Generating datasets for the project portfolio selection and scheduling problem.

The article presents two variants of the project portfolio selection and scheduling problem (PPSSP). The primary objective of the PPSSP is to maximise the total portfolio value through the selection and scheduling of a subset of projects subject to various operational constraints. This article describes two recently-proposed, generalised models of the PPSSP [1], [2] and proposes a set of synthetically generated problem instances for each. These datasets can be used by researchers to compare the performance of heuristic and meta-heuristic solution strategies. In addition, the Python program used to generate the problem instances is supplied, allowing researchers to generate new problem instances.

Effects of 'Candidatus Liberibacter solanacearum' haplotypes A and B on tomato gene expression and geotropism.

BACKGROUND: The tomato psyllid, Bactericera cockerelli Sulc (Hemiptera: Triozidae), is a pest of solanaceous crops such as tomato (Solanum lycopersicum L.) in the U.S. and vectors the disease-causing pathogen 'Candidatus Liberibacter solanacearum' (or Lso). Disease symptom severity is dependent on Lso haplotype: tomato plants infected with Lso haplotype B experience more severe symptoms and higher mortality compared to plants infected with Lso haplotype A. By characterizing the molecular differences in the tomato plant's responses to Lso haplotypes, the key components of LsoB virulence can be identified and, thus, targeted for disease mitigation strategies. RESULTS: To characterize the tomato plant genes putatively involved in the differential immune responses to Lso haplotypes A and B, RNA was extracted from tomato 'Moneymaker' leaves 3 weeks after psyllid infestation. Gene expression levels were compared between uninfected tomato plants (i.e., controls and plants infested with Lso-free psyllids) and infected plants (i.e., plants infested with psyllids infected with either Lso haplotype A or Lso haplotype B). Furthermore, expression levels were compared between plants infected with Lso haplotype A and plants infected with Lso haplotype B. A whole transcriptome analysis identified 578 differentially expressed genes (DEGs) between uninfected and infected plants as well as 451 DEGs between LsoA- and LsoB-infected plants. These DEGs were primarily associated with plant defense against abiotic and biotic stressors, growth/development, plant primary metabolism, transport and signaling, and transcription/translation. These gene expression changes suggested that tomato plants traded off plant growth and homeostasis for improved defense against pathogens, especially when infected with LsoB. Consistent with these results, tomato plant growth experiments determined that LsoB-infected plants were significantly stunted and had impaired negative geotropism. However, it appeared that the defense responses mounted by tomatoes were insufficient for overcoming the disease symptoms and mortality caused by LsoB infection, while these defenses could compensate for LsoA infection. CONCLUSION: The transcriptomic analysis and growth experiments demonstrated that Lso-infected tomato plants underwent gene expression changes related to abiotic and biotic stressors, impaired growth/development, impaired plant primary metabolism, impaired transport and signaling transduction, and impaired transcription/translation. Furthermore, the transcriptomic analysis also showed that LsoB-infected plants, relative to LsoA-infected, experienced more severe stunting, had improved responses to some stressors and impaired responses to others, had poorer transport and signaling transduction, and had impaired carbohydrate synthesis and photosynthesis.

Development and first evaluation of an attractant impregnated adhesive tape against blood-sucking flies.

Stable flies are one of the most important arthropod pests of livestock that reduce cattle weight gain and milk production leading to annual economic losses in excess of $2 billion to the US cattle industry. The host-seeking behavior is primarily mediated by associated odors from stable fly larval development environments and host animals. The present paper reports the development and evaluation of attractant-impregnated adhesive tapes to reduce stable fly attacks on cattle. Laboratory bioassays showed that only m-cresol impregnated adhesive tapes caught significantly more stable flies (16 ± 1) than the control tape without attractant added (7 ± 1), with a 77% fly recapture rate. Attractant-impregnated adhesive tapes deployed in cattle feedlots showed significant impacts in reducing fly population, with a total of one million stable flies captured over a period of three weeks (mean catches from 57 596 to 102 088 stable flies per trap per week). It further relieved cattle stress with a significant reduction of biting fly avoidance behavior, (6 ± 0.4 cows observed with tail wagging in control vs. 3 ± 0.4 from the trap-deployed). The efficacy of the developed tapes lasted up to 1-week longevity, although 70% of m-cresol was released starting from the second day. The m-cresol impregnated adhesive tape provided an 80% reduction in cattle stress due to stable fly attack. This is the first report of a technology developed by integrating an attractant compound into an adhesive material on a plastic film with demonstrated effectiveness in trapping biting flies that attack livestock animals.

