Genetic diversity of Fagopyrum homotropicum, a wild species related to common buckwheat

Nineteen natural populations of Fagopyrum homotropicum, a self-fertilizing close relative of common buckwheat, from the Yunnan and Sichuan provinces of China were investigated for their chromosome number and allozyme variation at 16 loci of 11 enzymes. Three populations, 'Deqin', 'Zhongdian', and 'Xiancheng', were revealed to be allotetraploid. Judging from allozyme constitution of the tetraploid and their possible progenitors, diploid progenitors are probably the diploid population of F. homotropicum from Lijiang and a natural population of F. esculentum ssp. ancestralis. Diploid populations of F. homotropicum are fixed for a given allele at almost all isozyme loci. Allozyme variation has been maintained in natural populations mainly by fixing different alleles in different populations, as they are highly differentiated among the populations (G_st = 0.969). The position of populations in the phylogenetic tree constructed from genetic distance nearly corresponded with the geographical position of the populations.     

The Distribution of <Emphasis Type="Italic">Perilla</Emphasis> Species

Perilla (Lamiaceae) contains one tetraploid species, P. frutescens (L.) Britt. and three diploid species, P. citriodora (Makino) Nakai, P. hirtella Nakai and P. setoyensis G. Honda. Tetraploid species have been traditionally cultivated in Asia for their seed oil and for their fragrant leaves that are used as medicine or as a garnish for fish. The center of diversity is still obscure. To conserve the genetic resources, it is important to know the diversity of the tetraploid species. The three diploid species, which are possible parents of the tetraploid species, are all believed to be indigenous to Japan. Their distribution in China and Korea was clarified on the basis of herbarium and field surveys. The tetraploid species is assumed to have originated somewhere around the mid-to downstream area of the Changjiang River. Though Perilla is not cultivated as often in these areas as in northern China, Korea, the Himalayan region, or Myanmar, these areas should also be important for the conservation of genetic resources of tetraploid Perilla crops because of the expected high genetic diversity.     

Levels and distribution of allozyme and RAPD variation in populations of Elymus fibrosus (Schrenk) Tzvel. (Poaceae)

To study the magnitude and nature of genetic variation in E. fibrosus, the levels and distribution of allozyme and RAPD variations were investigated in populations collected from Finland and Russia. The results obtained from the allozyme and RAPD studies were compared to each other in 10 of the populations. The allozyme analysis showed that 6 of 12 presumed loci (50%) were polymorphic within the species, while the mean number of polymorphic loci within populations was 4.8%. The mean number of allele per locus for the species was 1.5 and 1.05 across the populations. Genetic diversity at the species level was low (H _es = 0.025), and the mean population genetic diversity was even lower (H _ep = 0.007). Both these values were much lower than the average for other Elymus and self-fertilising species. The largest proportion of the total allozyme diversity was found among, rather than within the populations (G _ST = 0.70). The allozyme genetic distances between the populations did not reflect geographic distances. Cluster and principal coordinates analyses revealed the same allozyme relationship patterns among the populations. A comparison of allozyme and RAPD variation in 10 of the populations showed differences in the amount of genetic variation. The RAPD analysis revealed higher levels of variation (A _p = 1.19, P _p = 20.3 and H _ep = 0.09) than the allozyme one) A _p = 1.06, P _p = 5.8 and H _ep = 0.008). For both markers, the largest proportion of the total gene diversity was found among the populations studied (G _st = 0.63 for RAPDs and G _st = 0.65 for allozyme). In contrast to the allozyme analysis, the RAPD based genetic distances did reflect geographic distances. The cluster and principal coordinates analyses showed different grouping of populations for each data set. There was a positive, but not significant, correlation (r = 0.41) between the genetic distance matrices resulting from these markers. Regional comparison revealed that the Finnish populations had a higher diversity than the Russian ones. Generally, this study indicates that E. fibrosus contains low genetic variation in its populations. The results are discussed in the context of conservation of the species.     

