<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.     

Production and cytogenetics of trigeneric hybrid involving <Emphasis Type="Italic">Triticum</Emphasis>, <Emphasis Type="Italic">Psathyrostachys</Emphasis> and <Emphasis Type="Italic">Secale</Emphasis>

Trigeneric hybrids may help establish evolutionary relationships among different genomes present in the same cellular-genetic background, and also offers the possibility to transfer different alien characters into cultivated wheat. In this study, a new trigeneric hybrid involving species from the Triticum, Psathyrostachys and Secale was synthesized by crossing wheat-P. huashanica amphiploid (PHW-SA) with wheat-S. cereale amphiploid (Zhongsi 828). The crossability of F₁ hybrid was high with 35.13%, and the fertility was 41.95%. The morphological characteristics of F₁ plants resembled the parent Zhongsi 828. The trigeneric hybrids pollen mother cells (PMCs) regularly revealed averagely 19.88 univalents, 9.63 ring bivalents, 3.97 rod bivalents, 0.60 trivalents and 0.03 tetravalents per cell. Multivalents consisted of trivalents and tetravalents can be observed in 52.7% of cells. A variation of abnormal lagging chromosome, micronuclei and chromosome bridge were formed at anaphase I and telophase II. The mean chromosomes number of F₂ progenies was 2n = 46.13, and the distribution range was 42–53. GISH results revealed that most F₂ plants had 6–12 S. cereale chromosomes, and only 0–2 P. huashanica chromosomes were detected. The results indicated that S. cereale chromosomes can be preferentially transmitted in the F₂ progenies of trigeneric hybrid than P. huashanica chromosomes. A survey of disease resistances revealed that the stripe rust resistance from the PHW-SA were completely expressed in the F₁ and some F₂ plants. The trigeneric hybrid could be a useful bridge for the transference of P. huashanica and S. cereale chromatins to common wheat.     

<Emphasis Type="Italic">Rhizobium</Emphasis>,<Emphasis Type="Italic"> Bradyrhizobium</Emphasis> and<Emphasis Type="Italic"> Agrobacterium</Emphasis> strains isolated from cultivated legumes

The present study was conducted to isolate and characterize rhizobial strains from root nodules of cultivated legumes, i.e. chickpea, mungbean, pea and siratro. Preliminary characterization of these isolates was done on the basis of plant infectivity test, acetylene reduction assay, C-source utilization, phosphate solubilization, phytohormones and polysaccharide production. The plant infectivity test and acetylene reduction assay showed effective root nodule formation by all the isolates on their respective hosts, except for chickpea isolate Ca-18 that failed to infect its original host. All strains showed homology to a typical Rhizobium strain on the basis of growth pattern, C-source utilization and polysaccharide production. The strain Ca-18 was characterized by its phosphate solubilization and indole acetic acid (IAA) production. The genetic relationship of the six rhizobial strains was carried out by random amplified polymorphic DNA (RAPD) including a reference strain of Bradyrhizobium japonicum TAL-102. Analysis conducted with 60 primers discriminated between the strains of Rhizobium and Bradyrhizobium in two different clusters. One of the primers, OPB-5, yielded a unique RAPD pattern for the six strains and well discriminated the non-nodulating chickpea isolate Ca-18 from all the other nodulating rhizobial strains. Isolate Ca-18 showed the least homology of 15% and 18% with Rhizobium and Bradyrhizobium, respectively, and was probably not a (Brady)rhizobium strain. Partial 16S rRNA gene sequence analysis for MN-S, TAL-102 and Ca-18 strains showed 97% homology between MN-S and TAL-102 strains, supporting the view that they were strains of B. japonicum species. The non-infective isolate Ca-18 was 67% different from the other two strains and probably was an Agrobacterium strain.     

