Anti-inflammatory activity of endophytic bacterial isolates from Emilia sonchifolia (Linn.) DC.

ETHNOPHARMACOLOGICAL RELEVANCE: In the traditional medicine system, plants have been utilized as a rich source of anti-microbial, anti-inflammatory, anti-cancer, anti-viral and anti-oxidant compounds. The biological properties of plant-based drugs depend on their interaction with endophytes which persist as an important provider of bioactive secondary metabolites. Bacterial endophytes secrete anti-inflammatory molecules whose activity can be the base for the anti-inflammatory property of the plant. AIM OF THE STUDY: During the screening of endophytes from Emilia sonchifolia, we isolated six different bacteria whose potential as the sources of anti-inflamamtory compounds have been aimed at in this study. MATERIALS AND METHODS: Anti-inflammatory activity of the ethyl acetate extract of endophytes was studied by both in vitro and in vivo analyses. In vitro study was done using protein denaturation, COX, LOX, iNOS, myeloperoxidase and nitric oxide assays and in vivo analysis was carried out by carrageenan-induced and formalin-induced paw oedema tests. The expression level of anti-inflammatory genes such as COX-2 and NfKb was confirmed by real time PCR. RESULTS: We confirmed anti-inflammatory activity of the ethyl acetate extract of bacterial endophytes of E sonchifolia by both in vitro and in vivo experiments. Carrageenan- and formalin-induced inflammations in mice were effectively reduced by the administration of the bacterial extract. Among the isolates, strain ES1effectively reduced inflammation. Gene expression studies confirmed reduction in the expression of COX-2 and NfKb genes in the presence of ES1 extract. CONCLUSION: The present investigation demonstrated the anti-inflammatory property of the isolated bacterial endophyte ES1 (Bacillus subtilis strain-MG 692780) and thus justifies the possible role of endophytes in contributing anti-inflammatory property to E sonchifolia which is ethno-botanically important as a source of anti-inflammatory drug.

[Antibacterial secondary metabolites of Clonostachys rosea, an endophytic fungus from Blumea balsamifera (L.) DC.]

Endophytic fungus is an important treasure trove for discovery of structurally unusual and biologically diverse compounds. A phytochemical investigation on a fungus Clonostachys rosea inhabits inner tissue of Blumea balsamifera (L.) DC. was initiatedrecently in our lab. Six pure compounds were isolated through silica gel column chromatography, sephadex LH-20, and semi-preparative HPLC techniques, with bio-guided strategy. Their structures were characterized as verticillin A (1), (S)-(+)-fusarinolic acid (2), 8-hydroxyfusaric acid (3), cerebroside C (4), 3-Maleimide-5-oxime (5), and bionectriol A (6) by analyses of NMR and MS data. All compounds were tested in vitro antibacterial activities against four strains of bacteria, Escherichia coli, Staphylococcus aureus, Bacillus subtilis and Pseudomonas aeruginosa, and results revealed that 1, 4 and 6 display notableinhibition againstthree bacteria, with MIC values ranging from 2 to 16 µg/mL. Our findings provide references for mining novel antibiotics from endophytes originated from Li Minority medicinal plant B. balsamifera (L.) DC.

Cercospora beticola: The intoxicating lifestyle of the leaf spot pathogen of sugar beet.

