Diversity in Indian sesame collection and stratification of germplasm accessions in different diversity groups

Sesame (Sesamum indicum L.) is one of the ancient oil crops, grown in India since over 5,000 years ago. Diversity in the Indian sesame collection (3,129 accessions), representing all eco-geographical regions, for a range of morphological and agronomic characters was studied. Wide variation in plant habit (plant height and branching pattern), pubescence of various plant parts (stem, leaf, corolla and capsule), flower colour and number of flowers per leaf axil, capsule characteristics (shape, size, number in the axil of a leaf and number of locules in a capsule), number of capsules per plant, number of seeds per capsule, mean seed weight, and yield per plant was recorded. A detailed multivariate analysis was performed on a set of 100 selected accessions representing different agro-ecological zones. The accessions were classified into 7 discrete clusters. The principal components analysis described the spatial relationship among the entities and confirmed groupings obtained through clustering. Based on the clustering pattern of 100 accessions, the entire collection was allocated to different clusters. Representation of various zones in 7 clusters gives us the opportunity to form distinct diversity groups making combined use of passport and characterisation data. These diversity groups would subsequently be used for sampling the accessions for building up a core collection of sesame, a project already operative at the NBPGR.     

Genetic diversity of westerwold ryegrass landraces collected in Northwest Spain

Sixteen landraces of westerwold ryegrass (Lolium multiflorum Lam. var. westerwoldicum Wittm.) collected in Northwest Spain were evaluated at three locations: Mabegondo (La Corun~a), Puebla de Brollo´n (Lugo) and Salcedo (Pontevedra). Populations showed a high variability for morphologic, agronomic and isoenzimatic traits. Principal component analysis was carried out to identify clusters of morphologic and agronomic homogeneous behaviour. A hierarchical clustering method on the first five components was used to separate the different groups. A partition into four clusters was chosen (71% of variance explained). Each cluster was described by the means of the different traits and compared with the other clusters. Landraces were screened for allozyme diversity at nine loci. Population genetic statistics were higher than those previously reported for other outbreeding species (mean number of alleles = 3.59 and mean expected heterozygosity = 0.510). Genetic diversity was mainly explained by the within population component. The between population differentiation only accounted for 8% of the whole diversity. The use of these genetic resources is discussed.     

A bibliography and review of genetic diversity studies of African germplasm using protein and DNA markers

A review of the existing literature available on the bibliographic CD-ROM PlantGeneCD on the use of protein and molecular markers on plant material from sub-Saharan Africa was undertaken. The review showed that these molecular techniques have been used in a wide range of studies, from measurement of genetic diversity within single population to the elucidation of phylogenetic relationship among species in a genus or group of genera. The review revealed that 67% of the 146 studies examined used protein electrophoresis (58% isozymes, the rest mostly seed proteins), 20% used RFLPs, 8% RAPDs and 3% sequencing. Isozymes have been used for a whole range of applications, whereas electrophoresis of other proteins has mainly been used to study ecogeographic distribution of diversity in crops. RAPDs have been used particularly in the investigation of genetic relationship among accessions of a single species and phylogentic relationship among species. RFLPs of cpDNA have mostly been used at the interspecific level and nuclear markers at the intraspecific level. The studies covered most of the major crop species of Africa and their wild relatives, though important gaps remain, for example sweet potato. So-called minor crops were not well represented. Wild taxa not related to crops were also covered, in particular agroforestry and forest species.     

Patterns of morphological and allozyme variation in sorghum landraces of Northwestern Morocco

Patterns of variation in inflorescence and spikelet morphology and in allozyme markers were studied within and among six fields of sorghum sampled from different areas in Northwestern Morocco. Substantial variation for both types of markers is found within fields. Significant differentiation among fields occurs for both types of traits, with 63% of morphological variation and 20% of allozyme variation expressed among fields. Discrepancies between allozyme studies based on germplasm accessions conserved ex situ and this and other studies involving in situ sampling underline the need to use appropriate sampling schemes for assessing the patterns of genetic variation of local landraces.     

