Andromonoecy in <Emphasis Type="Italic">Gynandropsis gynandra</Emphasis> (L.) Briq. (Cleomaceae) and effects on fruit and seed production

Spider plant (Gynandropsis gynandra) is a traditional leafy vegetable widespread in sub-Saharan Africa and tropical Asia that is also valued for its medicinal properties. Developing a breeding program for the species requires detailed knowledge of its phenology, floral morphology and pollination system. This study investigates the effects of floral morphology and pollination mechanisms on the reproductive success in G. gynandra. The experiments were conducted in two locations in Benin. A split-plot design was used with four randomized complete blocks. Three accessions were randomly assigned to the whole plots and five treatments including natural self-pollination, hand self-pollination, geitonogamy, open pollination and hand cross-pollination were randomized over the sub-plots. We observed that individual plant exhibited 70% of staminate (male) flowers and 30% of hermaphrodite flowers. G. gynandra was andromonoecious. Open pollination and hand cross-pollination led to higher fruit and seed set. Natural self-pollination and hand self-pollination resulted in lower fruit and seed production. G. gynandra is a self-compatible and predominantly out-crossing species. Cross-pollination resulted in a significant increase in fruit set. This study set the ground for the development of improved cultivars in G. gynandra.     

The foliar spray of <Emphasis Type="Italic">Rhodopseudomonas palustris</Emphasis> grown under <Emphasis Type="Italic">Stevia</Emphasis> residue extract promotes plant growth via changing soil microbial community

Purpose

The extract of Stevia residue is an ideal substitute for cultivation of the purple nonsulfur bacterium, like Rhodopseudomonas palustris (R. palustris). But the influence of R. palustris grown under residue extract on its downstream application is still not well-characterized. The objective of this study was to assess the effect of foliar spray of R. palustris grown under Stevia residue extract on the plant growth and soil microbial properties.

Materials and methods

A pot experiment was carried out under the greenhouse condition, consisting of four treatments varying in the sprayed substances: sterilized water (control), R. palustris grown under the chemical medium supplemented with L-tryptophan (SyT), R. palustris grown under Stevia residue extract supplemented with L-tryptophan (ExT), and R. palustris grown under Stevia residue extract supplemented with NH₄Cl (ExT). The net photosynthesis rate of the uppermost leaves was measured with a portable photosynthesis system. Soil microbial activity was analyzed by microcalorimetry. Soil bacterial community components were determined by real-time quantitative PCR (qPCR) and high-throughput sequencing techniques.

Results and discussion

Compared with SyT, the R. palustris grown under Stevia residue extract not only improved the plant biomass and the net photosynthetic rate to a large extent, but also increased soil microbial metabolic activity and altered community compositions as well. The treatments receiving R. palustris, especially ExT and ExN, increased the relative abundances of some functional guilds involved in C turnover and nutrient cycling in soil, including Acidobacteria, Actinobacteria, Proteobacteria, Gemmatimonadaetes, Nitrospirae, and Planctomycetes.

Conclusions

R. palustris grown under the Stevia residue extract showed advantages over that under the chemical medium on both plant growth and soil microbial properties. One of the possible reasons could result from the increases in microbial activity and several bacterial keystone guilds involved into C and nutrient cycling, both of which potentially contribute to the improved plant growth. The results would be conducive to the downstream application of R. palustris in an economical way.

     

Morphological variation related with environmental factors in endemic and threatened <Emphasis Type="Italic">Jatropha</Emphasis> species of Tehuacan-Cuicatlan,Mexico

Jatropha spp. from Mexico includes high species richness and endemism; five species inhabit in the Tehuacan-Cuicatlan Biosphere Reserve (TCBR), and they are important resources as food, medicine and biofuel. The assessment of morphological and agronomic characteristics is essential to identify, use and maintain plant genetic resources. Given the lack of information on the morphological variability of Jatropha species in relation to environment, the objective was to analyze the influence of physiographic, climatic, and anthropogenic factors in the morphological variability of the species: Jatropha neopauciflora and J. rzedowskii, both not-endangered; J. oaxacana, special protection; J. ciliata and J. rufescens, both endangered in the Reserve. Twelve quantitative morphological variables were measured in 24 populations of these species; 14 environmental variables were registered, and the disturbance index in the sites was estimated. The information was analyzed with Principal Components Analysis (PCA), Cluster Analysis and Canonical Correspondence Analysis (CCA). PCA detected interspecific variation: J. ciliata and J. rufescens have longer and broader leaves and longer flowers, while the other three species have smaller leaves and flowers. J. oaxacana population has intermediate size of leaves, fruits and seeds, compared with those of J. neopauciflora and J. rzedowskii. CCA detected intra-specific variation among the populations of J. neopauciflora and J. rzedowskii, which were separated in two groups due to fruit and seed size. Axis 1 of CCA correlated positively with altitude and annual temperature range, and negatively with mean annual temperature; at the intra-specific level, both species are adapted to variations of temperature and altitude.     

