Resistance reaction to powdery mildew (<Emphasis Type="Italic">Erysiphe pisi</Emphasis>) in a germplasm collection of <Emphasis Type="Italic">Lathyrus cicera</Emphasis> from Iberian origin

Several Lathyrus species have a considerable potential as alternative pulses in sustainable dryland farming systems mainly due to their high tolerance to drought and disease resistance. Powdery mildew is a serious disease affecting several Lathyrus species. Little is known on the availability of resistance and the underlying resistance mechanisms against powdery mildew in the Lathyrus genus. The present study assessed and characterized the resistance reaction to powdery mildew, Erysiphe pisi, in a collection of Iberian Lathyrus cicera accessions. In general, a compatible reaction with no macroscopically visible necrosis was observed but accessions with reduced disease severity despite of a high infection type have also been identified. This Partial Resistance was in some accessions only expressed in the adult plant stage. The controlling genes of the Lathyrus resistance mechanisms can be of great interest not only for the Lathyrus improvement per se but also for related legume species, like field pea.     

Transfer of leaf rust and stripe rust resistance from <Emphasis Type="Italic">Aegilops umbellulata</Emphasis> Zhuk. to bread wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.)

Aegilops umbellulata acc. 3732, an excellent source of resistance to major wheat diseases, was used for transferring leaf rust and stripe rust resistance to cultivated wheat. An amphiploid between Ae. umbellulata acc. 3732 and Triticum durum cv. WH890 was crossed with cv. Chinese Spring Ph ^I to induce homoeologous pairing between Ae. umbellulata and wheat chromosomes. The F₁ was crossed to the susceptible Triticum aestivum cv. ‘WL711’ and leaf rust and stripe rust resistant plants were selected among the backcross progenies. Homozygous lines were selected and screened against six Puccinia triticina and four Puccinia striiformis f. sp. tritici pathotypes at the seedling stage and a mixture of prevalent pathotypes of both rust pathogens at the adult plant stage. Genomic in situ hybridization in some of the selected introgression lines detected two lines with complete Ae. umbellulata chromosomes. Depending on the rust reactions and allelism tests, the introgression lines could be classified into two groups, comprising of lines with seedling leaf rust resistance gene Lr9 and with new seedling leaf rust and stripe rust resistance genes. Inheritance studies detected an additional adult plant leaf rust resistance gene in one of the introgression lines. A minimum of three putatively new genes—two for leaf rust resistance (LrU1 and LrU2) and one for stripe rust resistance (YrU1) have been introgressed into wheat from Ae. umbellulata. Two lines with no apparent linkage drag have been identified. These lines could serve as sources of resistance to leaf rust and stripe rust in breeding programs.     

Dispersal of durum wheat [<Emphasis Type="Italic">Triticum turgidum</Emphasis> L. ssp. <Emphasis Type="Italic">turgidum</Emphasis> convar. <Emphasis Type="Italic">durum</Emphasis> (Desf.) MacKey] landraces across the Mediterranean basin assessed by AFLPs and microsatellites

A comprehensive characterization of crop germplasm is critical to the optimal improvement of the quality and productivity of crops. Genetic relationships and variability were evaluated among 63 durum wheat landraces from the Mediterranean basin using amplified fragment length polymorphisms (AFLPs) and microsatellites markers. The genetic diversity indices found were comparable to those of other crop species, with average polymorphism information content (PIC) values of 0.24 and 0.70 for AFLP and microsatellites, respectively. The mean number of alleles observed for the microsatellites loci was 9.15. Non-metric multi-dimensional scaling clustered the accessions according to their geographical origin with the landraces from the South shore of the Mediterranean Sea closely related. The results support two dispersal patterns of durum wheat in the Mediterranean basin, one through its north side and a second one through its south side.     