Putative Role of <Emphasis Type="Italic">Flavobacterium</Emphasis>, <Emphasis Type="Italic">Dokdonella</Emphasis> and <Emphasis Type="Italic">Methylophilus</Emphasis> Strains in Paracetamol Biodegradation

Paracetamol, the most widely and globally used analgesic and antipyretic, is easily accumulated in aquatic environments. In the present study, the biodegradation of paracetamol in different media (one for general growth, one specific for sulfate reducing bacteria, a mineral salts medium and municipal wastewater) inoculated with two types of sludge (from anaerobic lagoon and from oxidation ditch) under different oxygenic conditions (anoxic; moderate oxygenation in open flasks and high oxygenation by aeration) was investigated. In addition, bacteria with relative abundances increasing simultaneously with paracetamol degradation, when this drug was the only carbon source, thus with a putative role in its degradation, were identified using 16S rRNA gene sequences. The results show that aerobic microorganisms had a major role in the degradation of paracetamol, with 50 mg/L totally removed from municipal wastewater after 2 days incubation with aeration, and that the metabolites 4-aminophenol and hydroquinone plus one compound not identified in this work were produced in the process. The identification of bacteria with a role in the degradation of paracetamol revealed a strain from genus Pseudomonas with the highest final relative abundance of 21.2%, confirming previous works reporting strains of this genus as paracetamol decomposers. Besides, genera Flavobacterium, Dokdonella and Methylophilus were also in evidence, with initial relative abundances of 1.66%, 1.48 and 0.00% (not detected) in the inoculum and 6.91%, 3.80 and 3.83% after incubation, respectively. Therefore, a putative role of these genera in paracetamol biodegradation is suggested for the first time.

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Graphical Abstract ?

     

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 new mycorrhizal helper bacterium, <Emphasis Type="Italic">Ralstonia</Emphasis> species,in the ectomycorrhizal symbiosis between <Emphasis Type="Italic">Pinus thunbergii</Emphasis> and <Emphasis Type="Italic">Suillus granulatus</Emphasis>

In a Robinia-pseudoacacia-dominated coastal forest in Tottori prefecture Japan, the growth and survival of Pinus thunbergii seedlings and the natural regeneration of P. thunbergii was disturbed by R. pseudoacacia. In order to improve the growth of P. thunbergii seedling in the Tottori sand dune, we tried to find a mycorrhiza helper bacteria (MHB) from P. thunbergii mycorrhizosphere in a Tottori sand dune. Two MHB, Ralstonia sp. and Bacillus subtilis, were selected from the nine bacterial species isolated from the mycorrhizosphere of P. thunbergii. The bacterial effect on the ectomycorrhizal fungus Suillus granulatus was investigated by confrontation assay and a microcosm experiment. The confrontation assay showed that Ralstonia sp. promoted the hyphal growth of S. granulatus. Moreover, the S. granulatus–P. thunbergii symbiosis was significantly stimulated by Ralstonia sp. and B. subtilis. Ralstonia sp. and B. subtilis were regarded as MHB associated with P. thunbergii. This is the first report of Ralstonia sp. as an MHB.     

<Emphasis Type="Italic">Trichoderma</Emphasis> improves the growth of <Emphasis Type="Italic">Leymus chinensis</Emphasis>

Bio-fertilizer application has been proposed as a strategy for enhancing soil fertility, regulating soil microflora composition, and improving crop yields, and it has been widely applied in the agricultural yields. However, the application of bio-fertilizer in grassland has been poorly studied. We conducted in situ and pot experiments to investigate the practical effects of different fertilization regimes on Leymus chinensis growth, with a focus on the potential microecological mechanisms underlying the responses of soil microbial composition. L. chinensis biomass was significantly (P?<?0.05) increased by treatment with 6000 kg ha^?1 of Trichoderma bio-fertilizer compared with other treatments. We found a positive (R² =?0.6274, P <?0.001) correlation between bacterial alpha diversity and L. chinensis biomass. Hierarchical cluster analysis and nonmetric multidimensional scaling (NMDS) revealed that soil bacterial and fungal community compositions were all separated according to the fertilization regime used. The relative abundance of the most beneficial genera in bio-fertilizer (BOF) (6000 kg ha^?1Trichoderma bio-fertilizer) was significantly higher than in organic fertilizer (OF) (6000 kg ha^?1 organic fertilizer) or in CK (non-amend fertilizer), there the potential pathogenic genera were reduced. There were significant negative (P?<?0.05) correlations between L. chinensis biomass and the relative abundance of several potential pathogenic genera. However, the relative abundance of most beneficial genera were significantly (P?<?0.05) positively correlated with L. chinensis biomass. Soil properties had different effects on these beneficial and on these pathogenic genera, further influencing L. chinensis biomass.     

