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Premise: Soil microbes can influence patterns of diversity in plant communities via plant–soil feedbacks. Intraspecific plant–soil feedbacks occur when plant genotype leads to variations in soil microbial composition, resulting in differences in the performance of seedlings growing near their maternal plants versus seedlings growing near nonmaternal conspecific plants. How consistently such intraspecific plant–soil feedbacks occur in natural plant communities is unclear, especially in variable field conditions. Methods: In an in situ experiment with four native tree species on Barro Colorado Island (BCI), Panama, seedlings of each species were transplanted beneath their maternal tree or another conspecific tree in the BCI forest. Mortality and growth were assessed at the end of the wet season (~4 months post‐transplant) and at the end of the experiment (~7 months post‐transplant). Results: Differences in seedling performance among field treatments were inconsistent among species and eroded over time. Effects of field environment were detected at the end of the wet season in two of the four species: Virola surinamensis seedlings had higher survival beneath their maternal tree than other conspecific trees, while seedling survival of Ormosia macrocalyx was higher under other conspecific trees. However, these differences were gone by the end of the experiment. Conclusions: Our results suggest that intraspecific plant–soil feedbacks may not be consistent in the field for tropical tree species and may have a limited role in determining seedling performance in tropical tree communities. Future studies are needed to elucidate the environmental and genetic factors that determine the incidence and direction of intraspecific plant–soil feedbacks in plant communities. [ABSTRACT FROM AUTHOR]

This study examines how plant genotype can influence the microbiome by comparing six tomato genotypes (Solanum lycopersicum) based on their traditional vs. commercial backgrounds. Using Illumina-based sequencing of the V6-V8 regions of 16S and ITS2 rRNA genes, we analyzed and compared the endophytic bacterial and fungal communities in stems to understand how microbiota can differ and be altered in plant genotypes and the relation to human manipulation. Our results reflect that traditional genotypes harbor significantly more exclusive microbial taxa and a broader phylogenetic background than the commercial ones. Traditional genotypes were significantly richer in Eurotiomycetes and Sordariomycetes fungi, while Lasiosphaeriaceae was more prevalent in commercial genotypes. TH-30 exhibited the highest bacterial abundance, significantly more than commercial genotypes, particularly in Actinomycetia, Bacteroidia, and Gammaproteobacteria. Additionally, traditional genotypes had higher bacterial diversity, notably in orders like Cytophagales, Xanthomonadales, and Burkholderiales. Moreover, we performed an evaluation of the impact of a systemic fungicide (tebuconazole-dichlofluanide) to simulate a common agronomic practice and determined that a single fungicide treatment altered the stem endophytic microbiota. Control plants had a higher prevalence of fungal orders Pleosporales, Helotiales, and Glomerellales, while treated plants were dominated by Sordariomycetes and Laboulbeniomycetes. Fungal community diversity significantly decreased, but no significant impact was observed on bacterial diversity. Our study provides evidence that the background of the tomato variety impacts the fungal and bacterial stem endophytes. Furthermore, these findings suggest the potential benefits of using of traditional genotypes as a source of novel beneficial microbiota that may prove highly valuable in unpredicted challenges and the advancement in sustainable agriculture. [ABSTRACT FROM AUTHOR]

This study examines how plant genotype can influence the microbiome by comparing six tomato genotypes (Solanum lycopersicum) based on their traditional vs. commercial backgrounds. Using Illumina-based sequencing of the V6-V8 regions of 16S and ITS2 rRNA genes, we analyzed and compared the endophytic bacterial and fungal communities in stems to understand how microbiota can differ and be altered in plant genotypes and the relation to human manipulation. Our results reflect that traditional genotypes harbor significantly more exclusive microbial taxa and a broader phylogenetic background than the commercial ones. Traditional genotypes were significantly richer in Eurotiomycetes and Sordariomycetes fungi, while Lasiosphaeriaceae was more prevalent in commercial genotypes. TH-30 exhibited the highest bacterial abundance, significantly more than commercial genotypes, particularly in Actinomycetia, Bacteroidia, and Gammaproteobacteria. Additionally, traditional genotypes had higher bacterial diversity, notably in orders like Cytophagales, Xanthomonadales, and Burkholderiales. Moreover, we performed an evaluation of the impact of a systemic fungicide (tebuconazole-dichlofluanide) to simulate a common agronomic practice and determined that a single fungicide treatment altered the stem endophytic microbiota. Control plants had a higher prevalence of fungal orders Pleosporales, Helotiales, and Glomerellales, while treated plants were dominated by Sordariomycetes and Laboulbeniomycetes. Fungal community diversity significantly decreased, but no significant impact was observed on bacterial diversity. Our study provides evidence that the background of the tomato variety impacts the fungal and bacterial stem endophytes. Furthermore, these findings suggest the potential benefits of using of traditional genotypes as a source of novel beneficial microbiota that may prove highly valuable in unpredicted challenges and the advancement in sustainable agriculture. [ABSTRACT FROM AUTHOR]

Root-associated microbiota play a key role in plant growth, resilience, and health. In this study, the microbial community structure in the rhizosphere of 12 pumpkins accessions belonging to three Cucurbita species i.e. C. pepo, C. maxima, and C. moschata, was monitored using the soil dilution plating technique on specific media. All accessions tested were also screened for their production and yield parameters. Based on Principal Component Analysis (PCA), 4 accessions of C. maxima (namely C5, C23, C14.2 and C6.2) were characterized by the greatest average fruit weight and yield, the highest actinomycetes, bacterial, Trichoderma spp. and Aspergillus spp. communities, and the lowest total fungal population in their rhizosphere. Positive correlations were noted between fruit fresh weight, culturable bacteria and Trichoderma spp. populations in the rhizopshere of pumpkins accessions. Negative correlations were noted between fruit weight and yield parameters and the total culturable fungal populations. The current study clearly demonstrated that the rhizosphere soil microbial communities have been shaped by Cucurbita species and accessions. Based on the significant links observed between soil microbiota and yield parameters, future pumpkin breeding programs could be focused on the selection of accessions that are quite able to exploit these associated beneficial microbial communities.