Ploidic and Molecular Analysis of ‘Morado de Huetor’ Asparagus (Asparagus officinale L.) Population; A Spanish Tetraploid Landrace

A study has been conducted into the genetic variation analysis of the tetraploid asparagus landrace ‘Morado de Huetor’ and its relationship with current commercial cultivars using Random Amplified Polymorphic DNA (RAPD) molecular markers. The presence of different ploidic levels in the ‘Morado de Huetor’ landrace has been also studied using cytogenetic analysis. Ten decamer oligonucleotides were used to obtain RAPD markers and to characterise 52 individuals of ‘Morado de Huetor’, 7 of the tetraploid cultivar ‘Purple Passion’, and 55 of 5 diploid hybrid commercial cultivars. Jaccard similarity index was calculated and a cluster analysis using UPGMA (Unweighted Pair-Group Method using Arithmetic Average) was performed. Tetraploid asparagus, ‘Morado de Huetor’ and ‘Purple Passion’, were well differentiated from the diploid ones showing a higher genetic variability. This result suggests a different origin for tetraploid and diploid asparagus varieties. Within the diploid cultivars a variety distribution was obtained. A specific monomorphic band (OPB20₈₈₃) was found in tetraploid varieties. Within the diploid cultivars, two bands (OPB20₈₃₀, OPC15₇₀₅) can be used to distinguish between the hybrid cultivars used in this study. Tri-, penta-, hexa-, and octoploid plants were found in ‘Morado de Huetor’. The origin of these ploidic levels is discussed and their use in the development of new varieties is proposed. In conclusion, ‘Morado de Huetor’ is a genetic resource that could be used to increase the narrow genetic background reported in diploid asparagus cultivars.     

The flavonoid content in leaves and inflorescences of the wild perennial Fagopyrum cymosum complex

The Fagopyrum cymosum complex is a group of wild perennial buckwheats which includes the diploid species F. megaspartanium Q. F. Chen and F. pilus Q. F. Chen as well as the allotetraploid species F. cymosum (Trev.) Meisn. The flavonoid content in leaves and inflorescences of the accessions of the F. cymosum complex native to Guizhou, Yunnan, Sichuan, Hunan, Hubei, and Tibet has been studied by means of the spectrophotometry and high-performance liquid chromatography. The results showed that there are significant differences of flavonoid content among different species, different accessions and different plants. The average flavonoid content of leaves of F. megaspartanium is higher than that of F. pilus and of F. cymosum. The average flavonoid content of inflorescences of F. megaspartanium is higher than that of F. pilus. The results also showed that the flavonoid content in inflorescences was significantly higher than that in leaves, and that they have positive relationships to each other. There is a significant difference of rutin content between leaves and inflorescences, but there is no significant relationship to each other. There is also no significant relationship between leaf rutin contents and leaf flavonoid contents, but significant positive relationship between inflorescence rutin contents and inflorescence flavonoid contents.     

Assessment of genetic diversity in cultivars and wild accessions of Luohanguo (<Emphasis Type="Italic">Siraitia grosvenorii</Emphasis> [Swingle] A. M. Lu et Z. Y. Zhang), a species with edible and medicinal sweet fruits endemic to southern China,using RAPD and AFLP markers

Genetic variation of wild populations and cultivars of Luohanguo (Siraitia grosvenorii), a plant species endemic to southern China, was assessed using random amplified polymorphic DNA (RAPD) and amplified fragment length polymorphism (AFLP) markers. Based on the results for 130 individuals from seven populations, a high level of genetic diversity of Luohanguo was observed at the species level. The percentage of polymorphic loci (P) was 89.4%, Nei’s gene diversity (H _e) was 0.239, and Shannon’s information index (H _o) was 0.373 based on the combined AFLP and RAPD data. There was a high degree of genetic differentiation, with 45.1% of the genetic variation attributed to differences between the populations. The genetic diversity of the Luohanguo cultivars is much lower than that of wild populations (P = 41.8%, H _e = 0.141, H _o = 0.211), and a distinct genetic differentiation is observed between the cultivars and wild accessions. The pool of genetic variation in the wild populations provides an excellent gene resource for Luohanguo breeding.     