Effects of fire-derived charcoal on soil properties and seedling regeneration in a recently burned <Emphasis Type="Italic">Larix gmelinii</Emphasis>/<Emphasis Type="Italic">Pinus sylvestris</Emphasis> forest

Purpose  

Fire is a primary form of disturbance in boreal ecosystems. Charcoal is an important by-product of forest fire and has been reported to have the potential to influence the plant community establishing after fire. To date, however, no study has effectively tested the relationship between charcoal and plant regeneration in the actual post-fire forests. To determine the contribution of charcoal to soil properties and plant regeneration after forest fires, we conducted in situ investigations concerning the relationship between charcoal and the plant–soil system.     

Diversity of <Emphasis Type="Italic">Citrus</Emphasis><Emphasis Type="Italic">depressa</Emphasis> Hayata (Shiikuwasha) revealed by DNA analysis

Citrus depressa Hayata is an indigenous mandarin species on the Ryukyu Islands located in the subtropical region of Japan. We deduced its phylogenetic relationships by evaluating accessions grown on various Ryukyu Islands via cleaved amplified polymorphic sequence analysis of cpDNA and sequence-related amplified polymorphism (SRAP). The cpDNA results indicated that C. depressa could be classified into two types. SRAP revealed patterns of diversity within C. depressa consistent with our cpDNA results. These results indicate that maternal origin may influence or is correlated with the constitution of the nuclear genome of C. depressa. Another Japanese mandarin species, Citrus tachibana (Makino) Tanaka was distinguished from C. depressa by SRAP markers. Moreover, both C. depressa and C. tachibana could be distinguished from other Citrus species. Our results suggest that Japanese mandarin possesses a characteristic genome with the genus Citrus.     

Genetic Characterization of Brazilian Annual <Emphasis Type="Italic">Arachis</Emphasis> Species from Sections <Emphasis Type="Italic">Arachis</Emphasis> and <Emphasis Type="Italic">Heteranthae</Emphasis> using RAPD Markers

The genus Arachis is divided into nine taxonomic sections. Section Arachis is composed of annual and perennial species, while section Heteranthae has only annual species. The objective of this study was to investigate the genetic relationships among 15 Brazilian annual accessions from Arachis and Heteranthae using RAPD markers. Twenty-seven primers were tested, of which nine produced unique fingerprintings for all the accessions studied. A total of 88 polymorphic fragments were scored and the number of fragments per primer varied from 6 to 17 with a mean of 9.8. Two specific markers were identified for species with 2n = 18 chromosomes. The phenogram derived from the RAPD data corroborated the morphological classification. The bootstrap analysis divided the genotypes into two significant clusters. The first cluster contained all the section Arachis species, and the accessions within it were grouped based upon the presence or absence of the ‘A’ pair and the number of chromosomes. The second cluster grouped all accessions belonging to section Heteranthae.     

