Genetic variability in wild vs. cultivated Eruca vesicaria populations as assessed by morphological,agronomical and molecular analyses

In this study, the genetic diversity of 50 individuals of rocket, Eruca vesicaria, from five accessions, four of them wild type collected from different parts of Spain and one commercial, were evaluated using morphological, agronomical and inter simple sequence repeat DNA (ISSR) data. Molecular analysis was carried out using the ISSR technique with 20 primers. Out of these 20 primers, nine were polymorphic, producing a total of 395 DNA bands, 247 of which were polymorphic among the accessions. A dendrogram drawn on the basis of a similarity matrix using the UPGMA algorithm revealed that the 50 samples of rocket plants could be classified into three major clusters at a Nei's genetic distance of 0.36. The experiment shows that molecular markers such as ISSR are a good instrument for distinguishing and selecting rocket accessions to group different wild populations. In general, a high variation was observed for most of the 16 morphological and 6 agronomical traits showing significant differences. Some morphological traits such as leaf length, petiole length and lamina width explained 69.1% of the whole variation observed in the populations, and some agronomical traits such as leaf area, nitrate and chlorophyll contents accounted for 65.7%, but the clusters generated by means of agronomical and morphological variables were less evident than when ISSR markers used. Some accessions showed good qualities, such as small leaves, high chlorophyll content, late-flowering or low nitrate content. All these parameters, together with the high degree of genetic homogeneity found, could make the local accessions good candidates for a future breeding programme.     

Characterization of white sapote (Casimiroa edulis Llave & Lex.) germplasm using floral morphology,RAPD and AFLP markers

Floral morphology, random amplified polymorphic DNA (RAPD), and amplified fragment length polymorphism (AFLP) were used to characterize and verify genetic diversity within a white sapote cultivar collection and to develop molecular markers for germplasm identification. On the basis of floral morphology, the cultivars were classified into three types: type I included 23 cultivars with large ovaries and small anthers; type II included 13 cultivars with small ovaries and large anthers; and type III included one cultivar, named ‘Maltby’, with a large ovary and large anthers. DNA was isolated from 39 cultivars of white sapote and subjected to RAPD and AFLP analysis using 24 and 7 primers, respectively. One hundred and sixty-eight RAPD and 286 AFLP bands were used to assess genetic characterization among white sapote. Sixty percent of the RAPD and 77% of the AFLP amplification products were polymorphic among accessions. RAPD or AFLP markers differentiated all white sapote cultivars effectively. Moreover, each flower type was characterized as specially associated with two RAPD bands. UPGMA dendrograms based on RAPD and AFLP data, showed the majority of the cultivars from flower type I and flower type II clustering together. Finally 101 RAPD markers and 220 AFLP markers were used to construct a neighbor-joining dendrogram. This showed that the 37 cultivars could be classified into six distinct clusters, between which the similarity coefficient was as low as 0.00–0.55, even though the cultivars were morphologically very similar. The remaining two cultivars namely ‘Smathers’ and ‘Maltby’ were found genetically very distant from the other cultivars in RAPD, AFLP or combined RAPD and AFLP based dendrograms. The results suggested that the level of genetic variation among white sapote cultivars is diverse and the morphological and molecular data may lead to representation of the cultivar relationships as well as flower type discrimination.     

Genetic diversity of Chinese natural bermudagrass (Cynodon dactylon) germplasm using ISSR markers

Bermudagrass (Cynodon dactylon L.) is an important warm-season turfgrass. Although it is widely distributed in China, studies on the genetic variation and relationship among the large-scale indigenous bermudagrass were relatively insufficient, especially at molecular level. The purpose of this study was to assess the molecular variation and relationship among one commercial cultivar ‘Tift3’ and 95 wild bermudagrass accessions collected from 11 provinces in China by ISSR marker technique. The results indicated that 29 ISSR primers generated a total of 248 bands among which 242 (97.6%) were polymorphic bands. The genetic similarity coefficients among accessions ranged from 0.51 to 0.97 with an average of 0.74. All accessions could be clustered into 11 groups with UPGMA method. Accessions from the same or adjacent regions generally were clustered into the same group or subgroups. A few accessions, however, were greatly different from the majority of all accessions. The results suggested that ISSR marker is an effective tool for the study of genetic variation in Chinese natural bermudagrass.     

