The Pacific yam (<Emphasis Type="Italic">Dioscorea nummularia</Emphasis> Lam.), an under-exploited tuber crop from Melanesia

This study aims to explore the potential of Dioscorea nummularia Lam. and to gather information as a prelude to its improvement by plant breeding. After a taxonomic clarification and a review of the botanical data, its geographical areas of origin and distribution are determined. A germplasm survey conducted on nine islands of Vanuatu enabled the collection of 110 accessions corresponding to 84 cultivars. These were grouped into: (1) wild forms under domestication, (2) annual types, (3) perennial-type cultivars of D. nummularia and (4) natural interspecific hybrids with D. alata L. Within each group, remarkable morphological variation exists for stem spininess, leaf shape, emerging leaf colour, tuber shape and tuber flesh colour. Selected accessions examined for ploidy had chromosome numbers ranging from 2n = 3x = 60 to 2n = 6x = 120. Chloroplast counts conducted on stomatal guard cells confirmed the variation in ploidy levels. Eight different male cultivars were studied for pollen fertility, but <5% of the pollen grains appeared to be fertile when stained with acetocarmine. However, profuse flowering and synchrony favour pollination and result in fruit set. All accessions are resistant to anthracnose. Viruses were detected but are morphologically not discernible, with no incidence on yield. Physicochemical analyses of tubers from 16 accessions revealed that D. nummularia and interspecific hybrids have high percentages of dry matter (mean of 33.11%) and starch (82.81%). The Pacific yam could be improved through conventional hybridisation or used for interspecific crosses with related economically important species. Recommendations are made for further research.     

Domestication and saponins contents in a gradient of management intensity of agaves: <Emphasis Type="Italic">Agave cupreata</Emphasis>, <Emphasis Type="Italic">A. inaequidens</Emphasis> and <Emphasis Type="Italic">A. hookeri</Emphasis> in central Mexico

Saponins occur in numerous plants, including agaves, determining benefic and harmful properties to humans; their presence may favor using plants as soap and other products, but also they may cause caustic effects producing contact dermatitis. In domestication, favorable and unfavorable properties of saponins may cause an increase or decrease of their content, respectively. This study quantified and identified saponins among wild and managed populations of three agave species: A. cupreata Trel. et Berger, A. inaequidens Koch with wild and cultivated populations used for mescal production, and A. hookeri Jacobi, existing exclusively cultivated, used for production of the fermented beverage pulque. We studied 272 plants from 19 populations, quantifying contents of crude saponins through spectrometry. In 12 populations, the saponins types were identified by High Performance Liquid Chromatography–Mass-Spectrography-Time-of-Flight HPLC-MS-TOF. The highest crude saponins content was recorded in A. hookeri (26.09 mg/g), followed by A. cupreata (19.85 and 15.17 mg/g in wild and cultivated populations, respectively). For A. inaequidens, we recorded 14.21, 12.95, and 10.48 mg/g in wild, silvicultural managed and cultivated populations, respectively. We identified 18 saponins types, A. inaequidens showing all of them. A hecogenin glycoside (HG1) is found in high amounts in A. hookeri but in low quantities in A. inaequidens and A. cupreata. A. inaequidens had the greatest diversity of saponins. The contents of crude saponins in A. inaequidens and A. cupreata decrease with management intensity, but contrarily to what we expected, it was the highest in A. hookeri. We hypothesize that such high amount could be due to some saponins, probably HG1, may be precursors of sugars.     

Exploring the Serbian GenBank barley (Hordeum vulgare L. subsp. vulgare) collection for powdery mildew resistance