Cercospora leaf spot, caused by the fungal pathogen Cercospora beticola, is the most destructive foliar disease of sugar beet worldwide. This review discusses C. beticola genetics, genomics, and biology and summarizes our current understanding of the molecular interactions that occur between C. beticola and its sugar beet host. We highlight the known virulence arsenal of C. beticola as well as its ability to overcome currently used disease management strategies. Finally, we discuss future prospects for the study and management of C. beticola infections in the context of newly employed molecular tools to uncover additional information regarding the biology of this pathogen. TAXONOMY: Cercospora beticola Sacc.; Kingdom Fungi, Phylum Ascomycota, Class Dothideomycetes, Order Capnodiales, Family Mycosphaerellaceae, Genus Cercospora. HOST RANGE: Well-known pathogen of sugar beet (Beta vulgaris subsp. vulgaris) and most species of the Beta genus. Reported as pathogenic on other members of the Chenopodiaceae (e.g., lamb's quarters, spinach) as well as members of the Acanthaceae (e.g., bear's breeches), Apiaceae (e.g., Apium), Asteraceae (e.g., chrysanthemum, lettuce, safflower), Brassicaceae (e.g., wild mustard), Malvaceae (e.g., Malva), Plumbaginaceae (e.g., Limonium), and Polygonaceae (e.g., broad-leaved dock) families. DISEASE SYMPTOMS: Leaves infected with C. beticola exhibit circular lesions that are coloured tan to grey in the centre and are often delimited by tan-brown to reddish-purple rings. As disease progresses, spots can coalesce to form larger necrotic areas, causing severely infected leaves to wither and die. At the centre of these spots are black spore-bearing structures (pseudostromata). Older leaves often show symptoms first and younger leaves become infected as the disease progresses. MANAGEMENT: Application of a mixture of fungicides with different modes of action is currently performed although elevated resistance has been documented in most employed fungicide classes. Breeding for high-yielding cultivars with improved host resistance is an ongoing effort and prudent cultural practices, such as crop rotation, weed host management, and cultivation to reduce infested residue levels, are widely used to manage disease. USEFUL WEBSITE: https://www.ncbi.nlm.nih.gov/genome/11237?genome_assembly_id=352037.

Biotechnological applications of the medicinal plant Pseudobrickellia brasiliensis and its isolated endophytic bacteria.

AIM: This study aimed to isolate Pseudobrickellia brasiliensis endophytic bacteria and evaluate the production of hydrolytic enzymes and antibiotics by these bacterial strains. The study also measured the antibacterial activity of P. brasiliensis. METHODS AND RESULTS: Thirteen endophytic bacteria strains were isolated from stem and leaf fragments of P. brasiliensis. Extracellular enzyme production by the isolated endophytic bacteria was evaluated in an agar plate-based assay. The highest protease production was achieved by Bacillus subtilis P4 in alkaline medium. Antimicrobial activity of endophytic bacteria and P. brasiliensis extracts was investigated using microbroth dilution. An MIC value of 1000 µg ml-1 against Pseudomonas aeruginosa was found for B. subtilis P3, B. subtilis P5, Pseudomonas sp. P8 and Pseudomonas sp. P12. Leaf extract of P. brasiliensis showed the highest antibacterial activity against P. aeruginosa, with an MIC value of 0·781 mg ml-1 . CONCLUSIONS: Pseudobrickellia brasiliensis is a source of bacterial endophytes, which can produce antibacterial compounds and enzymes. This work also demonstrated the antibacterial potential of P. brasiliensis. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first study that revealed the antibacterial activity of P. brasiliensis and bioactive metabolite production by P. brasiliensis endophytic bacteria.

Enhancement the Cellulase Activity Induced by Endophytic Bacteria Using Calcium Nanoparticles.

The huge applications of cellulosic and lignocellulosic materials in the various fields of life lead to accumulation of its wastes that became one of the major sources of environmental pollution. In this study, a Gram-positive cellulose-decomposing endophytic bacterium (Chi-04) was isolated from medicinal plant Chiliadenus montanus which inhabitant Saint Catherine (Sinai) region in Egypt. The bacterial strain was identified based on the sequence analysis of 16S rRNA genes as Lysinibacillus xylanilyticus. This isolate was capable of degrading 58% of cellulosic filter paper (100 g/l) within 15 days of incubation. The soluble and reduced sugars were spectrophotometrically determined as cellulose decomposition metabolites. The bacterial isolate exhibited an obvious activity toward cellulase enzyme production. The maximum cellulase activity (0.18 U/min) was detected after 12 days of incubation while the maximum release of soluble sugars (11.85 mg/ml) was detected after 15 days of incubation. CaCl2 nanoparticles (100 nm) were chemically prepared to enhance the activity of the enzyme. The optimum concentration of CaCl2 nanoparticles that showed the highest activity of cellulase (0.3 mg/ml reduced sugar) was 0.6%. The bacterial isolates showed potential convert of cellulose into reducing sugars which could be used in several applications.

