We have created an open access web portal with pathosystem-wide resources and bioinformatics tools for the host citrus, the vector Asian citrus psyllid (ACP) and multiple pathogens including Ca. Liberibacter asiaticus. To the best of our knowledge, this is the first example of a database to use the pathosystem as a holistic framework to understand an insect transmitted plant disease. This endeavor integrates and enables the analysis of data sets generated by the community to study the citrus greening disease complex. Users can submit relevant data sets to enable sharing and allow the community to better analyze their data within an integrated system. The portal contains a variety of tools for omics data. Metabolic pathway databases, CitrusCyc and DiaphorinaCyc provide organism specific pathways that can be used to mine metabolomics, transcriptomics and proteomics results to identify pathways and regulatory mechanism involved in disease response. Psyllid Expression Network (PEN) contains expression profiles of ACP genes from multiple life stages, tissues, conditions and hosts. Citrus Expression Network (CEN) contains public expression data from multiple tissues and conditions for various citrus hosts. All tools like Apollo/JBrowse, Biocyc, Blast, CEN and PEN connect to a central database containing gene models for citrus, ACP and multiple Liberibacter pathogens. The portal also includes electrical penetration graph (EPG) recordings of ACP feeding on citrus, information about citrus rootstock trials and metabolomics data in addition to traditional omics data types with a goal of combining and mining all information related to a pathosystem. The portal includes user-friendly manual curation tools to allow the research community to continuously improve this knowledge base as more experimental research is published. Bulk downloads are available for all genome and annotation datasets from the FTP site (ftp://ftp.citrusgreening.org). The portal can be accessed at https://citrusgreening.org/.

"Candidatus Liberibacter asiaticus" is the causative bacterium associated with 24 citrus greening disease. "Ca. L. asiaticus" is transmitted by Diaphorina citri more efficiently 25 when it is acquired by nymphs rather than adults. Why this occurs is not known. We compared 26 midguts of D. citri reared on healthy or "Ca. L. asiaticus"-infected citrus trees using quantitative 27 PCR, confocal microscopy, and mitochondrial superoxide staining for evidence of oxidative 28 stress. Consistent with its classification as propagative, "Ca. L. asiaticus" titers were higher in 29 adults as compared to nymphs. Our previous work showed that adult D. citri show basal levels of 30 karyorrhexis, (fragmentation of the nucleus), in midgut epithelial cells which is increased in 31 severity and frequency in response to "Ca. L. asiaticus". Here, we show that nymphs exhibit 32 lower levels of early-stage karyorrhexis as compared to adults and are refractory to the induction 33 of advanced karyorrhexis by "Ca. L. asiaticus" in the midgut epithelium. MitoSox Red staining 34showed that guts of infected adults, particularly males, experience oxidative stress in response to 35 "Ca. L. asiaticus." A positive correlation between the titers of "Ca. L. asiaticus" and the 36Wolbachia endosymbiont was observed in adult and nymph midguts, suggesting an interplay 37 between these bacteria during development. We hypothesize that the resistance of the nymph 38 midgut to late stage karyorrhexis through as yet unknown molecular mechanisms benefits "Ca. 39

Vector-borne plant diseases have significant ecological and economic impacts, affecting farm profitability and forest composition throughout the world. Bacterial vector-borne pathogens have evolved sophisticated strategies to interact with their hemipteran insect vectors and plant hosts. These pathogens reside inplant vascular tissue, and their study represents an excellent opportunity to uncover novel biological mechanisms regulating intracellular pathogenesis and to contribute to the control of some of the world’s most invasive emerging diseases. In this perspective, we highlight recent advances and major unanswered questions in the realm of bacterial vector-borne disease, focusing on liberibacters, phytoplasmas, spiroplasmas, and Xylella fastidiosa .

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Diaphorina citri is a vector of ‘ Candidatus Liberibacter asiaticus, ’ ( C Las), associated with Huanglongbing, (HLB, or citrus greening) disease in citrus. D . citri exhibits three different color morph variants, blue, gray and yellow. Blue morphs have a greater capacity for long-distance flight as compared to non-blue morphs, but little else is known about how color morphology influences vector characteristics. In this study, we show that the color morphology of the insect is derived from pigmented cells of the fat body. Blue morphs acquire a lower level of C Las in their bodies from infected trees as compared to their gray and yellow conspecifics, referred to in this paper collectively as non-blue morphs. Accordingly, C Las titer in citrus leaves inoculated by non-blue insects was 6-fold higher than in leaves inoculated by blue insects. Blue color morphs harbored lower titers of Wolbachia and ‘ Candidatus Profftella armatura,’ two of the D . citri bacterial endosymbionts. Expression of hemocyanin, a copper-binding oxygen transport protein responsible for the blue coloration of hemolymph of other arthropods and mollusks, was previously correlated with blue color morphology and is highly up-regulated in insects continuously reared on C Las infected citrus trees. Based on our results, we hypothesized that a reduction of hemocyanin expression would reduce the D . citri immune response and an increase in the titer of C Las would be observed. Surprisingly, a specific 3-fold reduction of hemocyanin-1 transcript levels using RNA silencing in blue adult D . citri morphs had an approximately 2-fold reduction on the titer of C Las. These results suggest that hemocyanin signaling from the fat body may have multiple functions in the regulation of bacterial titers in D . citri , and that hemocyanin is one of multiple psyllid genes involved in regulating C Las titer.

