Fermentation for Disinfesting Fruit Waste From Drosophila Species (Diptera: Drosophilidae).

Economic losses in a range of fruit crops due to the Drosophila suzukii (Matsumura) have become severe. Removal and treatment of fruit waste, which may harbor D. suzukii, is a key step in preventing reinfestation of fruit production. Natural fermentation for disinfesting fruit wastes from D. suzukii was examined at ambient air temperatures of 12-20 °C. Soft and stone fruit wastes infested with eggs, larvae, and pupae of Drosophila melanogaster (Meigen) or D. suzukii were placed in sealed vessels containing fruit wastes, and samples were retrieved at intervals and tested for the emergence of adults. Mean temperatures of the fruit waste in the sealed vessels during fermentation were 15-23 °C. Fermentation for 3 d was effective in disinfesting waste from different life stages of D. suzukii. Treatment for 4 d also ensured that the waste was free of viable life stages of D. melanogaster, which could be used as an indicator species for disinfestation of waste from D. suzukii owing to its greater tolerance of fermentation. The O2 concentration of the headspace air in the vessels became undetectable after 13-16 h, with a corresponding increase in CO2 concentration, which exceeded 80% vol/vol. The resulting hypoxia and hypercapnia may explain the efficacy of the fermentation treatment in disinfesting the waste. Fermented fruit remained attractive to D. suzukii and retained its capacity to rear a life cycle. Covering or mixing fermented fruit with a sufficient depth (0.1 m) or volume (×9) of soil or coir prevented the reinfestation of treated waste.

Indicator organisms for assessing sanitization during composting of plant wastes.

The potential for using plant pathogens and seeds as indicator organisms for assessing sanitization of plant wastes during composting was tested in bench-scale flask and large-scale systems. Plasmodiophora brassicae was unsuitable due to high temperature tolerance in dry to moist composts, and detection of viable inoculum post-composting using bioassay plants not corresponding with that using TaqMan® PCR, possibly due to preservation of nucleic acids at elevated temperatures. Several other plant pathogens (Sclerotinia sclerotiorum, Microdochium nivale, Phytophthora cinnamomi and Phytophthora nicotianae) were unsuitable due their low temperature tolerance. Fusarium oxysporum f.sp. cepae and f.sp. radicis-lycopersici chlamydospores and tomato seeds were suitable indicators due to their moderate temperature tolerance and ease of viability testing post-composting. Abutilon seeds were more tolerant than tomato seeds of compost temperatures ≥52°C but more prone to degradation at lower temperatures and therefore less suitable as indicators. Relationships between compost temperature during exposures of 2-10 days and subsequent viability of the above chlamydospores or seeds enabled the sanitizing effect of composting processes to be predicted within 2-6 days. Plant waste type (woody or vegetable) had a small but significant effect on the relationship for tomato seeds but not for F. oxysporum chlamydospores.

Primordia initiation of mushroom (Agaricus bisporus) strains on axenic casing materials.

The mushroom (Agaricus bisporus) has a requirement for a "casing layer" that has specific physical, chemical and microbiological properties which stimulate and promote the initiation of primordia. Some of these primordia then may develop further into sporophores, involving differentiation of tissue. Wild and commercial strains of A. bisporus were cultured in axenic and nonaxenic microcosms, using a rye grain substrate covered by a range of organic and inorganic casing materials. In axenic culture, A. bisporus (commercial strain A15) was capable of producing primordia and mature sporophores on charcoal (wood and activated), anthracite coal, lignite and zeolite, but not on bark, coir, peat, rockwool, silica or vermiculite. Of six strains tested, only the developmental variant mutant, B430, produced rudimentary primordia on axenic peat-based casing material. However, none of these rudimentary primordia developed differentiated tissues or beyond 4 mm diameter, either on axenic casing material in the microcosms or in larger-scale culture. In larger-scale, nonaxenic culture, strain B430 produced severely malformed but mature sporophores in similar numbers to those of other strains. Typically, 3-6% of primordia developed into mature sporophores, but significant differences in this proportion, as well as in the numbers of primordia produced, were recorded between 12 A. bisporus strains.

Influence of straw types and nitrogen sources on mushroom composting emissions and compost productivity.