Rootassociated microbiota play a key role in plant growth, resilience, and health. In this study, the microbial community structure in the rhizosphere of 12 pumpkins accessions belonging to three Cucurbita species i.e. C. pepo, C. maxima, and C. moschata, was monitored using the soil dilution plating technique on specific media. All accessions tested were also screened for their production and yield parameters. Based on Principal Component Analysis (PCA), 4 accessions of C. maxima (namely C5, C23, C14.2 and C6.2) were characterized by the greatest average fruit weight and yield, the highest actinomycetes, bacterial, Trichoderma spp. and Aspergillus spp. communities, and the lowest total fungal population in their rhizosphere. Positive correlations were noted between fruit fresh weight, culturable bacteria and Trichoderma spp. populations in the rhizopshere of pumpkins accessions. Negative correlations were noted between fruit weight and yield parameters and the total culturable fungal populations. The current study clearly demonstrated that the rhizosphere soil microbial communities have been shaped by Cucurbita species and accessions. Based on the significant links observed between soil microbiota and yield parameters, future pumpkin breeding programs could be focused on the selection of accessions that are quite able to exploit these associated beneficial microbial communities. [ABSTRACT FROM AUTHOR]

Microbial communities in the rhizosphere influence nutrient acquisition and stress tolerance. How abiotic and biotic factors impact the plant microbiome in the wild has not been thoroughly addressed. We studied how plant genotype and soil affect the rhizosphere microbiome of Vaccinium floribundum, an endemic species of the Andean region that has not been domesticated or cultivated. Using high-throughput sequencing of the 16S rRNA and ITS region, we characterized 39 rhizosphere samples of V. floribundum from four plant genetic clusters in two soil regions from the Ecuadorian Highlands. Our results showed that Proteobacteria and Acidobacteria were the most abundant bacterial phyla and that fungal communities were not dominated by any specific taxa. Soil region was the main predictor for bacterial alpha diversity, phosphorous and lead being the most interesting edaphic factors explaining this diversity. The interaction of plant genotype and altitude was the most significant factor associated with fungal diversity. This study highlights how different factors govern the assembly of the rhizosphere microbiome of a wild plant. Bacterial communities depend more on the soil and its mineral content, while plant genetics influence the fungal community makeup. Our work illustrates plant–microbe associations and the drivers of their variation in a unique unexplored ecosystem from the Ecuadorian Andes. [ABSTRACT FROM AUTHOR]

Abstract Loss of plant biodiversity can result in reduced abundance and diversity of associated species with implications for ecosystem functioning. In ecosystems low in plant species diversity, such as Neotropical mangrove forests, it is thought that genetic diversity within the dominant plant species could play an important role in shaping associated communities. Here, we used a manipulative field experiment to study the effects of maternal genotypic identity and genetic diversity of the red mangrove Rhizophora mangle on the composition and richness of associated soil bacterial communities. Using terminal restriction fragment length polymorphism (T‐RFLP) community fingerprinting, we found that bacterial community composition differed among R. mangle maternal genotypes but not with genetic diversity. Bacterial taxa richness, total soil nitrogen, and total soil carbon were not significantly affected by maternal genotypic identity or genetic diversity of R. mangle. Our findings show that genotype selection in reforestation projects could influence soil bacterial community composition. Further research is needed to determine what impact these bacterial community differences might have on ecosystem processes, such as carbon and nitrogen cycling.

Microbial communities in the rhizosphere influence nutrient acquisition and stress tolerance. How abiotic and biotic factors impact the plant microbiome in the wild has not been thoroughly addressed. We studied how plant genotype and soil affect the rhizosphere microbiome of Vaccinium floribundum, an endemic species of the Andean region that has not been domesticated or cultivated. Using high-throughput sequencing of the 16S rRNA and ITS region, we characterized 39 rhizosphere samples of V. floribundum from four plant genetic clusters in two soil regions from the Ecuadorian Highlands. Our results showed that Proteobacteria and Acidobacteria were the most abundant bacterial phyla and that fungal communities were not dominated by any specific taxa. Soil region was the main predictor for bacterial alpha diversity, phosphorous and lead being the most interesting edaphic factors explaining this diversity. The interaction of plant genotype and altitude was the most significant factor associated with fungal diversity. This study highlights how different factors govern the assembly of the rhizosphere microbiome of a wild plant. Bacterial communities depend more on the soil and its mineral content, while plant genetics influence the fungal community makeup. Our work illustrates plant–microbe associations and the drivers of their variation in a unique unexplored ecosystem from the Ecuadorian Andes.

The microbiota colonizing the rhizosphere contributes to plant growth, productivity, carbon sequestration and phytoremediation. Several studies address plant-associated bacteria; however, few studies analyze the effect of plant genotype on the eukaryotic community. Here, we analyzed the eukaryotic composition of maize rhizosphere from three different plant landraces and one inbred line grown in the same soil (common garden approach). This experimental design, coupled with 18S rDNA gene amplicon sequencing, allowed us to test the influence of maize and its genotype on the rhizosphere's eukaryotic community. We found that plant growth modified the eukaryotic community in soil, as diversity comparisons between maize rhizosphere and unplanted soil revealed significantly different eukaryotic composition. Various genera of nematodes and fungi, predominantly bacterial feeding nematodes and mycorrhizal fungi among other taxa, were increased in the rhizosphere samples. We also observed that maize genotype differentially shaped the relative abundance of the following fungal families in the rhizosphere: Acaulosporaceae, Aspergillaceae, Chaetomiaceae, Claroideoglomeraceae, Corticiaceae, Mortierellaceae, Trichocomaceae and Trichomeriaceae. Thus, plant genotype has a selective influence on establishing fungal communities in the rhizosphere. This study emphasizes the importance of an integrated consideration of plant genetics for future agricultural applications of microbes to crops. [ABSTRACT FROM AUTHOR]

Azospirillum sp. strain B510 has been known as the plant growth-promoting endophyte; however, the growth-promotion effect is dependent on the plant genotype. Here, we aimed to identify quantitative trait loci (QTL) related to primary root length in rice at the seedling stage as a response to inoculation with B510. The primary root length of “Nipponbare” was significantly reduced by inoculation with B510, whereas that of “Kasalath” was not affected. Thus, we examined 98 backcrossed inbred lines and four chromosome segment substitution lines (CSSL) derived from a cross between Nipponbare and Kasalath. The primary root length was measured as a response to inoculation with B510, and the relative root length (RRL) was calculated based on the response to non-inoculation. Three QTL alleles, qRLI-6 and qRLC-6 on Chromosome (Chr.) 6 and qRRL-7 on Chr. 7 derived from Kasalath increased primary root length with inoculation (RLI), without inoculation, (RLC) and RRL and explained 20.2%, 21.3%, and 11.9% of the phenotypic variation, respectively. CSSL33, in which substitution occurred in the vicinity region of qRRL-7, showed a completely different response to inoculation with B510 compared with Nipponbare. Therefore, we suggest that qRRL-7 might strongly control root growth in response to inoculation with Azospirillum sp. strain B510.

