Comparison of the genetic diversity between <Emphasis Type="Italic">Triticum aestivum</Emphasis> ssp. <Emphasis Type="Italic">tibetanum</Emphasis> Shao and Tibetan wheat landraces (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.) by using intron-splice junction primers

In order to evaluate and compare the germplasm resources of wheat in Tibet, we analyzed the genetic diversity of 136 Triticum aestivum ssp. tibetanum Shao and 119 Tibetan wheat landraces (Triticum aestivum L.) by using Intron-Splice Junction (ISJ) primers. The results showed that polymorphism of PCR products were obtained by 33 primer combinations, which accounted for 11% of the 300 primer combinations produced by 26 ISJ primers. A total of 333 stable bands can be amplified from the T. aestivum ssp. tibetanum Shao and 243 bands were polymorphic, which accounted for 72.9% of the total bands. Tibetan wheat Landraces produced 316 stable bands, of which 197 bands were polymorphic. The polymorphic bands accounted for 62.34% of the total bands produced from Tibetan wheat landraces. The genetic diversity of T. aestivum ssp. tibetanum Shao was higher than that of Tibetan wheat landraces in Tibet, suggesting that T. aestivum ssp. tibetanum Shao can be used as important genetic resource for the breeding and genetic improvement of wheat in Tibet. Matrix (1, 0) was generated according to the presence or absence of the bands produced from a particular wheat accession. Clustering and principle coordinates analysis showed that T. aestivum ssp. tibetanum Shao and Tibetan wheat landraces were divided into two groups. We conclude that high polymorphisms produced by ISJ primers can reflect the genetic diversity between T. aestivum ssp. tibetanum Shao and Tibetan wheat landraces.     

A haplotype specific to North European wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.)

A previous study indicated decreased DNA content of chromosome 4A in the wheat (Triticum aestivum L. cv. Tähti) compared to cvs. Chinese Spring and Rennan. Here we show that the lower 4A DNA content is associated with a specific haplotype in the distal part of 4AL. In 41 cultivars of bread wheat (T. aestivum L.), including cv. Tähti, a common haplotype was identified in the linkage disequilibrium region on the long arm of chromosome 4A (4AL). The haplotype (haplotype A) is characterized by 7 SSR and 5 EST marker alleles, including five zero-alleles. Haplotype A was found in 46 % of the Swedish/Finnish/Estonian spring wheat genotypes, while only one of the modern wheat accessions from Germany carried the same haplotype. Fluorescent cytometry analysis linked haplotype A to diminished DNA content of chromosome 4A. The haplotype was introduced into the Canadian and US breeding programs at the beginning of the twentieth century (cvs. Marquis, Thatcher, Ruby) from the common progenitor, the Polish landrace Fife, and it is still found in modern wheat germplasm in these countries. Zero-alleles characteristic for haplotype A were also detected in several accessions of European spelt (Triticum spelta L.), and in two accessions of tetraploid Triticum timopheevii Zhuk. The presence of haplotype A in European spelt indicates the considerable antiquity of the haplotype, as it must have been inherited from the hexaploid or tetraploid parent of spelt in at least one hybridization event.     

<Emphasis Type="Italic">Achromobacter insolitus</Emphasis> and <Emphasis Type="Italic">Zoogloea ramigera</Emphasis> associated with wheat plants (<Emphasis Type="Italic">Triticum aestivum</Emphasis>)

This study reports for the first time the presence of diazotrophic bacteria belonging to the genera Achromobacter and Zoogloea associated with wheat plants. These bacterial strains were identified by the analysis of 16S rDNA sequences. The bacterium IAC-AT-8 was identified as Azospirillum brasiliense, whereas isolates IAC-HT-11 and IAC-HT-12 were identified as Achromobacter insolitus and Zoogloea ramigera, respectively. A greenhouse experiment involving a non-sterilized soil was carried out with the aim to study the endophytic feature of these strains. After 40 days from inoculation, all the strains were in the inner of roots, but they were not detected in soil. In order to assess the location inside wheat plants, an experiment was conducted under axenic conditions. Fifteen days after inoculation, preparations of inoculated plants were observed by the scanning electron microscope, using the cryofracture technique, and by the transmission electron microscope. It was observed that all isolates were present on the external part of the roots and in the inner part at the elongation region, in cortex cells, but not in the endodermis or in the vascular bundle region. No colonizing bacterial cells were observed in wheat leaves.     