Unlocking resistance genes in genbank collections are of prime importance for securing sustainable crop production. In this regard, the Serbian GenBank barley collection, comprising 93 local landraces and 36 commercial cultivars and elite barley breeding lines, was screened for novel resistances to powdery mildew (Blumeria graminis f. sp. hordei) using a set of 28 isolates with a wide spectrum of virulences/avirulences. No line was resistant to all the isolates, but one and three accessions showed resistance to 27 and 26 isolates, respectively. Twenty landraces (21.51 %) and ten cultivars (27.78 %) exhibited resistance to 50 % of the isolates. Infection type 2 was most frequent among resistant accessions. Nine B. graminis isolates were sufficient for gene postulation in 73 barley lines. In total, thirty-five different resistance spectra were recorded and the following known resistance genes were postulated namely, Mlra,Mlh,Mla12, Mla7(Mlu), Mlg, MlLa, Mla6, Mla7, Mlt, Mla22, Mlat, Mla1, Mlk. The majority of resistance profiles was constituted by only one line. Unidentified genes alone or in combination were proposed for twenty landraces and six cultivars. This report demonstrated that the barley collection held at the Serbian GenBank could be exploited as a new source for powdery mildew resistance.     

Genetic diversity in Japanese aromatic rice (Oryza sativa L.) as revealed by nuclear and organelle DNA markers

Aromatic rice (Oryza sativa L.) cultivated in Japan is regionally differentiated by geographical distribution and characteristics. We aimed to characterize the lineage of Japanese aromatic rice using DNA markers. Based on analyses with nuclear SSR markers, we found that Japanese aromatic rice cultivars belong, with one exception, to japonica but showed some differences from authentic japonica and were divided into two clades that were distributed in western and eastern Japan, respectively. Further analyses with organelle markers showed that most of the cultivars in eastern Japan had cytoplasm characterized by tropical japonica, whereas most of those in western Japan had cytoplasm characterized by temperate japonica. We postulate that the ancestor of the cultivars in eastern Japan differs from those of the cultivars in western Japan, and that the two groups may have been separately introduced from Taiwan into Japan. The cytoplasm of aromatic rice cultivars in western Japan may have originated from tropical japonica and been substituted into the cytoplasm of temperate japonica through hybridization between tropical japonica as a male parent and temperate japonica as a female parent.     

Evaluation of <Emphasis Type="Italic">Rubus</Emphasis> genetic resources on their resistance to cane disease

Raspberry cane disease, caused by a complex of fungi, is amongst the most devastating problems for raspberry production. Using resistant or highly tolerant genotypes is a promising strategy. However, until now, cultivars with good field resistance for German fruit growers as well as the primary causal pathogens of cane disease present in the eastern part of Germany, Saxony state are still unknown. The primary objective of this study was to identify the primary disease causing organisms and resistant Rubus germplasm for future breeding efforts. From 2012 to 2014, we evaluated the degree of susceptibility to cane diseases on 213 raspberry cultivars at two different locations using a rating scale. We also identified the main fungi growing on infected canes. Our results suggest that Fusarium avenaceum is the main fungus causing cane disease in Saxony. The Rubus hybrid cultivars ‘Tayberry’ (2n?=?6x?=?42), ‘Buckingham Tayberry’ (2n?=?6x?=?42) and ‘Dorman Red’ (2n?=?2x?=?14) displayed the highest levels of field resistance at both locations. Moreover, we established an in vitro assay for resistance evaluation which correlates significantly with field data and is particularly suitable for quick assessment of resistance against F. avenaceum in breeding material. Future breeding programs, aiming at cultivars with enhanced resistance towards cane diseases can use the presented data for parental selection and may employ our in vitro F. avenaceum inoculation method for parental testing and progeny selection.     

Cross-transferability of SSR markers in <Emphasis Type="Italic">Osmanthus</Emphasis>

Developing a molecular tool kit for hybrid breeding of Osmanthus species and related genera is an important step in creating a systematic breeding program for this species. To date, molecular resources have been aimed solely at Osmanthus fragrans with little work to develop markers for other species and cultivars. The objectives of this study were to (1) determine cross-transferability of O. fragrans and Chionanthus retusus derived SSRs in diverse Osmanthus taxa, (2) quantify the influence of locus-specific factors on cross-transferability, and (3) determine the genetic relationships between accessions. We tested 70 SSR markers derived from O. fragrans and C. retusus in 24 accessions of Osmanthus. Sixty-seven markers showed transfer to at least one other Osmanthus species with an overall transfer rate of 84% of loci across taxa. Genotyping with 42 microsatellite markers yielded a total of 367 loci. Number of alleles per locus ranged from 2 to 17 with a mean of 8.7 ± 4.8. Mean observed and expected heterozygosities were 0.560 ± 0.225 and 0.688 ± 0.230, respectively. Percent of polymorphic loci ranged from 40% in Osmanthus delavayi to 100% in O. fragrans. Osmanthus fragrans had the highest mean number of alleles per locus (4.2) while O. delavayi had the lowest (1.1). A reduced suite of eight-markers can distinguish between accessions with non-exclusion probabilities of identity from 3.91E?⁰⁴ to 2.90E?⁰⁷. The SSR markers described herein will be immediately useful to characterize germplasm, identify hybrids, and aid in understanding the level of genetic diversity and relationships within the cultivated germplasm.     