Diversity evaluation of wheat germplasm resources in China

A great number of wheat genetic resources are distributed in China, and more than 40,000 accessions have been conserved in the National Crop Gene Bank. The diversity of these wheat genetic resources was evaluated for the following fields: distribution areas and growth environments; collection status; genetic diversity in agronomic characters, grain quality, resistance to diseases, pests and environmental stresses, and crossability. According to the results of diversity evaluation, some collections with desirable characters have been obtained.     

Random amplified polymorphic DNA and genetic diversity in IndianMusa germplasm

Summary Fifty-seven accessions ofMusa including cultivated clones of 6 genomic groups (AA, AB, AAA, AAB, ABB, ABBB),M. balbisiana Colla (BB),M. acuminata Colla ssp.banksii F. Muell. (AA),M. acuminata Colla ssp.malaccensis Ridl. (AA) andM. velutina Wendl. & Drude were examined for random amplified polymorphic DNA (RAPD) genetic markers using PCR with sixty 10-mer random primers. Forty-nine of 60 tested primers gave reproducible DNA amplification patterns. The number of bands resolved per amplification was primer dependent and varied from 1 to a maximum of 24. The size range of the amplification products also differed with the selected primer sequence/genotype and ranged from 0.29 to 3.0 kb. RAPD data were used to generate Jaccard's similarity coefficients which were analyzed phenetically. Phenetic analysis separated clones into distinct groupings that were in agreement with clusterings revealed when data were subsequently analyzed by principal coordinate analysis (PCO). In both the phenetic and the PCO analyses, previously unclassified cultivars grouped with cultivars previously classified for their genomic group based on morphological keys. The implications of RAPD analysis forMusa germplasm classification, clonal identification, and management are discussed.     

Geographical, altitude and agro-ecological differentiation of isozyme and hordein genotypes of landrace barleys from Ethiopia: implications to germplasm conservation

An analysis of the variability of genes encoding six isozyme systems (15 loci) and two storage proteins (2 loci) in landrace barley from Ethiopia is reported. The materials consisted of populations collected from sites as low as 1650 and as high as 3750 meters, covering a wide range of agro-ecological conditions and geographical areas. Of the 17 loci 7 were polymorphic and 10 monomorphic when the 95% criterion of polymorphism was applied. Despite the disproportionate monomorphic loci, polymorphism was detected in all populations when this criterion is used. The populations were found to possess fairly low mean number of alleles per locus (A = 1.5), low mean value of expected heterozygosity (H = 0.134) and a fairly high mean percentage of polymorphic loci (P = 35.3%). The mean F_ST= 0.474 for the populations is typical of inbreeding species. The result indicated that allelic richness is concentrated in altitude class 3 (2500–3000 m) followed by altitude class 1 (<2000 m). Altitude class 2 (2000–2500) holds an intermediate place though it is the highest in terms of expected heterozygosity (H = 0.245). Higher genetic diversity is concentrated in some geographical regions such as Shewa, Arsi, Bale compared to others (Welo, Gamu Gofa, Gojam). Genetic differentiation among the agro-ecological zones was more profound than both among the altitudes and among regions. Correlation analysis between phenotypic diversity (Shannon-Weaver diversity index) and expected heterozygosity (H) for isozyme/hordein loci revealed non significant associations except with respect to agro-ecological zones. In general, it was detected that sites in highland areas in central and northern regions may be more desirable for in situ conservation than sites in peripheral regions in terms of isozyme/hordein diversity and current rate of varietal replacement.     

Phenotypic diversity for qualitative and phenologic characters in germplasm collections of tef (Eragrostis tef)

A total of 3600 entries of tef [Eragrostis tef (Zucc.) Trotter] germplasm collections representing 36 populations from six regions of Ethiopia were evaluated for phenotypic diversity in six qualitative and phenologic characters. High values of Shannon–Weaver diversity index ( ) were recorded for most characters in each population. Monomorphism was high for anther color (purple) and panicle form (loose). Larger variances for were obtained among regions than among populations within a region from hierarchical analysis of variance. Significant (P<0.05) to highly significant (P<0.01) t-values were observed among values of some regions for seed color, panicle form and days to maturity. A substantial level of variance (P<0.05) was obtained for populations within altitudinal zones only for days to maturity. Altitudinal zones exhibited similar levels of diversity across characters for these collections. Generally, considerable variations important for tef improvement work have been observed and regions with highest diversity for some traits have been suggested for future in situ or ex situ germplasm conservation works. Although similar mean diversity indices were obtained among regions, they were non overlapping.     