Lasting consequences of psyllid (Bactericera cockerelli L.) infestation on tomato defense, gene expression, and growth.

BACKGROUND: The tomato psyllid, Bactericera cockerelli Sulc (Hemiptera: Triozidae), is a pest of solanaceous crops such as tomato (Solanum lycopersicum L.) in the U.S. and vectors the disease-causing pathogen 'Candidatus Liberibacter solanacearum'. Currently, the only effective strategies for controlling the diseases associated with this pathogen involve regular pesticide applications to manage psyllid population density. However, such practices are unsustainable and will eventually lead to widespread pesticide resistance in psyllids. Therefore, new control strategies must be developed to increase host-plant resistance to insect vectors. For example, expression of constitutive and inducible plant defenses can be improved through selection. Currently, it is still unknown whether psyllid infestation has any lasting consequences on tomato plant defense or tomato plant gene expression in general. RESULTS: In order to characterize the genes putatively involved in tomato defense against psyllid infestation, RNA was extracted from psyllid-infested and uninfested tomato leaves (Moneymaker) 3 weeks post-infestation. Transcriptome analysis identified 362 differentially expressed genes. These differentially expressed genes were primarily associated with defense responses to abiotic/biotic stress, transcription/translation, cellular signaling/transport, and photosynthesis. These gene expression changes suggested that tomato plants underwent a reduction in plant growth/health in exchange for improved defense against stress that was observable 3 weeks after psyllid infestation. Consistent with these observations, tomato plant growth experiments determined that the plants were shorter 3 weeks after psyllid infestation. Furthermore, psyllid nymphs had lower survival rates on tomato plants that had been previously psyllid infested. CONCLUSION: These results suggested that psyllid infestation has lasting consequences for tomato gene expression, defense, and growth.

Methods for Surveying Stable Fly Populations.

Stable flies are among the most important pests of livestock throughout much of the world. Their painful bites induce costly behavioral and physiological stress responses and reduce productivity. Stable flies are anthropogenic and their population dynamics vary depending on agricultural and animal husbandry practices. Standardized sampling methods are needed to better identify the factors controlling stable fly populations, test novel control technologies, and determine optimal management strategies. The current study reviewed methods used for a long-term study of stable fly population dynamics in the central Great Plains. An additional study compared the relative size of flies sampled from the general population with that of flies sampled emerging from substrates associated with livestock production. Flies developing in livestock associated substrates are significantly larger than those in the general population indicating that other types of developmental sites are contributing significant numbers of flies to the general population. Because efforts to identify those sites have yet to be successful, we speculate that they may be sites with low densities of developing stable flies, but covering large areas such as croplands and grasslands. The stable fly surveillance methods discussed can be used and further improved for monitoring stable fly populations for research and management programs.

Mycorrhization Mitigates Disease Caused by "Candidatus Liberibacter solanacearum" in Tomato.

Disease caused by the bacterial pathogen "Candidatus Liberibacter solanacearum" (Lso) represents a serious threat to solanaceous crop production. Insecticide applications to control the psyllid vector, Bactericera cockerelli Sulc (Hemiptera: Triozidae) has led to the emergence of resistance in psyllids populations. Efforts to select natural resistant cultivars have been marginally successful and have been complicated by the presence of distinct Lso haplotypes (LsoA, LsoB) differing in symptoms severity on potato and tomato. A potentially promising management tool is to boost host resistance to the pathogen and/or the insect vector by promoting mycorrhization. Here we tested the hypothesis that mycorrhizal fungi can mitigate the effect of Lso infection on tomato plants. The presence of mycorrhizal fungi substantially delayed and reduced the incidence of Lso-induced symptoms on tomato as compared to non-mycorrhized plants. However, PCR with specific Lso primers revealed that mycorrhization did not prevent Lso transmission or translocation to newly formed leaves. Mycorrhization significantly reduced oviposition by psyllids harboring LsoA and survival of nymphs from these eggs. However, mycorrhization had no effect on oviposition by psyllids harboring LsoB or the survival of nymphs from parents harboring LsoB. These findings indicate the use of mycorrhizal fungi is a promising strategy for the mitigation of disease caused by both LsoA and LsoB and warrants additional field testing.