The genetic relationship and structure of some natural interspecific hybrids in <Emphasis Type="Italic">Prunus</Emphasis> subgenus <Emphasis Type="Italic">Prunophora</Emphasis>, based on nuclear and chloroplast simple sequence repeats

In the subgenus Prunophora of the genus Prunus, many transitional traits presented in interspecific hybrids, the so-called ‘new species’, were frequently named due to the complicated botanical classification system. In this study, we used 16 nuclear simple sequence repeats (nSSRs) and 10 chloroplast simple sequence repeats (cpSSRs) to evaluate genetic relationships among 42 accessions, which included 15 putative interspecific hybrids, and then to reveal the speciation and differentiation in the subgenus Prunophora. In total, 231 and 27 alleles were observed in nSSRs and cpSSRs respectively; and with cpSSRs 20 haplotypes were revealed among the accessions. Furthermore, the haplotype and genetic structure analysis implied that (1) Prunus simonii Carr. might be a subspecies or a forma of Prunus salicina L., rather than an interspecific hybrid between P. salicina and Prunus armeniaca L., (2) Prunus limeixing Zhang et Wang was derived from a natural hybrid with P. salicina as its maternal progenitor and P. armeniaca as the female parent, and (3) Prunus cathayana Fu et al. (or kernel-using apricot) was an interspecific hybridization species of P. armeniaca (maternal parent) and Prunus sibirica L. (female parent). These results will be useful for clarifying the problems in the botanical classification, and facilitate the conservation and management of plum and apricot genetic resources in the Chinese National Germplasm Repository for Plums and Apricots.     

Morphological,SSR and ploidy analysis of water yam (<Emphasis Type="Italic">Dioscorea alata</Emphasis> L.) accessions for utilization of aerial tubers as planting materials

The high cost and supply shortage of seed yam propagules for planting are major constraints in yam production. In the water yam (Dioscorea alata L.), aerial tubers have potential as alternative sources of planting material. In this study, we investigated morphological, molecular and ploidy variation across multiple aerial tuber producing accessions of Dioscorea alata. Initial screening of over 800 accessions from the International Institute of Tropical Agriculture germplasm collection for aerial tuber production identified a subset (15 %) of accessions, which produced aerial tubers. The aerial tuber producing accessions (along with 18 non-aerial tuber accessions) were further characterized for phenotypic and ploidy variation. In addition, using SSR markers we characterized the genetic diversity amongst all of the aerial tuber producing accessions, along with six non-aerial tuber producing accessions. Multiple Correspondence Analysis (MCA) using morphological data grouped the accessions according to their aerial tuber production. The aerial tuber production characteristics of accessions were associated with phenotypic variables and ploidy levels. The MCA analysis revealed three main groups consisting of; Group 1) all non aerial tuber producing accessions (n = 15), hastate leaf shape, less or no anthocyanin pigmentation and diploid (2n = 2x = 40), Group 2) group with some aerial tuber producing accessions, different extent of anthocyanin pigmentation, sagittate leaf shape, mainly diploid (n = 44) and three triploid (2n = 3x = 60) and 3) a group where all individuals bear aerial tuber, cordate leaf shape, intermediate anthocyanin pigmentation and majority (n = 74) tetraploid (2n = 4x = 80) and three triploid individuals. Aerial tuber production may be subject to a genome dosage effect as an increase in aerial tuber production was associated with increased ploidy level. For instance, tetraploid plants produce more aerial tubers per sprout than either triploids or diploids. Principal coordinate analysis based on SSR markers using Jaccard’s coefficient also revealed distinct groups associated with the pattern of aerial tuber formation, leaf shape and anthocyanin pigmentation. Overall our study indicates the usefulness of combining SSR markers, ploidy level and phenotypic data for identification and classification of Dioscorea alata accessions according to their extent of aerial tuber production.     