Identification of <Emphasis Type="Italic">Aegilops</Emphasis> L. species and <Emphasis Type="Italic">Triticum aestivum</Emphasis> L. based on chloroplast DNA

The genus Aegilops L. is a very important genetic resource for the breeding of bread wheat Triticum aestivum. Therefore, an accurate and easy identification of Aegilops species is required. Traditionally, identification of Aegilops species has relied heavily on morphological characters. These characters, however, are either not variable enough among Aegilops species or too plastic to be used for identification at the species level. Molecular markers that are more stable within species, therefore, could be the alternative strategy towards an accurate identification. Since the chloroplast DNA has a lower level of evolution compared to the nuclear genome, an attempt was made in this study to investigate polymorphism in the chloroplast DNA among 21 Aegilops species (including Ae. mutica that is now known as Amblyopyrum muticum) and between the latter and T. aestivum to generate markers for the diagnosis of all targeted species. Cleaved amplified polymorphic sequence (CAPS) applied on 22 coding and non-coding chloroplast regions using 80 endonucleases and sequencing of two of those regions revealed little polymorphism between T. aestivum and the various Aegilops species examined and to a less extent was the variation among Aegilops species. Polymorphism observed among species analysed allowed the discrimination of T. aestivum and 12 Aegilops species.     

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.     

Polymorphism of <Emphasis Type="Italic">Got2</Emphasis> DNA sequences sheds light on <Emphasis Type="Italic">Aegilops tauschii</Emphasis> Coss. intraspecies divergence and origin of <Emphasis Type="Italic">Triticum aestivum</Emphasis> L.

DNA sequences of nuclear gene Got2 was studied in 60 accessions of Aegilops tauschii, 29 of subsp. tauschii and 31 of subsp. strangulata. It was found that Got2 allozyme polymorphism in Ae. tauschii is due to a single, unique, mutation which led to replacement of glutamic acid by isoleucine in residue 256 of the enzyme molecule, encoded by Got2. As revealed by Got2 DNA sequences variation, initially in its history Ae. tauschii was presented by subsp. strangulata, and among phylogenetic lineages of subsp. strangulata, the lineage “t-9¹s” (TauL3) is the most ancient, a relict one. Subspecies tauschii is relatively “young”. Initially it was presented by the lineage marked by combination of allozyme alleles Got2 ¹⁰⁵ and Acph1 ¹⁰⁰. In the past it inhabited the Continental area from Caucasia to Pakistan, but later on it was forced out by newly originated, now—a major lineage of subsp. tauschii, marked by Got2 ¹⁰⁰. This lineage extended the Continental area of the species up to Kirgizstan, but actually failed to penetrate into pre-Caspian area, occupied by subsp. strangulata. These results essentially differ from those obtained previously, using chloroplast DNA (cpDNA) sequences polymorphism. As revealed by cpDNA, the major, “usual”, subsp. strangulata (TauL2) is “younger” than subsp. tauschii, which resided on phylogenetic tree between relict lineage “t-9¹s”of subsp. strangulata—and major subsp. strangulata. But both cpDNA and Got2 DNA sequences indicate that the level of genetic variation in subsp. tauschii is much lower than in subsp. strangulata. According to Got2 DNA sequences variation, it was Ae. tauschii subsp. strangulata lineage “k-109″ which donated genome D to Triticum aestivum L. This lineage includes accessions: k-109 from South-Eastern Precaspian Azerbaijan; KU-2105, KU-2159 from Western Precaspian Iran; KU-2080 from Eastern Precaspian Iran.     

<Emphasis Type="Italic">Ziziphus </Emphasis><Emphasis Type="Italic">spina-christi</Emphasis> (L.) Willd.: a multipurpose fruit tree

Neglected and underutilized species often play a vital role in securing food and livestock feed, income generation and energy needs of rural populations. In spite of their great potential little attention has been given to these species. This increases the possibility of genetic erosion which would further restrict the survival strategies of people in rural areas. Ziziphus spina-christi is a plant species that has edible fruits and a number of other beneficial applications that include the use of leaves as fodder, branches for fencing, wood as fuel, for construction and furniture making, and the utilization of different parts e.g. Fruits, leaves, roots and bark in folk medicine. Moreover, the plant is adapted to dry and hot climates which make it suitable for cultivation in an environment characterized by increasing degradation of land and water resources. Lack of research in Z. spina-christi hinders its successful improvement and promotion. Therefore, studies are needed to fully exploit this species. This article aims at summarizing information on different aspects of Z. spina-christi to stimulate interest in this crop which is of importance in Sudan and other countries of the semi-arid tropics.