Zinc deficiency has been reported after P fertilization of corn (Zea mays L.), but reasons for this deficiency are not clear. A field experiment was conducted for 3 years from 1970 to 1973 with a fixed wheat‐corn rotation to determine the effect of P and Zn fertilization on corn yield, uptake, and translocation of Zn, and to evaluate the parameters that would monitor best the P‐Zn interaction in corn. Five rates of P (0, 22, 44, 66, and 88 kg of P/ha), and four rates of Zn (0, 11, 22, and 44 kg of Zn/ha) were applied to P and Zn‐deficient soil (Ustipsamments) using a split‐plot design (with P in the main plots and Zn in the subplots). P was applied to all the six crops and Zn only to the first and second crops. Optimum response of corn to P was observed at 44 kg of P/ha. The high P supply beyond the optimum P rate produced severe Zn‐deficiency symptoms in treatments without added Zn and a significant decrease in grain and stover yields. This resulted from a significant decrease of Zn and a significant increase of P concentration in the shoots of the plant with a high P supply. An increase in the supply of Zn alleviated its deficiency symptoms, significantly increased Zn concentration and its uptake and resulted in a significant increase in growth and yield. The requirement of Zn increased at high (66 to 88 kg/ha) rates of P fertilization. The main effect of P on Zn utilization by corn was to reduce the rate of Zn entry into the roots and induce zinc deficiency. The P‐Zn disorder was better related with P/Zn ratio in the soil and in different parts of the corn plant than either with the P or Zn content of the tissues and soil. Values of P/Zn greater than 7.5 in the soil, 245 in grain, 130 in stover, 150 in the leaves (of 25‐day‐old plants) indicated a severe Zn deficiency in corn and a highly significant response to its application. The P/Zn values 4 to 7.5 in the soil, 150 to 245 in the grain, 90 to 130 in the stover, and 100 to 150 in the leaves indicated moderate Zn deficiency or response to its application.

Abstract. Single or multiple factors implicated in subsoil constraints including salinity, sodicity, and phytotoxic concentrations of chloride (Cl) are present in many Vertosols including those occurring in Queensland, Australia. The variable distribution and the complex interactions that exist between these constraints limit the agronomic or management options available to manage the soil with these subsoil constraints. The identification of crops and cultivars adapted to these adverse subsoil conditions and/or able to exploit subsoil water may be an option to maintain productivity of these soils. We evaluated relative performance of 5 winter crop species, in terms of grain yields, nutrient concentration, and ability to extract soil water, grown on soils with various levels and combinations of subsoil constraints in 19 field experiments over 2 years. Subsoil constraints were measured by levels of soil Cl, electrical conductivity of the saturation extract (EC se ), and exchangeable sodium percentage (ESP). Increasing levels of subsoil constraints significantly decreased maximum depth of water extraction, grain yield, and plant-available water capacity for all the 5 crops and more so for chickpea and durum wheat than bread wheat, barley, or canola. Increasing soil Cl levels had a greater restricting effect on water availability than did EC se and ESP. We developed empirical relationships between soil Cl, EC se , and ESP and crop lower limit (CLL) for estimating subsoil water extraction by 5 winter crops. However, the presence of gypsum influenced the ability to predict CLL based on the levels of EC se . Stronger relationships between apparent unused plant-available water (CLL -LL15; LL15 is lower limit at −1.5 MPa) and soil Cl concentrations than ESP or EC se suggested that the presence of high Cl in these soils most likely inhibited the subsoil water extraction by the crops. This was supported by increased sodium (Na) and Cl concentration with a corresponding decrease in calcium (Ca) and potassium (K) in young mature leaf of bread wheat, durum wheat, and chickpea with increasing levels of subsoil constraints. Of the 2 ions, Na and Cl, the latter appears to be more damaging than the former, resulting in plant dieback and reduced grain yields.

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