scholarly journals Plant hairy roots enable high throughput identification of antimicrobials against Candidatus Liberibacter spp.

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Sonia Irigoyen ◽  
Manikandan Ramasamy ◽  
Shankar Pant ◽  
Prakash Niraula ◽  
Renesh Bedre ◽  
...  
Keyword(s):  
Hairy Roots ◽  
Plant Diseases ◽  
Citrus Greening ◽  
Zebra Chip ◽  
Whole Plant ◽  
Candidatus Liberibacter ◽  
Major Bottleneck ◽  
Antimicrobial Evaluation ◽  
Plant Assays

AbstractA major bottleneck in identifying therapies to control citrus greening and other devastating plant diseases caused by fastidious pathogens is our inability to culture the pathogens in defined media or axenic cultures. As such, conventional approaches for antimicrobial evaluation (genetic or chemical) rely on time-consuming, low-throughput and inherently variable whole-plant assays. Here, we report that plant hairy roots support the growth of fastidious pathogens like Candidatus Liberibacter spp., the presumptive causal agents of citrus greening, potato zebra chip and tomato vein greening diseases. Importantly, we leverage the microbial hairy roots for rapid, reproducible efficacy screening of multiple therapies. We identify six antimicrobial peptides, two plant immune regulators and eight chemicals which inhibit Candidatus Liberibacter spp. in plant tissues. The antimicrobials, either singly or in combination, can be used as near- and long-term therapies to control citrus greening, potato zebra chip and tomato vein greening diseases.

scholarly journals ‘Candidatus Liberibacter solanacearum’ Titers in and Infection Effects on Potato Tuber Chemistry of Promising Germplasm Exhibiting Tolerance to Zebra Chip Disease

2015 ◽  
Vol 105 (12) ◽  
pp. 1573-1584 ◽  
Author(s):  
C. M. Wallis ◽  
J. E. Munyaneza ◽  
J. Chen ◽  
R. Novy ◽  
G. Bester ◽  
...  
Keyword(s):  
Host Responses ◽  
Zebra Chip ◽  
Candidatus Liberibacter Solanacearum ◽  
Potato Varieties ◽  
Potato Plants ◽  
Potato Germplasm ◽  
Zebra Chip Disease ◽  
Candidatus Liberibacter ◽  
Selection Of

Long-term sustainable management of zebra chip (ZC) disease of potato requires development of tolerant or resistant germplasm. To this end, 283 potato varieties and breeding clones were infected with the ZC putative causal agent ‘Candidatus Liberibacter solanacearum’ (Lso) by potato psyllid vector inoculations in 2010, 2011, 2012, and 2013. Potato germplasm was then examined for development of fresh and fried ZC symptoms. Over multiple years 29 breeding clones exhibited little to no symptoms in freshly cut tuber slices, and five exhibited little to no symptoms in fried slices. These five presumed tolerant breeding clones were chosen for further screening to determine whether the lack of physiological responses to Lso infection was the cause of observed tolerance. To this end, tuber amino acid, sugar, and phenolic levels were compared between noninfected and Lso-infected plants. The five putative tolerant clones had less dramatic shifts in host physiology following Lso infection than the susceptible Atlantic cultivar. This suggested lack of host responses to Lso infection that result in major changes in tuber biochemistry is a potential mechanism of ZC resistance. However, the susceptible Atlantic cultivar did have consistently greater Lso titers compared with two of the tolerant entries, so for these reductions in Lso pathogen progression also might be a factor. Regardless, lack of host responses could still remain one trait that could be used to aid in selection of ZC-resistant potato varieties, as other tolerant lines had infection levels consistent with susceptible Atlantic cultivar. These results also suggest that germplasm derived from relatives of cultivated potato plants are viable sources of ZC disease resistance.

