Susceptibility and Interactions of <Emphasis Type="Italic">Drosophila suzukii</Emphasis> and <Emphasis Type="Italic">Zaprionus indianus</Emphasis> (Diptera: Drosophilidae) in Damaging Strawberry

Drosophila suzukii (Matsumura) has been recently detected causing damage to strawberries in Brazil. Infestation in strawberry culture has often been observed jointly with the presence of Zaprionus indianus Gupta. This study investigated the susceptibility of strawberries at three ripening stages to infestation of D. suzukii and Z. indianus and their interaction. In the laboratory, strawberries cv. Albion at different ripening stages (green, semi-ripe and ripe) were exposed to D. suzukii and Z. indianus for 24 h in choice and no-choice bioassays. Additionally, we evaluated the effects of mechanical damage incurred artificially or by D. suzukii oviposition on Z. indianus infestation. In no-choice bioassay, there were no significant differences in fruit susceptibility to D. suzukii infestation at different ripening stages. However, in choice bioassay, D. suzukii adults preferred to oviposit on R fruit. The presence of mechanical damage did not increase susceptibility of fruit to D. suzukii oviposition. For Z. indianus, there was greater susceptibility of R fruit in relation to SR and G fruit in both the choice and no-choice bioassays. There was a significant and positive interaction of mechanical damage and damage caused by D. suzukii to R fruit and infestation by Z. indianus, which was not observed in SR and G fruit. Although infestation of Z. indianus is related to attack damaged or decaying fruit, this work shows that this species has the ability to oviposit and develop in healthy strawberry fruit with and increased infestation level when the fruit has damage to its epidermis.     

Impact of <Emphasis Type="Italic">Heterobasidion</Emphasis> root-rot on fine root morphology and associated fungi in <Emphasis Type="Italic">Picea abies</Emphasis> stands on peat soils

We examined differences in fine root morphology, mycorrhizal colonisation and root-inhabiting fungal communities between Picea abies individuals infected by Heterobasidion root-rot compared with healthy individuals in four stands on peat soils in Latvia. We hypothesised that decreased tree vitality and alteration in supply of photosynthates belowground due to root-rot infection might lead to changes in fungal communities of tree roots. Plots were established in places where trees were infected and in places where they were healthy. Within each stand, five replicate soil cores with roots were taken to 20 cm depth in each root-rot infected and uninfected plot. Root morphological parameters, mycorrhizal colonisation and associated fungal communities, and soil chemical properties were analysed. In three stands root morphological parameters and in all stands root mycorrhizal colonisation were similar between root-rot infected and uninfected plots. In one stand, there were significant differences in root morphological parameters between root-rot infected versus uninfected plots, but these were likely due to significant differences in soil chemical properties between the plots. Sequencing of the internal transcribed spacer of fungal nuclear rDNA from ectomycorrhizal (ECM) root morphotypes of P. abies revealed the presence of 42 fungal species, among which ECM basidiomycetes Tylospora asterophora (24.6 % of fine roots examined), Amphinema byssoides (14.5 %) and Russula sapinea (9.7 %) were most common. Within each stand, the richness of fungal species and the composition of fungal communities in root-rot infected versus uninfected plots were similar. In conclusion, Heterobasidion root-rot had little or no effect on fine root morphology, mycorrhizal colonisation and composition of fungal communities in fine roots of P. abies growing on peat soils.     

Functional Analysis of <Emphasis Type="Italic">VvBG1</Emphasis> During Fruit Development and Ripening of Grape

β-glucosidase (BG) was believed to take part in abscisic acid (ABA) synthesis via hydrolysis of ABA glucose ester to release active ABA during plant growth and development. However, there is no genetic evidence available to indicate the role of genes during fruit ripening. Here, the expression patterns of three genes (VvBG1, VvBG2, and VvBG3) encoding β-glucosidase were analyzed during grape fruit development, and it was found that β-glucosidase activity increased in grape fruit in response to various stresses. Furthermore, to verify the function of β-glucosidase during fruit ripening, heterogeneous expression of the VvBG1 gene in strawberry fruit was validated, and the results showed that the VvBG1 over-expression increased β-glucosidase and promoted the fruit ripening process in strawberry. In addition, we found that ABA contents increased in the VvBG1 over-expression of strawberry fruit, which induced fruit anthocyanin, soluble solid accumulation, and fruit softening. Moreover, genes related to coloring (CHS, CHI, F3H, and UFGT), softening (PG1, PL1, and EXP1), and aroma (SAAT, and QR) were up-regulated. This work will elucidate the specific roles of VvBGs in the synthesis of ABA and provide some new insights into the ABA-controlled grape ripening mechanism.     