Effects of ectomycorrhizal fungus <Emphasis Type="Italic">Boletus edulis</Emphasis> and mycorrhiza helper <Emphasis Type="Italic">Bacillus cereus</Emphasis> on the growth and nutrient uptake by <Emphasis Type="Italic">Pinus thunbergii</Emphasis>

The present greenhouse study was undertaken to evaluate the effects of co-inoculating the ectomycorrhizal (ECM) fungus Boletus edulis with the mycorrhiza helper bacterium Bacillus cereus HB12 or HB59 on the growth and nutrient uptake of Pinus thunbergii. The inoculation with mycorrhiza helper bacterium significantly (P?≤?0.05) increased the ectomycorrhizal colonization. Treatments with dual inoculum (the mycorrhiza helper bacterium plus mycorrhiza) significantly (P?≤?0.05) increased the P. thunbergii growth. Bacteria–mycorrhizae interactions resulted in a great utilization of phosphate and potassium. The single inoculation resulted in a higher root activity than the control while the co-inoculation led to the highest root activity. The 6-CFDA staining assay showed that B. cereus enhanced fungal activity in ectomycorrhizal symbiosis. The results conclusively suggest that B. cereus isolated from the rhizosphere of P. thunbergii can potentially be used as individual inoculant or co-inoculated with ECM fungi to increase the production in sustainable ecological systems. These results support the potential use of B. cereus (HB12 or HB59) and B. edulis as mixed inoculants stimulating growth of P. thunbergii.     

The survival of <Emphasis Type="Italic">Coxiella burnetii</Emphasis> in soils

Coxiella burnetii is a pathogen of Q-fever—a widespread zoonosis. The effective adaptation of C. burnetii to intracellular existence is in contrast with its ability to survive in the environment outside the host cells and its resistance to chemical and physical agents. Its mechanism of survival remains unknown. However, its survival appears to be related to the developmental cycle of the microorganism itself, i.e., to the formation of its dormant forms. The survival of Coxiella burnetii was studied for the first time. The pathogenic microorganism was inoculated into different types of soil and cultivated under different temperatures. The survival of the pathogen was verified using a model with laboratory animals (mice). Viable C. burnetii were found in the soil even 20 days after their inoculation. The relationship between the organic carbon content in the soils and the survival of C. burnetii was revealed. Thus, the results obtained were the first to demonstrate that the soil may serve as a reservoir for the preservation and further spreading of the Q-fever pathogen in the environment, on the one hand, and reduce the risk of epidemics, on the other.     

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.     

<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.

Phylogenetic relationships between <Emphasis Type="Italic">Ensete</Emphasis> and <Emphasis Type="Italic">Musa</Emphasis> species as revealed by the <Emphasis Type="Italic">trnT trnF</Emphasis> region of cpDNA

Complete sequences of transcribed spacers and introns from the trnT trnF region of chloroplast DNA (cp DNA) were generated from Musaceae species to establish the phylogenetic relationships among 3 species of Ensete including the economically important Ensete ventricosum (Welw.) Cheesman and 13 species of Musa. Parsimony analysis and pair wise distance data produced a single tree, with Ensete and Musa as clearly distinguished clades. Six Musa and three Ensete clades were generated. The topology of these clades did not change when the data were split into spacers and introns, although the split resulted in poor bootstrap support. Removing a hotspot from the entire data set improved clade support. The clades produced are discussed with reference to existing taxonomic and phylogenetic treatments. In contrast to previous suggestions, most of the Rhodochlamys species that we investigated clustered together with strong support establishing their distinctiveness from the Musa species studied. Ensete glaucum (Roxb.) Cheesman and Musa beccartii Simmonds appear to represent ancestral forms of Ensete and Musa, respectively for the presently studied species, and both genera have a common ancestor that is yet to be established. Our data also show that E. ventricosum cannot be reduced to E. glaucum, nor can E. gilleti (De Wild.) Cheesman be reduced to E. ventricosum, as some authorities have suggested. Ensete gilleti or a species very close to it appears to be the ancestral species of E. ventricosum.     