Phenotypic diversity of durum wheat (<Emphasis Type="Italic">Triticum durum</Emphasis> Desf.) from Jordan

Durum wheat landrace genotypes are disappearing from the main wheat areas in Jordan, because of spreading of new uniform cultivars and the serious reduction in wheat cultivation. This study was conducted to evaluate genetic diversity in durum wheat landraces from Jordan and to identify desirable agronomic traits. Landraces were collected from two target areas: Ajloun and Karak. The collected material was grown under rainfed conditions using an augmented design with five blocks and four repeated check cultivars. Data were collected for 14 morphological and agronomic traits. Phenotypic diversity index (H′) was estimated, and the relationships among accessions were measured using cluster analysis and dendrogram similarity matrix. The results revealed the presence of a wide range of variability among landraces., which possess high levels of variability for biological yield, fertile tillers, number of seeds per spike, seed weight per spike and weight of 1000 seeds. These landraces must be considered as a reservoir of genes that plant breeders need in their wheat improvement programs and should be conserved both ex situ and in situ.     

Diversity among landraces of Indian snapmelon (<Emphasis Type="Italic">Cucumis melo</Emphasis> var. <Emphasis Type="Italic">momordica</Emphasis>)

Diversity among 36 snapmelon landraces, collected from 2 agro-ecological regions of India (9 agro-climatic sub-regions), was assayed using RAPD primers, morphological traits of plant habit and fruit, 2 yield-associated traits, pest and disease resistance and biochemical composition (TSS, ascorbic acid, titrable acidity). Typical differences among accessions were observed in plant and fruit characteristics and snapmelon germplasm with high titrable acidity and possessing resistance to downy mildew, Cucumber mosaic virus, Zucchini yellow mosaic virus, Papaya ringspot virus, Aphis gossypii and Meloidogyne incognita was noticed in the collection. RAPD based grouping analysis revealed that Indian snapmelon was rich in genetic variation and region and sub-region approach should be followed across India for acquisition of additional melon landraces. Accessions of var. agrestis and var. momordica clustered together and there was a separate cluster of the accessions of var. reticulatus. Comparative analysis of the genetic variability among Indian snapmelons and an array of previously characterized reference accessions of melon from Spain, Israel, Korea, Japan, Maldives, Iraq, Pakistan and India using SSRs showed that Indian snapmelon germplasm contained a high degree of unique genetic variability which was needed to be preserved to broaden the genetic base of melon germplasm available with the scientific community. N. P. S. Dhillon and Ranjana contributed equally to this work and are considered the first authors.     

Characterization of intergeneric hybrids of <Emphasis Type="Italic">Erianthus rockii</Emphasis> and <Emphasis Type="Italic">Saccharum</Emphasis> using molecular markers

Erianthus rockii, a wild relative of sugarcane, is drought and cold tolerant, and both are potentially important agronomic traits to the sugarcane industry worldwide. As such it is of interest as a source of parental germplasm to sugarcane breeders and is currently being used in sugarcane introgression programs in both China and Australia. To date morphological characters have been used to verify the putative hybrids produced. Two crosses were generated between two different Saccharum species and two E. rockii accessions. Over 400 AFLP markers were used to identify the intergeneric hybrid progeny as well as determine hybrid diversity. Both crosses generated hybrids but efficiency levels were very different and are probably related to the different Saccharum parent used in each cross. Cross 1 was between a Saccharum officinarum and E. rockii and generated 100% hybrid progeny. Cross 2, however, was between a sugarcane hybrid (S. officinarum × Saccharum spontaneum) and E. rockii and only 10% of the progeny were intergeneric hybrids. Inheritance of markers in the progeny was analysed and for both crosses there were equal numbers of markers from both parents indicating n + n transmission of chromosomes. This is the first verification of E. rockii hybrids with molecular markers. It may now be possible to exploit genes of value from E. rockii in sugarcane breeding programs.     

Comparison of the genetic structure of populations of wild emmer wheat, <Emphasis Type="Italic">Triticum turgidum</Emphasis> ssp. <Emphasis Type="Italic">dicoccoides</Emphasis>, from Israel and Turkey revealed by AFLP analysis