The Impacts of Above- and Belowground Plant Input on Soil Microbiota: Invasive <Emphasis Type="Italic">Spartina alterniflora</Emphasis> Versus Native <Emphasis Type="Italic">Phragmites australis</Emphasis>

Invasive plants affect soil food webs through various resource inputs including shoot litter, root litter and living root input. The net impact of invasive plants on soil biota has been recognized; however, the relative contributions of different resource input pathways have not been quantified. Through a 2 × 2 × 2 factorial field experiment, a pair of invasive and native plant species (Spartina alterniflora vs. Phragmites australis) was compared to determine the relative impacts of their living roots or shoots and root litter on soil microbial and nematode communities. Living root identity affected bacteria-to-fungi PLFA ratios, abundance of total nematodes, plant-feeding nematodes and omnivorous nematodes. Specifically, the plant-feeding nematodes were 627% less abundant when living roots of invasive S. alterniflora were present than those of native P. australis. Likewise, shoot and root biomass (within soil at 0–10 cm depth) of S. alterniflora was, respectively, 300 and 100% greater than those of P. australis. These findings support the enemy release hypothesis of plant invasion. Root litter identity affected other components of soil microbiota (that is, bacterial-feeding nematodes), which were 34% more abundant in the presence of root litter of P. australis than S. alterniflora. Overall, more variation associated with nematode community structure and function was explained by differences in living roots than root or shoot litter for this pair of plant species sharing a common habitat but contrasting invasion degrees. We conclude that belowground resource input is an important mechanism used by invasive plants to affect ecosystem structure and function.     

<Emphasis Type="Italic">Piriformospora indica</Emphasis>-mediated salinity tolerance in <Emphasis Type="Italic">Aloe vera</Emphasis> plantlets

Piriformospora indica, a root endophytic fungus, has been reported to promote growth of many plants under normal condition and allow the plants to survive under stress conditions. However, its impact on an important medicinal plant Aloe vera L. has not been well studied. Therefore, this study was undertaken to investigate the effect of P. indica on salinity stress tolerance of A. vera plant. P. indica inoculated and non-inoculated A. vera plantlets were subjected to four levels of salinity treatment- 0, 100, 200 and 300 mM NaCl. The salinity stress decreased the ability of the fungus to colonize roots of A. vera but the interaction of A. vera with P. indica resulted in an overall increase in plant biomass and greater shoot and root length as well as number of shoots and roots. The photosynthetic pigment (Chl a, Chl b and total Chl) and gel content were significantly higher for the fungus inoculated A. vera plantlets, at respective salinity concentrations. Furthermore, the inoculated plantlets had higher phenol, flavonoid, flavonol, aloin contents and radical scavenging activity at all salinity concentrations. The higher phenolic and flavonoid content may help the plants ameliorate oxidative stress resulting from high salinity.     

Expression of <Emphasis Type="Italic">MAX2</Emphasis> under <Emphasis Type="Italic">SCARECROW</Emphasis> promoter enhances the strigolactone/MAX2 dependent response of <Emphasis Type="Italic">Arabidopsis</Emphasis> roots to low-phosphate conditions

Main conclusion

MAX2/strigolactone signaling in the endodermis and/or quiescent center of the root is partiallysufficient to exert changes in F-actin density and cellular trafficking in the root epidermis, and alter gene expression during plant response to low Pi conditions.Strigolactones (SLs) are a new group of plant hormones that regulate different developmental processes in the plant via MAX2, an F-box protein that interacts with their receptor. SLs and MAX2 are necessary for the marked increase in root-hair (RH) density in seedlings under conditions of phosphate (Pi) deprivation. This marked elevation was associated with an active reduction in actin-filament density and endosomal movement in root epidermal cells. Also, expression of MAX2 under the SCARECROW (SCR) promoter was sufficient to confer SL sensitivity in roots, suggesting that SL signaling pathways act through a root-specific, yet non-cell-autonomous regulatory mode of action. Here we show evidence for a non-cell autonomous signaling of SL/MAX2, originating from the root endodermis, and necessary for seedling response to conditions of Pi deprivation. SCR-derived expression of MAX2 in max2-1 mutant background promoted the root low Pi response, whereas supplementation of the synthetic SL GR24 to these SCR:MAX2 expressing lines further enhanced this response. Moreover, the SCR:MAX2 expression led to changes in actin density and endosome movement in epidermal cells and in TIR1 and PHO2 gene expression. These results demonstrate that MAX2 signaling in the endodermis and/or quiescent center is partially sufficient to exert changes in F-actin density and cellular trafficking in the epidermis, and alter gene expression under low Pi conditions.