Agro-morphological traits of <Emphasis Type="Italic">Cicer reticulatum</Emphasis> Ladizinsky in comparison to <Emphasis Type="Italic">C. echinospermum</Emphasis> P.H. Davis in terms of potential to improve cultivated chickpea (<Emphasis Type="Italic">C. arietinum</Emphasis> L.)

Germplasm collections of C. reticulatum and C. echinospermum are limited, while both species face threats from over-grazing and habitat change in their natural environments. Recently many new accessions of C. reticulatum and C. echinospermum were collected in east and south-east Anatolia (Turkey) but they have not yet been evaluated for agro-morphological traits. Therefore, the current study investigated agro-morphological traits of new germplasm sources of C. reticulatum and C. echinospermum and evaluated resistance to biotic and abiotic stresses for chickpea improvement. The most attractive agro-morphological traits were canopy width, number of stems and pods per plant and biological yield. The most productive accessions of C. reticulatum and C. echinospermum had 712 and 625 pods per plant, respectively. Two distinct seed, flower and leaf shapes were found in accessions of C. echinospermum. Path analyses indicated that biological yield and harvest index had the most direct influence on seed yield in both species. Factor analyses showed that high seed yield in C. reticulatum depended on high biological yield and number of pods per plant, whereas high seed yield in C. echinospermum depended on harvest index. It was concluded that most accessions of C. reticulatum and C. echinospermum were not only resistant to some biotic and abiotic stresses but also had hidden alleles that could produce transgressive segregation in crosses to cultivated material.     

Bacterial diversity in the rhizosphere of two phylogenetically closely related plant species across environmental gradients

Purpose

Rhizosphere soil bacterial communities are crucial to plant growth, health, and stress resistance. In order to detect how bacterial communities associated with the rhizosphere of phylogenetically related plant species vary in terms of composition, function, and diversity, we investigated the rhizosphere bacterial community structure of two perennial shrub species, Caragana jubata and Caragana roborovskyi, under natural field conditions in northwest China and analyzed the influence of soil properties and environmental factors.

Materials and methods

Eighteen root samples, eight for C. jubata, and ten for C. roborovskyi, along with any adherent soil particles, were collected from multiple sites in northwest China. The rhizosphere soil was washed from the roots, and bacterial communities were analyzed using Illumina MiSeq sequencing of 16S rRNA gene amplicons. Then, α-diversity and β-diversity were calculated using QIIME.

Results and discussion

Across species, Proteobacteria (29 %), Actinobacteria (15 %), Chloroflexi (10 %), Acidobacteria (10 %), Bacteroidetes (8 %), Firmicutes (8 %), Planctomycetes (7 %), Gemmatimonadetes (4 %), and Verrucomicrobia (3 %) were the most abundant phyla in the rhizosphere of C. jubata and C. roborovskyi. However, principal co-ordinates analysis indicated strong interspecific patterns of bacterial rhizosphere communities. Further, the richness of Proteobacteria, Acidobacteria, Bacteroidetes, Verrucomicrobia, Firmicutes, and Nitrospirae was significantly higher in the rhizosphere of C. jubata compared with C. roborovskyi, while the opposite was found for Actinobacteria and Cyanobacteria. However, the Shannon index showed no significant difference in α-diversity between C. jubata and C. roborovskyi. Distance-based redundancy analysis indicated that soil properties and environmental factors exerted strong influences on the structure of the rhizosphere bacterial community and explained 47 and 46 % of community variances between samples, respectively.

Conclusions

Our results showed strong interspecific clustering of the bacterial rhizosphere communities of C. roborovskyi and C. jubata. Altitude explained most of the variation in the composition of bacterial rhizosphere communities of C. roborovskyi and C. jubata, followed by soil pH, water content, organic matter content, total nitrogen content, and mean annual rainfall.