Exploration of genetic diversity within Cichoriumendivia and Cichorium intybus with focus on the gene pool of industrial chicory

The present study used 15 simple sequence repeat loci to characterize the genetic diversity of the germplasm that originated the current industrial chicory and to establish the relationships between and inside Cichoriumintybus L. and Cichorium endivia L. Initially we analyzed 19 cultivated C. endivia accessions, 27 wild and 155 cultivated C. intybus accessions distributed among three groups: 83 root chicories, 42 Witloof and 30 leaf chicories. The leaf chicories comprised cultivars corresponding to the Radicchio, Sugarloaf and Catalogne subgroups. The latter has not been previously included in any genetic diversity study. Subsequently, 1297 individuals from the 15 modern root chicory cultivars at the origin of the breeding of the current industrial root chicory cultivars were analyzed. Although the accessions of C. endivia and C. intybus were clearly separated from each other, seven wild C. intybus individuals were genetically closer to C. endivia than to C. intybus, revealing complex genetic interrelationships between these species. The differentiation of C. intybus into three cultivar groups (Witloof, root chicory and leaf chicory) was confirmed. The leaf chicory individuals were divided into three genetic subgroups, corresponding to the Radicchio, Sugarloaf and Catalogne cultivars, thus attesting to the validity of the classification based on morphological factors. Clear differentiation was observed among the Belgian, Polish and Austrian modern industrial root cultivars, but not among the French industrial modern root cultivars. The high phenotypic and genetic variability of the modern industrial root cultivars indicates that this germplasm constitutes a useful gene pool for cultivar improvement and selection.     

Oil concentration and fatty-acid profile of naturalized <Emphasis Type="Italic">Helianthus annuus</Emphasis> populations from Australia

Although wild annual sunflower (Helianthus annuus L.) is indigenous to North America, it has been both inadvertently and intentionally introduced into other countries, such as Australia, where it has become naturalized. Prior to this research, there were no collections of naturalized H. annuus from Australia in the USDA National Plant Germplasm System gene bank. The possibility exists that naturalized Australian populations may contain distinct traits, such as oil content and fatty-acid composition, differing from their North American progenitors due to the different environments, diseases, and insect-pest complexes. The objective of this study was to collect naturalized H. annuus populations from the five states of Australia and to analyze them for oil content and fatty-acid composition. Fifty-six populations were collected throughout the broad distributional range of this species and then analyzed for oil content and fatty-acid composition. The mean oil content of the H. annuus populations was 28%, ranging from a low of 19% to a high of 31%, similar to populations of this species in its native North American habitats. Fatty-acid profiles were also similar for North American wild populations, Australian naturalized populations, and improved cultivars. Oil concentration of hybrids can be rapidly increased to acceptable levels by backcrossing with cultivated sunflower. Based on this fact, there should be little concern about the relatively low oil content of these naturalized populations when they are used as a source of other unique traits for cultivated sunflower improvement.     

Diverse morphological and cytogenetic variation and differentiation of the two subspecies in <Emphasis Type="Italic">Aegilops geniculata</Emphasis> Roth,a wild relative of wheat