     

Enhanced multiplication and improved <Emphasis Type="Italic">ex vitro</Emphasis> acclimatization of <Emphasis Type="Italic">Decalepis arayalpathra</Emphasis>

The proposed work describes a protocol for high-frequency in vitro regeneration through nodal segments and shoot tips in Decalepsis arayalpathra, a critically endangered medicinal liana of the Western Ghats. Nodal segments were more responsive than shoot tips in terms of shoot proliferation. Murashige and Skoog’s (MS) basal medium supplemented with 5.0 μM 6-benzyladenine (BA) was optimum for shoot initiation through both the explants. Among different combinations of plant growth regulators and growth additive screened, MS medium added with 5.0 μM BA + 0.5 μM indole-3-acetic acid + 20.0 μM adenine sulphate effectuated the highest response: 11.8 shoots per nodal segment and 5.5 shoots per shoot tip with mean shoot length of 9.2 and 4.8 cm, respectively. Half-strength MS medium with 2.5 μM α-naphthalene acetic acid was optimum for in vitro root induction. The plantlets with the well developed shoot and root were acclimatized in Soilrite? with 92 % survival rate in the field conditions. During acclimatization, chlorophyll content, net photosynthetic rate, stomatal conductance, and transpiration rate were gradually changed in dependence of formation of new leaves. Further, the changes in activities of antioxidant enzymes, i.e., superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR) as well as activity of carbonic anhydrase were also observed: a continuous rise in SOD activity, but a rise and fall in the activities of CAT, APX, and GR were also noticed. Maximum fresh mass (3.1 g plant^-1), dry mass (0.35 g plant^-1) of roots and 2-hydroxy-4-methoxybenzaldehyde content of 9.22 μg cm^-3(root extract) were recorded after 8 weeks of acclimatization.     

Ectopic expression of cucumber (<Emphasis Type="Italic">Cucumis sativus</Emphasis> L.) <Emphasis Type="Italic">CsTIR</Emphasis>/<Emphasis Type="Italic">AFB</Emphasis> genes enhance salt tolerance in transgenic <Emphasis Type="Italic">Arabidopsis</Emphasis>

Auxin receptors TIR1/AFBs play an essential role in a series of signaling network cascades. These F-box proteins have also been identified to participate in different stress responses via the auxin signaling pathway in Arabidopsis. Cucumber (Cucumis sativus L.) is one of the most important crops worldwide, which is also a model plant for research. In the study herein, two cucumber homologous auxin receptor F-box genes CsTIR and CsAFB were cloned and studied for the first time. The deduced amino acid sequences showed a 78% identity between CsTIR and AtTIR1 and 76% between CsAFB and AtAFB2. All these proteins share similar characteristics of an F-box domain near the N-terminus, and several Leucine-rich repeat regions in the middle. Arabidopsis plants ectopically overexpressing CsTIR or CsAFB were obtained and verified. Shorter primary roots and more lateral roots were found in these transgenic lines with auxin signaling amplified. Results showed that expression of CsTIR/AFB genes in Arabidopsis could lead to higher seeds germination rates and plant survival rates than wild-type under salt stress. The enhanced salt tolerance in transgenic plants is probably caused by maintaining root growth and controlling water loss in seedlings, and by stabilizing life-sustaining substances as well as accumulating endogenous osmoregulation substances. We proposed that CsTIR/AFB-involved auxin signal regulation might trigger auxin mediated stress adaptation response and enhance the plant salt stress resistance by osmoregulation.     