Differences in Zebra Chip Severity between ‘Candidatus Liberibacter Solanacearum’ Haplotypes in Texas

2018 ◽  
Vol 96 (1) ◽  
pp. 86-93 ◽  
Author(s):  
Kyle Harrison ◽  
Cecilia Tamborindeguy ◽  
Douglas C. Scheuring ◽  
Azucena Mendoza Herrera ◽  
Adrian Silva ◽  
...  
Keyword(s):  
Zebra Chip ◽  
Candidatus Liberibacter Solanacearum ◽  
Candidatus Liberibacter

scholarly journals Testing for ion-mediated enhancement of the hydraulic conductance of the leaf xylem in diverse angiosperms

2017 ◽  
Vol 4 ◽  
pp. e004 ◽  
Author(s):  
Christine Scoffoni ◽  
Grace John ◽  
Herve Cochard ◽  
Lawren Sack
Keyword(s):  
Water Solution ◽  
Pure Water ◽  
Xylem Sap ◽  
Hydraulic Conductance ◽  
Membrane Pores ◽  
Whole Plant ◽  
Pit Membrane ◽  
Major Bottleneck ◽  
The Difference ◽  
Xylem Conduits

Replacing ultra-pure water solution with ion solution closer to the composition of natural xylem sap increases stem hydraulic conductance by up to 58%, likely due to changes in electroviscosity in the pit membrane pores. This effect has been proposed to contribute to the control of plant hydraulic and stomatal conductance and potentially to influence on carbon balance during dehydration. However, this effect has never been directly tested for leaf xylem, which constitutes a major bottleneck in the whole plant. We tested for an ion-mediated increase in the hydraulic conductance of the leaf xylem (Kx) for seven species diverse in phylogeny and drought tolerance. Across species, no significant changes in Kx were observed between 0 and 15 mM KCl. We further tested for an effect of ion solution during measurements of Kx vulnerability to dehydration in Quercus agrifolia and found no significant impact. These results for leaf xylem contrast with the often strong ion effect reported for stems, and we suggest several hypotheses to account for the difference, relating to the structure of xylem conduits across vein orders, and the ultrastructure of leaf xylem pores. A negligible ion response in leaves would weaken xylem sap ion-mediated control of plant hydraulic conductance, facilitating modeling of whole plant hydraulic behavior and its influence on productivity.

scholarly journals Population Dynamics of Released Potato Psyllids and their Bacteriliferous Status in Relation to Zebra Chip Incidence in Caged Field Plots

Plant Disease ◽  
2016 ◽  
Vol 100 (8) ◽  
pp. 1762-1767 ◽  
Author(s):  
F. Workneh ◽  
L. Paetzold ◽  
A. Rashed ◽  
C. M. Rush
Keyword(s):  
Disease Incidence ◽  
Sticky Trap ◽  
Research Station ◽  
Zebra Chip ◽  
Sticky Traps ◽  
Monitoring Tools ◽  
Candidatus Liberibacter ◽  
Yellow Sticky Trap ◽  
Successive Generations ◽  
Field Plots

Potato psyllids vector ‘Candidatus Liberibacter solanacearum’ (Lso), the putative causal agent of potato zebra chip (ZC). Currently, sticky traps are the primary psyllid monitoring tools used by growers for making management decisions. However, the reliability of sticky traps in predicting psyllid numbers in potato fields has always been questioned. In 2013 and 2014, experiments were conducted in covered field plots at the Texas A&M AgriLife Research Station at Bushland to investigate the relationships among initial psyllid numbers, psyllids captured on sticky traps and their Lso status, and zebra chip incidence. Three densities of Lso-positive psyllids (5, 15, or 30/cage) were released under 2-week-old potato canopies with four replications in plot sizes of 7.6 to 9 m by 5 rows. Psyllids were released under the first plant in the center row and monitored weekly with a yellow sticky trap from the opposite end. Number of plants with zebra chip symptoms also was counted weekly beginning one month after infestation with psyllids. The total number of psyllids captured on sticky traps and disease incidence levels generally corresponded to the levels of psyllid density treatments (5 < 15 < 30), but the differences became more apparent toward the end of the experiments. Psyllid numbers in the different density treatments fluctuated more or less in synchrony over time, which appeared to reflect periodic emergence of new generations of psyllids. Initially, all captured psyllids tested positive for Lso. However, the proportions of psyllids testing positive declined dramatically after a few weeks, which suggested that the new generations of psyllids were devoid of Lso. Over all, less than 50% of captured psyllids tested positive for the pathogen. The decline in proportions of psyllids testing positive for Lso following successive generations has significant relevance to field situations and may partly explain why there are generally low percentages of Lso-positive psyllids under field conditions.