Integration between molecular and morphological markers for the exploitation of olive germoplasm (Olea europaea)

Three olive cultivars (Oliva Nera di Colletorto, Noccioluta, and a probably a new local genotype) from two strictly related areas of Molise region (south-centre of Italy) were characterized by combining molecular data (eight SSRs analyzed on leaves) and morphological features (thirty-one parameters from leaves, drupes and pits). Both molecular and morphological analyses have shown a very good separation of the three endemic cultivars. A high correlation between morphological and molecular data was found using Mantel's test. The morphological traits of pits were less influenced by environmental pressure than the leaves and drupes; therefore, the pits are more affected by genetic control and might be considered a helpful tool for cultivar characterization and identification. Potential and limitations of three statistical models computed to perform cultivar identification by morphological measures is also discussed. We demonstrated that molecular and morphological analyses are useful for distinguishing new accessions and studying local varieties to preserve genetic diversity, even at small geographical scale in such an unequivocal way; hence the methodology could be proposed as a tool to discriminate widespread cultivars, with long genetic distances.     

利用ISSR分子标记对39份莲藕种质资源的遗传多样性分析

采用ISSR分子标记技术对39份莲藕品种进行遗传多样性分析。结果表明:8个ISSR引物共扩增出89条带,其中有55条多态带,平均每个引物扩增的多态性带数为6.88条,多态性比率平均为61.8%;通过遗传相似系数和聚类分析,能将39份莲藕品种完全区分开;说明ISSR标记技术能较好地从分子水平揭示出莲藕品种的遗传多样性。     

SRAP在葱栽培品种遗传多样性研究中的适用性分析

为评价SRAP技术对葱品种进行鉴定和遗传关系分析的适用性, 对20个葱栽培品种的表型特征进行了观察记载, 利用256个SRAP引物组合对其进行了遗传多样性研究。结果表明: (1) 256个SRAP引物组合中有161个引物组合产生多态性条带, 占所用引物组合数的62.9%。161个引物组合共产生336条多态性条带, 不同引物组合产生的多态性条带数为1～6个, 平均2.1个。20个葱栽培品种遗传相似系数变幅为0.464～0.938, 平均0.703。(2) 依据SRAP进行聚类分析的分类结果与依据表型特征分类的结果一致。上述结果说明SRAP标记可以在葱栽培品种的鉴定和遗传多样性研究中应用。     

The advancement of research on litchi and longan germplasm resources in China

Litchi and longan are famous southern subtropical fruits in China. Besides closely related to each other taxonomically, litchi and longan share many similarities in origin, cultivation history and environmental requirements; furthermore, the developments of research on litchi and longan germplasm resources are somewhat similar and comparable. This paper reviews the literature on origin and distribution, collection and conservation, classification and identification, selection and breeding of litchi and longan germplasm resources in China. The classification of litchi and longan can be divided into three stages: classification based on morphological traits, classification by isozyme analysis and DNA markers. The expression of morphological traits is often affected by environmental conditions; the number of loci that isozyme analysis can examine is small, cultivars, which are closely related often have identical isozyme patterns. The limitations of classification based on morphological traits and isozyme analysis are then overcome by the utilization of molecular markers. At present, most new litchi and longan cultivars are selected from superior seedlings obtained after open-pollination or sport; germplasm with desirable characteristics such as aborted seeds, rather big-fruit and rather late-bearing have not been fully exploited. In order to achieve the goal of improving fruit quality and agronomic characteristics, it is suggested that additional studies of genetic diversity on litchi and longan germplasm should be carried out with more powerful markers such as SSR and ISSR; marker assisted selection (MAS) should be employed to improve litchi and longan's cross breeding efficiency.     

Characterization of pea accessions by SRAP's markers

Sequence-related amplified polymorphism (SRAP) and morphological markers to estimate the genetic relations among forty pea varieties (Pisum sativum L.) were studied. Data on 15 morphological traits were collected and analyzed. A total of 162 polymorphic SRAP's bands were scored using seven combinations of primers. Cluster analysis and both principal component and principal coordinate analysis were carried out. The varieties were grouped in four clusters through procrustes generalized analysis. Relationships among varieties revealed by molecular markers were significantly correlated with those based on the agronomic traits, suggesting that the two systems give similar estimates of genetic relations among the varieties. Parents selection depend on the specific objectives in further breeding programs.     

