Orchard microclimate, tree water uptake and sweet cherry fruit quality under protected cropping.

Protected cropping systems (PCS) de-risk adverse climatic effects in intensive horticultural production but alter the growing environment. The objectives of this study were to investigate the effects of modern, commercial-scale PCS on sweet cherry orchard microclimate, tree water uptake and fruit quality. Sap flow sensors and weather stations were positioned at four locations under a 21 ha PCS at varying elevations (125, 114, 111, 102 m above sea level) and distances from the block boundary (105, 75, 60 or 50 m, referred to hereafter as Locations 1 to 4, respectively). Generalised additive models (GAMs) were used to predict the effect of individual climate parameters (temperature, relative humidity, solar radiation and wind speed) on tree sap flow at each of the four locations. Average and maximum temperatures and average minimum relative humidity (RH) were higher (15.9°C, 26.1°C and 49.0%) at locations with higher elevations and located further from the PCS boundary (locations 1 and 2) in contrast to locations at lower elevations and closer proximity to the PCS boundary (locations 3 and 4) (15.4°C, 24.6°C and 48.1%). Predicted sap flow was strongly correlated (r2 = 0.92) with time across the four locations under the PCS. GAMS modelling indicated that the hourly water uptake by trees within close proximity to the block boundary (locations 3 and 4) responded with greater intensity to increases in temperature and reductions in relative humidity, taking up on average 0.15 L h-1 (at temperatures >30°C) and 0.08 L h-1 (at RH<50%), respectively, in contrast to trees further under the PCS (locations 1 and 2) where average tree water uptake was 0.08 and 0.04 L h-1 at temperatures >30°C and RH<50%, respectively. Highest average predicted hourly tree sap flow was associated with high wind speeds (0.67 L h-1) and low relative humidity levels (0.61 L h-1). Fruit harvested from locations further from the PCS boundary had significantly higher dry matter content (18.2%), total soluble solids (17.8%) and compression firmness (311.3 g mm-1) in contrast to fruit closer to the PCS boundaries (16.1%, 15.7% and 258.3 g mm-1). This study provides greater understanding of the effects of PCS on microclimate and consequences for tree water uptake and fruit quality.

Spoilage potential of bacterial species from chilled vacuum-packed lamb.

The objective of this study was to establish whether specific organisms play important roles in the spoilage rate of vacuum-packed (VP) lamb at low storage temperatures. The spoilage potential of representative organisms (n = 13) of the spoilage community of VP lamb were investigated through a series of shelf-life challenge trials. Each isolate was individually inoculated onto sterile (irradiated) and non-sterile (i.e., containing natural microbial community) VP lamb meat. Meat quality was assessed over time by measuring sensorial qualities, bacterial growth and pH. Among all test organisms, Clostridium spp. had the highest spoilage potential and had a major effect on the spoilage rate of VP lamb (based on sensory assessment). C. estertheticum caused premature 'blown pack' spoilage; however, the spoilage was delayed in a community setting. C. putrefaciens and C. algidicarnis caused premature spoilage of VP lamb independently and in a community setting. In contrast, all facultative anaerobes and Pseudomonas sp. tested were not capable of spoiling meat independently or within a community, expect for Carnobacterium divergens and Serratia spp., which spoiled meat prematurely when present in a community. Overall, these results highlight that Clostridium could be one of the main taxa driving the faster rate of quality loss of chilled VP lamb compared to beef. This research can help to inform opportunities for shelf-life extension by targeting organisms with 'high' spoilage potential, such as Clostridium.

The effects of glucose on microbial spoilage of vacuum-packed lamb.

Vacuum-packed lamb produced in Australia has a shelf-life of 80-90 days under export conditions (-1 to 0 °C). However, access to some markets could involve >90 days transit time. Studies to understand the potential mechanisms of microbial spoilage of vacuum-packed lamb are, therefore, important to assist the development of shelf-life extension methods. Here, we investigated the effects of glucose on the shelf-life of vacuum-packed lamb. This was done by adding glucose (up to 4.64 mmol/kg) to the surface of meat and conducting a series of shelf-life trials, in which the sensorial qualities, bacterial growth, pH, and residual glucose and lactic acid were measured over time. Based on sensory analysis glucose extended the shelf-life, ranging from 8% to >76% increase relative to the control. Glucose reduced meat pH, potentially affecting the microbial community composition and the accumulation of spoilage metabolites. These results indicate that glucose plays an important role in microbial spoilage of vacuum-packed lamb possibly by pH reduction.