To address correlations between population sizes of microbes on the leaf surfaces and leaf morphological and physicochemical properties, various leaf morphological and physicochemical features as possible predictors of microbial population sizes on the leaf surfaces of four Napier grass cultivars were assessed. Results indicated microbes except for lactic acid bacteria (LAB) preferred to colonize the leaf surfaces bearing trichomes, and their population sizes were significantly correlated with trichomes, especially for yeasts. The population sizes of microbes were positively correlated with soluble sugar content (p < 0.05). Furthermore, no significant correlation was found between population sizes of microbes and wax content, except for yeasts. The multivariate regression trees (MRT) analysis showed different genotypes of leaf–microbe system could be characterized by four-leaf attributes with soluble sugar of leaf tissues being the primary explanatory attribute. Leaves with soluble sugar content below 9.72 mg g−1 fresh weight (FW) were rarely colonized. For leaves with soluble sugar content above 9.72 mg g−1 FW, water content was the next explanatory leaf attribute, followed by wax content on the leaf surfaces. Leaves with higher water content (> 73%) were more colonized, and small microbial population was associated with higher wax content (> 10.66 mg g−1 dry matter). In conclusion, leaf chemical attributes have a higher contribution than morphological structure properties in determining population sizes of microbes on the leaf surfaces. The exuded soluble sugar and protein promote the development of microbial populations. For different genotypes of leaf–microbe system, the relationship between microbial abundance on their leaf surfaces and leaf morphological structure or physicochemical properties may be predicted by the MRT. Population sizes of microbes are primarily influenced by soluble sugar content under the water-rich conditions. [ABSTRACT FROM AUTHOR]

Loss of plant biodiversity can result in reduced abundance and diversity of associated species with implications for ecosystem functioning. In ecosystems low in plant species diversity, such as Neotropical mangrove forests, it is thought that genetic diversity within the dominant plant species could play an important role in shaping associated communities. Here, we used a manipulative field experiment to study the effects of maternal genotypic identity and genetic diversity of the red mangrove Rhizophora mangle on the composition and richness of associated soil bacterial communities. Using terminal restriction fragment length polymorphism (T‐RFLP) community fingerprinting, we found that bacterial community composition differed among R. mangle maternal genotypes but not with genetic diversity. Bacterial taxa richness, total soil nitrogen, and total soil carbon were not significantly affected by maternal genotypic identity or genetic diversity of R. mangle. Our findings show that genotype selection in reforestation projects could influence soil bacterial community composition. Further research is needed to determine what impact these bacterial community differences might have on ecosystem processes, such as carbon and nitrogen cycling. [ABSTRACT FROM AUTHOR]

The New Zealand native plant mānuka (Leptospermum scoparium) is representative of the country’s North and South Islands flora. This species is essential to the growing community of honey producers due to its honey’s antimicrobial and antioxidant properties, attributed to the presence of methylglyoxal (MGO), derived from dihydroxyacetone (DHA) in the nectar. Several clones and cultivars have been selected to optimize DHA production. Still, nothing is known about the volatile emissions of these artificially selected plants. Volatile organic compounds (VOCs) can influence their interactions with the environment, such as pollinator foraging decisions, which may subsequently affect the plants’ products. This study explored the aboveground volatile organic compounds (VOCs) emitted by eight different mānuka genotypes (six clones and two wild cultivars) under field conditions during the spring season. Volatiles were collected using the “push–pull” headspace sampling technique and analyzed using gas chromatography-mass spectrometry (GC-MS). Our results show that mānuka plants emit large amounts of terpenoids, with sesquiterpenes and monoterpenoids being the most abundant groups of compounds. The results also show variation in the total green leaf volatiles, total sesquiterpenes, and specific compounds between genotypes and suggest that artificially selected plants have a significant variation in their chemical profiles. The potential impacts of these results on the plant’s defence, pollinator attraction and bee products are discussed.

Plant genetic variation, through its phenotypic display, can determine the composition of below ground microbial communities. Variation within a species is increasingly acknowledged to have substantial ecological consequences, particularly through trophic cascades. We hypothesized that the intraspecific genotypic variation of the tree host might impact the phylogenetic composition of its rhizospheric microbial communities, by favouring particular clades, that might be further reflected in ecosystem process rates.We tested whether the intraspecific genotypic variation of Pinus pinaster modulates nutrient cycling by determining the phylogenetic structure of its symbiotic ectomycorrhizal fungi and rhizospheric bacteria. We sequenced fungal and bacterial molecular markers and reconstructed phylogenies in the rhizosphere of P. pinaster trees belonging to three genotypic variants (Mediterranean, Atlantic, African) in three 45‐year‐old common garden experiments, and measured seven soil enzymatic activities.Local effects, based on differences in elevation and soil conditions across sites, were strong predictors of the ectomycorrhizal and bacterial communities thriving in tree's rhizosphere. Across‐site variation also explained differences in phosphorus cycling. We detected, however, a significant effect of the plant genotype on the phylogenetic structure of the root‐associated microbiota that was consistent across sites.The most productive Mediterranean plant genotype sheltered the most distinct root microbiome, with the dominant Basidiomycetes and Proteobacteria having a strong influence on the phylogenetic microbial community structure and associating with an enhanced hydrolysis of celluloses, hemicelluloses and chitin. Beneath the less productive Atlantic genotype, the less abundant Ascomycetes and up to thirteen bacterial phyla shaped the phylogenetic microbial structure, and predicted the rates of peptidase. Ectomycorrhizal fungi explained the activity of cellulases and protease, and bacteria that of hemicellulases and chitinase, suggesting functional complementarity.Synthesis. This is the first report using three‐replicated long‐term common gardens in mature forests to disentangle plant genotype‐ and site‐specific drivers of the rhizospheric microbiome and its enzymatic potential. We concluded that intraspecific variation in primary producers leaves a phylogenetic signature in mutualists and decomposers that further modulate key steps in carbon and nitrogen cycles. These results emphasize the ecological relevance of plant intraspecific diversity in determining essential plant–soil feedbacks that control ecosystem productivity and performance. [ABSTRACT FROM AUTHOR]

Abstract Phyllosphere fungi generally exhibit high species diversity and play important roles in both plant fitness and ecosystem functioning, but the relationship between host plant genotype and phyllosphere fungal community is still poorly understood. In this study, we investigated the fungal communities associated with Mussaenda pubescens var. alba leaves across a regional scale using Illumina MiSeq sequencing of ITS2 sequences. We then characterized both host plant genotype and genetic structure employing microsatellite techniques. A total of 1575 taxonomic operational units (OTUs) of fungi were obtained at a 97% sequence similarity level, which were dominated by members of Dothideomycetes and Eurotiomycetes. We found that fungal community composition was significantly structured by host genotype, and less by geographic distance. Furthermore, a significant genetic differentiation was detected among host plant populations, and plant genetic distance showed a significant positive relationship with fungal community dissimilarity. This study highlights the importance of intraspecific host genetic identity as a primary driver in shaping regional phyllosphere fungal community. [ABSTRACT FROM AUTHOR]

