592),聚类结果与这些羊的育成史、分化及地理分布一致.     

基于自适应小波偏微分方程的蝗虫切片图像去噪

蝗虫显微切片图像在获取的过程中不可避免地会受到噪声污染,其纹理、边缘与噪声又都属于高频分量,单独使用小波变换或偏微分方程(partial differential equation,PDE)扩散的方法都不能在有效去噪的同时保持边缘、纹理等。针对这一问题,提出了基于自适应小波PDE的去噪算法。首先对蝗虫切片含噪图像进行sym5小波软阈值去噪,分解层数根据去噪后图像的PSNR(peak signal to noise ratio)值自适应地选择,阈值门限使用Birge-Massart处罚算法获取。然后在此去噪的基础上进行Perona-Malik(PM)模型去噪,迭代次数根据去噪后图像的PSNR值自适应地选择,梯度阈值根据图像自身的2范数获取。为了验证所提出算法的去噪性能,进行了与常用去噪算法的对比试验。试验结果表明:视觉上,采用本文算法去噪后的图像噪声点较少且边缘、纹理清晰;客观上,采用该文算法去噪后的图像PSNR值比使用维纳滤波高出2 d B左右,比使用中值滤波高出3 d B左右,比使用小波阈值去噪高出2 d B左右,比使用PM模型去噪高出1 d B左右,并且在结构相似性(structural similarity image measurement,SSIM)上采用该文算法去噪后的图像与原始图像的相似度最高。因此,将自适应小波PDE的算法应用于蝗虫切片去噪是可行的、有效的,为其后续处理提供了技术支持。     

Genetic Analysis of Egyptian Date (<Emphasis Type="Italic">Phoenix dactylifera</Emphasis> L.) Accessions Using AFLP Markers

Forty-seven samples of date palm (Phoenix dactylifera L.) collected from eight locations in Egypt were studied using four sets of amplified fragment length polymorphism (AFLP) markers with near infrared fluorescence labeled primers. These samples belonged to 21 named accessions and 9 of unknown pedigrees. A total of 350 bands were scored and 233 (66.6%) were polymorphic. Twenty-seven Egyptian accessions and ‘Medjool’and ‘Deglet Noor’accessions from California could beclassified into the major cluster. This major cluster may represent a major group of date palm germplasm in North Africa. There were four other clusters, each containing one or two accessions. The variety ‘Halawy’and one accession of unknown provenance were most likely from hybridization between two clusters. Six groups of accessions of which had the same names, revealed similar but not identical AFLP profiles suggesting these accessions might derive from seedlings rather thanthrough clonal offshoot propagation.