Gynurincola endophyticus gen. nov., sp. nov., a novel bacterium of the family Chitinophagaceae.

A Gram-stain-negative, rod-shaped (0.2-0.4 µm×1.2-1.7 µm), endophytic bacterium, designated HBUM179779T, was isolated from the stem of a medicinal plant,Gynura bicolor, collected from Pixian county in Sichuan province, China. The strain did not produce endospores and its cells could secrete mucus. The predominant menaquinone was MK-7. The polar lipids were phosphatidylethanolamine, phosphatidylinositolmannosides, two unknown aminolipids, two unknown glycolipids and an unknown phospholipid. Branched fatty acids (iso-) and hydroxy fatty acids were the main fatty acids, which mainly included iso-C15 : 0, iso-C15 : 1 G and iso-C17 : 0 3-OH. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain HBUM179779T fell within the family Chitinophagaceae, and its closest neighbour was Pseudoflavitalea rhizosphaerae T16R-265T (94.46 %). However, strain HBUM179779T did not make a coherent clade with members of the recognized organisms. The average nucleotide identity value between strain HBUM179779T and Pseudoflavitalea rhizosphaerae T16R-265T was 67.1 %. On the basis of the phylogenetic and phenotypic characteristics of this bacterium, a novel genus and species, Gynurincola endophyticus gen. nov., sp. nov., is proposed. The type strain is HBUM179779T (=CGMCC 1.15525T=NBRC 112424T).

Statistical optimization of process parameters for inulinase production from Tithonia weed by Arthrobacter mysorens strain no.1.

Tithonia rotundifolia is an easily available and abundant inulin rich weed reported to be competitive and allelopathic. This weed inulin is hydrolyzed by inulinase into fructose. Response surface methodology was employed to optimize culture conditions for the inulinase production from Arthrobacter mysorens strain no.1 isolated from rhizospheric area of Tithonia weed. Initially, Plackett- Burman design was used for screening 11 nutritional parameters for inulinase production including inulin containing weeds as cost effective substrate. The experiment shows that amongst the 11 parameters studied, K2HPO4, Inulin, Agave sisalana extract and Tithonia rotundifolia were the most significant variables for inulinase production. Quantitative effects of these 4 factors were further investigated using Box Behnken design. The medium having 0.27% K2HPO4, 2.54% Inulin, 6.57% Agave sisalana extract and 7.27% Tithonia rotundifolia extract were found to be optimum for maximum inulinase production. The optimization strategies used showed 2.12 fold increase in inulinase yield (1669.45 EU/ml) compared to non-optimized medium (787 EU/ml). Fructose produced by the action of inulinase was further confirmed by spectrophotometer, osazone, HPTLC and FTIR methods. Thus Tithonia rotundifolia can be used as an eco-friendly, economically feasible and promising alternative substrate for commercial inulinase production yielding fructose from Arthrobacter mysorens strain no.1.

Molecular inter-kingdom interactions of endophytes isolated from Lychnophora ericoides.

The importance of microbial natural products has been widely demonstrated in the search for new antibiotics. However, the functional role of microbial metabolites in nature remains to be deciphered. Several natural products are known to mediate microbial interactions through metabolic exchange. One approach to investigate metabolic exchange in the laboratory is through microbial interactions. Here, we describe the chemical study of selected endophytes isolated from the Brazilian medicinal plant Lychnophora ericoides by pairwise inter-kingdom interactions in order to correlate the impact of co-cultivation to their metabolic profiles. Combining mass spectrometry tools and NMR analyses, a total of 29 compounds were identified. These compounds are members of polyene macrocycles, pyrroloindole alkaloids, angucyclines, and leupeptins chemical families. Two of the identified compounds correspond to a new fungal metabolite (29) and a new actinobacterial angucycline-derivative (23). Our results revealed a substantial arsenal of small molecules induced by microbial interactions, as we begin to unravel the complexity of microbial interactions associated with endophytic systems.