Aegilops geniculata Roth, a wild relative of wheat (2n = 4x = 28, genome UUMM), is distributed over the Mediterranean basin and nearby areas. The species consists of two subspecies, subsp. geniculata and subsp. gibberosa (Zhuk.) Hammer. The former is distributed over the whole species area and has been genetically analyzed, and the latter is endemic to Spain and North Africa and has not been genetically evaluated. In this study, to clarify the genetic variation and delineation of the two subspecies from a biosystematic viewpoint, morphological variation among 23 accessions of subsp. geniculata and three of subsp. gibberosa and chromosome pairing at meiosis and fertility in their intra- and inter-subspecific F₁ hybrids were examined. A principal component analysis based on the 11 spike characteristics clearly divided the 26 accessions into two groups representing the two subspecies. The inter-subspecific F₁ hybrids showed significantly lower frequencies of chromosome pairing, significantly higher frequencies of multivalents, and significantly lower fertilities relative to those of the intra-subspecific F₁ hybrids. It was concluded that wide-ranging cytogenetic variation is included in subsp. geniculata, that subsp. gibberosa, the intra-subspecific variation of which is small, is morphologically and cytogenetically differentiated from subsp. geniculata beyond the range of the intra-subspecific variation of subsp. geniculata, and that the two subspecies are effectively isolated reproductively by hybrid sterility. The results strongly suggested that western North Africa is one of the important diversity centers of Ae. geniculata, where two subspecies were differentiated in the past and grow together in the present.     

A review of genetic resources of almonds and stone fruits (<Emphasis Type="Italic">Prunus</Emphasis> spp.) in Iran

Iran is amongst the countries in the world widely known for cultivation of Prunus spp. (or stone fruits). It is both a centre of origin and diversity of the stone fruits. Numerous wild species as well as many cultivars and landraces of these fruit crops are important genetic resources today in Iran and can be used for improvement and breeding of scion and rootstock cultivars which are resistant to many biotic and abiotic stresses through modern genomics and genetic technologies. This paper discusses the distribution, ethno-botany, diversity and utilization of wild and domesticated genetic resources of stone fruits including almond (Prunus dulcis (Miller) D. A. Webb.), peach and nectarine (P. persica Batsch), European and Japanese plum (P. × domestica L., and P. salicina L., respectively), sweet and sour cherry (P. avium L., and P. cerasus L., respectively), and apricot (P. armeniaca L.), all of which are members of the Rosaceae family. The goal of this paper is to highlight the importance of Iran as a main contributor to the diversity of Prunus genetic resources in the world, as well as, present major achievements regarding identification, collection, evaluation, conservation and utilization of this valuable genetic resource in Iran.     

Geographical distribution of wild <Emphasis Type="Italic">Daucus</Emphasis> species in the natural grasslands of the Argentinian pampas

Three wild carrot species have been reported in the argentinian flora: Daucus montanus Humb. et Bonpl. ex Schult., D. montevidensis Link ex Sprengel and D. pusillus Michx. There is a discrepancy among authors about the distinctive morphological traits of the last two species; thus, it is difficult to ascertain if they are truly two distinct taxa. Based on the available literature and in the search of a paradigmatic site, four collection trips were carried out in 2004 and 2005 in Buenos Aires and Southern Entre Ríos provinces. Populations were sampled at 30 sites, and local environmental parameters and associated plant species were recorded. Morphological observations and chromosome counts were carried out on 10 plants/population. Three morphological phenotypes were distinguished: one in 18 populations, all with 2n = 2x = 18, and two in the remaining 12, with 2n = 2x = 22 or aneusomaty (2n = 2x = 20, 22). Populations of the first phenotype were assigned to wild D. carota and the rest, tentatively, to D. pusillus (D. montevidensis?), till further evaluations are carried out in test sites to verify this tentative conclusion.     

Species delimitation,genetic diversity and structure of the European indigenous wild pear (<Emphasis Type="Italic">Pyrus pyraster</Emphasis>) in Saxony,Germany

