Resporulation of Calcium Alginate Encapsulated Metarhizium anisopliae on Metham - Fumigated Soil and Infectivity on Larvae of Tenebrio molitor

Metarhizium anisopliae infects and kills a large range of insects and is a promising biocontrol agent to manage soil insects, such as wireworm in sweetpotato. The presence of other soil microbes, which exhibit competitive fungistasis, may inhibit the establishment of M. anisopliae in soil. Microbially depleted soil, for example, sterilized soil, has been shown to improve the resporulation of the fungus from nutrient-fortified M. anisopliae. Prior to planting, sweetpotato plant beds can be disinfected with fumigants, such as Metham®, to control soil-borne pests and weeds. Metham® is a broad-spectrum soil microbial suppressant; however, its effect on Metarhizium spp. is unclear. In the research presented here, fungal resporulation was examined in Metham®-fumigated soil and the infectivity of the resulting granule sporulation was evaluated on mealworm, as a proxy for wireworm. The fungal granules grown on different soil treatments (fumigated, field and pasteurized soil) resporulated profusely (for example, 4.14 × 107 (±2.17 × 106) conidia per granule on fumigated soil), but the resporulation was not significantly different among the three soil treatments. However, the conidial germination of the resporulated granules on fumigated soil was >80%, which was significantly higher than those on pasteurized soil or field soil. The resporulated fungal granules were highly infective, causing 100% insect mortality 9 days after the inoculation, regardless of soil treatments. The results from this research show that the fungal granules applied to soils could be an infective inoculant in sweetpotato fields in conjunction with soil fumigation. Additional field studies are required to validate these results and to demonstrate integration with current farming practice

Draft genome sequence of Bacillus thuringiensis strain DAR 81934, which exhibits molluscicidal activity

Bacillus thuringiensis has been widely used as a biopesticide for a long time. Its molluscicidal activity, however, is rarely realized. Here, we report the genome sequence of B. thuringiensis strain DAR 81934, a strain with molluscicidal activity against the pest snail Cernuella virgata

Whole genome phylogeny of Bacillus by feature frequency profiles (FFP)

Fifty complete Bacillus genome sequences and associated plasmids were compared using the “feature frequency profile” (FFP) method. The resulting whole-genome phylogeny supports the placement of three Bacillus species (B. thuringiensis, B. anthracis and B. cereus) as a single clade. The monophyletic status of B. anthracis was strongly supported by the analysis. FFP proved to be more effective in inferring the phylogeny of Bacillus than methods based on single gene sequences [16s rRNA gene, GryB (gyrase subunit B) and AroE (shikimate-5-dehydrogenase)] analyses. The findings of FFP analysis were verified using kSNP v2 (alignment-free sequence analysis method) and Harvest suite (core genome sequence alignment method)

Gulypyrones A and B and phomentrioloxins B and C produced by Diaporthe gulyae, a potential mycoherbicide for saffron thistle (Carthamus lanatus)

A virulent strain of Diaporthe gulyae, isolated from stem cankers of sunflower and known to be pathogenic to saffron thistle, has been shown to produce both known and previously undescribed metabolites when grown in either static liquid culture or a bioreactor. Together with phomentrioloxin, a phytotoxic geranylcyclohexenetriol recently isolated from a strain of Phomopsis sp., two new phytotoxic trisubstituted α-pyrones, named gulypyrones A and B (1 and 2), and two new 1,O- and 2,O-dehydro derivatives of phomentrioloxin, named phomentrioloxins B and C (3 and 4), were isolated from the liquid culture filtrates of D. gulyae. These four metabolites were characterized as 6-[(2S)2-hydroxy-1-methylpropyl]-4-methoxy-5-methylpyran-2-one (1), 6-[(1E)-3-hydroxy-1-methylpropenyl]- 4-methoxy-3-methylpyran-2-one (2), 4,6-dihydroxy-5-methoxy-2-(7-methyl-3-methyleneoct-6-en-1-ynyl)cyclohex-2-enone (3), and 2,5-dihydroxy-6-methoxy-3-(7-methyl-3-methyleneoct-6-en-1-ynyl)cyclohex-3-enone (4) using spectroscopic and chemical methods. The absolute configuration of the hydroxylated secondary carbon of the 2-hydroxy-1-methylpropyl side chain at C-6 of gulypyrone A was determined as S by applying a modified Mosher’s method. Other well-known metabolites were also isolated including 3-nitropropionic, succinic, and p-hydroxy- and p-methylbenzoic acids, p-hydroxybenzaldehyde, and nectriapyrone. When assayed using a 5 mM concentration on punctured leaf disks of weedy and crop plants, apart from 3-nitropropionic acid (the main metabolite responsible for the strong phytotoxicity of the culture filtrate), phomentrioloxin B caused small, but clear, necrotic spots on a number of plant species, whereas gulypyrone A caused leaf necrosis on Helianthus annuus plantlets. All other compounds were weakly active or inactive