Molecular Phylogeny, Diversity, and Bioprospecting of Endophytic Fungi Associated with wild Ethnomedicinal North American Plant Echinacea purpurea (Asteraceae).

The endophytic fungal community associated with the ethnomedicinal plant Echinacea purpurea was investigated as well as its potential for providing antifungal compounds against plant pathogenic fungi. A total of 233 endophytic fungal isolates were obtained and classified into 42 different taxa of 16 genera, of which Alternaria alternata, Colletotrichum dematium, and Stagonosporopsis sp. 2 are the most frequent colonizers. The extracts of 29 endophytic fungi displayed activities against important phytopathogenic fungi. Eight antifungal extracts were selected for chemical analysis. Forty fatty acids were identified by gas chromatography-flame-ionization detection (GC-FID) analysis. The compounds (-)-5-methylmellein and (-)-(3R)-8-hydroxy-6-methoxy-3,5-dimethyl-3,4-dihydroisocoumarin were isolated from Biscogniauxia mediterraneaEPU38CA crude extract. (-)-5-Methylmellein showed weak activity against Phomopsis obscurans, P. viticola, and Fusarium oxysporum, and caused growth stimulation of C. fragariae, C. acutatum, C. gloeosporioides, and Botrytis cinerea. (-)-(3R)-8-Hydroxy-6-methoxy-3,5-dimethyl-3,4-dihydroisocoumarin appeared slightly more active in the microtiter environment than 5-methylmellein. Our results indicate that E. purpurea lives symbiotically with different endophytic fungi, which are able to produce bioactive fatty acids and aromatic compounds active against important phytopathogenic fungi. The detection of the different fatty acids and aromatic compounds produced by the endophytic community associated with wild E. purpurea suggests that it may have intrinsic mutualistic resistance against phytopathogen attacks in its natural environment.

Endophytic Actinobacteria from the Brazilian Medicinal Plant Lychnophora ericoides Mart. and the Biological Potential of Their Secondary Metabolites.

Endophytic actinobacteria from the Brazilian medicinal plant Lychnophora ericoides were isolated for the first time, and the biological potential of their secondary metabolites was evaluated. A phylogenic analysis of isolated actinobacteria was accomplished with 16S rRNA gene sequencing, and the predominance of the genus Streptomyces was observed. All strains were cultured on solid rice medium, and ethanol extracts were evaluated with antimicrobial and cytotoxic assays against cancer cell lines. As a result, 92% of the extracts showed a high or moderate activity against at least one pathogenic microbial strain or cancer cell line. Based on the biological and chemical analyses of crude extracts, three endophytic strains were selected for further investigation of their chemical profiles. Sixteen compounds were isolated, and 3-hydroxy-4-methoxybenzamide (9) and 2,3-dihydro-2,2-dimethyl-4(1H)-quinazolinone (15) are reported as natural products for the first time in this study. The biological activity of the pure compounds was also assessed. Compound 15 displayed potent cytotoxic activity against all four tested cancer cell lines. Nocardamine (2) was only moderately active against two cancer cell lines but showed strong activity against Trypanosoma cruzi. Our results show that endophytic actinobacteria from L. ericoides are a promising source of bioactive compounds.

Yeast and mould dynamics in Caciofiore della Sibilla cheese coagulated with an aqueous extract of Carlina acanthifolia All.