<Emphasis Type="Italic">Calamintha nepeta</Emphasis> (L.) Savi and <Emphasis Type="Italic">Micromeria thymifolia</Emphasis> (Scop.) Fritsch cultivated in Italy

Calamintha nepeta and Micromeria thymifolia have been traditionally used in the Mediterranean area as condiments and medicinal plants for a long time. Whereas in parts of Italy C. nepeta (special recipes have been developed in Lazio and Tuscany) is also an established garden plant showing different evolutionary products and their interaction among each other and the wild progenitor, M. thymifolia is being developed into a new crop plant. Both plants and their uses are described with regard to Italy. There is a marked tendency to broaden the use of condiments and spices which results in new crop plants which have to be documented and elaborated in further studies. Many species of Labiatae are predisposed to use by man and new items can be found even in areas which have to be considered as well studied.     

Survey of glucosinolate variation in leaves of <Emphasis Type="Italic">Brassica rapa</Emphasis> crops

The breakdown products of glucosinolates (gsl) are biologically active secondary metabolites involved in plant defense and human nutrition. We identified and quantified 14 different gsl present in the young leaves of 82 different varieties of Brassica rapa, including the following crops: Chinese cabbage, broccoleto, Pak choi and other leafy vegetables, turnip, sarson and rapeseed. We did not find crop specific gsl, but their quantity varied extensively among varieties and crops, except that the Chinese cabbage accessions tended to have similar gsl profile and amount. Gluconapin, glucobrassicanapin (aliphatic), neoglucobrassicin, glucobrassicin (indolic), and gluconaturtiin (aromatic) are the predominant gsl in most of the varieties surveyed. We also found two gsl not commonly found in B. rapa, 2-methyl-2-propenyl and n-butyl. Their identities were confirmed by HPLC-MS. Most of the Chinese cabbages contain lower amount of aliphatic than indolic gsl, whereas broccoleto, turnip and rapeseed all have much higher aliphatic gsl content than indolic gsl content. The predominant aliphatic gsl in most of the varieties contain 4-carbon side-chains. The lack of significant correlation observed between the conversion of 3- to 4-carbon side-chain gsl and the conversion of 4- to 5-carbon side-chain gsl suggests that these two elongation cycles are probably under the control of two independent genes in B. rapa. The absence of glucoraphanin in all accessions indicates that only functional Brgsl-Alk alleles are present in B. rapa.     

Characteristics of the root system in the diploid genome donors of hexaploid wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.)

Wild crop relatives are of considerable interest in plant breeding and significant efforts have been made to transfer their genetic variation into modern crops. Of the three diploid progenitors of bread wheat (Triticum aestivum L.), only Aegilops tauschii Coss. has been explored and exploited and only for some above ground characteristics. The three wild progenitors (Aegilops speltoides Tausch., Triticum urartu Tumanian ex Gandilyan, and Aegilops tauschii) have never been assayed for root traits. Here we report such a root study, and include Triticum monococcum L. subsp. boeoticum (Boiss.) Hayek and T. turgidum L. subsp. dicoccoides (Koern. ex Asch. et Graebn.) Thell. Fifteen accessions were selected from the above wild species and tested in the presence of one bread wheat cultivar Pavon F76. Significant variation was observed between and within the taxa. Of all accessions tested, cv. Pavon F76 had the smallest root system at maturity while A. speltoides had the largest root system. Moreover, Aegilops spp. had larger mean values for root biomass when compared with Triticum spp. These results suggest there is significant unexplored potential for the use of wheat wild relatives in wheat breeding to improve the root system, or to develop synthetic mapping populations to study root traits.     

