Plant Science


Publications (695)

Effects of ‘Candidatus Liberibacter solanacearum’ haplotypes A and B on tomato gene expression and geotropism

Citation
Harrison et al. (2022). BMC Plant Biology 22 (1)
Names
Ca. Liberibacter solanacearum
Subjects
Plant Science
Abstract
Abstract Background The tomato psyllid, Bactericera cockerelli Šulc (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.

<i>Candidatus</i> Liberibacter asiaticus accumulation in the phloem inhibits callose and reactive oxygen species

Citation
Bernardini et al. (2022). Plant Physiology 190 (2)
Names
Ca. Liberibacter asiaticus
Subjects
Genetics Physiology Plant Science
Abstract
CLas inhibits callose deposition in the sieve pores and the accumulation of reactive oxygen species to favor its cell-to-cell movement.

Candidatus Phytoplasma Australasia Associated with Alfalfa Witches’ Broom: Symptomatology, Quantitative Loss, Qualitative Loss and Molecular Characterization

Citation
Mahesha et al. (2022). LEGUME RESEARCH - AN INTERNATIONAL JOURNAL (Of)
Names
Ca. Phytoplasma australasia Ca. Phytoplasma
Subjects
Agronomy and Crop Science Plant Science Soil Science
Abstract
Background: Alfalfa, Medicago sativa L. is the most important and widely grown leguminous fodder crop in temperate and tropical regions of the world. The production of alfalfa crop is limited by several biotic stresses, among which witches’ broom disease (AWB) was reported to cause significant economic losses. Methods: The phytoplasma infected alfalfa plants were collected from a central research farm, ICAR-IGFRI, Jhansi, U.P. Qualitative parameters such as crude protein content, acid detergent fibre and neutral detergent fibre were estimated in diseased and healthy plants. Phytoplasma universal primer (P1/P7) and nested primer (R16mF2/R16mR1) were used for the molecular characterization of AWB infected plants and phytoplasma infected, Parthenium hysterophorus. Result: The incidence of AWB disease ranged from 8-10%. The quantitative analysis of disease plants showed reduced plant height (-35%), fresh weight (-46.89%) and dry weight (-50.08%) compared to healthy plants. The diseased plant recorded low crude protein content (-21.38%) and higher dry matter content (+0.68%), acid detergent fibre (+33.72%) and neutral detergent fibre (+13.06%). The association of phytoplasma in diseased alfalfa and parthenium samples was confirmed by using P1/P7 and R16mF2/R16mR1 primer pair and Blastn analysis shared 99.6-100% similarity with ‘Candidatus Phytoplasma australasia’ belongs to the 16Sr group II-D.

SÍNTOMAS FOLIARES, BIOMASA Y CALIDAD DE TUBÉRCULO DE GENOTIPOS DE PAPA INOCULADOS CON Candidatus Liberibacter solanacearum

Citation
Hidalgo-Gómez et al. (2022). Revista Fitotecnia Mexicana 45 (3)
Names
Ca. Liberibacter solanacearum
Subjects
Agronomy and Crop Science Genetics Horticulture Plant Science
Abstract
Las variedades de papa (Solanum tuberosum L.) producidas en México son susceptibles a Candidatus Liberibacter solanacearum (CaLso), causante de la enfermedad conocida como ‘manchado interno de la pulpa’, por lo que se requiere conocer la respuesta de genotipos experimentales a la bacteria. El presente estudio tuvo como objetivo evaluar el efecto de la infección de los haplotipos LsoA + LsoB de CaLso en el follaje, la biomasa seca y la calidad de tubérculo de papa, variedad Fianna, una colecta de Solanum demissum y los clones experimentales T90-1-63 y T05-13-21 de Solanum spp. El manchado interno de la pulpa del tubérculo se determinó mediante análisis de imágenes de tubérculos. Las plantas de Fianna mostraron la mayor severidad de daño foliar; en cambio, los clones experimentales presentaron 17 % menos daño foliar que Fianna y 8 % más daño foliar que S. demissum. Este último fue el genotipo con la mayor biomasa seca de hoja y produjo tubérculos de un tamaño pequeño; las plantas infectadas de S. demissum presentaron mayor número de tubérculos y mayor rendimiento de tubérculo fresco que las plantas sin inoculación, aunque tuvieron la menor proporción de superficie sana del tubérculo. El clon T90-1-63 presentó los porcentajes más altos de superficie sana de tubérculo (&gt; 79 %) y las menores intensidades del manchado interno de la pulpa del tubérculo.

Insight into resistance to ‘Candidatus Liberibacter asiaticus,’ associated with Huanglongbing, in Oceanian citrus genotypes

Citation
Alves et al. (2022). Frontiers in Plant Science 13
Names
Ca. Liberibacter asiaticus Liberibacter
Subjects
Plant Science
Abstract
Huanglongbing (HLB), the most destructive citrus disease, is associated with unculturable, phloem-limited Candidatus Liberibacter species, mainly Ca. L. asiaticus (Las). Las is transmitted naturally by the insect Diaphorina citri. In a previous study, we determined that the Oceanian citrus relatives Eremocitrus glauca, Microcitrus warburgiana, Microcitrus papuana, and Microcitrus australis and three hybrids among them and Citrus were full-resistant to Las. After 2 years of evaluations, leaves of those seven genotypes remained Las-free even with their susceptible rootstock being infected. However, Las was detected in their stem bark above the scion-rootstock graft union. Aiming to gain an understanding of the full-resistance phenotype, new experiments were carried out with the challenge-inoculated Oceanian citrus genotypes through which we evaluated: (1) Las acquisition by D. citri fed onto them; (2) Las infection in sweet orange plants grafted with bark or budwood from them; (3) Las infection in sweet orange plants top-grafted onto them; (4) Las infection in new shoots from rooted plants of them; and (5) Las infection in new shoots of them after drastic back-pruning. Overall, results showed that insects that fed on plants from the Oceanian citrus genotypes, their canopies, new flushes, and leaves from rooted cuttings evaluated remained quantitative real-time polymerase chain reaction (qPCR)-negative. Moreover, their budwood pieces were unable to infect sweet orange through grafting. Furthermore, sweet orange control leaves resulted infected when insects fed onto them and graft-receptor susceptible plants. Genomic and morphological analysis of the Oceanian genotypes corroborated that E. glauca and M. warburgiana are pure species while our M. australis accession is an M. australis × M. inodora hybrid and M. papuana is probably a M. papuana × M. warburgiana hybrid. E. glauca × C. sinensis hybrid was found coming from a cross between E. glauca and mandarin or tangor. Eremocitrus × Microcitrus hybrid is a complex admixture of M. australasica, M. australis, and E. glauca while the last hybrid is an M. australasica × M. australis admixture. Confirmation of consistent full resistance in these genotypes with proper validation of their genomic parentages is essential to map properly genomic regions for breeding programs aimed to generate new Citrus-like cultivars yielding immunity to HLB.