     

Taxon-specific responses of soil microbial communities to different soil priming effects induced by addition of plant residues and their biochars

Purpose

This work investigated changes in priming effects and the taxonomy of soil microbial communities after being amended with plant feedstock and its corresponding biochar.

Materials and methods

A soil incubation was conducted for 180 days to monitor the mineralization and evolution of soil-primed C after addition of maize and its biochar pyrolysed at 450 °C. Responses of individual microbial taxa were identified and compared using the next-generation sequencing method.

Results and discussion

Cumulative CO₂ showed similar trends but different magnitudes in soil supplied with feedstock and its biochar. Feedstock addition resulted in a positive priming effect of 1999 mg C kg^?1 soil (+253.7 %) while biochar gave negative primed C of ?872.1 mg C kg^?1 soil (?254.3 %). Linear relationships between mineralized material and mineralized soil C were detected. Most priming occurred in the first 15 days, indicating co-metabolism. Differences in priming may be explained by differences in properties of plant material, especially the water-extractable organic C. Predominant phyla were affiliated to Acidobacteria, Actinobacteria, Chloroflexi, Gemmatimonadetes, Firmicutes, Planctomycetes, Proteobacteria, Verrucomicrobia, Ascomycota, Basidiomycota, Blastocladiomycota, Chytridiomycota, Zygomycota, Euryarchaeota, and Thaumarchaeota during decomposition. Cluster analysis resulted in separate phylogenetic grouping of feedstock and biochar. Bacteria (Acidobacteria, Firmicutes, Gemmatimonadetes, Planctomycetes), fungi (Ascomycota), and archaea (Euryarchaeota) were closely correlated to primed soil C (R ²?=??0.98, ?0.99, 0.84, 0.81, 0.91, and 0.91, respectively).

Conclusions

Quality of plant materials (especially labile C) shifted microbial community (specific microbial taxa) responses, resulting in a distinctive priming intensity, giving a better understanding of the functional role of soil microbial community as an important driver of priming effect.

     

<Emphasis Type="Italic">p</Emphasis>-Coumaric can alter the composition of cucumber rhizosphere microbial communities and induce negative plant-microbial interactions

Phenolics from root exudates or decaying residues are usually referred as autotoxins of several plant species. However, how phenolics affect soil microbial communities and their functional significances are poorly understood. Rhizosphere bacterial and fungal communities from cucumber (Cucumis sativus L.) seedlings treated with p-coumaric acid, an autotoxin of cucumber, were analyzed by high-throughput sequencing of 16S rRNA gene and internal transcribed spacer amplicons. Then, feedback effects of the rhizosphere biota on cucumber seedlings were evaluated by inoculating non-sterilized and sterilized rhizosphere soils to sterilized background soils. p-Coumaric acid decreased the bacterial diversity of rhizosphere but increased fungal diversity and altered the compositions of both the bacterial and fungal communities. p-Coumaric acid increased the relative abundances of microbial taxa with phenol-degrading capability (such as Chaetomium, Humicola, and Mortierella spp.) and microbial taxa which contained plant pathogens (such as Fusarium spp.). However, p-coumaric acid inhibited the relative abundances of Lysobacter, Haliangium, and Gymnoascus spp., whose species can have pathogen-antagonistic and/or plant-growth-promoting effects. The positive effect of cucumber rhizosphere microbiota on cucumber seedling growth was reduced by p-coumaric acid. Overall, our results showed that, besides its direct phytotoxicity, p-coumaric acid can inhibit cucumber seedling growth through generating negative plant-soil microbial interactions.     

Relationships among <Emphasis Type="Italic">Crataegus</Emphasis> accessions sampled from Hatay,Turkey, as assessed by fruit characteristics and RAPD