The present study investigated genetic diversity, structure and hybridization in a collection of the endangered wild pear species Pyrus pyraster (L.) Burgd. A total of 278 putative ‘true type’ P. pyraster trees originating from seven populations in the federal state of Saxony in Germany were analyzed along with 35 pear cultivars commonly cultivated in Saxony. The genetic analysis was performed using nine nuclear microsatellite markers (ncSSR) and two paternally inherited chloroplast marker (cpDNA) amplifying in the intergenic spacer region trnQ–rps16 and the intron region rps16. On basis of the ncSSR dataset after STRUCTURE analysis 80 % of the wild pear individuals were assigned as ‘true type’ P. pyraster genotypes. The cpDNA analysis showed shared haplotypes in P. pyraster and P. communis but with an unequal frequency in both species. The analysis of molecular variance resulted in a moderate (ncSSR) and great (cpDNA) variation among ‘true type’ P. pyraster and the pear cultivars. The genetic diversity in the ‘true type’ P. pyraster populations was still high and the genetic structure between the populations low (ncSSR and cpDNA) indicating a genetic exchange between the populations by pollen and seeds. The clear discrimination between the P. pyraster and P. communis confirms our expectation of the existence of ‘true type’ P. pyraster individuals in the study area. The existing genetic integrity and the high genetic diversity argue for the implementation of preservation measures in P. pyraster.     

Morphological and genetic diversity of shea tree (<Emphasis Type="Italic">Vitellaria paradoxa</Emphasis>) in the savannah regions of Ghana

Vitellaria paradoxa C. F. Gaertn., commonly known as shea tree or Vitellaria, is ranked the most important tree species of the savannah regions in the most African countries due to its ecological and economic importance for livelihoods and national economies. However, the savannah regions are the most vulnerable areas to the global climate change. Moreover, the Vitellaria populations on farmlands are threatened by the dominance of old trees with low or lack of regeneration. In this study both morphological and genetic diversity were assessed using several phenotypic traits and 10 microsatellite markers, respectively, to assess the impact of land use and agro-ecozone types on Vitellaria in Ghana. The land use types were forests and farmlands, and the agro-ecozone types included the Transitional, Guinea, and Sudan savannah zones. The mean values of morphological traits, such as diameter at breast height (DBH) and canopy diameter (CD), were statistically different between forest (DBH = 22.20, CD = 5.37) and farmland (DBH = 39.85 CD = 7.49) populations (P < 0.00001). The Sudan savannah zone with mean petiole length of 4.96 cm showed significant difference from the other zones, likely as a result of adaptation to drier climate conditions. Genetic data analysis was based on 10 microsatellite markers and revealed high genetic diversity of Vitellaria in Ghana: mean expected heterozygosity, H _e was 0.667, and allelic richness, measured as number of effective alleles A _e , was 4.066. Both farmlands and forests were very diverse indicating lack of negative influence of farmer’s selection on genetic diversity. Fixation index was positive for all populations (mean F _IS = 0.136) with farmlands recording relatively higher values than forests in all ecological zone types studied, probably indicating less gene flow in the farmlands. Moderate differentiation (F′ _ST = 0.113) was comparable to other similar tree species. Both land use and ecological zone types influenced genetic differentiation of Vitellaria at varying levels. The species was spatially structured across three ecozones and following climatic gradient. The forest reserves are used in situ conservation for Vitellaria in Ghana. High diversity observed in the most arid zones provides opportunity to find and use appropriate plant materials for breeding climate change resilient trees.     

Investigation and taxonomy of wild <Emphasis Type="Italic">Fragaria</Emphasis> resources in Tibet,China

Tibet is one of the main distribution centers of wild Fragaria species in China. There are abundant, precious and rare wild strawberry resources. This paper focused on the classification, distribution and evaluation of the 65 wild strawberry accessions collected from 17 counties in Tibet. The main taxonomical characters, such as stolon branching, leaflet type, flower sex, fruit shape, status of achene and sepal, and chromosome number were observed for each accession. All accessions were identified and classified into seven Fragaria species and two forms, including F. daltoniana J. Gay (2x), F. nilgerrensis Schlecht. (2x), F. nubicola Lindl. (2x), F. pentaphylla Losinsk. (2x), F. gracilis A. Los. (4x), F. moupinensis (French.) Card. (4x) and F. tibetica Staudt et Dickoré. (4x). The two white-fruited forms were F. nubicola f. alba (2x) and F. moupinensis f. alba (4x). The analytic hierarchy process (AHP) method was used to perform a comprehensive assessment on the value of seven Fragaria species and two forms. The results showed that F. nilgerrensis had better fruit quality, disease resistance and waterlogging tolerance than any other species in Tibet. The collection and identification of wild strawberry resources in Tibet would be helpful to improve the fruit quality and stress resistance of modern strawberry cultivars.     