Germplasm diversity and genetic relationships among walnut (Juglans regia L.) cultivars and Greek local selections revealed by Inter-Simple Sequence Repeat (ISSR) markers

Inter-Simple Sequence Repeat (ISSR) markers were used for the assessment of genetic diversity among walnut (Juglans regia L.) selections from Greek native populations in comparison to internationally cultivated walnut genotypes. Similarity coefficient values from 0.13 to 0.93 (with an average of 0.48) were found among the 56 accessions examined, which indicated the presence of a high degree of genetic variability. Most international cultivars were grouped together while most Greek native populations could not be placed into a distinct group. The Greek native population genotypes were found more diverse than the international cultivars. The mean similarity coefficient values for the former and latter were 0.44 and 0.56, respectively. In the cultivar group, two subgroups were distinguished; one consisted of genotypes involving ‘Payne’ and the other ‘Franquette’ in their pedigrees. Some cultivars and populations could not be grouped according to their pedigrees or collection area. Analysis of molecular variance (AMOVA) revealed that a larger part of the genetic variation exists among Greek walnut populations within a collection region (89%) than among the regions (11%). The pairwise regional PhiPT values indicated that the most geographically distant regions are the most genetically differentiated. The high variability existing in the Greek germplasm in combination with their valuable agro-morphological traits suggested that it would be beneficial to utilize this native germplasm pool in walnut breeding programs and germplasm management activities to maximize genetic diversity in cultivated walnut.     

十一份不同地理居群野菊的ISSR分析

对11份野菊材料分别用ISSR分子标记和形态学特征进行了遗传分析。用13个引物共得到176个位点,其中166个为多态性位点,多态性比率(PPB)高达94.32%;结果表明:2种分类方法得到的结果不甚一致。说明了野菊是一个多型性的种,在形态上表现出体态、叶型、叶序、伞房花序式样以及茎叶毛被性等诸特征上的极大的多样性。从ISSR标记分析,湖北神农架野菊和安徽天堂寨野菊之间的遗传系数最大,为0.727;安徽天柱山野菊和南京野菊之间的遗传系数最小,为0.591。     

Genetic diversity of apricot revealed by a set of SSR markers from linkage group G1

Eight polymorphic simple sequence repeat (SSR) markers located in the G1 linkage group of apricot (Prunus armeniaca L.) were previously developed and evaluated in a small set of cultivars. Those primers were used for studying variability in 77 apricot cultivars belonging to five different geographical groups, such as Chinese, Asian (Irano-Caucasian and Central Asian), North American, Mediterranean and Western European as well as Middle European cultivars. Six of the markers were polymorphic and revealed a total of 71 alleles ranging from 5 (aprigms11) to 20 (aprigms1) alleles per locus with a mean value of 11.83 alleles per locus. In conclusion, the SSR loci located in the G1 linkage group show a level of polymorphism which is similar to loci dispersed throughout the entire genome. The total number of alleles and the number of unique alleles were the highest in Chinese apricots and the lowest in Middle European cultivars. Heterozygosity also showed a decrease from Asia and China to Middle Europe. No association could have been observed between any SSR markers tested and plum pox virus (PPV) resistant phenotype of cultivars. PPV resistant cultivars did not form a separate clade on the dendrogram obtained by UPGMA cluster analysis. Middle European and Chinese cultivars formed separate clusters while other genotypes formed smaller multiple sub-groups or scattered among different clusters. Our results support previous hypotheses on the origin of PPV resistance in North American apricots. The allele data was also presented in a form that allowed the easy observation of allele frequencies in each geographical group at each locus. Using this data field, differences and similarities between cultivar groups can be easily assessed. The analysis demonstrated the links between the North American and Mediterranean apricot germplasm and confirmed that the Chinese and Eastern European cultivars are distantly related.     

Microsatellite markers based assessment of genetic diversity in Iranian olive (Olea europaea L.) collections

To study the genetic variation in Iranian olive collections and some foreign olive cultivars, 47 accessions of 18 local cultivars from 6 olive collections of Iran (Roudbar, Zanjan, Ahvaz, Dezful, Kazeroon and Shiraz), were analyzed along with 30 imported cultivars using 16 microsatellite primer pairs. All the used microsatellite loci revealed polymorphism in the studied genotypes, except GAPU14 and GAPU113 markers. Fourteen microsatellite primers amplified 126 polymorphic alleles in the 87 selected olive accessions. The average number of alleles per locus was 9, ranging from 3 to 14. Polymorphic information content (PIC) was 0.85. The genetic similarity based on Jaccard coefficient ranged from 0.15 to 1. The genetic relationships among accessions were investigated using cluster analysis and principal component analysis (PCA). Most of the accessions with the same name were grouped together; some exceptions were also observed. As expected, close relationship was observed among accessions within same cultivar. Most of the Iranian olive accessions were clustered to a main distinct group. Two-dimensional scatter plot of principal component analysis revealed a clear separation of most of the Iranian olives from Syrian and other introduced cultivars. These suggest that Iranian cultivars have different origin related to West Mediterranean basin cultivars and have evolved independently from the others. Between and within Iranian and foreign cultivars (cultivars including three or more accessions) genetic diversity was analyzed using analysis of molecular variance (AMOVA). AMOVA revealed higher within cultivar genetic variation (62.76%) as compare to that between cultivar variations (37.24%). The intra- and inter-cultivar variance tested by permutation test showed significant genetic variation at both levels. The high level within cultivar genetic variance could be due to mislabeling and presence of homonyms in cultivars produced by vegetative propagation from original plants.     