The aim of the present study was to assess the genetic variation in several Israeli and Turkish populations of wild emmer wheat, Triticum turgidum ssp. dicoccoides, the progenitor of most domesticated wheat. Single spikes were collected in 2002 from 60 plants that grew in six different habitats in Ammiad, northeastern Israel (8–12 plants from each habitat), and in 1998 from 56 plants that grew in seven different habitats in Diyarbakir, southeastern Turkey (8 plants from each habitat). Seeds were planted in a nursery and DNA was extracted from every plant and analyzed by the fluorescent-based amplified fragment length polymorphism (AFLP) method. Seven primer combinations produced 788 discernible loci of which 48.6% were polymorphic in Israel and 40.5% in Turkey. The genetic diversity estimates P (frequency of polymorphic loci) and He (gene diversity) were higher in Ammiad than in Diyarbakir (means of P = 0.34 and He = 0.13 in Ammiad vs. P = 0.20 and He = 0.08 in Diyarbakir). Ammiad populations contained more unique alleles than Diyarbakir populations. The relative genetic diversity estimates (θ) values were 0.188 in Ammiad and 0.407 in Diyarbakir, suggesting better differentiation of the populations in Turkey. Genetic distance was larger between Israeli and Turkish populations than between populations of each country. The data indicate that the Israeli and Turkish populations are considerably diverged and that the Israeli populations are more polymorphic than the Turkish ones, having a larger within-populations genetic variation than among-populations one. The significance of the results in relation to the differentiation pattern of wild emmer in the Near East is discussed.     

Evaluation of perennial wild <Emphasis Type="Italic">Cicer</Emphasis> species for drought resistance

About 90% of chickpea (Cicer arietinum L.) in the world is grown under rainfed conditions where drought is one of the major constraints limiting its productivity. Unlike the cultivated chickpea, wild Cicer species possesses sources of resistance to multiple stresses; we therefore evaluated perennial wild Cicer species for resistance to drought. C. anatolicum, C. microphyllum, C. montbretii, C. oxydon and C. songaricum were compared with special checks; C. echinospermum, C. pinnatifidum and C. reticulatum and five cultivated chickpeas. After the cultivated chickpeas were killed, accessions were evaluated using a 1–5 scale, where 1 = highly drought resistant (no visible drought effect and full recovery after three successive wiltings) and 5 = highly drought susceptible (leaves and branches dried out, no recovery at all). All accessions of perennial wild Cicer species were significantly superior to those annual wild species and the cultivated chickpeas including the best drought tolerant chickpea, ICC 4958 under drought conditions. Perennial wild Cicer species did not only recover after wilting and drying out above ground level, they also tolerated high temperatures up to 41.8°C. But, they do not cross with the cultivated chickpeas. C. anatolicum should be taken account in long term breeding programs because it has closer affinities to the first crossability group than the others.     

Characterisation and Variation of Morphological Traits and Storage Proteins in Spanish Emmer Wheat Germplasm (<Emphasis Type="Italic">Triticum Dicoccon</Emphasis>)

Emmer wheat is hulled wheat that was wide cultivated in Spain at the past. Actually, the most of this germplasm is conserved in Germplasm Banks, and only two small populations have been found in Asturias (North of Spain) in a recent collecting mission. In this work, a collection of 31 Spanish emmer lines developed from identical number of accessions of two Germplasm Banks was analysed for morphological spike traits and seed storage protein composition. Up to seven different botanical varieties were detected, which suggest the presence of a wide diversity, although lower than the historically described 10 botanical varieties. At level of seed storage proteins, the lines showed a high diversity, although the new alleles were present with low frequency in materials with scarce agronomic interest for the farmers (var. atratum, var. lagascae or var. pycnurum). This last circumstance could translate in a lost of variability by genetic drift.     

Simple sequence repeats marker polymorphism in emmer wheat (<Emphasis Type="Italic">Triticum dicoccon</Emphasis> Schrank): Analysis of genetic diversity and differentiation