Cytotoxic and apoptotic activities of extract of <Emphasis Type="Italic">Amaranthus</Emphasis><Emphasis Type="Italic">spinosus</Emphasis> L. in <Emphasis Type="Italic">Allium cepa</Emphasis> and human erythrocytes

The present study examined the apoptosis inducing effects of Amaranthus spinosus L. aqueous extract in Allium cepa root meristematic cells and human erythrocytes. Cytogenetic assay revealed many apoptosis inducing cytogenetic aberrations viz., cytoplasmic breakage, cytoplasmic disintegration, cytoplasmic shrinkage, receding of cytoplasm, cytoplasmic vacuolation, enucleated cell, ghost cell, nuclear vacuolation, nuclear fragmentation and nuclear disintegration. A remarkable modification of red blood cell surface morphology was observed in the result of RBC assay. The treated RBCs show membrane blebbing and shrinkage, features typical for apoptosis in nucleated cells. Significant induction of cell death was observed in treated Allium root tip cells after Evans blue staining, disclosing the membrane damage potential of the plant extract. TTC assay results in reduced mitochondrial/metabolic activity in Allium root tip cells after treatment, designating the adverse effect of plant extract on mitochondrial respiratory chain. These results confirm the apoptosis inducing potential of A. spinosus extract. Confirming the present results by further in vitro studies, it can be effectively targeted against cell proliferation during cancer treatment by inducing apoptosis. Thus from the present investigation it can be concluded that the aqueous extract of A. spinosus exhibited apoptosis induction and cytotoxic activities.     

Effect of <Emphasis Type="Italic">Pseudomonas</Emphasis> Bacteria on Peroxidase Activity in Wheat Plants when Infected with <Emphasis Type="Italic">Bipolaris sorokiniana</Emphasis>

We investigated the effect of treating soft wheat seeds (Triticum aestivum L.) with two Pseudomonas bacteria strains, isolated from earthworm coprolites, showing a significant antifungal and growth-promoting action in preliminary screening on the activity of guaiacol-dependant peroxidase under phytopathogenic load in the presence of Bipolaris sorokiniana (Sacc.) Shoemaker as a mechanism for inducing plant resistance to the pathogen. We established a statistically significant decrease (P < 0.05) in root rot disease incidence and severity during bacterization, which is indicative both of antifungal activity of the used bacterial isolates and of their successful colonizing the rhizosphere of wheat plants. We noted a response of free and weakly bound peroxidase of wheat plants to infection with B. sorokiniana: the enzyme activity increased during pathogenesis. Bacterization also increased peroxidase activity in plant leaves and roots, the greatest differences from non-bacterized plants being observed in wheat roots in the presence of the pathogen. We detected a direct link between peroxidase activity in wheat roots and leaf tissues in the absence of the pathogen and the feedback between peroxidase activity and plant infestation by the root rot pathogen. In the presence of the phytopathogen, there is a lack of correlation between peroxidase activity in wheat roots and leaves, and there is a shift of activity towards its increase in roots, which plays an important role in the development of systemic resistance against the root rot pathogen that penetrates into plants through the roots and root collar.     

Development and relations of <Emphasis Type="Italic">Fusarium culmorum</Emphasis> and <Emphasis Type="Italic">Pseudomonas fluorescens</Emphasis> in soil

The development of Fusarium culmorum and Pseudomonas fluorescens in soil, and the relations between them, were studied using membrane filters containing the fungus, the bacterium, or both microorganisms; the filters were incubated in soil. F. culmorum was identified by indirect immunofluorescence; the GUS-labeled strain was used to visualize P. fluorescens. It was found that F. culmorum introduced in soil can develop as a saprotroph, with the formation of mycelium, macroconidia, and a small amount of chlamydospores. Introduction of glucose and cellulose resulted in increased density of the F. culmorum mycelium and macroconidia. P. fluorescens suppressed the development of the F. culmorum mycelium in soil, but stimulated chlamydospore formation. Decreased mycelial density in the presence of P. fluorescens was more pronounced in soil without additions and less pronounced in the case of introduction of glucose or cellulose. F. culmorum had no effect on P. fluorescens growth in soil.     