Plant tissues host complex fungal and bacterial communities, and their composition is determined by host traits such as tissue age, plant genotype and environmental conditions. Despite the importance of bark as a possible reservoir of plant pathogenic microorganisms, little is known about the associated microbial communities. In this work, we evaluated the composition of fungal and bacterial communities in the pear (Abate and Williams cultivars) and apple (Golden Delicious and Gala cultivars) bark of three/four-year-old shoots (old bark) or one-year-old shoots (young bark), using a meta-barcoding approach. The results showed that both fungal and bacterial communities are dominated by genera with ubiquitous attitudes, such as Aureobasidium , Cryptococcus , Deinococcus and Hymenobacter , indicating intense microbial migration to surrounding environments. The shoot age, plant species and plant cultivar influenced the composition of bark fungal and bacterial communities. In particular, bark communities included potential biocontrol agents that could maintain an equilibrium with potential plant pathogens. The abundance of fungal (e.g. Alternaria , Penicillium , Rosellinia , Stemphylium and Taphrina ) and bacterial (e.g. Curtobacterium and Pseudomonas ) plant pathogens was affected by bark age and host genotype, as well as those of fungal genera (e.g. Arthrinium , Aureobasidium , Rhodotorula , Sporobolomyces ) and bacterial genera (e.g. Bacillus, Brevibacillus , Methylobacterium , Sphingomonas and Stenotrophomonas ) with possible biocontrol and plant growth promotion properties. [ABSTRACT FROM AUTHOR]

Azospirillum sp. strain B510 has been known as the plant growth-promoting endophyte; however, the growth-promotion effect is dependent on the plant genotype. Here, we aimed to identify quantitative trait loci (QTL) related to primary root length in rice at the seedling stage as a response to inoculation with B510. The primary root length of “Nipponbare” was significantly reduced by inoculation with B510, whereas that of “Kasalath” was not affected. Thus, we examined 98 backcrossed inbred lines and four chromosome segment substitution lines (CSSL) derived from a cross between Nipponbare and Kasalath. The primary root length was measured as a response to inoculation with B510, and the relative root length (RRL) was calculated based on the response to non-inoculation. Three QTL alleles, qRLI-6 and qRLC-6 on Chromosome (Chr.) 6 and qRRL-7 on Chr. 7 derived from Kasalath increased primary root length with inoculation (RLI), without inoculation, (RLC) and RRL and explained 20.2%, 21.3%, and 11.9% of the phenotypic variation, respectively. CSSL33, in which substitution occurred in the vicinity region of qRRL-7, showed a completely different response to inoculation with B510 compared with Nipponbare. Therefore, we suggest that qRRL-7 might strongly control root growth in response to inoculation with Azospirillum sp. strain B510. [ABSTRACT FROM AUTHOR]

Plant roots host symbiotic arbuscular mycorrhizal (AM) fungi and other fungal endophytes that can impact plant growth and health. The impact of microbial interactions in roots may depend on the genetic properties of the host plant and its interactions with root-associated fungi. We conducted a controlled condition experiment to investigate the effect of several chickpea ( Cicer arietinum L.) genotypes on the efficiency of the symbiosis with AM fungi and non-AM fungal endophytes. Whereas the AM symbiosis increased the biomass of most of the chickpea cultivars, inoculation with non-AM fungal endophytes had a neutral effect. The chickpea cultivars responded differently to co-inoculation with AM fungi and non-AM fungal endophytes. Co-inoculation had additive effects on the biomass of some cultivars (CDC Corrine, CDC Anna, and CDC Cory), but non-AM fungal endophytes reduced the positive effect of AM fungi on Amit and CDC Vanguard. This study demonstrated that the response of plant genotypes to an AM symbiosis can be modified by the simultaneous colonization of the roots by non-AM fungal endophytes. Intraspecific variations in the response of chickpea to AM fungi and non-AM fungal endophytes indicate that the selection of suitable genotypes may improve the ability of crop plants to take advantage of soil ecosystem services. [ABSTRACT FROM AUTHOR]

It is important to investigate sun light interception by plant canopy as it affects different crop activities, most importantly the photosynthesis process and hence biomass production. It was hypothesized that the light response of barley and corn, is affected by genetic (crop species) and environmental conditions. Accordingly, field experiments were conducted to evaluate the effects of drought stress, crop genotype and nitrogen (N) fertilization on barley and silage maize growth and yield. The experiments were split plot on the basis of completely randomized block design in three replicates. In the barley experiment, the drought levels (70, 90 and 110 mm evaporation from the pan, class A) and the barley genotypes were devoted to the main and sub plots, respectively. In the silage maize experiment the N fertilization rates and maize genotypes were used as the main and sub plots, respectively. Different crop parameters including leaf area index (LAI), plant dry matter, light absorption, and silage and grain yield were determined for both barley and maize. Using the Beer-Lambert Law, the light extinction coefficients ( k ) were calculated. Although the highest level of k by barley genotypes was resulted at the control level of stress (0.4797), the corresponding values were not different at the medium and high level of stress (0.3958 and 0.3931, respectively). Drought significantly affected the grain yield of barley and resulted in a 16%, 15% and 6% decrease in plant dry matter, LAI and light absorption, respectively. The effects of genotype were significant on all determined parameters, and the interaction of genotype and stress was significant on light absorption and grain yield. The genotypes Nosrat ( k =0.4624) and Yusef ( k =0.4763) were the most efficient barley genotypes when grown under drought stress with respect to growth and yield parameters determined in the experiment. Although the effect of N fertilization was not significant on the rate of light absorption, the interaction of genotype and N fertilization significantly affected maize light absorption. The most efficient rate of N fertilization for maize silage and grain yield production was 100 kg/ha with respect to the rate of light intercepted ( k =0.5113). The dry matter of silage maize was in the range of 1837–2535 g/m 2 . The interception of light and the other determined parameters for genotype 704 indicated that among different genotypes, it was the most efficient genotype. The growth and yield of both barley and maize were positively related with the light extinction coefficients. The results indicate that determination of light extinction coefficients is a suitable indictor of canopy response to different crop and environment parameters, and accordingly can be used for designing more efficient canopies with a higher rate of biomass and yield production. [ABSTRACT FROM AUTHOR]

Agricultural food products with high nutritive value are always preferred over food products with low nutritive value. Efforts are being made to increase the nutritive value of food by incorporating dietary supplements to the food products. The same is more desirous if the nutritive value of food is increased under natural conditions in the food products especially in the agricultural produces. Fragmented researches have led to the conclusion that it is possible to increase nutritive value of the agricultural products naturally in agricultural fields. The rhizosphere is of vital importance in this regard for not only health and nutritional status of plants but also for the microorganisms colonising the rhizosphere. Remarkably robust composition of plant microbiome with respect to other soil environments clearly suggests the role of plant host in discriminating its colonisers. A large amount of biotic and abiotic factors are believed to manipulate the microbial communities in the rhizosphere. However, plant genotype has proven to be the key in giving the final shape of the rhizosphere microbiome.