The genus Crataegus known as hawthorns, is the largest genus among the Maloideae, which comprises 265 species. Turkey is one of the genetic centers of Crataegus and there are more than 20 species found in Turkey. The fruits of Crataegus are used as food and have high flavonoid, vitamin C, glycoside, anthocyanidin, saponin, tannin, and antioxidant levels. In this study, we attempted to characterize 15 Crataegus accessions sampled from Hatay, located in Eastern Mediterranean region of Turkey. The accessions belonged to several species; C. aronia (L.) DC. var. aronia, C. aronia var. dentata Browicz, C. aronia var. minuta Browicz, C. monogyna Jacq. subsp. azarella (Griseb.) Franco, and C. orientalis Pall. ex M. Bieb. var. orientalis. Fruit characteristics of the accessions exhibited considerable variation. The multivariate, principle component and cluster analyses indicated that the accessions belonged to three groups: (1) C. aronia var. arona accessions; (2) C. aronia var. dentata accessions; and, (3) C. monogyna subsp. azarella and C. orientalis var. orientalis accessions. The principle component analysis results also revealed that the first three components explained 46, 21, and 14% of the variation, comprising a total of 81%. The fruit length and width, leaf area, and soluble solids contents were highly correlated characteristics for the first three components. The 19 RAPD primers generated a total of 107 bands, where 76 of these were polymorphic. The molecular data analyses by principle coordinate and clustering showed similar results to those of pomological characteristics. There were three groups, (1) C. aronia var. arona accessions; (2) C. aronia var. dentata accession; and, (3) C. monogyna subsp. azarella. C. orientalis var. orientalis accession grouped with C. aronia var. arona accessions. Therefore, it can be concluded that, overall, the diversity patterns of pomological and molecular data, generated by RAPD, for Crataegus are in good agreement and the accessions of C. aronia var. aronia, C. aronia var. minuta, C. monogyna subsp. azarella and C. orientalis var. orientalis accessions.     

Arbuscular mycorrhizal fungi optimize the acquisition and translocation of Cd and P by cucumber (<Emphasis Type="Italic">Cucumis sativus</Emphasis> L.) plant cultivated on a Cd-contaminated soil

Purpose

Fruiting vegetables are generally considered to be safer than other vegetables for planting on cadmium (Cd)-contaminated farms. However, the risk of transferring Cd that has accumulated in the stems and leaves of fruiting vegetables is a major issue encountered with the usage of such non-edible parts. The objective of this study was to resolve the contribution of arbuscular mycorrhizal (AM) fungi to the production of low-Cd fruiting vegetables (focusing on the non-edible parts) on Cd-contaminated fields.

Materials and methods

An 8-week pot experiment was conducted to investigate the acquisition and translocation of Cd by cucumber (Cucumis sativus L.) plants on an unsterilized Cd-contaminated (1.6 mg kg^?1) soil in response to inoculation with the AM fungus, Funneliformis caledonium (Fc) or Glomus versiforme (Gv). Mycorrhizal colonization rates of cucumber roots were assessed. Dry biomass and Cd and phosphorus (P) concentrations in the cucumber shoots and roots were all measured. Soil pH, EC, total Cd, phytoavailable (DTPA-extractable) Cd, available P, and acid phosphatase activity were also tested.

Results and discussion

Both Fc and Gv significantly increased (P?<?0.05) root mycorrhizal colonization rates and P acquisition efficiencies, and thus the total P acquisition and biomass of cucumber plants, whereas only Fc significantly increased (P?<?0.05) soil acid phosphatase activity and the available P concentration. Both Fc and Gv significantly increased (P?<?0.05) root to shoot P translocation factors, inducing significantly higher (P?<?0.05) shoot P concentrations and shoot/root biomass ratios. In contrast, both Fc and Gv significantly decreased (P?<?0.05) root and shoot Cd concentrations, resulting in significantly increased (P?<?0.05) P/Cd concentration ratios, whereas only Gv significantly decreased (P?<?0.05) the root Cd acquisition efficiency and increased (P?<?0.05) the root to shoot Cd translocation factor. Additionally, AM fungi also tended to decrease soil total and phytoavailable Cd concentrations by elevating plant total Cd acquisition and soil pH, respectively.

Conclusions

Inoculation with AM fungi increased the P acquisition and biomass of cucumber plants, but decreased plant Cd concentrations by reducing the root Cd acquisition efficiency, and resulted in a tendency toward decreases in soil phytoavailable and total Cd concentrations via increases in soil pH and total Cd acquisition by cucumber plants, respectively. These results demonstrate the potential application of AM fungi for the production of fruiting vegetables with non-edible parts that contain low Cd levels on Cd-contaminated soils.