scholarly journals ‘Candidatus Liberibacter asiaticus’ Encodes a Functional Salicylic Acid (SA) Hydroxylase That Degrades SA to Suppress Plant Defenses

2017 ◽  
Vol 30 (8) ◽  
pp. 620-630 ◽  
Author(s):  
Jinyun Li ◽  
Zhiqian Pang ◽  
Pankaj Trivedi ◽  
Xiaofeng Zhou ◽  
Xiaobao Ying ◽  
...  
Keyword(s):  
Salicylic Acid ◽  
Enzymatic Activity ◽  
Plant Defenses ◽  
Plant Diseases ◽  
Transgenic Tobacco Plants ◽  
Candidatus Liberibacter Asiaticus ◽  
Tobacco Plants ◽  
Candidatus Liberibacter ◽  
Liberibacter Asiaticus ◽  
Management Approaches

Pathogens from the fastidious, phloem-restricted ‘Candidatus Liberibacter’ species cause the devastating Huanglongbing (HLB) disease in citrus worldwide and cause diseases on many solanaceous crops and plants in the Apiaceae family. However, little is known about the pathogenic mechanisms due to the difficulty in culturing the corresponding ‘Ca. Liberibacter’ species. Here, we report that the citrus HLB pathogen ‘Ca. L. asiaticus’ uses an active salicylate hydroxylase SahA to degrade salicylic acid (SA) and suppress plant defenses. Purified SahA protein displays strong enzymatic activity to degrade SA and its derivatives. Overexpression of SahA in transgenic tobacco plants abolishes SA accumulation and hypersensitive response (HR) induced by nonhost pathogen infection. By degrading SA, ‘Ca. L. asiaticus’ not only enhances the susceptibility of citrus plants to both nonpathogenic and pathogenic Xanthomonas citri but also attenuates the responses of citrus plants to exogenous SA. In addition, foliar spraying of 2,1,3-benzothiadiazole and 2,6-dichloroisonicotinic acid, SA functional analogs not degradable by SahA, displays comparable (and even better) effectiveness with SA in suppressing ‘Ca. L. asiaticus’ population growth and HLB disease progression in infected citrus trees under field conditions. This study demonstrates one or more pathogens suppress plant defenses by degrading SA and establish clues for developing novel SA derivatives-based management approaches to control the associated plant diseases.

scholarly journals The emergent diseases in grapevine nursery: Critical point analysis for developing a protected and sustainable propagation process

2019 ◽  
Vol 15 ◽  
pp. 01026
Author(s):  
E. Battiston ◽  
S. Di Marco ◽  
E. Angelini ◽  
L. Mugnai
Keyword(s):  
Critical Point ◽  
Economic Impact ◽  
Environmental Sustainability ◽  
Plant Diseases ◽  
Propagation Process ◽  
Point Analysis ◽  
Propagation Material ◽  
Critical Point Analysis

The diffusion of emergent pathogens in grapevine nursery is increasingly compromising the sanitary quality of the propagation material. The complexity of the problem lies on the plurality of plant diseases involved and on the high environmental and economic impact of the conventional methods applied to comply the phytosanitary standards. By a critical point analysis, the study suggests the development of nursery strategies focused on the sanitary quality of the production and on its long-term environmental sustainability.

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