Caciofiore della Sibilla is a speciality ewes' milk cheese traditionally manufactured in a foothill area of the Marche region (Central Italy) with a crude extract of fresh young leaves of Carlina acanthifolia All. subsp. acanthifolia as a coagulating agent. The fungal dynamics and diversity of this speciality cheese were investigated throughout the manufacturing and 20-day ripening process, using a combined PCR-DGGE approach. The fungal biota of a control ewes' milk cheese, manufactured with the same batch of milk coagulated with a commercial animal rennet, was also monitored by PCR-DGGE, in order to investigate the contribution of the peculiar vegetable coagulant to the fungal diversity and dynamics of the cheese. Based on the overall results collected, the raw milk and the dairy environment represented the main sources of fungal contamination, with a marginal or null contribution of thistle rennet to the fungal diversity and dynamics of Caciofiore della Sibilla cheese. Copyright © 2016 John Wiley & Sons, Ltd.

Biological activities of ophiobolin K and 6-epi-ophiobolin K produced by the endophytic fungus Aspergillus calidoustus.

Endophytic fungi represent ubiquitous microbial organisms able to live in the tissues of different plants around the world and represent a prolific source of bioactive metabolites. In the present study, the endophytic fungus Aspergillus calidoustus was isolated from the medicinal plant Acanthospermum australe (Asteraceae), and identified using molecular, physiological and morphological methods. A methylene chloride crude extract of A. calidoustus has been produced and subjected to antifungal bioassay-directed fractionation which resulted in the isolation of the two bioactive compounds: ophiobolin K and 6-epi-ophiobolin K. These pure compounds displayed antifungal activity against fungal plant pathogens, protozoal activity against Trypanosoma cruzi, and cytotoxic activity against human tumoral cell lines. The results show that A. calidoustus was able to produce the antifungal and cytotoxic metabolites ophiobolin K and 6-epi-ophiobolin K, which may help the fungus to colonise and occupy the substratum as well as survive in natural environments.

Stability of a functional beverage composed by tropical fruits and yacon (Smallanthus sonchiyo- lius) under refrigerated storage.

The development of beverages with functional properties must consider the preservation of the bioactive or functional properties during storage. For this reason, the aim of this study was to evaluate the stability of a functional beverage of tropical fruits and yacon, stored under refrigeration. The beverage, composed by 50% of yacon and 50% of a blended tropical fruits (camu-camu, acerola, cashew-apple, yellow mombin, acai and pineapple), was pasteurized (90 seconds/ 85°C) and stored under refrigeration (5°C). After processing and on 45 day intervals until the end of storage, were assayed the bioactive compounds (ascorbic acid and total extractable polyphenols), antioxidant activity, total soluble solids, titratable total acidity, pH, color (L*, a* and b*), total sugar content, sucrose, glucose and fructose, and nd the physical and chemical analyzes were limited by decreased total antioxidant activity and their bioactive components. The beverage showed relative physical and chemical quality during storage period, and in the 225 days of storage, the total extractable polyphenols and total antioxidant activity showed a significantly decline, and thus , these parameters were evaluated only until this period. However, the main limitation for the beverage storage was due to. sensory acceptability and microbiological safety, which although in accordance with Brazilian legislation, limited storage period for 90 days.

Endophytic Bacteria Associated with Hieracium piloselloides: Their Potential for Hydrocarbon-Utilizing and Plant Growth-Promotion.