Virtual fencing technology to intensively graze lactating dairy cattle. I: Technology efficacy and pasture utilization.

Virtual fencing is promoted as the next advancement for rotational grazing systems. This experiment compared the capacity of conventional temporary electric versus virtual fencing to contain a herd of 30 lactating dairy cows within the boundaries of their daily pasture allocation (inclusion zone). Cows were moved each day to a new rectangular paddock that was divided crosswise into an inclusion and exclusion zone by a single linear electric (first 10 d) or virtual (second 10 d) front-fence. A 3-d virtual fence training period separated the 2 treatments. Virtual fences were imposed using a pre-commercial prototype of the eShepherd virtual fencing system (Agersens Pty Ltd.). Neckband-mounted devices replaced the visual cue of an electric fence with benign audio cues, which if ignored were accompanied by an aversive electrical stimulus. Cows learned to respond to the audio cues to avoid receiving electrical stimuli, with the daily ratio of electrical to audio signals for individual cows averaging (± standard deviation) 0.18 ± 0.27 over the 10 d of virtual fence deployment. Unlike the electric fence, the virtual fence did not fully eliminate cow entry into the exclusion zone, but individual cows were generally contained within the inclusion zone ≥99% of the time. Pasture depletion within the inclusion zone reduced the efficacy of the virtual fence in preventing cows from entering the exclusion zone, but the magnitude of this effect was insignificant in practical terms (i.e., increased time spent in the exclusion zone by ≤28 s/h per cow). This highlights the potential for virtual fences to control grazing dairy cow movement even when pasture availability is limited (i.e., 1 kg of dry matter/cow above a target residual of 1,500 kg of dry matter/ha), but requires confirmation under longer and more complex virtual fencing applications. Within each treatment period, uniform daily pasture utilization (% of pasture consumed above a target residual of 1,500 kg of dry matter/ha) within inclusion zones indicates that cows did not avoid grazing near electric or virtual front-fences. Overall, this study demonstrated a successful simple application of this virtual fencing system to contain a herd of grazing lactating dairy cows within the boundaries of their daily pasture allocation.

Cherry damage and the spatial distribution of European earwigs, (Forficula auricularia L.) in sweet cherry trees.

BACKGROUND: The European earwig, Forficula auricularia is an invasive insect pest found in many temperate regions of the world. Despite being well known predators, earwigs are considered pests in sweet cherry though this has never been empirically tested. Our aim was to quantify the relationship between damaged cherry fruit and earwig population size, cherry bunch size and earwig distribution in cherry tree canopies in the cherry varieties Ron's Seedling, Lewis, Sweet Georgia, and Lapin. RESULTS: Significant differences in earwig damage type and frequency were observed between varieties with earwig exclusion significantly reducing damage by 21% in Lapin and 34% in Ron's Seedling. Earwigs were strongly aggregated within cherry bunches, with greater numbers and damage observed in larger bunch sizes in all varieties except Ron's Seedling where stem damage was independent of bunch size. In Ron's Seedling, cherry stems were 40× more likely to be damaged than Lewis stems and Lewis fruit two times more likely to be damaged than Ron's Seedling fruit. Sweet Georgia fruit were 4.5 times and stems five times more likely to be damaged than in Lapin. No predictive relationship between cherry damage levels and earwig numbers either within the tree canopies or within monitoring traps could be determined. CONCLUSION: European earwigs may have a significant economic impact to sweet cherry production. The nature of this impact differs between cherry varieties and severity is strongly influenced by factors including bunch size. However, why damage differs between varieties remains unknown and warrants further investigation if the impact of earwigs to sweet cherry production is to be minimized.

Effect of Storage Conditions on Shelf Stability of Undiluted Neutral Electrolyzed Water.