Light absorption and light extinction of wheat (Triticum aestivum L.) are among the most important parameters affecting wheat growth and yield production. However, these properties are affected by plant and environmental factors. Despite wheat being an important food crop, there is not much information on these light parameters in wheat. Accordingly, light parameters were investigated in wheat plants in the present study in three field experiments under two distinct climatic conditions, awarmarid and semi-arid climate and a cool climate. The aims of the study were to determinehowlight absorption and light extinction of wheat are affected by: (1) planting date and plant genotype under arid and semi-arid conditions (Experiment I); and (2) N chemical fertilisation and plant genotype under arid and semi-arid conditions (Experiment II) and cool temperate conditions (Experiment III). Light absorption by the canopy was determined using a lightmeter and coefficients of extinction were calculated. Analyses of variance indicated significant effects of experimental treatments on light properties, wheat growth and yield production. There was a high rate of variability in light absorption, with a maximum of 59.27%, and light extinction coefficients were in the range 0.45-0.66. The experimental treatments resulted in high variability in the leaf area index (2.08-7.49), wheat biological yield (7831.1-22 515.96 kg ha-1), grain yield (2481.3-9273.57 kg ha-1) and harvest index (32.86-53.90%). The interaction between planting date and plant genotypes indicated that the responses of different wheat genotypes to planting date were highly variable, significantly affecting light absorption and light extinction by wheat. It is possible to make the optimum use of solar light and produce the highest rate of yield if the most efficient genotype (Line 14-C81, Pishvaz and Pishtaz) is planted on the right planting date (15 November) using the optimum rate of N chemical fertilisation (50, 100, 150 kg ha-1). [ABSTRACT FROM AUTHOR]

Asexual Epichloë endophytes are prevalent in cool season grasses, and many are of hybrid origin. Hybridization of asexual endophytes is thought to provide a rapid influx of genetic variation that may be adaptive to endophyte-host grass symbiota in stressful environments. For Arizona fescue ( Festuca arizonica), hybrid symbiota are commonly found in resource-poor environments, whereas non-hybrid symbiota are more common in resource-rich environments. There have been very few experimental tests where infection, hybrid and non-hybrid status, and plant genotype have been controlled to tease apart their effects on host phenotype and fitness in different environments. We conducted a greenhouse experiment where hybrid (H) and non-hybrid (NH) endophytes were inoculated into plant genotypes that were originally uninfected (E−) or once infected with either the H or NH endophytes. Nine endophyte and plant genotypic group combinations were grown under low and high water and nutrient treatments. Inoculation with the resident H endophyte enhanced growth and altered allocation to roots and shoots, but these effects were greatest in resource-rich environments, contrary to expectations. We found no evidence of co-adaptation between endophyte species and their associated host genotypes. However, naturally E− plants performed better when inoculated with the hybrid endophyte, suggesting these plants were derived from H infected lineages. Our results show complex interactions between endophyte species of hybrid and non-hybrid origin with their host plant genotypes and environmental factors. [ABSTRACT FROM AUTHOR]

Background Interactions between aboveground and belowground terrestrial communities are often mediated by plants, with soil organisms interacting via the roots and aboveground organisms via the shoots and leaves. Many studies now show that plant genetics can drive changes in the structure of both above and belowground communities; however, the role of plant genetic variation in mediating aboveground-belowground interactions is still unclear. We used an earthworm-plant-aphid model system with two aphid species (Aphis fabae and Acyrthosiphon pisum) to test the effect of host-plant (Vicia faba) genetic variation on the indirect interaction between the belowground earthworms (Eisenia veneta) on the aboveground aphid populations. Results Our data shows that host-plant variety mediated an indirect ecological effect of earthworms on generalist black bean aphids (A. fabae), with earthworms increasing aphid growth rate in three plant varieties but decreasing it in another variety. We found no effect of earthworms on the second aphid species, the pea aphid (A. pisum), and no effect of competition between the aphid species. Plant biomass was increased when earthworms were present, and decreased when A. pisum was feeding on the plant (mediated by plant variety). Although A. fabae aphids were influenced by the plants and worms, they did not, in turn, alter plant biomass. Conclusions Previous work has shown inconsistent effects of earthworms on aphids, but we suggest these differences could be explained by plant genetic variation and variation among aphid species. This study demonstrates that the outcome of belowground-aboveground interactions can be mediated by genetic variation in the host-plant, but depends on the identity of the species involved. [ABSTRACT FROM AUTHOR]

1. Elevated CO2 can alter plant physiology and morphology, and these changes are expected to impact diet quality for insect herbivores. While the plastic responses of insect herbivores have been well studied, less is known about the propensity of insects to adapt to such changes. Genetic variation in insect responses to elevated CO2 and genetic interactions between insects and their host plants may exist and provide the necessary raw material for adaptation. 2. We used clonal lines of Rhopalosiphum padi (L.) aphids to examine genotype-specific responses to elevated CO2. We used the host plant Schedonorus arundinaceus (tall fescue; Schreb), which is capable of asexual reproduction, to investigate host plant genotype-specific effects and possible host plant-by-insect genotype interactions. The abundance and density of three R. padi genotypes on three tall fescue genotypes under three concentrations of CO2 (ambient, 700, and 1000 ppm) in a controlled greenhouse environment were examined. 3. Aphid abundance decreased in the 700 ppm CO2 concentration, but increased in the 1000 ppm concentration relative to ambient. The effect of CO2 on aphid density was dependent on host plant genotype; the density of aphids in high CO2 decreased for two plant genotypes but was unchanged in one. No interaction between aphid genotype and elevated CO2 was found, nor did we find significant genotype-by-genotype interactions. 4. This study suggests that the density of R. padi aphids feeding on tall fescue may decrease under elevated CO2 for some plant genotypes. The likely impact of genotype-specific responses on future changes in the genetic structure of plant and insect populations is discussed. [ABSTRACT FROM AUTHOR]