     

<Emphasis Type="Italic">Panax</Emphasis> species identification with the assistance of DNA data

Panax species have been used as medicinal plants in China and adjacent areas, but the difficulty in wild species identification based on morphological characters prevents the exploration and utilization of these resources. To assist in identifying the species, three plastid intergenic spacers and four nuclear genes of 129 samples from 20 different localities were sequenced to conduct the clustering analyses. P. stipuleanatus and P. notoginseng were relatively easy to be distinguished from other species based on morphological characters and clustering results. Three samples collected from Laos grouped together with those collected from Jinping (China), and they were all identified as P. vietnamensis. However, the fourth one LW4 had closer genetic relationship to P. notoginseng than to P. vietnamensis. Although they were morphologically different in petiolule length, the samples preliminarily identified as P. zingiberensis grouped together in the clustering analyses, and the results of STRUCTURE analysis suggested that samples collected from Zhenyuan shared some genetic component with P. vietnamensis. As for the samples identified as P. japonicus and P. wangianus, there were so many variations in leaves, rhizomes and rootstocks that it was difficult to differentiate them from each other. Molecular data also showed that these taxa were genetically admixed and the samples identified as P. wangianus could be classified into P. japonicus. The nucleotide diversity results indicated that the wild relatives had more substantial genetic diversity compared to P. notoginseng.     

Collection and evaluation of wild tulip (<Emphasis Type="Italic">Tulipa</Emphasis> spp.) resources in China

China is known throughout the world as one of the most diverse centres of wild Tulipa L. resources. There are 17 wild Tulipa species distributed in China, and 12 species are only distributed in Xinjiang Province. In this paper, total 83 accessions were collected from Xinjiang, Liaoning and several other provinces. Their distribution, collection, classification and evaluation were described. According to morphological characteristics, they were classified into eight species, which included T. sinkiangensis Z. M. Mao, T. altaica Pall. ex Spreng., T. iliensis Regel, T. heterophylla Baker, T. buhseana Boiss., T. thianschanica Regel, T. schrenkii Regel and T. edulis (Miq.) Baker. Their phenotypic genetic relationships were analysed and showed that the eight Tulipa species were divided into two groups: Group I included one species T. edulis, and Group II included the other seven species. Bulb renewal was observed in eight wild Tulipa species; T. iliensis and T. edulis showed that one or more long fleshy stolons formed horizontally or vertically at the basal plate of the mother bulbs, new bulblets (dropper) appeared at the top of each fleshy stolon, and the mother bulbs eventually disappeared. The analytic hierarchy process was used to evaluate the ornamental value, utilization potential and ecological adaptability of the eight identified species. The results showed that T. iliensis, T. buhseana and T. thianschanica had better ornamental value and utilization potential than any other species. The distribution, collection, classification, and evaluation of wild Tulipa species could be helpful in creating novel tulip germplasms in China.     

Evidence that fresh weight measurement is imprecise for reporting the effect of plant growth-promoting (rhizo)bacteria on growth promotion of crop plants

Eight greenhouse experiments were performed to compare the effect of seven plant growth-promoting (rhizo)bacteria (PGPR/PGPB) on fresh and dry weights of four crop plants. This has been done to validate if fresh weight measurements of plant variables can serve as reliable values when reporting the effect of these bacteria on plant growth. These experiments show that the growth promotion effects by the tested PGPR/PGPB, including Bacillus amyloliquefaciens GB03, Bacillus subtilis IN-937B, Bacillus altitudinis INR7, and Pseudomonas mandelii 89B-27 in corn and cucumber and Azospirillum brasilense Cd, A. brasilense Sp 245, and Azospirillum lipoferum Br 17 in pepper and tomato, varied significantly between fresh and dry weights of shoot, root, and/or whole plant in the repeated greenhouse experiments. These results support our hypothesis that using fresh weight determination for assessing plant growth promotion by beneficial bacteria is inherently faulty. Therefore, it is recommended that dry weight determination rather than fresh weight determination is used for plant growth promotion tests.     

Molecular cytogenetic characterization,leaf anatomy and ultrastructure of the medicinal plant <Emphasis Type="Italic">Potentilla alba</Emphasis> L.

Potentilla alba L. is a valuable medicinal plant widely used in folk and traditional medicine and particularly promising in complex treatment of thyroid pathology. Natural resources of this species are insufficient due to ever-growing use in contemporary medicine. Comprehensive investigations of different P. alba populations are essential for the successful extension of P. alba plantings. Aiming for a better understanding of karyotype structure, chromosome behaviour in meiosis and developing new diagnostic characters, we performed molecular cytogenetic characterization and leaf structure and ultrastructure analyses of two introduced P. alba samples originating from different habitats. Based on chromosome morphology, distribution of 45S/5S rDNA and DAPI-banding patterns, all chromosomes in the karyotypes were identified and the P. alba chromosomal idiogram was constructed. Our findings confirmed P. alba karyotype stability and also revealed several diagnostic characters of this species: the features of cells of upper and lower leaf epidermis, the presence of calcium oxalate druses and three types of leaf indumentum, essential for evaluation of genetic diversity in different populations, validation of raw materials and further selection progress. The meiotic abnormalities were detected probably related to low pollen activity and indicated the advantages of vegetative propagation in the development of a P. alba plantation system.     