Genetic diversity was investigated in 73 accessions of emmer wheat (Triticum dicoccon Schrank) from 11 geographical regions using a set of 29 simple-sequence repeat (SSR or microsatellite) markers, representing at least two markers for each chromosome. The SSR primers amplified a total of 357 different alleles with an average of 12.31 alleles per locus. The number of fragments detected by each primer ranged between 6 (Xgwm1066) and 21 (Xgwm268). Null alleles were detected in nine of the 29 primers used. A high level of gene diversity index was observed. Across the 29 primers, gene diversity ranged from 0.60 (Xgwm46) to 0.94 (Xgwm655), with a mean of 0.82. There was a highly significant correlation (r=0.882; p<0.01) between gene diversity index and the number of loci, showing the number of loci per se is a strong indicator of diversity. Analysis of genetic diversity within and among eleven geographical regions revealed most of the genetic diversity of the total sample resided within regions. The coefficient of gene differentiation (Gst = 0.27) showed that the genetic variation within and among the 11 geographical regions was 73 and 27%, respectively. High value of mean number of alleles per locus was found in Iran (4.86) followed by Morocco (4.10) and Armenia (4.03). On the contrary, lower mean number of alleles per locus was detected in Yemen (2.83). The average gene diversity index across regions ranged from 0.52 (Slovakia) to 0.67 (Morocco) with an average of 0.60. Multivariate techniques of principal component analysis and clustering were employed to examine genetic relationship among the 73 emmer wheat accessions vis-à-vis geographical regions of collections. The genetic distance coefficients for all possible 55 pairs of regional comparisons ranged from 0.63 (between Iran and Armenia, Georgia and Azerbaijan, Georgia and Slovakia) to 0.97 (between Morocco and Yemen, Spain and Georgia, and Turkey and Iran) with a mean of 0.82. From the PCA results, a two dimensional plot of PC1 versus PC2 was constructed. The scatter plot of the first two principal components which explained altogether 27% of the total variation depicted the presence of a clear pattern of geographical differentiation except in few cases like accessions from Caucasian region. Similar pattern of genetic relationships among accessions was observed in cluster analysis. The study provided genetic information of emmer wheat in relation to geographical regions of origin. The information could be utilized in crop improvement, germplasm conservation programs, and in further investigation.     

Genetic diversity of <Emphasis Type="Italic">Nelumbo</Emphasis> accessions revealed by RAPD

Total 65 lotus accessions in genus Nelumbo mainly collected from China, were subjected to random amplified polymorphic DNA (RAPD) markers to estimate the genetic diversity and to test the genetic basis of the relationships between morphotypes and molecular markers. Seventeen primers generated a total of 195 highly reproducible and discernible loci, among which 173 were polymorphic. Percent polymorphism varied from 66.7 to 100 with an average of 88.72, and five primers out of them, OPC05, OPG10, OPN20, OPP09 and OPS17, showed 100% polymorphism. A relatively high genetic diversity was detected among all the samples with the similarity coefficient values ranging from 0.45 to 0.85, and Nei’s gene diversity (h) 0.30, and Shannon index (I) 0.46. The UPGMA dendrogram clustered 65 accessions in four clusters and the clustering pattern showed two groups, N. nucifera ssp. nucifera and those accessions related to the American lotus, and some special cultivars, landraces, hybrids and the American lotus. Principal Coordinate Analysis (PCA) further indicated that the genetic diversity of Nelumbo accessions was not evenly distributed, instead, was presented by a clustered distribution pattern. Similar to the results revealed by the dendrogram, two main groups representing the two subspecies of N. nucifera, as well as some special landraces, cultivars of Chinese lotus, the Japanese lotus and hybrids out of the two groups were obtained. Neither the UPGMA dendrogram nor the PCA analysis exhibited strict relationship with geographic distribution and morphotypes among the accessions.     

Evaluation and utilization of <Emphasis Type="Italic">Aegilops</Emphasis> and wild <Emphasis Type="Italic">Triticum</Emphasis> species for enhancing iron and zinc content in wheat