Microsatellite mapping of the <Emphasis Type="Italic">Scr1</Emphasis> locus conferring screwed spike rachis to modify the spatial orientation of spikelets in <Emphasis Type="Italic">Triticum aestivum</Emphasis> L.

In the wheat (Triticum aestivum L.) inflorescence, spikelets are arranged in two opposite rows on the main axis. Spikelet primordia initiate alternately on opposite sides at angles of 180°. Genotypes exhibiting screwed spike rachis (SCR) have been selected as a gene resource having non-standard spike morphology in wheat. Although the SCR phenotype is a prospective gene resource, it is under-utilized. The SCR phenotype is due to the attachment of spikelets to the rachis nodes on the SCR. Seed number and individual kernel size are critical economic parameters and increasing seed number and single grain weight causes competition among the growing seeds. The SCR phenotype is hypothesized to avoid competition by assuring kernel growth space in each floret. The SCR trait has been observed in spikes and peduncles of KM 60-96. The semi-dwarfism of KM 60-96 was GA₃-sensitive, and it was determined by the presence of Rht8 gene. The response of KM 60-96 to microtubule depolymerizing and stabilizing drugs indicated that the SCR phenotype was not caused by a defect in the α-Tubulin gene. The F₂ of two hexaploid hybrids and a pentaploid hybrid between SCR/normal types segregated 3 SCR:1 normal indicating that the SCR phenotype was determined by a single dominant gene, Scr1. Analysis with microsatellite markers indicated that the Scr1 allele was located in the region between markers Xgwm191 and Xgwm371 in chromosome arm 5BL. From the observation of the backcross generation, introgression of the Scr1 allele into locally adapted wheat cultivars is feasible to increase kernel growth space in each spikelet in the limited spike length.     

Genetic diversity of dihydrochalcone content in <Emphasis Type="Italic">Malus</Emphasis> germplasm

Dihydrochalcones, beneficial phenolic compounds, are abundant in Malus Mill. species, particularly in vegetative tissues and seeds. Phloridzin (phloretin 2′-O-glucoside) is the primary dihydrochalcone in most Malus species including cultivated apple, Malus?×?domestica Borkh. A few species contain sieboldin (3-hydroxyphloretin 4′-O-glucoside) or trilobatin (phloretin 4′-O-glucoside) in place of phloridzin, and interspecific hybrids may contain combinations of phloridzin, sieboldin, and trilobatin. Proposed health benefits of phloridzin include anti-cancer, antioxidant, and anti-diabetic properties, suggesting the potential to breed apples for nutritional improvement. Sieboldin and trilobatin are being investigated for nutritional value and unique chemical properties. Although some of the biosynthetic steps of dihydrochalcones are known, little is known about the extent of variation within Malus germplasm. This research explores the genetic diversity of leaf dihydrochalcone content and composition in Malus germplasm. Dihydrochalcone content was measured using high performance liquid chromatography (HPLC) from leaf samples of 377 accessions, representing 50 species and interspecific hybrids from the USDA-Agricultural Research Service (ARS) National Plant Germplasm System Malus collection. Within the accessions sampled, 284 accessions contained phloridzin as the primary dihydrochalcone, one had only trilobatin, two had phloridzin and trilobatin, 36 had sieboldin and trilobatin, and 54 had all three. Leaf phloridzin content ranged from 17.3 to 113.7 mg/g with a heritability of 0.76 across all accessions. Beyond the potential of dihydrochalcones for breeding purposes, dihydrochalcone composition may be indicative of hybridization or species misclassification.     