Karyotype and genetic relationship based on RAPD markers of six wild buckwheat species (<Emphasis Type="Italic">Fagopyrum</Emphasis> spp.) from southwest of China

Karyotypes of six wild buckwheat species from Sichuan Pan’xi Regions of China were investigated in present study. This study will help in understanding evolutionary mechanisms and relationships among the taxes in this section. The karyotypes of three species, F. densovillosum, F. gracilipes var. odontopterum and F. gracilipes are being reported for the first time. F. esculentum, F. cymosum, F. tataricum and F. densovillosum are diploid while F. gracilipes var. odontopterum and F. gracilipes are tetraploid, 2n = 4x = 32. At diploid level, the variation of the buckwheat chromosome karyotypes is bigger; however, on the tetraploid level, it shows a higher similarity. The karyotype evolutionary trend of buckwheat indicated that F. densovillosum seemed to be more advanced than F. gracilipes var. odontopterum and F. gracilipes. F. densovillosum, F. gracilipes var. odontopterum. and F. gracilipes were found more closely related genetically whereas F. tataricum clustered into a separate group. F. esculentum and F. cymosum clustered together in one separate group.     

Genetic diversity in populations of wild diploid wheat Triticum urartu Tum. ex. Gandil. revealed by isozyme markers

Genetic variation and its distribution within and among 23 populations of Triticum urartu collected from Syria, Lebanon, Turkey, Armenia, and Iran was estimated using isozyme markers at eight polymorphic loci. The number of alleles per locus (A= 1.21), percentage polymorphic loci (P= 20.1%), and mean gene diversity (H_e= 0.024) were relatively low. In a population from Lebanon, a high number of alleles per locus (A= 2.13) and percentage polymorphic loci (P= 87.5%) was found. On average, genetic variation among populations (G_ST= 0.407) was smaller than within-population variation (0.593). However, different patterns of genetic structure were found among various geographic regions. Interpopulation variation was highest for the Iranian populations (0.89) followed by the Turkish populations (0.66). A reverse pattern was observed for the Syrian (0.11) and for the Lebanese (0.13) populations. The Armenian populations exhibited similar interpopulation and within-population variation. Principal component and cluster analyses resulted in distinct grouping of the geographically proximal populations, with the exception of the two Iranian populations. The Turkish populations were different from the neighboring Armenian populations compared to other countries. The populations from southern Syria and those from Lebanon also exhibited a high degree of genetic diversity. The two most heterozygous loci, Mdh-2 and Pgi-2, separated the populations along the first and second principal components, respectively. Most of the rare alleles were scattered sporadically throughout the geographic regions. Rare alleles with high frequencies were found in the Turkish and Armenian populations. These results indicated that different geographic regions require specific sampling procedures in order to capture the range of genetic variation observed in T. urartu populations.     

Population Genetics of <Emphasis Type="Italic">Escontria chiotilla</Emphasis> in Wild and Silvicultural Managed Populations in the Tehuacán Valley,Central Mexico

Escontria chiotilla is a columnar cactus that grows in the arid and semiarid lands of Central Mexico and produces edible fruit with economic. In the wild, this plant species is distributed as part of thorn-scrub and tropical deciduous forests, but in the Tehuacán Valley also occurs in silvicultural managed in situ populations, in which people practise artificial selection enhancing phenotypes with larger fruits. The population genetics of wild and managed populations was studied to analyse the effects of management on genetic structure of E. chiotilla. A total of 150 individuals from six populations were studied, analysing 13 loci for eight enzymes by starch gel electrophoresis. The genetic variation in wild populations was significantly higher than in managed populations (H_o = 0.079, H_e = 0.134, H_T = 0.370, and H_o = 0.052, H_e = 0.110, H_T = 0.298, respectively), indicating that silvicultural management has caused a reduction of the genetic variation in populations. Most of the genetic variation in both wild and managed populations occurs within populations (D_ST = 0.027 in the wild and 0.018 in managed populations). The genetic distance coefficients were slightly different for silvicultural managed populations than in wild ones, illustrating an incipient effect of management on the genetic structure of populations. However, values of Nm_GST = 3.845 and Nm_FST = 3.848 indicate that a high gene flow counteracts the effects of human selection on the differentiation of populations.     