Genetic diversity of Indonesian cauliflower cultivars and their relationships with hybrid cultivars grown in Australia

The objectives of this study were to investigate genetic variation and relationships between Indonesia-, Australian- and European-based cultivars and to evaluate variation within Indonesia cultivars as all cultivars are open-pollinated. Eight cauliflower cultivars collected from three production regions in Indonesia and four F₁ hybrids cultivars grown in Australia were evaluated using RAPD and ISSR markers. DNA polymorphisms generated from 10 polymorphic RAPD primers were used to construct a dendogram using the unweighted pair-group method with arithmetic averages (UPGMA) and to generate a fingerprinting key. ISSR marker analysis using 14 primers were attempted but DNA polymorphisms could not be clearly identified. The RAPD technique indicated that variation occurred both within and between Indonesian cultivars. Comparison between Indonesian-, Australian- and European-based cultivars showed that Indonesian cultivars have unique genotypes and would be good sources of genes for future crop improvement.     

李种质资源ISSR鉴定及亲缘关系分析

为了更好的利用目前收集得到的李资源,对重庆地方李品系和国内外引进的李品种共40份资源进行了ISSR分析。从100条引物中筛选出13条多态性引物,共扩增得到134条带,多态性条带109条,多态性百分率为81.3%,其中9条特征性谱带可用于品种鉴定和系谱分析的参考性标记。此外,13条引物可将40份材料完全区分开来,图谱分析表明不存在同物异名现象。UPGMA聚类分析将供试品种分成2组,进一步可细分为4个亚组;主坐标分析将其分成6类,其中奉节李、脆红李和万盛鸡血李分别单独成类。2种分析方法所得的结果均与按原产地划分的结果不完全相符,奉节李、脆红李和万盛鸡血李与其余品种(品系)的亲缘关系较远。来自江苏的早黄李与日本和美国李品种间的亲缘关系相对较近,初步推测国外中国李可能来源于我国华东地区。     

基于ISSR标记的红花檵木品种亲缘关系分析

采用ISSR分子标记技术对红花檵木41个品种的遗传多样性进行了分析。从60条ISSR引物中筛选出14条引物分别对供试材料基因组DNA进行扩增,共获得203条清晰可辨谱带,其中多态性带148条,多态位点百分率为72.9%。应用NTSYS-pc（version 2.10e）软件计算得到各品种间的Jaccard相似系数介于0.626 ~ 0.926之间。用UPGMA法将41个品种分成5个类群,支持叶色作为最高分类等级,其次应重视花瓣形状的利用,这两个性状最为稳定且能反映品种间系统演化;同时由于品种起源和选育的原因,品种分类还应适当考虑育种过程及其亲本的性状;花色、叶形、分枝性等变化没有明显规律,不宜作为太高的分类等级。     

6个新疆矮化核桃品种的指纹图谱构建及亲缘关系分析

以8个核桃品种叶片为材料,利用ISSR技术,从100条ISSR引物中筛选出2条对8份DNA进行PCR扩增,共扩增位点34个,其中多态位点24个(比例达70.58%),构建出8个核桃品种的数字化指纹图谱。以NTSYSpc2.1软件计算品种指纹图谱的相似系数(GS)并进行(UPGMA)聚类分析,样品间的GS在0.54～0.94之间,在GS=0.64处将8个核桃品种分成2组:第一组母本为‘扎343’(1号),矮化品种有‘新温724’(4号)和‘新温908’(5号);第二组母本为‘新早丰’(2号),矮化品种有‘新温609’(3号)、‘新温915’(6号)、‘新温916’(7号)和‘新温917’(8号),与田间表现基本一致。