Variation in Copper Accumulation at the Tissue Level of Five Hybrid Poplars Subjected to Copper Stress

Heavy metal contamination causes significant environmental problems around the world and poses a threat to human health. Poplar hybrids present features for potential uses in phytoremediation systems in areas with heavy metal contamination. The purpose of this study was to assess the copper (Cu) accumulation level in five poplar inter-species hybrids [(Populus trichocarpa × Populus deltoides) × P. deltoides; P. deltoides × Populus nigra; P. trichocarpa × Populus maximowiczii; P. trichocarpa × P. nigra; and (P. trichocarpa × P. deltoides) × (P. trichocarpa × P. deltoides)] grown in a hydroponic system. The treatments entailed the application of low and high doses of Cu of 8.0 and 16.0 μM, respectively. Cu accumulation was observed in roots, stems, and leaves, which was determined using flame atomic absorption spectroscopy, prior acid digestion of each sample. The methodology was validated according to certified reference material (Cypress BIMEP 432). Significant differences in Cu accumulation were found among genotypes for both roots and leaves, but not for stems. In roots, the genotype P. deltoides × P. nigra had a Cu accumulation level of 169.8% higher than the average accumulation found in the other genotypes. The (P. trichocarpa × P. deltoides) × P. deltoides hybrid showed the least Cu accumulation in leaves. The results of this study can potentially be used for proper crossovers and hybrids selection within the genus Populus for phytoremediation of Cu contaminated land.     

Genetic diversity in cultivated yam bean (<Emphasis Type="Italic">Pachyrhizus</Emphasis> spp.) evaluated through multivariate analysis of morphological and agronomic traits

Yam bean [Pachyrhizus DC.] is a legume genus of the subtribe Glycininae with three root crop species [P. erosus (L.) Urban, P. tuberosus (Lam.) Spreng., and P. ahipa (Wedd.) Parodi]. Two of the four cultivar groups found in P. tuberosus were studied: the roots of ‘Ashipa’ cultivars with low root dry matter (DM) content similar to P. erosus and P. ahipa are traditionally consumed raw as fruits, whereas ‘Chuin’ cultivars with high root DM content are cooked and consumed like manioc roots. Interspecific hybrids between yam bean species are generally completely fertile. This study examines the genetic diversity of the three crop species, their potentials for breeding and the identification of useful traits to differentiate among yam bean genotypes and accessions. In total, 34 entries (genotypes and accessions) were grown during 2000?2001 at two locations in Benin, West Africa, and 75 morphological and agronomical traits, encompassing 50 quantitative and 25 qualitative characters were measured. Diversity between entries was analyzed using principal component analysis, cluster analysis, multivariate analysis of variance and discriminant function analysis. Furthermore, phenotypic variation within and among species was investigated. Intra- and interspecific phenotypic diversity was quantified using the Shannon–Weaver diversity index. A character discard was tested by variance component estimations and multiple regression analysis. Quantitative trait variation ranged from 0.81 (for total harvest index) to 49.35% (for no. of storage roots per plant). Interspecific phenotypic variation was higher than intraspecific for quantitative traits in contrast to qualitative characters. Phenotypic variation was higher in overall for quantitative than qualitative traits. In general, intraspecific phenotypic variation ranged from 0.00 to 82.61%, and from 0.00 to 80.03% for quantitative and qualitative traits, respectively. Interspecific phenotypic variation ranged from 0.00 to 95.02%, and 0.00?81.58% for the two trait types, respectively. The Shannon–Weaver diversity index (H′) was in general high and over 0.80 for most of the trait. Diversity within P. tuberosus was higher than within P. erosus and P. ahipa. Across the 50 quantitative and 25 qualitative traits, the Shannon–Weaver diversity index of intra- and interspecific variation was around 0.83 and 0.51, respectively and was lower for qualitative than for quantitative traits. Monomorphism was observed in eight qualitative traits and one quantitative character. The first, second and third principal components explained, respectively, 39.1, 21.3 and 8.3% of the total variation in all traits. Pachyrhizus erosus, P. ahipa, and P. tuberosus (‘Chuin’ and ‘Ashipa’) were clearly separated from each other by these analyses. Multivariate analysis of variance indicates significant differences between Pachyrhizus species for all individual or grouped traits. Discriminant function analysis revealed that the first two discriminant functions were almost significant. Biases due to unbalanced sample size used per species were small. Within each species a similar amount of diversity was observed and was determinable to 70% by only ten traits. We conclude that the cultivated yam bean species represent distinct genepools and each exhibits similarly large amounts of genetic diversity.