Salt tolerance in <Emphasis Type="Italic">Zea mays</Emphasis> (L). following inoculation with <Emphasis Type="Italic">Rhizobium</Emphasis> and <Emphasis Type="Italic">Pseudomonas</Emphasis>

This study aimed to investigate the effect of inoculation with plant growth-promoting Rhizobium and Pseudomonas species on NaCl-affected maize. Two cultivars of maize (cv. Agaiti 2002 and cv. Av 4001) selected on the basis of their yield potential were grown in pots outdoors under natural conditions during July. Microorganisms were applied at seedling stage and salt stress was induced 21 days after sowing and maintained up to 50% flowering after 120 days of stress. The salt treatment caused a detrimental effect on growth and development of plants. Co-inoculation resulted in some positive adaptative responses of maize plants under salinity. The salt tolerance from inoculation was generally mediated by decreases in electrolyte leakage and in osmotic potential, an increase in osmoregulant (proline) production, maintenance of relative water content of leaves, and selective uptake of K ions. Generally, the microbial strain acted synergistically. However, under unstressed conditions, Rhizobium was more effective than Pseudomonas but under salt stress the favorable effect was observed even if some exceptions were also observed. The maize cv. Agaiti 2002 appeared to be more responsive to inoculation and was relatively less tolerant to salt compared to that of cv. Av 4001.     

A significant proportion of indigenous rhizobia from India associated with soybean (<Emphasis Type="Italic">Glycine max</Emphasis> L.) distinctly belong to <Emphasis Type="Italic">Bradyrhizobium</Emphasis> and <Emphasis Type="Italic">Ensifer</Emphasis> genera

The diversity among 269 rhizobia isolated from naturally occurring root nodules of soybean collected from two different agro-ecological regions of India, based on RFLP and sequences of the intergenic spacer (IGS) between the 16S and 23S rRNA genes, growth rate, and indole acetic acid production, revealed their significant, site-dependent genomic diversity. Among these bacteria, nine IGS genotypes were identified with two endonucleases. They were distributed into five divergent lineages by sequence analysis of each IGS representative strain, i.e., (1) comprising IGS genotypes I, II, III, and reference Bradyrhizobium yuanmingense; (2) with genotype IV and strains of unclassified bradyrhizobia genomic species; (3) including genotypes V, VI, and Bradyrhizobium liaoningense; (4) with IGS genotype VII and Bradyrhizobium elkanii strains; and (5) comprising IGS genotypes VIII, IX, and different Ensifer genus bacteria. Host-specificity test revealed that all rhizobia-nodulated soybean and cowpea and only part of them formed nodules on Arachis hypogeae and Cajanus cajan. The great diversity of soybean nodulators observed in this study emphasises that Indian soil is an important reservoir of nitrogen-fixing rhizobia.     

A semi-fertile interspecific hybrid of <Emphasis Type="Italic">Brassica rapa</Emphasis> and <Emphasis Type="Italic">B. nigra</Emphasis> and the cytogenetic analysis of its progeny

Black rot is a bacterial disease of Brassica rapa caused by Xanthomonas campestris pv. campestris (Xcc.). Sources of resistance to this disease within B. rapa are insufficient and control measures are limited, making the development of resistant breeding lines extremely important. Certain lines of B. nigra exhibit very high resistance to Xcc. For this study, an interspecific cross between Brassica rapa and B. nigra was performed, and a total of 6 F₁ hybrids were obtained through ovary culture. Five plants (H_1–5) were relatively slow-growing, entirely sterile, and had 18 chromosomes in the majority of pollen mother cells (PMCs). GISH analysis showed that most of the PMCs had 8 B. nigra chromosomes, which indicated the expected AB genomic constitution. The last plant (H₆) was partially fertile and the majority of PMCs contained 10 chromosomes of B. rapa and 16 chromosomes of B. nigra, indicating an ABB genomic constitution. Ovary culture techniques were not necessary for the development of the first- or second-backcross generation. Sequence-related amplified polymorphism analysis of F₁, BC₁, and BC₂ plants indicated that some fragments from B. nigra were lost, particularly in the genome of BC₁/BC₂ in successive generation(s). The BC₂ plants expressing good resistance to Xcc. were observed.     