1. Elevated CO2 can alter plant physiology and morphology, and these changes are expected to impact diet quality for insect herbivores. While the plastic responses of insect herbivores have been well studied, less is known about the propensity of insects to adapt to such changes. Genetic variation in insect responses to elevated CO2 and genetic interactions between insects and their host plants may exist and provide the necessary raw material for adaptation. 2. We used clonal lines of Rhopalosiphum padi (L.) aphids to examine genotype-specific responses to elevated CO2. We used the host plant Schedonorus arundinaceus (tall fescue; Schreb), which is capable of asexual reproduction, to investigate host plant genotype-specific effects and possible host plant-by-insect genotype interactions. The abundance and density of three R. padi genotypes on three tall fescue genotypes under three concentrations of CO2 (ambient, 700, and 1000 ppm) in a controlled greenhouse environment were examined. 3. Aphid abundance decreased in the 700 ppm CO2 concentration, but increased in the 1000 ppm concentration relative to ambient. The effect of CO2 on aphid density was dependent on host plant genotype; the density of aphids in high CO2 decreased for two plant genotypes but was unchanged in one. No interaction between aphid genotype and elevated CO2 was found, nor did we find significant genotype-by-genotype interactions. 4. This study suggests that the density of R. padi aphids feeding on tall fescue may decrease under elevated CO2 for some plant genotypes. The likely impact of genotype-specific responses on future changes in the genetic structure of plant and insect populations is discussed. [ABSTRACT FROM AUTHOR]

Abstract: Accumulating evidence supports the feasibility of creating biotic soil environments that promote root health using selected plant genotypes. Five years of field experimentation conducted in the semiarid grasslands of North America revealed genotypic variation in the influence of chickpea on the composition of the soil microbial community and on the establishment of the subsequent crop. A 2-year experiment documented the effects of four chickpea cultivars on the arable soil microbiome using cultural methods, the cloning and sequencing of soil-extracted DNA, and fatty acid methyl ester profiling. Cultivar CDC Frontier was characterized by low bacterial biomass, whereas Amit and CDC Anna selected similarly structured bacterial communities but contrasting soil fungal communities. Amit and CDC Anna became colonized by arbuscular mycorrhizal (AM) fungi to the same extent, but the arable soil planted with CDC Anna hosted the highest level of culturable fungal diversity, whereas the soil planted with Amit hosted the lowest. The highest diversity of culturable fungi and the richness of AM fungal ribotypes (11) were also associated with CDC Anna. Amit was preferentially associated with the antagonist species Penicillium canescens. Higher durum wheat stand density was found after CDC Anna than after Amit, indicating that microbial diversity is an important feature of productive soils. The influence of chickpea genotype on the arable soil microbiome and on the establishment of the subsequent durum wheat crop was related to the soil water reserve at depths of 30–120 cm and was eliminated when the chickpea crops experienced drought. Genetic variation in the influence of chickpea on the soil microbiome suggests the possibility of selecting genotypes to engineer beneficial soil biotic environments. Inadequate levels of soil water could limit the success of this strategy, however, in rainfed cropping systems of the semiarid grasslands of North America. [Copyright &y& Elsevier]

Sorghum is used as bioenergy feedstock, animal feed, and food. Economical methods for disease prevention and control are valuable for producers. Fluorescent Pseudomonas spp. were isolated from sorghum roots and surrounding soil with the goal of finding isolates that significantly inhibited sorghum fungal pathogens. Fluorescent pseudomonads were collected from seedlings of sorghum cultivars RTx433 and Redlan and wheat cultivar Lewjain, grown in two soils. Lewjain is known to support growth of producers of the antibiotic, 2,4-diacetylphloroglucinol (2,4-DAPG). Isolates from all three plants were assessed for hydrogen cyanide (HCN) and extracellular protease production, and for a 2,4-DAPG gene, phlD. Both soil type and plant type affected HCN- and protease-production, but phlD was not affected. Subsets of phlD isolates were chosen to determine phlD genotypes and to conduct in vitro inhibition assays against sorghum pathogens. Most isolates from sorghum and wheat were genotype D, previously associated with superior root colonization. phlD sorghum isolates were co-cultured with five sorghum pathogens. One isolate from each sorghum line exhibited inhibition to all five pathogens but more Redlan isolates were inhibitory to the virulent pathogen, Fusarium thapsinum, than RTx433 isolates. Nearly all inhibitory isolates from either sorghum cultivar were from one soil type. This is consistent with what had been previously observed in field studies: that soil type played a significant role in determining characteristics of fluorescent Pseudomonas spp. isolated from roots or soil, but sorghum genotype also had a considerable effect. [ABSTRACT FROM AUTHOR]

A biological monitoring survey was carried out in central Uganda for two consecutive seasons to provide information on species composition and occurrence of thrips on tomato and pepper as influenced by farmers' management practices. A total of 50 farms for each crop participated in the study. Data was collected on cropping system, crop variety, type of pesticide used, pesticide spray regime, and on thrips populations. Results indicated that a total of six thrips species: Frankliniella occidentalis, Thrips tabaci, F. schultzei, Scirtothrips dorsalis, Ceratothrips ericae and Megalurothrips sjostedti infest tomato in the region. Pepper had the same thrips profile with the exception of F. schultzei. There was a distinct seasonal effect on thrips occurrence in the case of tomato. Higher thrips populations (61%) were recorded in the first season of the study as compared to the second. The majority of the thrips were recorded in the flowering stage of crop development for both crops, and 100% in the case of pepper. Generally, for both crops, plants in intercropped arrangements had higher thrips counts than the monocropped ones. Different tomato/pepper varieties sustained variable thrips populations. All the farmers applied pesticides to manage the complex of pests on the crops, albeit to variable extents. In this region, thrips populations were reduced when an increase in the number of pesticide applications in a given week was used. [ABSTRACT FROM AUTHOR]