The aim of this study was to assess the potential of 18 crude-oil-degrading endophytic bacteria for removal of hydrocarbons and promotion of plant growth. Strains were isolated from Hieracium piloselloides (tall hawkweed), which grows in soil heavily polluted with petroleum hydrocarbons. Bacteria from the genus Pseudomonas were abundant among the isolates. The potential for hydrocarbon degradation was evaluated by polymerase chain reaction (PCR) analyses of the genes alkB, alkH, C23O, P450, and pah. It was found that 88.89% of the endophytic bacteria contained gene-encoding polycyclic aromatic hydrocarbon (PAH) initial dioxygenase, 61% possessed the 2,3-catechol dioxygenase gene, and 39% of strains that were tested had the cytochrome P-450 hydroxylase gene. All isolates were capable of producing indole-3-acetic acid (1.8-76.4 µg/ml). Only 17% of them were able to produce siderophores, excrete cellulase, and solubilize phosphate. Hydrogen cyanide synthesis occurred in 33% of endophytic bacteria. The 1-aminocyclopropane-1-carboxylate deaminase activity in isolates that were screened was in the range of 2.6 to 74.1 µmol α-ketobutyrate/mg/h. This feature of the bacteria indicated that isolates may enhance the phytoremediation process. Data suggest that crude-oil-degrading endophytic bacteria possess potential to be promising candidates for enhancement of phytoremediation of hydrocarbon-contaminated soil. Further evaluation of these bacteria is needed in order to assess the role played in the degradation of petroleum hydrocarbons.

Lignan formation in hairy root cultures of Edelweiss (Leontopodium nivale ssp. alpinum (Cass.) Greuter).

A hairy root line of Edelweiss (Leontopodium nivale ssp. alpinum (Cass.) Greuter) was obtained upon transformation with Agrobacterium rhizogenes strain ATCC15834. Elicitation of this line with silver nitrate, sucrose, methyl jasmonate and yeast extract at various concentrations in most cases resulted in a stimulation of lignan biosynthesis. Through elicitation with 6% sucrose the roots accumulated the pharmacologically active lignans leoligin and 5-methoxy-leoligin at levels of 0.0678% and 0.0372%, respectively, without significant growth inhibition. These lignan levels were comparable to those found in intact roots of cultivated Edelweiss. The biotechnological production of leoligin could be an attractive option for the continuous, field culture-independent production of the valuable secondary metabolites leoligin and 5-methoxy-leoligin.

Leucanthemum vulgare lam. germination, growth and mycorrhizal symbiosis under crude oil contamination.

Oil contamination of soil limits plants' access to water and nutrients. Leucanthemum vulgare colonized by mycorrhizae could provide an effective tool in remedying oil contamination. Seeds of L. vulgare were planted in pots containing soil mixed with petroleum at 0, 2.5, 5, 7.5, and 10% w/w and propagules of mycorrhizal fungi. Plants were grown under ambient conditions for 16 weeks. Seed germination data were collected weekly for three weeks. Mycorrhizal percentage, spore counts, length and weight of roots and shoots were determined after harvesting. Results showed significant differences in seed germination rates between oil-treated, mycorrhizal and non-mycorrhizal plants. The overall germination rate was greater at 7.5% w/w crude oil contamination (p = 0.05) in mycorrhizal and non-mycorrhizal pots with significant differences between their respective Root:Shoot ratios (both length and weight). Results of this research showed L. vulgare could be germinated and grown in crude oil contaminated soils and could be used to augment plant establishment as part of phytoremediation practices.

Investigating the potential of under-utilised plants from the Asteraceae family as a source of natural antimicrobial and antioxidant extracts.

Antimicrobial properties of ethanol and water extracts from eight Asteraceae species were investigated against three Gram positive (Staphylococcus aureus, MRSA and Bacillus cereus) and two Gram negative (Escherichia coli and Salmonella typhimurium) bacterial strains. Ethanol extracts from Centaurea scabiosa, Arctium minus, Taraxacum officinale, Centaurea nigra and Cirsium palustre demonstrated antimicrobial activity against strains of S. aureus, MRSA and B. cereus (MIC=187.5-365µg/ml). Ethanol extracts also had higher antioxidant activities and phenolic content demonstrating a link between these compounds and the bioactivity of these extracts. Further investigation into the phenolic content of ethanol extracts using UPLC-MS/MS lead to the identification and quantification of numerous phenolic compounds in all species including; 18 from Cirsium arvense, 16 from Cirsium vulgare, 19 from C. palustre, 15 from C. nigra, 17 from C. scabiosa, 14 from Sonchus asper, 17 from A. minus and 11 from T. officinale.