Grains of 80 accessions of nine species of wild Triticum and Aegilops along with 15 semi-dwarf cultivars of bread and durum wheat grown over 2 years at Indian Institute of Technology, Roorkee, were analyzed for grain iron and zinc content. The bread and durum cultivars had very low content and little variability for both of these micronutrients. The related non-progenitor wild species with S, U and M genomes showed up to 3–4 folds higher iron and zinc content in their grains as compared to bread and durum wheat. For confirmation, two Ae. kotschyi Boiss. accessions were analyzed after ashing and were found to have more than 30% higher grain ash content than the wheat cultivars containing more than 75% higher iron and 60% higher zinc than that of wheat. There were highly significant differences for iron and zinc contents among various cultivars and wild relatives over both the years with very high broad sense heritability. There was a significantly high positive correlation between flag leaf iron and grain iron (r = 0.82) and flag leaf zinc and grain zinc (r = 0.92) content of the selected donors suggesting that the leaf analysis could be used for early selection for high iron and zinc content. ‘Chinese Spring’ (Ph ^I ) was used for inducing homoeologous chromosome pairing between Aegilops and wheat genomes and transferring these useful traits from the wild species to the elite wheat cultivars. A majority of the interspecific hybrids had higher leaf iron and zinc content than their wheat parents and equivalent or higher content than their Aegilops parents suggesting that the parental Aegilops donors possess a more efficient system for uptake and translocation of the micronutrients which could ultimately be utilized for wheat grain biofortification. Partially fertile to sterile BC₁ derivatives with variable chromosomes of Aegilops species had also higher leaf iron and zinc content confirming the possibility of transfer of required variability. Some of the fertile BC₁F₃ and BC₂F₂ derivatives had as high grain ash and grain ash iron and zinc content as that of the donor Aegilops parent. Further work on backcrossing, selfing, selection of fertile derivatives, leaf and grain analyses for iron and zinc for developing biofortified bread and durum wheat cultivars is in progress. Nidhi Rawat, Vijay K. Tiwari, and Neelam Singh have contributed equally to the work.     

Genetic diversity and structure of Ethiopian,Yemen and Brazilian C<Emphasis Type="Italic">offea arabica</Emphasis> L. accessions using microsatellites markers

Genetic diversity among 115 coffee accessions from the Coffea Germplasm Collection of IAC was assessed using SSR markers. The germplasm represents 73 accessions of Coffea arabica derived from spontaneous and subspontaneous plants in Ethiopia and Eritrea, species center of origin and diversity, 13 commercial cultivars of C. arabica developed by the Breeding Program of IAC, 1 accession of C. arabica cv. ‘Geisha’, 13 accessions of C. arabica from Yemen, 5 accessions of C. eugenioides, 4 accessions of C. racemosa and 6 accessions of C. canephora. Genetic analysis was performed using average number of alleles per locus (A), proportion of polymorphic loci (P), Shannon’s genetic index (H′ and G′_ST) and clustering analysis. All evaluated species were distinguished by a cluster analysis based on Jaccard’s coefficient. Differentiation between the cultivated plants of C. arabica and accessions derived from spontaneous and subspontaneous plants was observed. Spontaneous and subspontaneous accessions from Ethiopia were separated according to the geographical origin: east and west of the Great Rift Valley. Cultivated plants showed a low genetic diversity with a division in two groups: accessions from Yemen (H′=0,028) and Brazilian commercial cultivars (H′=0,030). The results agreed with previously reported narrow genetic basis of cultivated plants of C. arabica and supported the hypotheses about domestication of the species. This study also showed a significant genetic diversity among accessions from Ethiopia and Eritrea present in the Germplasm Collection of IAC. This diversity is specially observed in accessions from Sidamo (H′=0,143), Kaffa (H′=0,142) and Illubabor (H′=0,147) indicating their importance as source of genetic variability for coffee breeding programs.     

Adult plant resistance to <Emphasis Type="Italic">Puccinia triticina</Emphasis> in a geographically diverse collection of <Emphasis Type="Italic">Aegilops tauschii</Emphasis>

Despite extensive genetics and breeding research, effective control of leaf rust caused by Puccinia triticina Eriks. and an important foliar disease of wheat, has not been achieved. This is mainly due to the widespread use of race-specific seedling resistance genes, which are rapidly overcome by new virulent races. There is increased emphasis now on the use of race-nonspecific adult plant resistance (APR) genes for durable control of leaf rust. The objective of this study was the evaluation of Aegilops tauschii Coss. (the D-genome donor of bread wheat) for APR, previously known to be a rich source of seedling resistance genes to leaf rust. A geographically diverse collection of A. tauschii maintained by the Wheat Genetics Resource Center was evaluated for APR in the field with a leaf rust composite culture of predominant races. Out of a total of 371 A. tauschii accessions, 50 with low to moderate levels of disease severity were subsequently tested at the seedling stage in the greenhouse with four races and one composite culture of leaf rust. Nine accessions displayed moderate resistance to one or more races of leaf rust at the seedling stage. The remaining 41 seedling-susceptible accessions are potential sources of new APR genes. Accessions from Afghanistan only displayed APR whereas both seedling resistance and APR were common in the Caspian Sea region (Iran and Azerbaijan). The APR in these newly identified A. tauschii accessions will be further characterized for novelty, effectiveness, and race-specificity.     