Analysis based on RAPD and ISSR Markers Reveals Closer Similarities among <Emphasis Type="Italic">Citrullus</Emphasis> and <Emphasis Type="Italic"> Cucumis</Emphasis> Species than with <Emphasis Type="Italic">Praecitrullus fistulosus</Emphasis> (Stocks) Pangalo

A cucurbit species named Praecitrullus fistulosus (Stocks) Pangalo, which thrives in India, is considered to be a distant relative of watermelon. Recent experiments indicated that it has mild resistance to whiteflies (Bemisia tabaci). However, our attempts to cross various US plant introductions (PIs) of P. fistulosus with watermelon or other Citrullus PIs have not been successful. Thus, to determine genetic relatedness among those species, phylogenetic analysis [based on simple sequence repeat (SSR)–anchored (also termed ISSR), and randomly amplified polymorphic DNA (RAPD) markers] was conducted among PIs of P. fistulosus, Citrullus lanatus var. lanatus (watermelon), C. lanatus var. citroides and the wild Citrullus colocynthis. Phylogenetic relationships were also examined with Cucumis melo (melon), Cucumis sativus (cucumber), and wild Cucumis species including C. africanus, C. metuliferus, C. anguria, C. meeusei, and C. zeyheri. Wide genetic distance exists between Citrullus and Cucumis groups (8% genetic similarity). Phylogenetic relationships among Citrullus species and subspecies are closer (25–55% genetic similarity) as compared with those among most Cucumis species (14–68% genetic similarity). P. fistulosus appeared to be distant from both Cucumis and Citrullus species (genetic similarity between P. fistulosus and Cucumis or Citrullus groups is less than 3%). Although wide genetic differences and reproductive barriers exist among cucurbit species examined in this study, they are still considered as potential germplasm source for enhancing watermelon and melon crops using traditional breeding and biotechnology procedures.     

Exploitation of <Emphasis Type="Italic">Malus</Emphasis> EST-SSRs and the utility in evaluation of genetic diversity in <Emphasis Type="Italic">Malus</Emphasis> and <Emphasis Type="Italic">Pyrus</Emphasis>

A total of 8117 suitable SSR-contaning ESTs were acquired by screening from a Malus EST database, among which dinudeotide SSRs were the most abundant repeat motif, within which, CT/TC followed by AG/GA were predominant. Based on the suitable sequences, we developed 147 SSR primer pairs, of which 94 pairs gave amplifications within the expected size range while 65 pairs were found to be polymorphic after a preliminary test. Eighteen primer pairs selected randomly were further used to assess genetic relationship among 20 Malus species or cultivars. As a result, these primers displayed high level of polymorphism with a mean of 6.94 alleles per locus and UPGMA cluster analysis grouped twenty Malus accessions into five groups at the similarity level of 0.6800 that were largely congruent to the traditional taxonomy. Subsequently, all of the 94 primer pairs were tested on four accessions of Pyrus to evaluate the transferability of the markers, and 40 of 72 functional SSRs produced polymorphic amplicons from which 8 SSR loci selected randomly were employed to analyze genetic diversity and relationship among a collection of Pyrus. The 8 primer pairs produced expected bands with the similar size in apples with an average of 7.375 alleles per locus. The observed heterozygosity of different loci ranged from 0.29 (MES₉₆) to 0.83 (MES₁₃₈), with a mean of 0.55 which is lower than 0.63 reported in genome-derived SSR marker analysis in Pyrus. The UPGMA dendrogram was similar to the previous results obtained by using RAPD and AFLP markers. Our results showed that these EST-SSR markers displayed reliable amplification and considerable polymorphism in both Malus and Pyrus, and will contribute to the knowledge of genetic study of Malus and genetically closed genera.     