The effects of different straw types and organic and inorganic nitrogen (N) sources on the chemical composition and odor concentration (OC) of mushroom composting emissions, compost parameters, and mushroom yield were examined using bench-scale and large-scale (windrows and aerated tunnels) composting systems. There were close correlations between the butanol or combined H(2)S+dimethyl sulfide (DMS) concentration and OC of air samples taken from different composting ingredients (r=0.83 and 0.76-0.87, P<0.01, for log(e)-transformed data). Differences in N availability, in terms of NH(3) and N losses during composting, were found between different N sources. Materials in which the N was less available (chipboard and digester wastes, cocoa shells, ammonium sulfate) produced lower mushroom yields than materials in which the N was more readily available (poultry manure, urea, brewers' grains, hop and molasses wastes, cocoa meal). Replacement of poultry manure with the other N sources at 50-100% or wheat straw with rape, bean, or linseed straw in aerated tunnel or windrow composts reduced the OC and emissions of odorous sulfur-containing compounds, but also reduced yield. Urea and cocoa meal may be suitable for "low odor" prewetting of straw, with addition of poultry manure immediately before aerated tunnel composting. Rape straw in compost reduces the formation of anaerobic zones and resulting odorous emissions, since it maintains its structure and porosity better than wheat straw.

Olfactory response to mushroom composting emissions as a function of chemical concentration.

Odor pollution is a major problem facing mushroom [Agaricus bisporus (Lange) Imbach] compost production. Techniques for quantifying mushroom composting odors are needed to assess the effectiveness of odor control measures. Odor samples were obtained in nalophane bags from 11 mushroom composting sites. Samples were collected 0.2 m downwind from the pre-wetting heaps (aerated or unaerated) of raw composting ingredients (wheat straw, poultry and horse manures, and gypsum) and subsequent Phase I composting windrows or aerated tunnels. The odor concentrations (OCs) of the samples were assessed using serial dilution olfactometry and the chemical composition of the samples was determined using gas chromatography-mass spectrometry (GC-MS), both 24 h after sampling. Gas detector tubes were used for on-site measurement of gaseous compounds. Odorants that exceeded their published olfactory detection thresholds by the greatest order of magnitude, in decreasing order, were: H2S, dimethyl sulfide (DMS), butanoic acid, methanethiol, and trimethylamine. Concentrations of NH3 were not significantly correlated with OC, and they were not significantly affected by the use of aeration. Aeration reduced the OC and the combined H2S + DMS concentrations by 87 and 92%, respectively. There was a very close correlation (r = 0.948, P < 0.001) between the OC of bag samples and the combined H2S + DMS concentrations, measured on-site with detector tubes. This relationship was unaffected by the NH3 concentration or the type of compost: aerated or unaerated, pre-wet or Phase I, poultry manure-based or horse and poultry manure-based compost. Prediction of the OC will enable rapid and low-cost identification of odor sources on mushroom composting sites.

Sexuality and genetic identity in the Agaricus section Arvenses.

Twelve wild collections and one commercial strain were used to characterize breeding systems and to develop molecular identities in the Arvenses section of the genus Agaricus, which includes the "horse mushroom" A. arvensis. Two morphotypes were identified based on macro- and micromorphological features. However, not all collections could be delimited by conventional taxonomic characters. Sequencing of the small subunit intergenic spacer (ITS) region (368 to 370 bp) of the rRNA genes clearly resolved the 13 collections into two clusters consistent with the identified morphotypes. Single-spore progenies and mating type testers were established and used to test intra- and interstock compatibility. The two compatibility groups identified were consistent with ITS clusters. Compatibility group I stocks readily interbred within the constraints of a unifactorial heterothallic system with a multiallelic mating type factor. Compatibility group II had a more restricted breeding pattern, and interactions were difficult to predict on the basis of mating type. Morphological data, ITS sequences, and the ability to interbreed suggest that these collections are part of a complex of interrelated species. Single-spore, homokaryotic isolates from both compatibility groups were able to fruit in compost culture, and two of the collections may represent natural homokaryotic fruiting. We conclude that species from the section Arvenses have versatile unifactorial heterothallic life cycles that permit both interbreeding and homokaryotic fruiting.