The impact of modern plant breeding on dominant Chinese wheat cultivars (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.) revealed by SSR and functional markers

The modern plant breeding is generally considered to be a practice that leads to a narrowing in genetic diversity of crops. The objective of the present study was to assess whether this practice has led to the reduction of genetic diversity in modern Chinese wheat cultivars. A set of 80 dominant Chinese wheat cultivars released from 1942 to 2011 was used to describe the genetic diversity based on 137 simple sequence repeat (SSR) and 52 functional markers. Several important properties about the genetic diversity were revealed. First, relative low genetic diversity level was detected on a genome-wide scale. A total of 752 alleles were detected with a range from 1 to 15, and the mean polymorphic information content value was 0.53 with a range from 0.00 to 0.87. Second, the genetic diversity significantly decreased from 2001 to 2011 at the genome-wide level. More importantly, significant differences of genetic diversity among the three different genomes were observed by the analysis of variance (ANOVA). The three genomes had clearly different changing trends over time: the A genome displayed a decreasing trend (regression coefficient (b) = ?0.01); in contrast, the other two genomes, B and D, showed the increasing trends (b = 0.01 for the B genome, P = 0.05; b = 0.01 for the D genome, P = 0.05). Third, the analysis of qualitative variations in allelic composition over time indicated that, the more recent the cultivars were, the more similar they were to each other. Finally, the frequencies of favorable alleles related to important agronomic traits had been increasing over time or maintained high frequencies in all seven temporal groups. These findings indicate that modern wheat breeding results in not only a qualitative, but also a quantitative change in genetic diversity in the dominant Chinese wheat cultivars. A special attention should be paid to broaden the genetic base in the A genome.     

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.     

Trace elements bioavailability to <Emphasis Type="Italic">Triticum aestivum</Emphasis> and <Emphasis Type="Italic">Dendrobaena veneta</Emphasis> in a multielement-contaminated agricultural soil amended with drinking water treatment residues

Purpose

The in situ stabilization of multielement-contaminated agricultural soils has limited effectiveness when using common single amendments. This study examined the use of drinking water treatment residues (WTR), based on (hydr)oxides of Fe, Al, or Mn, as a cost-effective solution to optimize the immobilization of metals (Cd, Pb, Zn) and As.

Materials and methods

Trace elements (TE) bioavailability was assessed under semi-controlled conditions in a pot study cultivating winter wheat (Triticum aestivum L. cv. Tiger) until maturity. An Fe-based WTR and a Mn-based WTR, applied at rates of 0.5 and 1% (m/m), were related to effects of lime marl (LM) application. Additionally, a bioassay with earthworms (Dendrobaena veneta) was conducted. Both bioassays were compared with measurements of NH₄NO₃-soluble, diffusive gradients in thin film (DGT)-available and soil solution TE concentrations, representing well-established surrogates for mimicking the bioavailable element fractions in soil.

Results and discussion

The application of the Fe-based WTR reduced As accumulation in vegetative wheat tissues (by up to 75%) and earthworms (by up to 41%), which corresponded with the findings from soil chemical analyses and improved plant growth and earthworm body weight. However, As concentrations in cereal grains were not affected, Cd or Pb accumulation by wheat was not mitigated, and Zn uptake was enhanced. By contrast, the Mn-based WTR effected the greatest reduction in Pb uptake, and lowered Cd transfer to wheat grain (by up to 25%). Neither the NH₄NO₃-soluble nor DGT-available concentrations matched with Cd and Zn accumulation in plants or earthworms, indicating interferences due to competition for binding sites according to the biotic ligand model.

Conclusions

The results obtained in this study suggest that a bioassay with key species prior to field application should be mandatory when designing in situ stabilization options. The application of WTR to an agricultural soil strongly affected TE bioavailability to plants and earthworms. Low application rates tended to improve biomass production of biota. Higher application rates involved risks (e.g., P fixation, TE inputs), and none of the amendments tested could immobilize all targeted elements.

     

Gliadin Electrophoretic Analysis of the Genetic Integrity of Wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.) Accessions After Frequent Seed Reproductions

A standard electrophoretic method for wheat cultivar identification was used on single seeds to analyse the genetic integrity of 11 wheat (Triticum aestivum L.) accessions after up to 24 seed reproductions in the Gatersleben genebank. It was clearly demonstrated that the gliadin pattern of single seeds can be used to analyse the genotype composition of wheat accessions. Stability of electrophoretic banding patterns was detected in eight accessions. Very week genetic drift was observed in three accessions. Our investigations confirm experiences of the successful utilisation of protein markers for cultivar verification and genetic integrity testing and demonstrate the high standard of wheat accessions maintenance in the Gatersleben genebank.     