Genetic evidence for speciation in <Emphasis Type="Italic">Cannabis</Emphasis> (Cannabaceae)

Sample populations of 157 Cannabis accessions of diverse geographic origin were surveyed for allozyme variation at 17 gene loci. The frequencies of 52 alleles were subjected to principal components analysis. A scatter plot revealed two major groups of accessions. The sativa gene pool includes fiber/seed landraces from Europe, Asia Minor, and Central Asia, and ruderal populations from Eastern Europe. The indica gene pool includes fiber/seed landraces from eastern Asia, narrow-leafleted drug strains from southern Asia, Africa, and Latin America, wide-leafleted drug strains from Afghanistan and Pakistan, and feral populations from India and Nepal. A third putative gene pool includes ruderal populations from Central Asia. None of the previous taxonomic concepts that were tested adequately circumscribe the sativa and indica gene pools. A polytypic concept of Cannabis is proposed, which recognizes three species, C. sativa, C. indica and C. ruderalis, and seven putative taxa.     

Reduced effective population size in an overexploited population of the Nile crocodile (Crocodylus niloticus)

Unchecked exploitation of wildlife resources is one of the major factors influencing species persistence throughout the world today. A significant consequence of exploitation is the increasing rate at which genetic diversity is lost as populations decline. Recent studies suggest that life history traits affecting population growth, particularly in long-lived species, may act to moderate the impact of population decline on genetic variation and lead to remnant populations that appear genetically diverse despite having passed through substantial demographic bottlenecks. In this study we show that the retention of genetic variation in a partially recovered population of Nile crocodile is deceptive, as it masks the reality of a significant decline in the population’s effective size (N_e). Repeated episodes of unchecked hunting in the mid to late 20th century have today led to a five-fold decrease in the population’s N_e. Using current census data we estimate the contemporary N_e/N ratio as 0.05 and, in light of quotas that permit the ongoing removal of adults, simulated the likely effects of genetic drift on extant levels of variation. Results indicate that even if the current effective size is maintained, both allelic diversity and heterozygosity will decline. Our findings have complex implications for long-lived species; an emphasis on the retention of genetic variation alone, whilst disregarding the effects of population decline on effective size, may ultimately obscure the continued decline and extinction of exploited populations.     

Determination of Ploidy Level and Nuclear DNA Content in Tunisian Populations of Atriplex halimus L.

Atriplex halimus L. (Chenopodiaceae) (Saltbush) is a perennial species used as a fodder shrub for livestock in arid and semi-arid areas, particularly in North Africa. The aim of this work was to determine whether differences in ploidy level and/or nuclear DNA content exist among populations from widely-separated sites in Tunisia. We determined nuclear DNA content and chromosome numbers for populations of A. halimus from seven different locations (Gabes, Medenine, Tataouine, Monastir, Tunis, Sidi Bouzid, Kairouan). The chromosome counts showed that all the Tunisian populations, plus a population from Eraclea (Italy), were tetraploid (2n = 4x = 36) whereas a population from Cala Tarida (Spain) was diploid (2n = 2x = 18). With respect to nuclear DNA, the 2C DNA content of population Cala Tarida was estimated to be 2.41 pg. There was no significant difference among the tetraploid populations (or among plants within populations), whose 2C DNA content ranged from 4.92 to 4.97 pg.     

Genetic Diversity of Asian Cotton (Gossypium arboreum L.) in China Evaluated by Microsatellite Analysis

Asian cotton (Gossypium arboreum L.) was once widely cultivated in China. It has also been a valuable source of genetic variation in modern cotton improvement. In this study, the genetic diversity of selected G. arboreum accessions collected from different regions of China was evaluated by microsatellite (simple sequence repeats, SSRs) analysis. Of the 358 microsatellite markers analyzed, 74 primer pairs detected 165 polymorphic DNA fragments among 39 G. arboreum accessions examined. Twelve accessions could be fingerprinted with one or more SSR markers. With the exception of two accessions, DaZiJie and DaZiMian, genetic similarity coefficients among all accessions ranged from 0.58 to 0.87 suggesting high level of genetic variation in the G. arboreum collections. The UPGMA dendrogram constructed from genetic similarity coefficients revealed positive correlation between cluster groupings and geographic distances. In addition, comparison of the microsatellite amplification profiles of the diploid G. arboreum and tetraploid Gossypium hirsutum L. found that size distribution of amplified products in G. arboreum was dispersive and that of G. hirsutum was relatively concentrated. The information on the genetic diversity and SSR fingerprinting from this study is useful for developing mapping populations for constructing diploid cotton genetic linkage map and tagging economically important traits.Diqiu Liu, Xiaoping Guo: These two authors contributed equally to this work.     