华南型黄瓜主要农艺性状遗传多样性评价

为研究华南型黄瓜的遗传多样性及亲缘关系,以69份黄瓜自交系为试材,对其24个主要农艺性状进行遗传变异、相关性、主成分和聚类分析。结果表明,不同农艺性状的变异系数为6.19%~73.89%,各性状至少与其他1个性状存在极显著或显著相关。选取累积贡献率为73.597%的前7个主成分,其包含的17个农艺性状是黄瓜种质评价的主要指标,其中14份材料综合表现较优(F1.5)。进一步系统聚类,可将黄瓜种质分为4类:第Ⅰ类下胚轴较长,第1雌花节位低,瓜呈短圆筒形、具点状黄色斑纹,可用于早熟品种选育;第Ⅱ类下胚轴和节间短、第1分枝节位低,叶片小,第1雌花节位较低,瓜小、具点状黄色斑纹,综合性状与近缘野生种接近,可用于早熟、稳产、抗逆品种的选育;第Ⅲ类下胚轴和节间长,瓜皮白绿、具点状白色斑纹,可用于白皮品种选育;第Ⅳ类节间长、主蔓粗、第1分枝节位高,叶片大,第1雌花节位高,瓜大、呈长圆筒形、具点状白色斑纹,可用于黄瓜高产育种。综合评价结果表明华南型黄瓜种质具有丰富的遗传多样性,适用于黄瓜优异资源的挖掘及品种选育。本研究结果为华南型黄瓜资源利用和新品种选育奠定了基础。     

Analysis of genetic diversity of soybean germplasm from five different origins using RAPD markers

The pattern of genetic diversity among 92 genotypes of soybean from 5 different origins/sources (Pakistan, the USA, Asian Vegetable Research Development Centre (AVRDC), Japan and North Korea) was analyzed using randomly amplified polymorphic DNA markers. Out of 20 random primers 6 tested, 10 were polymorphic among genotypes and they yielded 107 markers, with an average of 10.7 markers per primer. The proportion of polymorphic bands within genotypes ranged from 0.47 to 0.71 with an average of 0.59. Pakistani and US genotypes exhibited the highest number of polymorphic bands (95%), while North Korean genotypes revealed the lowest (60%). The mean band frequency of the primers among genotypes was 0.57 with a range of 0.08–0.99. The Shannon’s index and Nei’s genetic diversity index revealed that primer OPF-06 showed maximum genetic diversity among the genotypes. Dendrogram constructed using Unweighted Pair Group Mean Average (UPGMA) method divided the genotypes into 5 main groups consisting of 13 clusters. The results of cluster analysis indicated that the genetic diversity between Pakistani and US or AVRDC genotypes is much larger than that between Pakistani and North Korean or Japanese genotypes. The Pakistani genotypes had distinct bands from plant introductions. Therefore, the Pakistani genotypes may be useful to soybean breeders.     

Diversity in pearl millet germplasm from Central African Republic

Most of the pearl millet (Pennisetum glaucum (L.) R. Br.) growing areas in Central African Republic (CAR) were explored by the GRD, ICRISAT in collaboration with the Ministry of Rural Development, CAR, Bangui and 129 pearl millet samples were collected during December 1988–January 1989. Considerable diversity was observed for several characters when 146 accessions including 17 collected by Institut francais de recherche scientifique pour le développement en coopération (ORSTOM) were evaluated at ICRISAT Asia Center (IAC), Patancheru. Time to flower ranged from 57 to 140 days with a mean of 128±1.1 days in rainy season and from 57 to 132 days with a mean of 73±0.8 days during postrainy season. Plant height ranged from 140 to 410 cm with a mean of 311±6.1 cm in the rainy season and from 75 to 310 cm with a mean of 155±2.6 cm during the postrainy season. The number of tillers varied between 1 to 6 per plant, spikes were mostly cylindrical and medium sized with a mean length of 20 cm during both seasons. They produced mostly gray or cream colored, globular grain, with partly corneous endosperm. Cluster analysis categorized accessions into similarity groups facilitating sampling a limited number of entries to represent the diversity of the pearl millet germplasm from Central African Republic.Submitted as ICRISAT Journal Article No. 1807.     