Assessing the potential of using biochar in mine rehabilitation under elevated atmospheric CO<Subscript>2</Subscript> concentration

Purpose

Re-establishment of soil nitrogen (N) capital is a priority in mine rehabilitation. We aimed to evaluate the effects of biochar addition on improving mine spoil N pools and the influence of elevated CO₂ concentration on mine rehabilitation.

Materials and methods

We assessed the effects of pinewood biochar, produced at three temperatures (650, 750 and 850 °C, referred as B₆₅₀, B₇₅₀ and B₈₅₀, respectively), on mine spoil total N concentrations with five different plant species, including a tree species (Eucalyptus crebra), N-fixing shrubs (Acacia floribunda and Allocasuarina littoralis) and C₃ and C₄ grasses (Austrodanthonia tenuior and Themeda australis) incubated at ambient (400 μL L^?1) and elevated (700 μL L^?1) atmospheric CO₂ concentrations, as well as the effects of elevated CO₂ on mine rehabilitation.

Results and discussion

Soil total N significantly improved following biochar incorporation under all plant species (P < 0.05) except for T. Australis. E. crebra had the highest soil total N (0.197%, 0.198% and 0.212% for B₆₅₀, B₇₅₀ and B₈₅₀, respectively). Different from the negligible influence of elevated CO₂ on soil properties under the grasses and the N-fixing shrubs, elevated CO₂ significantly increased soil water and hot water extractable organic C (WEOC and HWEOC, respectively) and decreased total C under E. crebra, indicating that the nutrient demands were not met.

Conclusions

Biochar addition showed the potential in mine rehabilitation in terms of improving soil N pool, especially with E. crebra. However, it would be more difficulty to rehabilitate mine spoils in future with the rising atmospheric CO₂ concentration.

     

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.     

Estimation of natural outcrossing rate and genetic diversity in Lima bean (<Emphasis Type="Italic">Phaseolus lunatus</Emphasis> L. var. <Emphasis Type="Italic">lunatus</Emphasis>) from Brazil using SSR markers: implications for conservation and breeding

Lima bean (Phaseolus lunatus L.) is an important food source in Brazil, especially in the northeast region, where its production and consumption are high. The goals of the present study were to estimate natural outcrossing rates and genetic diversity levels of Lima bean from Brazil, using ten microsatellite loci to obtain information for their conservation and breeding. Fourteen accessions were selected from an experiment in field with open-pollinated and with the presence of pollinating insects. Twelve seeds of each of the 14 selected accessions were grown in screenhouse for tissue harvest and DNA extraction. The multilocus model was used to determine the reproductive system. The outcrossing rate was 38.1 % (t_m = 0.381; t_s = 0.078), and the results indicated a mixed mating system with a predominance of selfing (1 ? t_m = 61.9 %). The biparental inbreeding rate was high (t _m  ? t _s  = 0.303) and the multilocus correlated paternity was quite high (r _p(m) = 0.889), indicating that the progeny was mostly composed of full sibs. The average effective number of pollen donors per maternal plant (N _ep ) was low (1.12), and the fixation index for maternal genotypes (F _m ) was 0.945, indicating that most genitors resulted from inbreeding. The studied families presented considerable genetic variability: A = 6.10;  %P = 30; H _e  = 0.60 and H _o  = 0.077. Total diversity was high (H _T = 0.596), and a portion was distributed within families (H _S = 0.058). In addition, diversity was higher between families (D _ST = 0.538), and genetic differentiation was high (G _ST = 0.902). The results presented here can be used in the implementation of Lima bean conservation and breeding programs in Brazil.     

Increases in soil CO<Subscript>2</Subscript> and N<Subscript>2</Subscript>O emissions with warming depend on plant species in restored alpine meadows of Wugong Mountain,China

Purpose

Ecosystem restorations can impact carbon dioxide (CO₂) and nitrous oxide (N₂O) emissions which are important greenhouse gasses. Alpine meadows are degraded worldwide, but restorations are increasing. Because their soils represent large carbon (C) and nitrogen (N) pools, they may produce significant amounts of CO₂ and N₂O depending on the plant species used in restorations. In addition, warming and N deposition may impact soil CO₂ and N₂O emissions from restored meadows.

