Andre Freire Cruz

Phytochemicals to suppress Fusarium head blight in wheat–chickpea rotation

Fusarium diseases cause major economic losses in wheat-based crop rotations. Volatile organic compounds (VOC) in wheat and rotation crops, such as chickpea, may negatively impact pathogenic Fusarium. Using the headspace GC-MS method, 16 VOC were found in greenhouse-grown wheat leaves: dimethylamine, 2-methyl-1-propanol, octanoic acid-ethyl ester, acetic acid, 2-ethyl-1-hexanol, nonanoic acid-ethyl ester, nonanol, N-ethyl-benzenamine, naphthalene, butylated hydroxytoluene, dimethoxy methane, phenol, 3-methyl-phenol, 3,4-dimethoxy-phenol, 2,4-bis (1,1-dimethyethyl)-phenol, and 1,4,7,10,13,16-hexaoxacyclooctadecane; and 10 VOC in field-grown chickpea leaves: ethanol, 1-penten-3-ol, 1-hexanol, cis-3-hexen-1-ol, trans-2-hexen-1-ol, trans-2-hexenal, 3-methyl-1-butanol, 3-hydroxy-2-butanone, 3-methyl-benzaldehyde and naphthalene. Also found was 1-penten-3-ol in chickpea roots and in the root nodules of two of the three cultivars tested. Chickpea VOC production pattern was related (P=0.023) to Ascochyta blight severity, suggesting that 1-penten-3-ol and cis-3-hexen-1-ol were induced by Ascochyta rabiei. Bioassays conducted in Petri plates established that chickpea-produced VOC used in isolation were generally more potent against Fusarium graminearum and Fusarium avenaceum than wheat-produced VOC, except for 2-ethyl-1-hexanol, which was rare in wheat and toxic to both Fusarium and tetraploid wheat. Whereas exposure to 1-penten-3-ol and 2-methyl-1-propanol could suppress radial growth by over 50% and octanoic acid-ethyl ester, nonanol, and nonanoic acid-ethyl ester had only weak effects, F. graminearum and F. avenaceum growth was completely inhibited by exposure to trans-2-hexenal, trans-2-hexen-1-ol, cis-3-hexen-1-ol, and 1-hexanol. Among these VOC, trans-2-hexenal and 1-hexanol protected wheat seedlings against F. avenaceum and F. graminearum, respectively, in a controlled condition experiment. Genetic variation in the production of 2-ethyl-1-hexanol, a potent VOC produced in low amount by wheat, suggests the possibility of selecting Fusarium resistance in wheat on the basis of leaf VOC concentration. Results also suggests that the level of Fusarium inoculum in chickpea-wheat rotation systems may be reduced by growing chickpea genotypes with high root and shoot levels of trans-2-hexen-1-ol and 1-hexanol.

Arbuscular mycorrhizal fungal spores host bacteria that affect nutrient biodynamics and biocontrol of soil-borne plant pathogens.

Summary The aim of this research was to isolate and characterize bacteria from spores of arbuscular mycorrhizal fungi (AMF). We designated these bacteria ‘probable endobacteria’ (PE). Three bacterial strains were isolated from approximately 500 spores of Gigaspora margarita (Becker and Hall) using a hypodermic needle (diameter, 200 &mgr;m). The bacteria were identified by morphological methods and on the basis of ribosomal gene sequences as Bacillus sp. (KTCIGM01), Bacillus thuringiensis (KTCIGM02), and Paenibacillus rhizospherae (KTCIGM03). We evaluated the effect of these probable endobacteria on antagonistic activity to the soil‐borne plant pathogens (SBPPs) Fusarium oxysporum f. sp. lactucae MAFF 744088, Rosellinia necatrix, Rhizoctonia solani MAFF 237426, and Pythium ultimum NBRC 100123. We also tested whether these probable endobacteria affected phosphorus solubilization, ethylene production, nitrogenase activity (NA), and stimulation of AMF hyphal growth. In addition, fresh samples of spores and hyphae were photographed using an in situ scanning electron microscope (SEM) (Quanta 250FEG; FEI Co., Japan). Bacterial aggregates (BAs), structures similar to biofilms, could be detected on the surface of hyphae and spores. We demonstrate that using extraction with an ultrathin needle, it is possible to isolate AMF‐associated bacterial species that are likely derived from inside the fungal spores.

Isolation and analysis of bacteria associated with spores of Gigaspora margarita

Aims:  The aim of this work was to observe bacteria associated with the spores of Gigaspora margarita, an arbuscular mycorrhizal fungus (AMF).