Encapsulation of flutriafol fungicide into electrospun biodegredable poly (L-lactide) nanofibers

The application of biodegradable, electrospun nanofibers in agriculture has attracted a lot of interest as they are cost-effective and offer a versatile technique to fabricate eco-friendly, high surface-to-volume ratio and porous nanofibrous structures from polymeric solutions. Flutriafol is a commonly used fungicide in plant protection in Australia. This study aimed to encapsulate flutriafol into poly(L-lactide) (PLLA) nanofibers matrix by optimizing electrospinnig conditions. The PLLA solution was prepared at concentration of PLLA (5% w/w) in chloroform-Aceton (75–25 v/v) containing 10% (w/w) flutriafol relative to the PLLA. The PLLA/flutriafol mixture was fed with a syringe to a basic electrospinning setup. Optimum electrospinning conditions were observed at 32 °C with a flow rate speed of 1mL/ h, and 12kV high voltage. SEM images were used to characterize the morphology of electrospun nanofibers. Energy-dispersive detector (EDS) was employed to identify successful encapsultion of flutrifol into PLLA nanofibers

Integration of entomopathogenic fungi into IPM programs: studies involving weevils (Coleoptera: Curculionoidea) affecting horticultural crops

Weevils are significant pests of horticultural crops and are largely managed with insecticides. In response to concerns about negative impacts of synthetic insecticides on humans and the environment, entomopathogenic fungi (EPF) have been developed as an alternative method of control, and as such appear to be “ready-made” components of integrated pest management (IPM) programs. As the success of pest control requires a thorough knowledge of the biology of the pests, this review summarises our current knowledge of weevil biology on nut trees, fruit crops, plant storage roots, and palm trees. In addition, three groups of life cycles are defined based on weevil developmental habitats, and together with information from studies of EPF activity on these groups, we discuss the tactics for integrating EPF into IPM programs. Finally, we highlight the gaps in the research required to optimise the performance of EPF and provide recommendations for the improvement of EPF efficacy for the management of key weevils of horticultural crops

Kinetics of slow release of nitrogen fertiliser from multi-layered nanofibrous structures

Fertilisers are essential in modern agriculture to enhance plant growth, crop production and product quality. Recent research has focused on the development of delivery systems designed to prolong fertiliser release. This study introduces a new technology to encapsulate and release molecules of fertilisers by using multi-layered electrospun nanofibre as a carrier. Single-layer poly L-lactic acid (PLLA) nanofibres loaded with urea were fabricated using electrospinning. Triple-layer nanofibrous structures were produced by electrospinning polyhydroxybutyrate (PHB) nanofibres as external layers with PLLA nanofibres impregnated with urea fertiliser as the middle layer. Scanning electron microscopy (SEM) and Fourier transform infrared spectrophotometry (FTIR) were employed to characterize the morphology of electrospun nanofibres. Urea release dynamic was analysed using a total nitrogen instrument (TNM-1). The results indicated that triple-layered urea-impregnated nanofibrous structures led to lower initial rate of nitrogen release and slower release rate of cumulative nitrogen which extended for more than three months. It is concluded that triple-layer nanofibrous structures have the potential for slow release delivery of fertilisers

Identification of virulence associated loci in the emerging broad host range plant pathogen Pseudomonas fuscovaginae

BACKGROUND: Pseudomonas fuscovaginae (Pfv) is an emerging plant pathogen of rice and also of other gramineae plants. It causes sheath brown rot disease in rice with symptoms that are characterized by brown lesions on the flag leaf sheath, grain discoloration and sterility. It was first isolated as a high altitude pathogen in Japan and has since been reported in several countries throughout the world. Pfv is a broad host range pathogen and very little is known about its virulence mechanisms. RESULTS: An in planta screen of 1000 random independent Tn5 genomic mutants resulted in the isolation of nine mutants which showed altered virulence. Some of these isolates are mutated for functions which are known to be virulence associated factors in other phytopathogenic bacteria (eg. pil gene, phytotoxins and T6SS) and others might represent novel virulence loci. CONCLUSIONS: Being an emerging pathogen worldwide, the broad host range pathogen Pfv has not yet been studied for its virulence functions. The roles of the nine loci identified in the in planta screen are discussed in relation to pathogenicity of Pfv. In summary, this article reports a first study on the virulence of this pathogen involving in planta screening studies and suggests the presence of several virulence features with known and novel functions in the Pseudomonas group of bacteria