ABSTRACT: Neutral electrolyzed water (NEW) is an oxidizing sanitizer that can be made locally on-site; it is often stored in a ready-to-use format to accumulate the large volumes required for periodic or seasonal use. The shelf stability of NEW sanitizer was, therefore, assessed under various storage conditions to guide the development of protocols for its industrial application. To that end, fresh NEW with an available chlorine concentration (ACC) of 480 mg/L, pH 6.96, and oxidation reduction potential (ORP) of 916 mV was stored under different conditions. These were open or sealed polypropylene bottles, three different surface area-to-volume (SA:V) ratios (0.9, 1.7, and 8.7), and two temperatures (4 and 25°C). NEW stored at 4°C was significantly more stable than NEW stored at 25°C; ACC and pH decreased by 137 mg/L and 0.7, respectively, whereas ORP increased by 23 mV, after 101 days of storage. At 25°C, ACC decreased to <0.01 mg/L after 52 days in bottles with a SA:V ratio of 8.7, with a similar decrease after 101 days in bottles with a SA:V ratio of 1.7. However, pH decreased by up to 3.7 pH units, and ORP increased by up to 208 mV. The antimicrobial efficacy of "aged" electrolyzed oxidizing (EO) water with different ACC and ORP, but the same pH (i.e., 3.4 ± 0.2), was evaluated against Escherichia coli and Listeria innocua to determine any differences in residual antimicrobial activity. EO water with an ACC of ≥7 mg/L and an ORP of 1,094 mV caused a reduction of at least 4.7 log, whereas EO water with nondetectable ACC and considerably high ORP (716 mV) had little antimicrobial effect (<1-log reduction). Results from this study indicate that the efficacy of NEW as a sanitizer for large-scale applications such as horticulture can be maintained for at least 3 months when it is stored in closed containers with low SA:V ratio at low temperatures.

Quantifying risk factors associated with light-induced potato tuber greening in retail stores.

Light conditions in retail stores may contribute to potato greening. In this study, we aimed to develop a potato tuber greening risk rating model for retail stores based on light quality and intensity parameters. This was achieved by firstly exposing three potato varieties (Nicola, Maranca and Kennebec) to seven specific light wavelengths (370, 420, 450, 530, 630, 660 and 735 nm) to determine the tuber greening propensity. Detailed light quality and intensity measurements from 25 retail stores were then combined with the greening propensity data to develop a tuber greening risk rating model. Our study showed that maximum greening occurred under blue light (450 nm), while 53%, 65% and 75% less occurred under green (530 nm), red (660 nm) and orange (630 nm) light, respectively. Greening risk, which varied between stores, was found to be related to light intensity level, and partially explained potato stock loss in stores. Our results from this study suggested that other in-store management practices, including lighting duration, average potato turnover, and light protection during non-retail periods, likely influence tuber greening risk.

A synthesis of bacterial and archaeal phenotypic trait data.

A synthesis of phenotypic and quantitative genomic traits is provided for bacteria and archaea, in the form of a scripted, reproducible workflow that standardizes and merges 26 sources. The resulting unified dataset covers 14 phenotypic traits, 5 quantitative genomic traits, and 4 environmental characteristics for approximately 170,000 strain-level and 15,000 species-aggregated records. It spans all habitats including soils, marine and fresh waters and sediments, host-associated and thermal. Trait data can find use in clarifying major dimensions of ecological strategy variation across species. They can also be used in conjunction with species and abundance sampling to characterize trait mixtures in communities and responses of traits along environmental gradients.

Sampling, extraction and incidence of redberry mites (Acalitus essigi) on blackberries in Australia.

'Redberry disease' on blackberries is hypothesised to be caused by the redberry mite (RBM), Acalitus essigi (Hassan), and results in uneven ripening of blackberry drupelets, which become bright red, hard and inedible. This damage has been reported to cause significant crop losses in commercial blackberry production in most regions where commercial blackberries are grown. However, RBM are difficult to detect and manage due to their tiny body size. In this study, a new 'shake and wash' extraction method has been developed, enabling faster, more accurate mite detection and quantification. The 'shake and wash' method extracted significantly more RBM and predatory mites (Phytoseiidae) than the previously recommended 'sticky tape' method, where mite extraction using this technique was increased by 53 and 60%, respectively. RBM counts were then made from the fruit of wild and commercial blackberry cultivars. Significantly higher RBM populations were isolated in cultivars 'BL454' (mean = 12.1 per fruit) and 'Chester' (mean = 2.6 per fruit) from several sites indicating potential RBM susceptibility in these cultivars. The highest levels of disease incidence and RBM numbers were observed on wild blackberry fruit. The redberry disease incidence increased from 13.5 to 44.9% as the mean population of RBM increased on wild fruit. Further methods were developed to extract mites from winter buds on canes. RBM numbers were lower in the fruit compared to winter buds. RBM detection is best achieved in winter buds rather than fruit and may be an important tool for RBM detection and subsequent management in the cropping season.

Suberin deposition in potato periderm: a novel resistance mechanism against tuber greening.