Network establishment of arbuscular mycorrhizal hyphae in the rhizospheres between citrus rootstocks and Paspalum notatum or Vulpia myuros grown in sand substrate

A greenhouse experiment was conducted to examine the favorable effects of sod culture system with bahiagrass (Paspalum notatum Flügge.) and Vulpia myuros (L.) C. C. Gmel. intercropped with citrus trees on the establishment of the network of arbuscular mycorrhizal (AM) fungus hyphae in their rhizospheres. Special acrylic root boxes with three compartments were used for the experiment. Four types of citrus rootstock seedlings, trifoliate orange (Poncirus trifoliata Raf.), sour orange (Citrus aurantium L.), rough lemon (Citrus jambhiri Lush.), and Citrus natsudaidai Hayata, were separately transplanted into one outer compartment in each box, and the seedlings of bahiagrass and V.myuros were separately transplanted into the other outer compartment. An AM fungus, Gigaspora margarita Becker and Hall, was inoculated in the center compartment of each box. Some boxes with both outer compartments without plants and with some plants in only one outer compartment were also prepared. The box with bare × bare had very low density of AM hyphae. There were a few hyphae in bare compartments in the boxes of trifoliate orange × bare, sour orange × bare, rough lemon × bare, and C. natsudaidai × bare. The density of hyphae in the compartments with citrus seedlings and grasses, however, was significantly higher than in every bare compartment, and the hyphae in the compartments with plants penetrated deeply into the sand. In particular, the density in the compartments of citrus seedlings increased when bahiagrass or V. myuros was transplanted as a neighboring plant. The percentage of AM fungus colonization in every plant root was high. New spore formation was observed in compartments with plants, whereas there were few spores in every bare compartment. In particular, the spore formation in bahiagrass compartments was superior to that in other compartments with plants. Our results suggest that the network system by AM hyphae is easily discernible in the rhizospheres between citrus rootstocks and bahiagrass or V. myuros, but bare ground severely inhibits the formation and development of AM hyphal network and reduces the number of AM spores in the soil.

Phytochemicals induced in chickpea roots selectively and non-selectively stimulate and suppress fungal endophytes and pathogens

AimsPlant roots shape the structure of the soil microbiome by producing a wide array of phytochemicals, which in turn impact plant growth and health. The synthesis of root metabolites is a dynamic process that is modulated by interactions with soil microorganisms. This study explored the regulation of soil-borne fungal endophytes and pathogens by the production of phytochemicals in chickpea (Cicer arietinum L.) roots colonized or not colonized by the arbuscular mycorrhizal (AM) fungus Rhizophagus irregularis.MethodsProteins and low-molecular-mass phytochemicals were extracted from chickpea roots and fractionated by flash chromatography and high pressure liquid chromatography (HPLC). The effects of these metabolites on the soil-borne fungal endophytes Trichoderma harzianum and Geomyces vinaceus and on the pathogens Fusarium oxysporum and Rhizoctonia solani were tested in 96-well plate assays.ResultsOne protein fraction from the AM roots, which contained an apparent 34 KDa chitinase/chitin-binding domain and 24 KDa non-specific lipid transfer protein, non-selectively repressed the fungal endophytes and pathogens. By contrast to the protein fraction, the low-molecular-mass fractions were often selective. Eighteen fractions stimulated specific fungal species and seven fractions inhibited others.ConclusionsSeveral protein and low-molecular-mass phytochemicals in chickpea roots influence fungal endophytes. The difference in the response of fungal species to the phytochemicals suggests that these metabolites could be involved in the so called host ‘preference’ of fungal endophytes or ‘resistance’ to pathogens. This research reveals that the majority of the bioactive root metabolites could be involved in the selective association of chickpea and fungal endophytes while a few compounds provided resistance by suppressing the pathogenic species.

Control of Post-harvest Anthracnose Infection in Guava (Psidium guajava) Fruits with Phosphites, Calcium Chloride, Acetyl Salicylic Acid, Hot Water, and 1-MCP

The control of anthracnose (Colletotrichum simmondsii) during the post-harvest stage in guava fruits (Psidium guajava L.) was performed by the application of phosphites [phosphite-K (40% P2O5 and 30% K2O) and phosphite-Ca (10.7% P2O5, 3.89% Ca, and 0.5% B)] including the Carbendazim as reference, calcium chloride (CaCl2), acetyl salicylic acid (ASA), hot water (HW), and 1-methylcyclopropene (1-MCP). These treatments were applied individually or in combination each other with two or three compounds. The evaluated parameters were diameter of anthracnose lesion (DL), number of lesions (NL), and fruit quality (fresh weight loss, pH, total soluble solids, and titrable acidity]. The fruits were disinfested, inoculated, and maintained in an incubator containing fluorescent lights at 75 µmol·m-2·s-1 (25°C, 12h photoperiod) for 5 days and were then analyzed. The results showed that the DL and the NL were reduced following treatments, and that the HW (47°C for 20 min) was the strongest and the 1-MCP treatment was the least effective. The physico-chemical characteristics of fruits were affected by some treatments without compromising fruit quality. The combination of treatments was also able to alleviate the anthracnose effect on fruits compared to individual treatments and the control without affect the fruit quality. The combinations which included the HW treatment showed the best performance to control this disease, particularly when combined with the 1-MCP and phosphite.