Generic and functional diversity in endophytic actinomycetes from wild Compositae plant species at South Sinai - Egypt.

The diversity of culturable endophytic actinomycetes associated with wild Compositae plants is scantily explored. In this study, one hundred and thirty one endophytic actinobacteria were isolated from ten Compositae plant species collected from South Sinai in Egypt. Microscopic and chemotaxonomic investigation of the isolates indicated fourteen genera. Rare genera, such as Microtetraspora, and Intrasporangium, which have never been previously reported to be endophytic, were identified. Each plant species accommodated between three to eight genera of actinobacteria and unidentified strains were recovered from seven plant species. The generic diversity analysis of endophytic assemblages grouped the plant species into three main clusters, representing high, moderate and low endophytic diversity. The endophytes showed high functional diversity, based on forty four catabolic and plant growth promotion traits; providing some evidence that such traits could represent key criteria for successful residence of endophytes in the endosphere. Stress-tolerance traits were more predictive measure of functional diversity differences between the endophyte assemblages (Shannon's index, p = 0.01). The results indicate a potential prominent role of endophytes for their hosts and emphasize the potency of plant endosphere as a habitat for actinobacteria with promising future applications.

Impact of weed control on arbuscular mycorrhizal fungi in a tropical agroecosystem: a long-term experiment.

Cover crop species represent an affordable and effective weed control method in agroecosystems; nonetheless, the effect of its use on arbuscular mycorrhizal fungi (AMF) has been scantily studied. The goal of this study was to determine root colonization levels and AMF species richness in the rhizosphere of maize plants and weed species growing under different cover crop and weed control regimes in a long-term experiment. The treatment levels used were (1) cover of Mucuna deeringian (Muc), (2) "mulch" of Leucaena leucocephala (Leu), (3) "mulch" of Lysiloma latisiliquum (Lys), (4) herbicide (Her), (5) manual weeding (CD), (6) no weeding (SD), and (7) no maize and no weeding (B). A total of 18 species of AMF belonging to eight genera (Acaulospora, Ambispora, Claroideoglomus, Funneliformis, Glomus, Rhizophagus, Sclerocystis, and Scutellospora) were identified from trap cultures. Muc and Lys treatments had a positive impact on AMF species richness (11 and seven species, respectively), while Leu and B treatments on the other hand gave the lowest richness values (six species each). AMF colonization levels in roots of maize and weeds differed significantly between treatment levels. Overall, the use of cover crop species had a positive impact on AMF species richness as well as on the percentage of root colonized by AMF. These findings have important implications for the management of traditional agroecosystems and show that the use of cover crop species for weed control can result in a more diverse AMF community which should potentially increase crop production in the long run.

Polyketide derivatives active against Botrytis cinerea in Gerbera hybrida.

A previously isolated cDNA molecule from Gerbera hybrida (Asteraceae) codes for a new chalcone synthase-like polyketide synthase, 2-pyrone synthase (2PS). 2PS is able to synthesise 4-hydroxy-6-methyl-2-pyrone (triacetolactone), a putative precursor for gerberin and parasorboside, two abundant glucosides in gerbera. In this study, we show that gerbera plants transformed with the gene for 2PS in an antisense orientation and unable to synthesise gerberin and parasorboside are susceptible to Botrytis cinerea infection. In addition to the preformed glucosides, the transgenic plants also lack several compounds that are induced in control plants when infected with the mould. Some of these induced substances are effective in inhibiting fungal growth both in vitro and in vivo. Two of the phytoalexins were identified as the aglycones of gerberin and trans-parasorboside. The third phytoalexin is a rare coumarin, 4-hydroxy-5-methylcoumarin; however, it is typical of many plants of the sunflower family Asteraceae. The coumarin cannot be structurally derived from either gerberin or parasorboside, but may be derived from a related polyketide intermediate.