Materials and methods

We collected soils from degraded meadows and plots restored using three different plant species at Wugong Mountain (Jiangxi, China). We measured CO₂ and N₂O emissions when soils were incubated at different temperatures (15, 25 or 35 °C) and levels of N addition (control vs. 4 g m^?2) to understand their responses to warming and N deposition.

Results and discussion

Dissolved organic C was higher in restored plots (especially with Fimbristylis dichotoma) compared to non-restored bare soils, and their soil inorganic N was lower. CO₂ emission rates were increased by vegetation restorations, decreased by N deposition, and increased by warming. CO₂ emission rates were similar for the three grass species at 15 and 25 °C, but they were lower with Miscanthus floridulus at 35 °C. Soils from F. dichotoma and Carex chinensis plots had higher N₂O emissions than degraded or M. floridulus plots, especially at 25 °C.

Conclusions

These results show that the effects of restorations on soil greenhouse gas emissions depended on plant species. In addition, these differences varied with temperature suggesting that future climate should be considered when choosing plant species in restorations to predict soil CO₂ and N₂O emissions and global warming potential.

     

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

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

Suitability of a municipal solid waste as organic amendment for agricultural and metal(loid)-contaminated soils: effects on soil properties,plant growth and metal(loid) allocation in <Emphasis Type="Italic">Zea mays</Emphasis> L.

Purpose

The use of municipal solid wastes (MSWs) as a low-cost source of organic matter for soils should be considered after discarding the environmental risks related to their metal(loid) load. The goal of this work was to assess the employment of a MSW as an organic amendment in two types of soil (an agricultural soil, A, and a metal(loid)-enriched mine tailings soil, T) attending to changes in soil properties and in plant growth, nutrition and metal(loid) translocation from roots to aerial parts of Zea mays L. (stalk, leaves, tassel, husk, cob and kernel).

Materials and methods

After a comprehensive characterisation of each soil treatment (A, A + MSW, T, T + MSW), a pot-designed experiment was carried out. Soil solution was monthly monitored throughout the experiment, and metal(loid) concentrations were measured.

Results and discussion

The MSW improved some fertility-related parameters in both soils, A and T: increased total and dissolved organic carbon, total nitrogen and soil microbiology. However, an increase in 0.01 M CaCl₂-extractable metal(loid) concentration was also observed. No differences in dry biomass were found between amended and not amended treatments. A fractionation of metal(loid) concentrations among plant organs occurred. For instance, the highest Cu and Pb concentrations were found in roots, while for Zn occurred in the stalk and the cob. The amended treatments favoured the accumulation of Mn in all plant organs. Kernels showed in general the lowest metal(loid) concentrations.

Conclusions

The addition of municipal solid wastes as organic amendment could be a suitable tool to increase soil fertility. However, due to the high metal(loid) content of this particular MSW, its use on agricultural soils would not be appropriate. By other hand, along with the improvement of soil fertility, the MSW was useful to promote plant development in the mine tailings soil which should be then considered as a potential tool to promote plant establishment in those metal(loid)-impacted soils.

     

The impact of adsorption on the exposure assessment of <Emphasis Type="Italic">Bacillus thuringiensis</Emphasis> in the water-sediment system: a mathematical model approach

A model to assess the environmental fate of bacteria to be used as plant protection products or biocides is presented. The model, based on a black-box approach, takes into account the bacterial cell adsorption on the sediment phase and the degradation kinetics and allows the calculation of the expected environmental density of bacterial cells and the predicted environmental concentration of bacterial toxins in the water-sediment system. An example of calculation results is reported for the study cases of Bacillus thuringiensis subsp. aizawai strain GC-91, B. thuringiensis subsp. kurstaki strain ABTS-351, and B. thuringiensis subsp. tenebrionis strain NB 176, used as plant protection products, and B. thuringiensis subsp. israelensis strains AM 65–52 and SA3A, used as biocides. The calculation of expected environmental density and predicted environmental concentration for bacteria in soil-water systems allows to achieve an appropriate risk assessment of the environmental fate and of the impact of bacterial pest control agents or bacterial biocides on non-target organisms.