Multitrophic Assessment of Copper Contamination Using Watercress (<Emphasis Type="Italic">Nasturtium officinale</Emphasis>) and the Mustard Beetle (<Emphasis Type="Italic">Phaedon viridis</Emphasis><Emphasis Type="Bold">)</Emphasis>

Copper is an active component of some commercial algaecides and is commonly found in low concentrations in contaminated aquatic systems. Unintended consequences of algaecide application include macrophyte bioaccumulation and possible trophic level bioamplification especially by specialist herbivores. Trophic level effects of copper contamination were observed through feeding trials using the mustard beetle (Phaedon viridis). Several metals, including copper, interfere with the myrosinase enzyme system responsible for the watercress (Nasturtium officinale) allelopathic defense against herbivory. The mustard beetle is a specialist herbivore that has evolved a detection system that is stimulated by the products of the glucosinolate-myrosinase system. Because copper interferes with myrosinase enzymes, mustard beetles were expected to avoid copper-contaminated plants. While larvae exhibited a slight preference for contaminated plants, adult mustard beetles in this experiment exhibited a statistically significant preference for plants uncontaminated with copper.     

Greenbug (<Emphasis Type="Italic">Schizaphis graminum</Emphasis>) resistance in oat (<Emphasis Type="Italic">Avena</Emphasis> spp.) landraces from Asia

Among 371 oat accessions from the world collection of the Vavilov Institute of Plant Genetic Resources (VIR) mostly represented by the landraces from Asia (Maritime Territory of Russian Federation, Mongolia, China, Japan, North Korea, India, Iran, Afghanistan, and Bhutan) ninety five were heterogeneous for resistance to the North Caucasus populations of the greenbug (Schizaphis graminum Rondani). Damage ratings of resistance in 47 accessions were high, low level of resistance was identified in 48 genotypes. Higher frequency of greenbug resistant accessions (60.5%) was found among landraces from Mongolia. Lines with high expression of the resistance were selected from seven landraces with wide range of damage ratings. North Caucasus populations of S. graminum from Krasnodar area and Dagestan significantly differ by the frequencies of virulence to host plant. Seven virulence phenotypes differentially interacting with oat genotypes were found in the Krasnodar population and 10 phenotypes were revealed in the Dagestan population. Results of the experiments with the greenbug test clones revealed that all the lines selected from the accessions VIR-2490, VIR-2539, VIR-4074, VIR-12213, VIR-12214 (Mongolia), VIR-6688 (India) and VIR-13624 (North Korea) are protected by diverse alleles of resistance genes which differ from the earlier identified gene Grb3. These lines are supposed to have aphid resistance genes nonidentical to the Grb1 and Grb2. The accessions VIR-6688, VIR-4074 and VIR-12214 possess high resistance to Krasnodar and Dagestan greenbug populations and the accession VIR-13624 is protected by the most effective gene (genes) of resistance to the both populations from North Caucasus.     

Morphological characterization of snake melon (<Emphasis Type="Italic">Cucumis melo</Emphasis> var. <Emphasis Type="Italic">flexuosus</Emphasis>) populations from Palestine

Genetic diversity in 50 snake melon accessions collected from Palestine (West Bank) was assessed by examining variation in 17 phenotypic characters. These accessions belonged to four important landraces of Cucumis melo var. flexuosus: Green “Baladi” (GB), white Baladi (WB), green Sahouri (GS), and white Sahouri (WS). Principal component analysis (PCA) and a dendrogram were performed to determine relationships among populations and to obtain information on the usefulness of those characters for the definition of cultivars. PCA revealed that secondary fruit skin color, flesh color, primary fruit skin color, and secondary skin color pattern were the principal characters to discriminate melon accessions examined in the present study. According to the scatter diagram and dendrogram, landraces of C. melo var. flexuosus: GB, WB, GS, and WS formed different clusters. However, based on Euclidean genetic coefficient distances, GB and WB had the least degree of relatedness with GS and WS, indicating distantly related landraces (Baladi and Sahouri). On the other hand, the highest degree of relatedness was detected between WS on one hand, and both GS and WB on the other indicating closely related cultivars. Fruit traits variability among the different snake melon landraces was evaluated and discussed in this study. This evaluation of fruit trait variability can assist geneticists and breeders to identify populations with desirable characteristics for inclusion in cultivars breeding programs.