Light-induced tuber greening is one of the most important quality defects of potato. Although varietal and maturity factors are known to affect greening resistance, physiological mechanisms of resistance are poorly understood. We proposed that physiological and biochemical factors within the tuber periderm provide resistance and hypothesised that resistance is primarily related to suberin content. We investigated differences in the tuber periderm between genotypes and tuber maturities that varied in greening propensity. We examined suberin and light-induced pigment accumulation, and phellem cell development and studied greening propensity in mutant and chemically treated tubers with enhanced suberisation. Resistance to greening was strongly linked to increased suberin in the periderm, which varied with variety and tuber maturity. Furthermore, greening was reduced in mutant and chemically treated tubers with enhanced suberisation. Increases in phellem cell layers and light-induced carotenoids and anthocyanins were identified as secondary resistance factors. Our work represents the first physiological mechanism of varietal and tuber maturity resistance to greening, expanding the known functionality of suberin and providing for the first time a biomarker that will aid producers and breeders in selection and improvement of potato varieties for greening resistance.

The Biokinetic Spectrum for Temperature and optimal Darwinian fitness.

Darwinian fitness is maximised at a temperature below Topt, but what this temperature is remains unclear. By linking our previous work on the Biokinetic Spectrum for Temperature with a model for temperature-dependent biological growth rate we obtain a plausible value for such a temperature. We find this approach reveals considerable commonalities in how life responds to temperature with implications that follow in evolution, physiology and ecology. We described a data set consisting of 17,021 observations of temperature-dependent population growth rates from 2411 bacterial, archaeal and eukaryal strains. We fitted a thermodynamic model to describe the strains' temperature-dependent growth rate curves that assumed growth was limited by a single rate-limiting enzyme. We defined Umes as an empirical measure of the temperature at which strains grew as fast and also as efficiently as possible. We propose that Darwinian fitness is optimised at Umes by trading-off growth rate and physiological efficiency. Using the full data set we calculated the Biokinetic Spectrum for Temperature (BKST): the distribution of temperature-dependent growth rates for each temperature. We used quantile regression to fit alternative models to the BKST to obtain quantile curves. A quantile is a value that contains a particular proportion of the data. The quantile curves suggested commonalities in temperature-dependencies spanning taxa and ecotype, consistent with the single rate-limiting enzyme concept. We showed that on the log scale, the slopes of the quantile curves were the same as the slopes of the thermodynamic model growth curves at Umes. This was true for Bacteria, Archaea, and Eukarya, and across other conditions (pH, water activity, metabolic type and trophic type). We showed that the quantile curves were the loci of the temperatures and growth rates that optimised Darwinian fitness for each strain at a given temperature-dependence and independently of other conditions. The quantile curves for Archaea and Bacteria shared a number of similarities attributable to the influence of the properties of water on protein folding. Other implications have impact on evolutionary biology, ecology, and physiology. The model predicts the existence of eurythermic strains that grow with about equal efficiency over a broad temperature range. These strains will have higher evolutionary rates with lower mutational costs that are independent of environmental conditions, a factor likely to have been significant during the Precambrian if the early Earth was warmer than today. The model predicts that random mutations are likely to result in shifts along the quantile curves and not across them. It predicts that some psychrophiles will be capable of performing well under climate change, and that selection will favour faster growth rates as the temperature increases. Last, it predicts trade-offs between growth rate and soma production, so that temperature-dependence, and possibly Darwinian fitness, remain constant over a broad temperature range and growth rates.

The Boring Billion, a slingshot for Complex Life on Earth.

The period 1800 to 800 Ma ("Boring Billion") is believed to mark a delay in the evolution of complex life, primarily due to low levels of oxygen in the atmosphere. Earlier studies highlight the remarkably flat C, Cr isotopes and low trace element trends during the so-called stasis, caused by prolonged nutrient, climatic, atmospheric and tectonic stability. In contrast, we suggest a first-order variability of bio-essential trace element availability in the oceans by combining systematic sampling of the Proterozoic rock record with sensitive geochemical analyses of marine pyrite by LA-ICP-MS technique. We also recall that several critical biological evolutionary events, such as the appearance of eukaryotes, origin of multicellularity & sexual reproduction, and the first major diversification of eukaryotes (crown group) occurred during this period. Therefore, it appears possible that the period of low nutrient trace elements (1800-1400 Ma) caused evolutionary pressures which became an essential trigger for promoting biological innovations in the eukaryotic domain. Later periods of stress-free conditions, with relatively high nutrient trace element concentration, facilitated diversification. We propose that the "Boring Billion" was a period of sequential stepwise evolution and diversification of complex eukaryotes, triggering evolutionary pathways that made possible the later rise of micro-metazoans and their macroscopic counterparts.