Characterization of fertile amphidiploid between <Emphasis Type="Italic">Raphanus sativus</Emphasis> and <Emphasis Type="Italic">Brassica alboglabra</Emphasis> and the crossability with <Emphasis Type="Italic">Brassica</Emphasis> species

A fertile amphidiploid × Brassicoraphanus (RRCC, 2n = 36) between Raphanus sativus cv. HQ-04 (2n = 18, RR) and Brassica alboglabra Bailey (2n = 18, CC) was synthesized and successive selections for seed fertility were made from F₄ to F₁₀. F₁₀ plants exhibited good fertility with 14.9 seeds per siliqua and 32.3 g seeds per plant. Cytological observation revealed that frequent secondary pairing occurred among 3 chromosome pairs in pollen mother cells of plants (F₄) with lower fertility, but not of plants with high fertility (F₁₀). GISH analysis indicated that these F₁₀ plants included the expected 18 chromosomes from R. sativus and B. alboglabra, respectively, but they lost approximately 27.6% R. sativus and 35.6% B. alboglabra AFLP (amplified fragment length polymorphism) bands. The crossability of the Raphanobrassica with R. sativus and 5 Brassica species (13 cultivars) were investigated. Seeds or F₁ seedlings were easy to be produced from crosses × Brassicoraphanus × R. sativus, and B. napus, B. juncea and B. carinata × Brassicoraphanus. Fewer seeds or seedlings were obtained from crosses × Brassicoraphanus × B. napus, B. juncea and B. carinata. However, few seeds were harvested in the reciprocals of × Brassicoraphanus with B. rapa and B. oleracea. The possible cause of fertility improvements and the potential of the present × Brassicoraphanus for breeding were discussed.     

Comparative Study of Common Bean (<Emphasis Type="Italic"> Phaseolus vulgaris</Emphasis>L.) Landraces Conserved <Emphasis Type="Italic">ex situ</Emphasis> in Genebanks and <Emphasis Type="Italic">in situ</Emphasis> by Farmers

Genetic diversity of populations stored ex situ or in situ can be altered due to the management practices they are subjected to. In this paper, we compare populations of two common bean (Phaseolus vulgaris L.) landraces grown on farms with material collected from the same farms and now kept in two ex situ collections (CIAT and REGEN) with the purpose to monitor any changes that have occurred due to ex situ conservation. The diversity was measured using seven bean microsatellite markers. Further phenotypic and developmental traits were registered in a field experiment. Compared with the in situ populations, the ex situ ones had a lower level of gene diversity and we suggest that this is due to the regeneration process. Most of the phenotypic traits did not differ significantly between ex situ and in situ populations, although for yield and 100-seed weight, the CIAT material showed significant lower values. We assume that these populations have gone through an adaptational change. Overall, the conservation ex situ has been successful in maintaining the majority of the adaptations found in the landraces studied, however, the probable loss of genetic diversity that we have observed, suggest that protocols for the regeneration process must be carefully worked out if the majority of alleles are to be preserved for the future. This study also highlights the complementarity of ex situ and in situ conservation methods in order to preserve landrace adaptations and to capture new, useful diversity generated in in situ populations.     

Crossability of <Emphasis Type="Italic">Vigna rhomboidea</Emphasis> Burtt. Davy with Cowpea (<Emphasis Type="Italic">V. unguiculata</Emphasis> (L.) Walp.)

V. rhomboidea is a wild Vigna species that is a potential source of genes for pubescence which could be incorporated into cultivated cowpea for insect pests resistance. Due to the lack of reliable records on the crossability and gene pool relationships between V. rhomboidea and cowpea, crossing trials were conducted in the screenhouse to observe if V. rhomboidea is reciprocally crossable (compatible) with cowpea. Crossability of V. rhomboidea (as seed parent) with cowpea (as pollen parent) was, for the first time, successfully achieved at the rate of 5.7% from 1145 crosses. Reciprocal crosses with cowpea as seed parent and V. rhomboidea pollen parent gave an average of 22.6% pod set from 2299 crosses. It is concluded that V. rhomboidea is reciprocally compatible with cowpea. This implies that V. rhomboidea belongs to the primary gene pool of cowpea.