Did maize domestication and early spread mediate the population genetics of corn leafhopper?

Investigating how crop domestication and early farming mediated crop attributes, distributions, and interactions with antagonists may shed light on today's agricultural pest problems. Crop domestication generally involved artificial selection for traits desirable to early farmers, for example, increased productivity or yield, and enhanced qualities, though invariably it altered the interactions between crops and insects, and expanded the geographical ranges of crops. Thus, some studies suggest that with crop domestication and spread, insect populations on wild crop ancestors gave rise to pestiferous insect populations on crops. Here, we addressed whether the emergence of corn leafhopper (Dalbulus maidis) as an agricultural pest may be associated with domestication and early spread of maize (Zea mays mays). We used AFLP markers and mitochondrial COI sequences to assess population genetic structuring and haplotype relationships among corn leafhopper samples from maize and its wild relative Zea diploperennis from multiple locations in Mexico and Argentina. We uncovered seven corn leafhopper haplotypes contained within two haplogroups, one haplogroup containing haplotypes associated with maize and the other containing haplotypes associated with Z. diploperennis in a mountainous habitat. Within the first haplogroup, one haplotype was predominant across Mexican locations, and another across Argentinean locations; both were considered pestiferous. We suggested that the divergence times of the maize-associated haplogroup and of the "pestiferous" haplotypes are correlated with the chronology of maize spread following its domestication. Overall, our results support a hypothesis positing that maize domestication favored corn leafhopper genotypes preadapted for exploiting maize so that they became pestiferous, and that with the geographical expansion of maize farming, corn leafhopper colonized Z. diploperennis, a host exclusive to secluded habitats that serves as a refuge for archaic corn leafhopper genotypic diversity. Broadly, our results help explain the extents to which crop domestication and early spread may have mediated the emergence of today's agricultural pests.

Infection by Candidatus Liberibacter solanacearum' haplotypes A and B in Solanum lycopersicum 'Moneymaker'.

'Candidatus Liberibacter solanacearum' is a plant pathogen associated with diseases affecting several crops of the Solanaceae and Apiaceae families. Two 'Ca. L. solanacearum' haplotypes (LsoA and LsoB) infect solanaceous crops in North America and are transmitted by the tomato psyllid Bactericera cockerelli. Although both 'Ca. L. solanacearum' haplotypes cause zebra chip in potato, the diseases associated with each haplotype in tomato (Solanum lycopersicum) have not been described. 'Ca. L. solanacearum'-infected tomato plants exhibit symptoms resembling those of permanent yellowing disease (known in Mexico as "permanente del tomate") and sometimes called psyllid yellows. In this study, the symptoms associated with each 'Ca. L. solanacearum' haplotype in tomato were compared, and the bacterial abundance in different nodes of the plants was measured by quantitative polymerase chain reaction. Surprisingly, both plant phenotype and bacterium distribution were different between LsoA- and LsoB-infected plants. Plants infected with LsoB died prematurely, whereas those infected with LsoA did not. Across the measured time points, LsoB abundance in infected plants was consistent with previous reports describing a sink to source gradient, while such gradient was only observed in LsoA-infected plants early after infection. This is the first report describing the differences in symptoms in tomato associated with two 'Ca. L. solanacearum' haplotypes, LsoA and LsoB.

Development of an Objective Structured Clinical Examination Using the American Board of Anesthesiology Content Outline for the Objective Structured Clinical Examination Component of the APPLIED Certification Examination.

The goal of this study was to use the American Board of Anesthesiology Objective Structured Clinical Examination (OSCE) content outline as a blueprint to develop and administer a 9-station mock OSCE with station-specific checklists to senior residents (n = 14). The G- and Ф-coefficient reliability estimates were 0.76 and 0.61, respectively. Residents judged the scenarios as either extremely or somewhat realistic (88%). It is feasible to develop and administer a mock OSCE with rigorous psychometric characteristics.