Allozyme Diversity and Population Structure of Caragana korshinskyi Kom.in China

Caragana korshinskyi Kom. is a long-lived shrub species indigenous to northwestern China, and important in vegetation rehabilitation of widely degraded and degrading semiarid and arid regions because of its high ecological and economic values. Information at molecular level on its genetic diversity, however, is not available. Accordingly, the extent and distribution for genetic diversity and population structure in 11 populations of C. korshinskyi were assessed using polyacrylamide gel electrophoresis for seven enzymes including aminopeptidase, aspartate aminotransferase, glucose-6-phosphate dehydrogenase, malate dehydrogenase, phosphoglucoisomerase, phosphogluconate dehydrogenase, and peroxidase. The seven-enzyme systems produced 11 loci encompassing 19 alleles demonstrating high genetic variation at both species and population levels. A considerable excess of heterozygotes relative to Hardy–Weinberg expectations was detected at the both levels as well. G_ST ranged from 0.0074 for AMP-1 to 0.4646 for PGD with a mean of 0.1517, indicating that approximately 84.8% of the total allozyme variation occurred within populations. An indirect estimate of the number of migrants per generation indicated that gene flow was high among populations of the species.     

Rediscovery of a diploid cytotype of Dasypyrum breviaristatum in Morocco

The chromosome numbers of a total of 273 Dasypyrumbreviaristatum plants sampled from 20 Moroccan and one Greek naturalpopulations were examined. 270 plants from all of the populations weretetraploids. Among them, 223 were eu-tetraploids with 28 chromosomes and 47 wereaneuploids with 25, 27 and 29 chromosomes. Besides, three plants were found tobe diploids among 16 plants from a population in the Moyen Atlas Mountains ofMorocco. This is the second report of a diploid cytotype ofD. breviaristatum since the firstcommunication in 1957. Morphologically, the diploids were similar to but smallerthan the tetraploids in plant height, spike length, spikelet number and leafepidermis cell size. However, it was not possible to distinguish between the twocytotypes based on those morphological characteristics alone. A distinctdifference was found between the two cytotypes only in the number of trichomeson the leaf surfaces. The karyotype of the diploid cytotype consisted of a pairof SAT-chromosomes, five pairs of metacentric and a pair of submetacentricchromosomes. Based on the similarity in karyotype and in plant morphologybetween the two cytotypes of D.breviaristatum, we suggest that the diploid cytotype is themost probable candidate for the ancestral form of the tetraploid cytotype.     

Genetic Diversity in AA and CC Genome Oryza Species in Southern South Asia

The CC genome of Oryza is found in nine species of Oryza that are distributed on all continents having a tropical climate. Three diploid Oryza species with CC genome are found in Africa and Asia to Papua New Guinea. In southern South Asia these three CC genome diploid species can be found, O. eichingeri and O. rhizomatis in Sri Lanka and O. officinalis in India. AA genome wild relatives of rice are also found in the same geographic region. Germplasm of both diploid CC and AA genome Oryza germplasm has recently been collected from Sri Lanka. AFLP analysis was used to compare the genetic diversity of the two Oryza genomes from a similar geographic region in southern South Asia. In addition, the diploid CC Oryza germplasm was also analyzed by RAPD and SSR methodologies and the combined results were analyzed. The results show that in southern South Asia the diploid CC genome species have a high level of genetic diversity compared to the diploid AA genome species. Molecular marker analysis revealed that populations of O. rhizomatis from northern and southeastern Sri Lanka are genetically differentiated. One accession of O. rhizomatis was aligned with O. eichingeri. This accession was collected from the site of O. rhizomatis that is the closest to a population of O. eichingeri. O. eichingeri showed lower genetic diversity than the other two diploid Oryza CC genome species. O. officinalis accessions from Assam, India, and China were genetically less diverged from O. eichingeri and O. rhizomatis than two accessions of O. officinalis from Kerala state, India. The first two authors contributed equally to this research     

Geographic distribution and genetic resources of Dactylis in Galicia (northwest Spain)

