Complete chloroplast genome sequencing of ten wild Fragaria species in China provides evidence for phylogenetic evolution of Fragaria.

Complete chloroplast genomes of ten wild Fragaria species native to China were sequenced. Phylogenetic analysis clustered Fragaria species into two clades: The south clade (F. iinumae, F. chinensis, F. pentaphylla, F. nilgerrensis, F. daltoniana, F. corymbosa, F. moupinensis, F. tibetica, F. nipponica, F. gracilis, and F. nubicola and north clade (F. viridis, F. orientalis, F. moschata, F. mandshurica, F. vesca, F. chiloensis, F. virginiana, and F. × ananassa), while F. iinumae is the oldest extant species. Molecular clock analysis suggested present Fragaria species share a common ancestor 3.57 million years ago (Ma), F. moschata and octoploid species evolve 0.89 and 0.97 Ma, respectively, but F. moschata be not directly involved in current octoploid species formation. Drastic global temperature change since the Palaeocene-Eocene, approx. 55 Ma, especially during uplifting of the Qinghai-Tibet plateau and quaternary glaciation may have driven the formation of Fragaria, separation of two groups and polyploidization.

DOES SIZE MATTER? A CRITICAL REVIEW OF META-ANALYSIS IN AGRONOMY.

Intended to test broad hypotheses and arrive at unifying conclusions, meta-analysis is the process of extracting, assembling, and analyzing large quantities of data from multiple publications to increase statistical power and uncover explanatory patterns. This paper describes the ways in which meta-analysis has been applied to support claims and counter-claims regarding two topics widely debated in agricultural research, namely organic agriculture (OA) and conservation agriculture (CA). We describe the origins of debate for each topic and assess prominent meta-analyses considering data-selection criteria, research question framing, and the interpretation and extrapolation of meta-analytical results. Meta-analyses of OA and CA are also examined in the context of the political economy of development-oriented agricultural research. Does size matter? We suggest that it does, although somewhat ironically. While meta-analysis aims to pool all relevant studies and generate comprehensive databases from which broad insights can be drawn, our case studies suggest that the organization of many meta-analyses may affect the generalizability and usefulness of research results. The politicized nature of debates over OA and CA also appear to affect the divergent ways in which meta-analytical results may be interpreted and extrapolated in struggles over the legitimacy of both practices. Rather than resolving scientific contestation, these factors appear to contribute to the ongoing debate. Meta-analysis is nonetheless becoming increasingly popular with agricultural researchers attracted by the power for the statistical inference offered by large datasets. This paper consequently offers three suggestions for how scientists and readers of scientific literature can more carefully evaluate meta-analyses. First, the ways in which papers and data are collected should be critically assessed. Second, the justification of research questions, framing of farming systems, and the scales at which research results are extrapolated and discussed should be carefully evaluated. Third, when applied to strongly politicized topics situated in an arena of scientific debate, as is the case with OA and CA, more conservative interpretations of meta-analytical results that recognize the socially and politically embedded nature of agricultural research is are needed.

Analysis of Environmental Variables and Carbon Input on Soil Microbiome, Metabolome and Disease Control Efficacy in Strawberry Attributable to Anaerobic Soil Disinfestation.

Charcoal rot and Fusarium wilt, caused by Macrophomina phaseolina and Fusarium oxysporum f. sp. fragariae, respectively, are major soil-borne diseases of strawberry that have caused significant crop losses in California. Anaerobic soil disinfestation has been studied as an industry-level option to replace soil fumigants to manage these serious diseases. Studies were conducted to discern whether Gramineae carbon input type, incubation temperature, or incubation duration influences the efficacy of this disease control tactic. In experiments conducted using 'low rate' amendment applications at moderate day/night temperatures (24/18 °C), and carbon inputs (orchard grass, wheat, and rice bran) induced an initial proliferation and subsequent decline in soil density of the Fusarium wilt pathogen. This trend coincided with the onset of anaerobic conditions and a corresponding generation of various anti-fungal compounds, including volatile organic acids, hydrocarbons, and sulfur compounds. Generation of these metabolites was associated with increases in populations of Clostridium spp. Overall, carbon input and incubation temperature, but not incubation duration, significantly influenced disease suppression. All Gramineae carbon inputs altered the soil microbiome and metabolome in a similar fashion, though the timing and maximum yield of specific metabolites varied with input type. Fusarium wilt and charcoal rot suppression were superior when anaerobic soil disinfestation was conducted using standard amendment rates of 20 t ha-1 at elevated temperatures combined with a 3-week incubation period. Findings indicate that anaerobic soil disinfestation can be further optimized by modulating carbon source and incubation temperature, allowing the maximum generation of antifungal toxic volatile compounds. Outcomes also indicate that carbon input and environmental variables may influence treatment efficacy in a target pathogen-dependent manner which will require pathogen-specific optimization of treatment protocols.