. 1. Effects of the genotypic identity of a plant can extend beyond the individual phenotype to the community. Because plant material is moved around at an increasing rate, introductions of non-local plant genotypes that are difficult to distinguish from local ones are probably common. Even though such introductions can cause cryptic invasions, their effects on local communities remain largely unexplored. 2. Ammophila arenaria is transported and planted throughout the world for dune stabilisation. We used this grass to address the impact of the introduction of non-local genotypes on the diversity of the local invertebrate community. We installed plants from the local population and five introduced populations from regions throughout the natural range in a common environment and identified all naturally colonising aboveground invertebrates. 3. The diversity of the entire invertebrate community, as well as that of herbivores, decreased with increasing geographical distance of the plants' location of origin. Differences between plant populations in predator and detritivore diversity were less consistent with this pattern. Invertebrate species turnover was not related to genetic distance between populations. 4. Our study demonstrates that introduction of non-local genotypes of a resident plant species can negatively affect the invertebrate community. This confirms the idea that caution should be exerted when selecting plant material for restoration or sand stabilisation purposes. Hitherto, explanations for the invasiveness of A. arenaria in other continents have been sought in its release from belowground pathogens. Our observation of lower shoot herbivore diversity on non-local plants, however, may indicate a role for release from aboveground enemies. [ABSTRACT FROM AUTHOR]

Abstract: Plant growth-promoting rhizobacteria (PGPR) are found in association with a large range of host plants. Although the subject of plant host specificity has been well studied in parasitic and mutualistic interactions, the question of whether phytostimulating rhizobacteria efficiently interact only with a specific host remains poorly discussed. This review presents elements suggesting the existence of specificity in three-step establishment of associative symbiosis between phytostimulating rhizobacteria and plants: bacterial attraction by the host plant, bacterial colonization of roots, and functioning of associative symbiosis. [Copyright &y& Elsevier]

Abstract: Plants trigger various responses in the organisms living around them using a wide array of phytochemicals, which are components of their adaptation to a biological environment. The roots of five varieties of chickpea inoculated with Glomus intraradices were extracted, and extracts were fractionated, first based on solubility in methanol and further by HPLC. We found a relationship between chickpea genotype and root phytochemical composition. Several HPLC fractions repressed the germination of AM fungal spores in bioassays conducted in multi-well plates with extracts from the variety CDC Anna. This repression may be an expression of the control of the plant on the AM fungal symbionts. Glomus etunicatum and Gigaspora rosea spore germination responded differently to exposure to the HPLC fractions soluble in 25% methanol. A differential response of AM fungal species to plant phytochemicals could be involved in the so called “host preference” of AM fungi. Whereas extensin and other proteins were identified in a bioactive root extract fraction, other proteins undetected by LC–MS/MS analysis and non-peptidic compounds may be involved in AMF spore germination suppression. [Copyright &y& Elsevier]

Background and aims: Rice cultivars, in combination with diazotrophic bacteria, can obtain variable contributions from Biological Nitrogen Fixation (BNF). Plant genetic controls and the genotype of the bacterial strains might regulate in particular ways the plant responses during these associations. Some of this regulation is likely to occur during the first stages of bacterial infection and plant colonization, and some of the early plant responses might involve ethylene signaling, as previously reported for sugarcane. The aim of this work was to investigate whether rice early responses to inoculation with beneficial diazotrophic bacteria and the expression of ethylene receptors (ERs) by the host are dependent on plant and bacterial genotypes. Methods: Bacterial colonization, lateral root development and expression of ERs were measured in seedlings of two rice cultivars, IR42 and IAC4440, which, respectively, are known to have higher and lower BNF capabilities. Inoculation experiments were performed with two strains of bacteria: Azospirillum brasilense sp245 and Burkholderia kururiensis M130. Results: Cultivar IR42, which has a relatively high BNF capability, was more colonized by the bacteria early after inoculation in comparison with cv. IAC 4440, which has a lower BNF capability. However, although both cultivars showed a significant increase in lateral root numbers 10 days after inoculation with A. brasilense sp245, plants inoculated with B. kururiensis M130 did not. In addition, a differential ER expression pattern was observed between IR42 and IAC4440 in response to inoculation with the two strains. The expression of ERs was higher in the more BNF-effective cultivar IR42, than in the less BNF-effective cv. IAC4440, especially when cv. IR42 was inoculated with A. brasilense sp245. Moreover, plants associated with B. kururiensis M130 showed a different ER expression profile compared to those inoculated with A. brasilense sp245, with the latter exhibiting greater increases of ER mRNA levels three days after bacterial inoculation. Conclusions: We have shown that two rice genotypes contrasting in their BNF capability responded differentially to early inoculation with different strains of diazotrophic bacteria. The two rice genotypes were colonized with different bacterial numbers during their early association with two strains of diazotrophic bacteria, and the two strains had different effects on the promotion of lateral root development early after inoculation. They also triggered distinct ER expression patterns in the two rice cultivars. These data thus suggest that rice ethylene responses to beneficial diazotrophic bacteria are controlled by both plant and bacterial genotypes. [ABSTRACT FROM AUTHOR]

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Abstract: Frequency and distribution of symbiosis in nature depend both on the direct symbiont effect on the host fitness and on its efficiency to spread within host populations (transmission). For vertically transmitted Neotyphodium fungi, the attention has been centered on the endophyte effect on host grass plants but little is known about the controls of transmission. Environmental and genetic factors have been suggested as important controls of transmission efficiency. We studied the effect of these two factors on the transmission efficiency of the Neotyphodium endophyte in Lolium multiflorum plants. Plant genotype of a host population naturally endophyte-infected (95%) was manipulated by conducting controlled crosses with genetically distant plant populations. The resulting progeny was subjected to two types of factors, resource shortage and oxidative stress induced by an herbicide. Irrespective of plant genotype, high resource level increased seed yield per plant by 26-fold, spike-to-seed transmission by 12%, and plant-to-seed transmission by 10% (not significant). Although herbicide effects could be mediated indirectly by changes in plant density or directly by oxidative stress, neither plant fitness nor transmission efficiency was affected. An interesting pattern between transmission efficiency and seed yield per plant was revealed when plants (from both experiments) were plotted together. Low yielding plants, that is plants that grew under low resource level at high plant density, showed high transmission failures whereas high yielding plants, that is plants growing at low density with and without herbicide treatment, showed high transmission rates. Transmission failures may be a consequence of the endophyte cost for host plants growing under restrictive conditions, suggesting that lower transmission efficiency may partially explain previous evidence showing lower endophyte infection frequency for grasses under stressful conditions. Host plants could be penalizing the endophyte through a competition-like mechanism, instead of depressing their own fitness. [Copyright &y& Elsevier]