Three Dactylis glomerata subspecies can occur in Galicia (Spain): subsp. glomerata, subsp. izcoi and subsp. marina. The second includes diploid and tetraploid populations adapted to acid soils. The third subspecies comprises natural tetraploid populations mainly on sea cliffs, with high digestibility. Dactylis taxonomy is difficult due to the existence of different ploidy levels and to free hybridization at the tetraploid level. This difficulty increases in Galicia, where there is a rich flora with relics and hybrids. The advance of human technology makes necessary the collection of natural Dactylis resources. In this paper, Dactylis distribution in Galicia is described. Tetraploid populations from subsp. izcoi have a wider ecological range than diploids (Galician diploid). These diploids and the subsp. marina are more widespread than formerly recognized. Morphologically, subsp. glomerata and izcoi are more similar than hitherto reported. It is suggested that the subspecies are adapted ecotypes which hybridize. They are useful genetic resources for pasciculture on acid soils and agroforestry.     

High proportion of diploid hybrids produced by interspecific diploid × tetraploid <Emphasis Type="Italic">Sorghum</Emphasis> hybridization

A perennial version of grain sorghum [S. bicolor (L.) Moench] would create opportunities for greatly reducing tillage and preventing soil degradation. Efforts to select for perenniality and grain production among progeny of hybrids between S. bicolor (2n = 20) and the weedy tetraploid perennial S. halepense (L.) Pers. (2n = 40) are complicated in that F₁ hybrids produced by diploid × tetraploid sorghum crosses are usually tetraploid. In 2013, a set of random pollinations between 19 diploid cytoplasmic male-sterile inbred lines and 43 tetraploid perennial plants produced 165 F₁ hybrid plants, more than 75% of which had highly atypical plant, panicle, and seed phenotypes. Phenotypic segregation in F₂ populations derived from atypical hybrids was also anomalous. Examination of mitotic metaphase cells in F₁ or F₂ root tips revealed that 129 of the 165 hybrids were diploid. Parentage of the diploid progenies was confirmed using simple-sequence repeat analysis. The mechanism by which diploid hybrids arise from diploid × tetraploid crosses is unknown, but it may involve either production of monohaploid (n = 10) pollen by the tetraploid parent or chromosome elimination during early cell divisions following formation of the triploid zygote. The ability to produce diploid germplasm segregating for S. bicolor and S. halepense alleles could have great utility, both for the development of perennial sorghum and for the improvement of conventional grain sorghum.     

Genetic variation and species relationships in Himalayan buckwheats as revealed by SDS PAGE of endosperm proteins extracted from single seeds and RAPD based DNA fingerprints

SDS PAGE of endosperm proteins and␣RAPD profiles from different accessions of Himalayan buckwheat were studied to determine their genetic variation and phylogenetic relationships. Comparisons based on Jaccard’s coefficient and UPGMA clustering revealed interrelationships broadly in conformity with conventional treatments. Cluster analysis of the endosperm protein profiles of the selected accessions revealed three broad clusters. A moderate level of intraspecific variability was detected in the endosperm protein profile of different accessions of Fagopyrum esculentum, Moench. Three subgroups were detected in cluster 1. Subgroup 1 included varieties designated as Local, Kamroo local, OC-2 and␣VL-7 which were collected from VPKAS, Almora. Local, Kamroo local and OC-2 showed a similarity coefficient of 1.0 inspite of their being identified as different accessions. VL-7 emerged out separately from the rest of the three accessions. Accessions having winged grains and those having striations on the seed coat formed a 2nd and 3rd subgroup, respectively. IC-13145 which been identified as “F. himalianum”, showed 100%␣similarity in endosperm protein profile with IC-13376 (F. esculentum) and 85–90% similarity which other accessions of F. esculentum. Our results indicate that “F. himalianum” belongs to the esculentum group and should not be regarded as a different species. Cluster 2 included all the accessions of F. tataricum (L.) Gaertn. with Sangla 1, 2, 3, 5, 6, 7 and IC-412863 showing 100% similarity. F. cymosum emerged as a separate group distinct from both esculentum and tataricum. Accessions of F. tataricum and F. cymosum did not show significant intraspecific variation in the SDS PAGE profile of endosperm proteins. Out of the 20 primers used, 3 generated robust, easily interpretable amplified products. While a 1490 bp and a 300 bp RAPD was detected only in F. tataricum, a 1154 bp RAPD was detected in all accessions of F. tataricum except in Shimla B-1. This variety is early maturing and has high seed yields.