Preliminary screening and selection for cold tolerance in annual wild <Emphasis Type="Italic">Cicer</Emphasis> species

The study was aimed to select cold tolerant accessions of annual wild Cicer species in the highlands in the west Mediterranean area of Turkey. A total of 43 accessions of eight annual wild Cicer species was screened for cold tolerance and compared with the best cold tolerant cultivars, ILC 8262 and FLIP 93-53C. After the sensitive check, ILC 533, was killed, accessions were evaluated using a 1–9 scale. Three accessions of Cicer bijugum, 2 accessions of Cicer reticulatum and 2 accessions of Cicer echinospermum were highly cold tolerant, while 3 accessions of C. bijugum, 9 accessions of C. reticulatum, 2 accessions of C. echinospermum and 1 accession of Cicer pinnatifidum were cold tolerant. All accessions of Cicer judaicum were sensitive to cold. Whereas Cicer chorassanicum and Cicer cuneatum were killed, Cicer yamashitae was recorded as highly sensitive to cold. The cold tolerant accessions of annual wild Cicer species were superior to the best cultivar as far as hardiness is concerned.     

Analysis of Genetic Variation Among Accessions of <Emphasis Type="Italic">Pueraria montana</Emphasis> (Lour.) Merr. var. <Emphasis Type="Italic">lobata</Emphasis> and <Emphasis Type="Italic">Pueraria phaseoloides</Emphasis> (Roxb.) Benth. based on RAPD Markers

Pueraria montana var. lobata and P. phaseoloides originating from tropical Asia and parts of Oceania are ecologically and economically important legumes that are used as green manure, cover crop or forage plants. Conservation and use of plant genetic resources require an understanding of the extent and distribution of genetic diversity in any given region. In this study, genetic variation of five P. montana var. lobata and 16 P. phaseoloides accessions was analysed developing a random amplified polymorphic DNA (RAPD) marker methodology for Pueraria species and thereby creating basic data for follow-up research and the development of conservation strategies. Seeds were collected from native populations in Bac Kan Province, a mountainous region in Northeast Vietnam. P. montana var. lobata presented a high level of variation with 54.3% of the detected markers being polymorphic, whereas P. phaseoloides exhibited an intermediate to high level of variation (45.5%). The P. montana var. lobata accessions clustered in congruence with their eco-geographical origin. For P. phaseoloides no correspondence between sampling sites and genetic differentiation was found. Inter-population differentiation was measured as Jaccard's similarity coefficient (JSC). Mean JSC amounted to 0.35 in P. montana var. lobata and 0.52 in P. phaseoloides. Results are compared to other genetic studies of herbaceous legumes and conservation strategies are suggested.     

A-genome cotton as a source of genetic variability for Upland cotton (<Emphasis Type="Italic">Gossypium hirsutum</Emphasis>)

Since Upland cotton (Gossypium hirsutum) is known to have relatively low levels of genetic diversity, a better understanding of variation and relationships among possible sources of novel genes would be valuable. Therefore, analysis of genetic variation of the genus Gossypium, especially the diploids, which are the putative donors of the A and D genomes for the commercially important allotetraploid cottons (AADD), G. hirsutum and G. barbadense, could provide important information about the feasibility of using these genetic resources for cotton improvement. The primary objective of this study was to analyze the genetic diversity in A-genome diploid cotton species, G. herbaceum (A1) and G.␣arboreum (A2) by using microsatellite markers. Forty-one A-genome germplasm accessions were evaluated with 32 microsatellite loci. Genetic similarities between A1 and A2 ranged from 0.62 to 0.86 with a mean of 0.70. Within each A-genome species similarities ranged from 0.80 to 0.97 with a mean of 0.89 for A1 and from 0.82 to 0.98 with a mean of 0.89 for A2. A UPGMA tree and principal coordinate analysis based on genetic similarity matrices showed distinct clusters consistent with the genomic groups.     