EVALUATION OF THE MYCELIAL NETWORK FORMED BY ARBUSCULAR MYCORRHIZAL HYPHAE IN THE RHIZOSPHERE OF PAPAYA AND OTHER PLANTS UNDER INTERCROPPING SYSTEM

Um experimento foi conduzido em casa-de-vegetacao para observar a distribuicao de hifas de fungos micorrizicos arbusculares (FMA), na rizosfera do mamoeiro intercalado com outras plantas. Para isto foram construidos vasos de acrilico divididos em tres compartimentos. Mudas de mamoeiro (Carica papaya L.) foram transplantadas para um dos compartimentos laterais em todos os vasos, enquanto que mudas de grama batatais (Paspalum notatum Flugge) e milheto (Pennisetum glaucum L. R. Br.) foram separadamente transplantadas para o outro compartimento situado na outra extremidade. Um outro tratamento foi constituido de mudas de mamoeiro em um compartimento e 25% de extrato metanolico de raizes de grama batatais (BRE) ou de milheto (MRE), fracionados em cromatografo de coluna. Um vaso com apenas mudas de mamoeiro foi preparado como testemunha. O compartimento central foi inoculado com o fungo Gigaspora margarita. A densidade de hifas, a percentagem de infeccao micorrizica e o numero de esporos nos compartimentos com grama batatais e milheto foram maiores do que naqueles com mamoeiro. Nos compartimentos com BRE e MRE e algumas hifas e esporos foram observados nestes compartimentos. Naqueles sem planta, foram observadas poucas hifas ou esporos.

Impact of the Arbuscular Mycorrhizal Fungi and Bacteria on Biocontrol of White Root Rot in Fruit Seedlings

Impact of the Arbuscular Mycorrhizal Fungi and Bacteria on Biocontrol of White Root Rot in Fruit Seedlings This currently investigation aimed to evaluate the synergistic effect of the arbuscular mycorrhizal fungus (AMF), Gigaspora margarita, and the bacteria Paenibacillus rhizospherae on the alleviation of white root rot of Japanese apricot (Prunus mume) seedlings. Three experiments were carried out to evaluate that. In the first one, J.apricot “Nanko” seedlings were inoculated with (5, 10 and 20 %)inoculums containing the pathogen Rosellinia necatrix (NRBC 5954). In the second experiment the same kind of seedlings were submitted to four treatments: Control (C), AMF (A), Bacteria (B), AMF+Bacteria (A+B). Disease severity, root infection and AMF colonization were evaluated in this experiment.

Soil-Borne Plant Pathogens Associated to Declineof Grapevine Grown in Greenhouse

Soil-Borne Plant Pathogens Associated to Decline of Grapevine Grown in Greenhouse The purpose of the study was to determine which fungal species were associated with a decline in greenhouse grown grapevine (“Fujiminori”). Two species of fungi, characterized as soil-borne plant pathogens were isolated from roots. The fungi were identified by DNA sequencing methods and by their morphology. The fungi were identified as Cylindrocarpon destructans (FJMB2) and Fusarium Oxysporum (FJBM3) according to the DNA sequences and similarities after BLAST search.

Variability of Fusarium spp. isolates, causal agents of the soybean sudden death syndrome

Soybean (Glycine max L.) is the most widely cultivated crop in the world and an important commodity. Besides its main role in human nutrition, this grain is also used in animal feed and production of biofuels, among other purposes. Due to these factors, soybean became important in the global economy and is the most exported agricultural product from Brazil. Fungal diseases are among the limiting factors on soybean production; sudden death syndrome, caused by Fusarium spp., has been responsible for severe losses on this crop in Brazil. Four species of Fusarium can be considered causal pathogens: F. brasiliense, F. crassistipitatum, F. tucumaniae, and F. virguliforme. The Fusarium spp. isolates characterized in this work were collected in different soybean-producing regions in Brazil. The genetic variability of these isolates was determined through the random amplified polymorphic DNA (RAPD) technique. Disease severity was evaluated on moderately resistant and susceptible soybean cultivars in greenhouse trials. RAPD analysis demonstrated a great genetic diversity among the isolates and a clear tendency to split into two main species groups, F. tucumaniae and F. brasiliense, both prevalent in Brazil. The disease severity experiments, in which soybean plants were artificially inoculated, have shown that all isolates caused significant damage to the seedling root system. In fact, the genetic diversity of isolates does not correlate with disease severity, and also does not correlate with geographic distribution.