The influence of lameness and individuality on movement patterns in sheep.

We investigated how individuality and lameness altered social organisation by assessing food-directed movement patterns in sheep. One hundred and ninety-six mature Merino ewes were walked in 16 different runs around a 1.1 km track following a food source. Flock position and lameness were measured and temperament was assessed using an Isolation Box Test. The mean value for the correlations of position between a run and the run preceding it was r = 0.55 ±â€¯SEM 0.03. All correlations between runs were positive (r = 0.08-0.76) and all but two were statistically significant (P < 0.05). The weakest and least statistically significant correlations were for run 14: where all 16 runs were conducted approximately 3 times a week, except with an interval of 20 weeks between runs 13 and 14. Additionally, there were differences in overall positions for a lame versus a non-lame individual (all P < 0.05) with lame sheep being further back in position when compared to their non-lame mean positions. These results indicate the movement patterns, as measured by flock position during a food-directed forced movement order are relatively stable provided tests occur frequently, possibly on a bi-weekly basis. However, further work will be required to better account for individual animal variation.

Receiver Operating Characteristic curve analysis determines association of individual potato foliage volatiles with onion thrips preference, cultivar and plant age.

Tomato spotted wilt virus (TSWV) causes sporadic but serious disease in Australian potato crops. TSWV is naturally spread to potato by thrips of which Thrips tabaci is the most important. Prior studies indicated possible non-preference of potato cultivars to T. tabaci. Select potato cultivars were assessed for non-preference to T. tabaci in paired and group choice trials. Cultivars 'Bismark', 'Tasman' and 'King Edward' were less preferred than 'Atlantic', 'Russet Burbank' and 'Shepody'. Green leaf volatiles were sampled using solid-phase microextraction from the headspace of potato cultivars of two ages that differed in T. tabaci preference. Analysis of headspace volatile data using Receiver Operating Characteristic curves identified individual volatiles associated with T. tabaci preference and non-preference, young and old plants and individual cultivars. These data could be used to inform breeding programs for selection of T. tabaci resistance to assist with TSWV management, and biological testing of novel thrips management compounds.

Hematologic and serum biochemical changes associated with Devil Facial Tumor Disease in Tasmanian Devils.

BACKGROUND: Devil Facial Tumor Disease (DFTD) is an infectious tumor causing significant population declines in wild Tasmanian Devils. While clinical assessment and pathology have been well reported for DFTD, there is a lack of information on hematologic and biochemical alterations associated with DFTD. OBJECTIVES: The purpose of the study was to determine hematologic and serum biochemical variation in healthy, wounded, and DFTD-affected Tasmanian Devils. METHODS: Blood samples were collected from wild Tasmanian Devils at 5 sites in Tasmania. Hematology and clinical biochemistry variables were compared between clinically healthy, wounded, and DFTD-affected devils. Differences were also analyzed among stages of DFTD, including individuals pre- and postclinical signs developing, and between ulcerated and nonulcerated DFTD tumors. RESULTS: Statistically significantly increased counts in WBC, neutrophils, and platelets, and concentration of fibrinogen, as well as decreased counts in lymphocytes, erythrocytes, and HGB concentration were observed in DFTD-affected devils compared to healthy devils. Activities of ALP, ALT, and GLDH, concentrations of sodium, potassium and albumin, and sodium-to-potassium ratio and albumin-to-globulin ratio were significantly lower, and AST activity was significantly higher in animals with DFTD when compared to clinically healthy animals. No significant differences were found among stages of DFTD or ulcerated and nonulcerated tumors. CONCLUSIONS: The differences in hematology and clinical chemistry variables in devils with DFTD compared to healthy devils are nonspecific and reflective of acute phase response and inflammation, and anemia of chronic disease. Similar changes are observed with wounds but to a lesser extent.

Correction: The Biokinetic Spectrum for Temperature.

[This corrects the article DOI: 10.1371/journal.pone.0153343.].

The Biokinetic Spectrum for Temperature.

We identify and describe the distribution of temperature-dependent specific growth rates for life on Earth, which we term the biokinetic spectrum for temperature. The spectrum has the potential to provide for more robust modeling in thermal ecology since any conclusions derived from it will be based on observed data rather than using theoretical assumptions. It may also provide constraints for systems biology model predictions and provide insights in physiology. The spectrum has a Δ-shape with a sharp peak at around 42°C. At higher temperatures up to 60°C there was a gap of attenuated growth rates. We found another peak at 67°C and a steady decline in maximum rates thereafter. By using Bayesian quantile regression to summarise and explore the data we were able to conclude that the gap represented an actual biological transition between mesophiles and thermophiles that we term the Mesophile-Thermophile Gap (MTG). We have not identified any organism that grows above the maximum rate of the spectrum. We used a thermodynamic model to recover the Δ-shape, suggesting that the growth rate limits arise from a trade-off between activity and stability of proteins. The spectrum provides underpinning principles that will find utility in models concerned with the thermal responses of biological processes.