Assessing Anaerobic Soil Disinfestation as a Control Tactic for Delia radicum (Diptera: Anthomyiidae) in California Brussels Sprouts.

Fumigants are often the primary material used to manage plant disease agents, soil-borne arthropods, and weeds in California agriculture, particularly in the absence of crop rotation. However, some fumigants have come under increased regulatory scrutiny and are therefore no longer available for use. We tested two biologically based preplant crop-protection fumigant alternatives for their effectiveness in reducing populations of Delia radicum (L.), a soil-borne insect pest of cole crops. Laboratory and field tests compared pest survival in untreated control soil with survival under anaerobic soil disinfestation (ASD), which is induced by incorporating a carbon source (rice bran or grape pomace) and subsequently saturating the soil with water. We also measured and compared the effects of standard grower practices (fumigation), ASD and biofumigation (mustard seed meal incorporated before planting), and untreated control soils on fly abundance, pupal survival, and root damage in Brussels sprout fields. In both laboratory and field studies, D. radicum pupal survivorship was reduced in ASD-treated soils relative to control soils. Pupal survivorship of Musca domestica (L.) (Diptera: Muscidae), which was used as a proxy for D. radicum in some field experiments, was also reduced in ASD- and biofumigation-treated soils, when compared with untreated control soils. These results indicate that fumigant alternatives may provide useful insect pest management opportunities for compatible cropping systems.

Relative densities of natural enemy and pest insects within California hedgerows.

Research on hedgerow design for supporting communities of natural enemies for biological control lags behind farmer innovation in California, where assemblages of perennial plant species have been used on crop field margins in the last decade. We compared natural enemy to pest ratios between fields with hedgerows and fields with weedy margins by sampling beneficial insects and key pests of vegetables on sticky cards. We used biweekly vacuum samples to measure the distribution of key insect taxa among native perennial plant species with respect to the timing and intensity of bloom. Sticky cards indicated a trend that field margins with hedgerows support a higher ratio of natural enemies to pests compared with weedy borders. Hedgerow plant species hosted different relative densities of a generally overlapping insect community, and the timing and intensity of bloom only explained a small proportion of the variation in insect abundance at plant species and among hedgerows, with the exception of Orius spp. on Achillea millefolium L. and Baccharis pilularis De Candolle. Indicator Species Analysis showed an affinity of parasitic wasps, especially in the super-family Chalcidoidea, for B. pilularis whether or not it was in flower. A. millefolium was attractive to predatory and herbivorous homopterans; Heteromeles arbutifolia (Lindley) Roemer and B. pilularis to Diabrotica undecimpunctata undecimpunctata Mannerheim; and Rhamnus californica Eschsch to Hemerobiidae. Perennial hedgerows can be designed through species selection to support particular beneficial insect taxa, but plant resources beyond floral availability may be critical in providing structural refuges, alternative prey, and other attractive qualities that are often overlooked.

Biotic interactions, ecological knowledge and agriculture.

This paper discusses biotic interactions in agroecosystems and how they may be manipulated to support crop productivity and environmental health by provision of ecosystem services such as weed, pest and disease management, nutrient cycling and biodiversity conservation. Important elements for understanding biotic interactions include consideration of the effects of diversity, species composition and food web structure on ecosystem processes; the impacts of timing, frequency and intensity of disturbance; and the importance of multitrophic interactions. All of these elements need to be considered at multiple scales that depend in part on the range of the movement of the organisms involved. These issues are first discussed in general, followed by an examination of the application of these concepts in agricultural management. The potential for a greater use of ecological management approaches is high; however, owing to the nature of complex interactions in ecosystems, there is some inherent unpredictability about responses to management interventions under different conditions. Such uncertainty needs to be accommodated in the development of recommendations for farm management. This requires an increased emphasis on the effective synthesis of complex and often apparently contradictory information and on field-based adaptive research, monitoring and social learning by farmer/researcher collaborations.