中国南瓜种质资源农艺性状与RAPD标记分析

本研究利用形态学标记和RAPD分子标记同时对70份来自我国不同地区的中国南瓜种质进行遗传多样性和亲缘关系分析。在所观察的56个有差异的农艺性状中,变异系数从6.60%~262.22%,平均变异系数为37.50%。从150个随机引物中筛选出21个进行RAPD分析,结果表明,在检测到的167条带中有130条具有多态性,多态带比率为73.23%;平均每个引物检测到的条带数多达8条,平均Shannon信息指数(Ⅰ)为0.268。基于农艺性状的聚类分析将70份中国南瓜种质分为七类。基于RAPD标记的聚类分析将70份中国南瓜种质分为五类,其聚类结果与形态特征有一定的相关性。但两种聚类结果均无法从地理来源上进行区分。     

Genetic diversity of winter wheat in Shaanxi province, China, and other common wheat germplasm pools

Cultivated Chinese wheat germplasm has been a valuable genetic resourcein international plant breeding. Landraces endemic to China are a geneticresource that is distinct from other wheat germplasm. Patterns of geneticdiversity among cultivated Chinese accessions and relationship to othergermplasm pools are unknown, despite the proven value and potential novelty. Theobjective of this work was to determine the level of genetic diversity withinimproved Chinese germplasm in the context of several other wheat germplasmpools. We analyzed a set of improved accessions cultivated from the 1940s to the1990s in Shaanxi province, China, using six simple sequence repeat (SSR) primerpairs and 30 restriction fragment length polymorphism - probe enzymecombinations (RFLP-PEC) previously used to characterize 21 geographically basedgermplasm pools. Shaanxi germplasm consists of three groups based on foreignintroductions from Italy, Australia, Denmark, and Russia. There was a decreasein genetic diversity among Shaanxi accessions cultivated in the 1970s and 1980sto the 1990s, and accession classifications based on primary decade ofcultivation were found to be significantly undifferentiated. The analysis of themean genetic distance among 22 geographically based pools of germplasm suggestsseveral regions are significantly undifferentiated. A vast majority of the totalamount of variation was found within pools; therefore, pools appear to belargely differentiated based on small differences in band relative frequency andfew if any unique bands. Previous studies have identified some Chinese landracepools as morphologically and genetically unique. The Shaanxi pool does not havethe same unique morphological or genetic features, nor is it more similar to thelandrace pools than other improved germplasm pools.     

基于形态性状和指标成分的远志遗传多样性分析及综合评价

为了揭示远志种质资源遗传多样性地理分布的特点和种质资源群体间的遗传关系,并筛选出相对合理的评价指标,本研究利用形态性状数据以及3个主要指标成分(远志皂苷、远志𠮿酮Ⅲ和3,6'-二芥子酰基蔗糖)含量,对省内11个不同来源的26份和省外7个不同来源的16份三年生远志进行遗传多样性分析。研究发现远志在形态性状以及指标成分含量上具有明显差异,变异系数和遗传多样性指数分别在13%~49%、19%~30%和0.7~1.7、0.9~1.4之间;远志𠮿酮Ⅲ含量与花色深度呈极显著正相关性,与株高呈显著正相关性,与木芯粗呈极显著负相关性;3,6'-二芥子酰基蔗糖含量与细叶远志皂苷含量呈显著正相关性,与株高呈极显著负相关性;细叶远志皂苷含量与茎分支数呈显著负相关性。主成分分析将15个指标简化为4个因子,累计贡献率达67.764%;形态性状和指标成分含量的聚类分析结果均将远志分为三大类群,但各类群成员并不一致,利用综合评价F值筛选出8份优良种质;各种质的综合得分范围为-1.15~1.23;利用逐步回归分析筛选到远志种质评价的7个关键性指标,分别为茎分支、叶色、花色、根重、木芯重、远志𠮿酮Ⅲ含量和3,6'-二芥子酰基蔗糖含量。综上所述,参试远志种质资源主要形态性状和指标成分的遗传多样性较为丰富,变异幅度较大。本研究从42份种质资源中筛选出8份综合表现良好的优异单株,可用于进一步开发和利用,为远志种质创新利用、品种改良提供了理论依据。     