Media derived from brown seaweeds <Emphasis Type="Italic">Cystoseira myriophylloides</Emphasis> and <Emphasis Type="Italic">Fucus spiralis</Emphasis> for in vitro plant tissue culture

In the present study, the effect of seaweed extract (SE) from Fucus spiralis (Fs), Cystoseira myriophylloides (Cm) and Laminaria digitata (Ld) on in vitro plant tissue culture was examined. Combination of 25?% of SE from Cm with 25?% of MS medium increased adventitious shoot regeneration from Nicotiana benthamiana leaf discs explants by 620?%, when compared to the conventional regeneration medium. Similarly SE from Fs and Ld enhanced regeneration by about 500?%. However, when increasing SE to 50?%, only Cm significantly enhanced shoot regeneration. The effect of SE was also evaluated on in vitro micropropagation of N. benthamiana, grape, plum and apricot by assessing shoot length, number of leaves and internodes. When used alone but at lower concentrations (2.5 and 12.5?%), SE from Fs and Cm resulted in at least the same efficacy as MS alone for micropropagation of N. benthamiana shoots. However, for micropropagation of grapevine, plum and apricot woody plants, a combination of 50?% of SE from Cm or Fs with 50?% of their conventional micropropagation media was necessary. Rooting was also enhanced in N. benthamiana and grapevine, and was correlated with their higher concentrations of indole acetic acid when compared to SE from Ld. This finding, in addition to mineral analysis data, suggests that SE of Fs and Cm contain necessary nutrients and growth regulators to allow their use as medium for in vitro plant culture.     

<Emphasis Type="Italic">Rhizophagus irregularis</Emphasis> as an elicitor of rosmarinic acid and antioxidant production by transformed roots of <Emphasis Type="Italic">Ocimum basilicum</Emphasis> in an in vitro co-culture system

Arbuscular mycorrhiza is a symbiotic association formed between plant roots and soil borne fungi that alter and at times improve the production of secondary metabolites. Detailed information is available on mycorrhizal development and its influence on plants grown under various edapho-climatic conditions, however, very little is known about their influence on transformed roots that are rich reserves of secondary metabolites. This raises the question of how mycorrhizal colonization progresses in transformed roots grown in vitro and whether the mycorrhizal fungus presence influences the production of secondary metabolites. To fully understand mycorrhizal ontogenesis and its effect on root morphology, root biomass, total phenolics, rosmarinic acid, caffeic acid and antioxidant production under in vitro conditions, a co-culture was developed between three Agrobacterium rhizogenes-derived, elite-transformed root lines of Ocimum basilicum and Rhizophagus irregularis. We found that mycorrhizal ontogenesis in transformed roots was similar to mycorrhizal roots obtained from an in planta system. Mycorrhizal establishment was also found to be transformed root line-specific. Colonization of transformed roots increased the concentration of rosmarinic acid, caffeic acid and antioxidant production while no effect was observed on root morphological traits and biomass. Enhancement of total phenolics and rosmarinic acid in the three mycorrhizal transformed root lines was found to be transformed root line-specific and age dependent. We reveal the potential of R. irregularis as a biotic elicitor in vitro and propose its incorporation into commercial in vitro secondary metabolite production via transformed roots.     

Ectomycorrhizal pre-inoculation of <Emphasis Type="Italic">Pinus hartwegii</Emphasis> and <Emphasis Type="Italic">Abies religiosa</Emphasis> is replaced by native fungi in a temperate forest of central Mexico

Few studies have focused on analyzing the effect of native inoculated ectomycorrhizal (ECM) fungal strains on seedlings under field conditions in temperate forests. However, it is crucial to verify that the positive effects of ECM under nursery conditions also occur in the field, favoring their performance. We evaluated the short-term effect of ECM on three-year-old seedlings of Pinus hartwegii and Abies religiosa in central Mexico by subjecting them to four treatments: inoculation with Inocybe splendens, inoculation with Suillus brevipes (both native strains), inoculation with forest soil, and non-inoculated plants. Percentage of ECM colonization, plant growth (shoot height and stem diameter), and physiological (osmotic potential, stomatal conductance, CO₂ assimilation and water use efficiency) responses were evaluated. We found that these two ECM species were partial (P. hartwegii) or totally (A. religiosa) replaced after one and a half years in the field. P. hartwegii seedlings increased their water use efficiency during the dry season, but in A. religiosa seedlings, a clear strategy for avoiding water stress was not detected. This ECM replacement had a negative effect on the physiological performance Of A. religiosa. Our results emphasize the importance of selecting compatible fungal-host species combinations for nursery inoculation and of using sources of inoculum adapted to the environmental conditions of the transplant site, ensuring root colonization prior to field transplanting to minimize seedling mortality due to water stress.