Hematologic and serum biochemical reference intervals for wild Tasmanian devils (Sarcophilus harrisii).

BACKGROUND: The Tasmanian devil (Sarcophilus harrisii) is a carnivorous marsupial threatened with extinction by a fatally infectious cancer known as devil facial tumor disease (DFTD). Conservation efforts including captive breeding and island translocations are underway to address this threat. OBJECTIVES: The objectives of this study were to determine hematologic and serum biochemical reference intervals (RI) to aid in health assessment of Tasmanian devils, and to examine seasonal, sex, reproductive status and age variations. METHODS: We collected jugular blood samples from individual wild Tasmanian devils at 2 different locations over a 2-year period to determine hematologic and serum biochemical RI by nonparametric methods using the central 0.95 fraction. RESULTS: A total of 307 blood samples were collected from 187 devils. Significant age differences were found for ALP, CK, cholesterol, calcium, phosphate, albumin, globulins, albumin: globulin ratio, and glucose. Significant differences between sexes were observed for AST, creatinine, and potassium. Significant seasonal or reproductive status variation in adult males or breeding females were observed for PCV, HGB, RBC, MCHC, MCH, MCV, neutrophils and lymphocytes, fibrinogen, total plasma protein, AST, ALP, ALT, GLDH, bilirubin, urea, calcium, chloride, total protein, albumin, A:G, and glucose. CONCLUSIONS: Many of the differences observed between subgroups can be explained by growth requirements, reproductive demands, and seasonal effects on activity. This study has determined comprehensive RI for the Tasmanian devil, which will be used to assess animals targeted for captive breeding and translocations, or affected by DFTD.

Perception of climate change and its impact by smallholders in pastoral/agropastoral systems of Borana, South Ethiopia.

This study investigates the perception of historic changes in climate and associated impact on local agriculture among smallholders in pastoral/agropastoral systems of Borana in southern Ethiopia. We drew on empirical data obtained from farm household surveys conducted in 5 districts, 20 pastoral/agropastoral associations and 480 farm households. Using this data, this study analyses smallholders' perception of climate change and its associated impact on local agriculture, and the effect of various household and farm attributes on perception. Results suggest that most participants perceived climatic change and its negative impact on agricultural and considered climate change as a salient risk to their future livelihoods and economic development. Different levels of perception were expressed in terms of climate change and the impact on traditional rain-fed agriculture. Age, education level, livestock holding, access to climate information and extension services significantly affected perception levels. Household size, production system, farm and non-farm incomes did not significantly affect perception levels of smallholders. Smallholders attributed climate change to a range of biophysical, deistic and anthropogenic causes. Increased access to agricultural support services, which improves the availability and the quality of relevant climate information will further enhance awareness of climate change within of the rural community and result in better management of climate-induced risks in these vulnerable agricultural systems.

Modeling Pathogen DNA Content and Visual Disease Assessment in Seed Tubers to Inform Disease in Potato Progeny Root, Stolon, and Tubers.

Measurement of pathogens on seed tubers is essential for informing likelihood of subsequent potato disease. Here we utilized quantitative PCR assessment of pathogen DNA and visual assessment of disease to measure seed tuber inoculum and used this to model development of disease in potato grown in pathogen-free soil. Analysis by recursive partitioning and modeling using receiver operating curves indicated both abundance of Rhizoctonia solani AG3 and Streptomyces scabies DNA, and disease symptoms associated with these pathogens on seed tubers could predict subsequent disease in progeny tubers and for R. solani, stolons. In contrast, abundance of Spongospora subterranea DNA and disease symptoms on seed tubers were not consistently associated with powdery scab in progeny tubers. The relationship between S. subterranea DNA and seed tuber symptoms on root galling was stronger. Symptomless seed tubers that carried high levels of S. subterranea DNA were also associated with greater root galling than those with low pathogen DNA levels. There was a modest association between root galling and powdery scab in progeny tubers. These results highlight the importance of using certified seed tubers, and demonstrate a statistical tool for measuring the impact of seed tuber-borne inoculum.