Multivariate analysis of morphological variation in sorghum (Sorghum bicolor (L.) Moench) germplasm from Ethiopia and Eritrea

Multivariate methods, including principal component, cluster and discriminant analyses, were used to assess the patterns of morphological variation and to group 415 sorghum accessions for 15 quantitative characters. The first five principal components explained 79% of the total variation with plant height and days to 50% flowering being the most important characters in the first principal component. Cluster analysis grouped the accessions into ten clusters. A greater proportion of accessions of similar adaptation zones and accessions from regions of origin with similar agro-climatic conditions were grouped together. Moreover, discrimination of accessions was more pronounced when discriminant analysis was based on zone of adaptation rather than regions of origin. Based on the observed patterns of variation, it is concluded that the morphological variation in the material studied is structured by environmental factors. The implications of the results for plant breeding and germplasm conservation programmes arediscussed.     

Genetic diversity and systematic relationships in sweetpotato (Ipomoea batatas (L.) Lam.) and related species as revealed by RAPD analysis

Summary Fifteen 10mer primers, in combination with the Stoffel fragment, were used to detect random amplified polymorphic DNA (RAPDs) among 26 accessions of sweetpotato (I. batatas (L.) Lam.) from Oceania, Peru, the Philippines, and the United States and between 8 Ipomoea species from section Batatas. Phenetic and principal coordinate analysis of the 56 polymorphisms detected within the hexaploid I. batatas clearly delineated the South Pacific and the Peruvian sweetpotato lines. The two U.S. cultivars clustered with the Oceanic materials. Cladistic and phenetic analysis of 8 Ipomoea species supports previously published phylogenies based on morphological and RFLP data. Among the species examined, I. tabascana, I. trifida and the tetraploid forms of I. batatas from Mexico and Ecuador, including I. batatas var. apiculata, are the taxa most closely related to the cultivated hexaploid I. batatas. These findings support the utility of RAPD markers for evaluating genetic diversity in sweetpotato and for establishing taxonomic and evolutionary relationships in Ipomoea.     

Genetic variation of Ethiopian and Eritrean sorghum (Sorghum bicolor (L.) Moench) germplasm assessed by random amplified polymorphic DNA (RAPD)

The extent and patterns of distribution of genetic variation among 80 sorghum (Sorghum bicolor (L.) Moench) germplasm accessions from Ethiopia and Eritrea were investigated using RAPD with 20 oligonucleotide primers. The primers generated a total of 147 polymorphic bands across the 80 accessions with a mean of 7.35 bands per primer. Estimation of the extent of variation by the Shannon-Weaver diversity index revealed an intermediate level of overall variation (H = 53), although the levels varied among regions of origin of the accessions. Partitioning of the total variation revealed considerable variation (77%) within the region of origin of the accessions and the remainder (23%) among regions of origin. Similarly, a large portion (94%) of the total variation was found within the adaptation zones compared to among the adaptation zones (6%). The results suggest a weak differentiation of the sorghum material both on regional and agro-ecological bases, which could be ascribed to the high rate of outcrossing in cultivated sorghum and its free natural hybridization with its wild and weedy relatives, as well as to seed movement by humans. The average genetic dissimilarity was found to be 36% among the 80 accessions and 13% among the 15 regions of origin. Cluster analysis failed to group accessions of the same region or the same adaptation zone, which further confirmed the weak differentiation of the material studied. The clustering pattern of the regions of origin was broadly concordant with previous clustering patterns obtained using morphological characters, in which regions with broad agro-climatic conditions were grouped together.