Aspects of the evolution of <Emphasis Type="Italic">Nicotiana tabacum</Emphasis> L. and the status of the United States <Emphasis Type="Italic">Nicotiana</Emphasis> Germplasm Collection

The genus Nicotiana is a member of the nightshade (Solanaceae) family, and is comprised of 70 currently recognized, naturally occurring species. Genetic variability within N. tabacum L., the species of primary economic importance, was likely affected by several genetic bottlenecks. Nicotiana tabacum is a classic amphidiploid that arose after chance interspecific hybridization between N. sylvestris Spegazinni et Comes and a member of section Tomentosae, likely N. tomentosiformis Goodspeed, N. otophora Grisebach, or an introgressive hybrid between the two. Only a fraction of the genetic variability that existed in the diploid progenitor gene pools probably entered into N. tabacum. Genetic drift, coupled with natural and human selection, subsequently resulted in the formation of narrow genetic pools corresponding to modern commercial market classes. Genetic variability in Nicotiana has gained increased attention in recent years because of investment in Nicotiana genomics research, interest in development of tobacco products with reduced harm characteristics, and concentration on using Nicotiana species for plant-based production of commercially useful proteins. A storehouse of genetic diversity for N. tabacum is available in approximately 1,900 accessions maintained by the United States Nicotiana Germplasm Collection. Seeds of 224 accessions representing 59 wild Nicotiana species are also maintained. The collection is currently maintained by North Carolina State University and is part of the United States National Plant Germplasm System (NPGS). The collection’s curator satisfies hundreds of seed requests made annually by scientists using Nicotiana germplasm for basic biological investigations and by researchers in the area of applied tobacco science.     

Genetic diversity of <Emphasis Type="Italic">rbc</Emphasis>L gene in <Emphasis Type="Italic">Elymus trachycaulus</Emphasis> complex and their phylogenetic relationships to several Triticeae species

Elymus trachycaulus complex species are known for their morphological variability, but little is known about their genetic basis. The phylogenetic relationships among the E. trachycaulus complex, and their systematic relation to other species in Triticeae remain unknown. Nucleotide diversity of ribulose-1,5 bisphosphate-carboxylase (rbcL) gene in E. trachycaulus complex species and several other Triticeae was first characterized and compared. A primary conclusion of the present study is that nucleotide diversity for rbcL gene in E. trachycaulus species was detected with the estimates of nucleotide diversity θ = 0.00039 and π = 0.00043. The estimate of nucleotide diversity in rbcL gene for species with different genome constitution here ranged from 0.00099 (π) and 0.00099 (θ) for the species with Ns genome to 0.00226 (π) and 0.00291 (θ) for the species with St genome. The phylogenetic relationships of these species were assessed using these rbcL sequences. A total of 47 variable positions including 19 parsimony-informative sites were detected among 24 accessions of 18 species/subspecies. The species with St, H/I and Ns genomes well separated from each other, and formed a three distinct clades with higher bootstrap values support for both Parsimony and NJ analyses. The St genome containing species is sister group of H/I genome containing species. Our result confirms that Pseudoroegneria is the maternal genome donor to these Elymus species studied here, regardless of their distribution. Elymus trachycaulus complex are more related to each other than to E. glaucescens, E. patagonicus, and E. solandri. This study suggested that Elymus species with StH genomes may form from multiple closely related sets of donors.     

The Inheritance of Morphological and Biochemical Traits Introgressed into Common Wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.) from <Emphasis Type="Italic">Aegilops speltoides</Emphasis> Tausch

The genetic control of morphological characters and gliadin composition was studied in two bread wheat lines with introgressed segments from Aegilops speltoides Tausch. It was found that the transferred trait of leaf hairiness is controlled by one dominant gene, non-allelic to the known gene, Hl1. It was localized in 7B chromosome. Whole plant non-glaucousness is under the control of an inhibitor gene, allelic to the gene W1^I of wheat located on chromosome 2B. This gene was found to be epistatic to the gene controlling spike waxlessness. The introgressed gene for spike glume color was found to be allelic to the Rg1 gene located on 1BS of common wheat, but it was linked with another allele of the gliadin locus Gli-B1.