Sugarcane is an economically important culture in Brazil, being the world most important source of sugar and ethanol production. Brazilian sugarcane culture is able to obtain large and significant contributions of nitrogen from plant-associated Biological Nitrogen Fixation (BNF), reducing the use of nitrogen fertilizers and leading to an increase in energy balance of the culture. Different populations of endophytic N-fixing bacteria associated with sugarcane were identified. Besides BNF, these bacteria exhibit growth promoting traits by mechanisms involving nutrient solubilization, plant hormone production and pathogens antagonistic activity. BNF contribution efficiency to sugarcane is controlled by plant and bacteria genotypes as well as environmental conditions. Here, there will be reviewed the advances made in studies on molecular, cellular and physiological mechanisms by which sugarcane controls establishment and efficiency of endophytic association. Transcriptome profile analysis indentified several differentially expressed sugarcane genes during early stages of the association. Regulatory networks involved in various plant processes such as plant-microorganism recognition, defense, plant hormone signaling, plant growth and nitrogen metabolism were reported to be responsive to endophytic diazotrophic bacteria colonization. The data indicate that sugarcane actively participates in the association with these bacteria. Comprehension of how various sugarcane regulatory mechanisms are coordinated and connected to genotype and environmental signals, in order to control the establishment of a beneficial and endophytic type of association is still a big challenge. Nevertheless, the knowledge being accumulated may guide studies to improve plant association with endophytic diazotrophic bacteria and, possibly, to extend it to other crops. [ABSTRACT FROM AUTHOR]

We investigated the effect of vermicompost on the germination and early development of six different progenies of the maritime pine (Pinus pinaster Ait.). We compared the effects of incorporating solid vermicompost into the potting media to those of vermicompost water extract. The incorporation of vermicompost in the growing media of maritime pine increased germination by 16%, and particularly, addition of vermicompost water extract produced the best results. Plants germinated with vermicompost showed higher N content as compared to control plants, and this could have determined the faster maturation of the treated seedlings. Since the best effects on pine germination were observed after application of vermicompost water extract, other mechanisms, rather than the physical amelioration of the substrate, such as the presence of water soluble nutrients and organic compounds (i.e. humic acids and plant growth regulating substances) in the vermicompost, might be involved in the promotion of germination. We also report variation in the response of the different pine progenies to vermicompost application thereby confirming the necessity of taking into account genetic variability in order to study the potential of vermicompost and other biologically-active organic materials as a potting amendments. [ABSTRACT FROM AUTHOR]

The phyllosphere represents the habitat provided by the aboveground parts of plants, and on a global scale supports a large and complex microbial community. Microbial interactions in the phyllosphere can affect the fitness of plants in natural communities, the productivity of agricultural crops, and the safety of horticultural produce for human consumption. The structure of phyllosphere communities reflects immigration, survival and growth of microbial colonists, which is influenced by numerous environmental factors in addition to leaf physico-chemical properties. The recent use of culture-independent techniques has demonstrated considerable previously unrecognized diversity in phyllosphere bacterial communities. Furthermore, there is significant recent evidence that plant genotype can play a major role in determining the structure of phyllosphere microbial communities. The main aims of this review are: (i) to discuss the diversity of phyllosphere microbial populations; (ii) to consider the processes by which microbes colonize the phyllosphere; (iii) to address the leaf characteristics and environmental factors that determine the survival and growth of colonists; (iv) to discuss microbial adaptations that allow establishment in the phyllosphere habitat and (v) to evaluate evidence for plant genotypic control of phyllosphere communities. Finally, we suggest approaches and priority areas for future research on phyllosphere microbiology. [ABSTRACT FROM AUTHOR]

Plant species litter mixtures often result in nonadditive differences in ecosystem processes when compared to the average of their individual components. However, these studies are just beginning to be extended to the genotype level and to our knowledge have not incorporated the effects of herbivory or genotype-by-herbivore interactions. With a two-year field study, using genotypes that differed by as few as three restriction length polymorphism (RFLP) molecular markers, we found three major patterns when we mixed leaf litters from different genotypes both with and without previous herbivory. First, leaf litter genotype mixtures, regardless of herbivory, demonstrated nonadditive rates of decomposition and nutrient flux. Second, mixed genotype litter without herbivory decomposed faster than the same genotypes with herbivory. Third, in genotype mixtures, with and without herbivory, we found that net rates of immobilization of both nitrogen and phosphorus can differ from expected values (based on genotype means) by as much as 57%. These results show that mixing litter genotypes can alter rates of decay and nutrient flux and that the effects are reduced with herbivory. Nonadditive effects at the genotype level that we report here are nearly as large as what has been recorded for plant species mixtures and may have important, though under-appreciated, roles in ecosystems. These data further suggest that genetic diversity and genotype-by-herbivore interactions can affect fundamental ecosystem processes such as litter decomposition and nutrient flux. [ABSTRACT FROM AUTHOR]

The New Zealand native plant mānuka (Leptospermum scoparium) is representative of the country's North and South Islands flora. This species is essential to the growing community of honey producers due to its honey's antimicrobial and antioxidant properties, attributed to the presence of methylglyoxal (MGO), derived from dihydroxyacetone (DHA) in the nectar. Several clones and cultivars have been selected to optimize DHA production. Still, nothing is known about the volatile emissions of these artificially selected plants. Volatile organic compounds (VOCs) can influence their interactions with the environment, such as pollinator foraging decisions, which may subsequently affect the plants' products. This study explored the aboveground volatile organic compounds (VOCs) emitted by eight different mānuka genotypes (six clones and two wild cultivars) under field conditions during the spring season. Volatiles were collected using the "push–pull" headspace sampling technique and analyzed using gas chromatography-mass spectrometry (GC-MS). Our results show that mānuka plants emit large amounts of terpenoids, with sesquiterpenes and monoterpenoids being the most abundant groups of compounds. The results also show variation in the total green leaf volatiles, total sesquiterpenes, and specific compounds between genotypes and suggest that artificially selected plants have a significant variation in their chemical profiles. The potential impacts of these results on the plant's defence, pollinator attraction and bee products are discussed. [ABSTRACT FROM AUTHOR]

Agricultural food products with high nutritional value should always be preferred over food products with low nutritional value. Efforts are being made to increase nutritional value of food by incorporating dietary supplements to the food products. The same is more desirous if the nutritional value of food is increased under natural environmental conditions especially in agricultural farms. Fragmented researches have demonstrated possibilities in achieving the same. The rhizosphere is vital in this regard for not only health and nutritional status of plants but also for the microorganisms colonizing the rhizosphere. Remarkably robust composition of plant microbiome with respect to other soil environments clearly suggests the role of a plant host in discriminating its colonizers (Zancarini et al., 2012). A large number of biotic and abiotic factors are believed to manipulate the microbial communities in the rhizosphere. However, plant genotype has proven to be the key in giving the final shape of the rhizosphere microbiome (Berendsen et al., 2012; Marques et al., 2014). [ABSTRACT FROM AUTHOR]