Flexible regression model for predicting the dissemination of Liberibacter asiaticus under variable climatic conditions.

Greening, or Huanglongbing (HLB), poses a severe threat to global citrus cultivation, affecting various citrus species and compromising fruit production. Primarily transmitted by psyllids during phloem feeding, the bacterium Liberibacter induces detrimental symptoms, including leaf yellowing and reduced fruit quality. Given the limitations of conventional control strategies, the search for innovative approaches, such as resistant genotypes and early diagnostic methods, becomes essential for the sustainability of citrus cultivation.

Impacts of huanglongbing on fruit yield and quality and on flushing dynamics of Sicilian lemon trees.

Introduction: The severe Asian form of huanglongbing (HLB), a vascular disease associated with the phloem-limited bacterium ' Liberibacter asiaticus', is transmitted by the Asian citrus psyllid (ACP) . Disease impacts are known for sweet oranges and acid limes but not lemons.

Methods: In a five-year study (2017-2021) we compared yield and fruit quality between naturally-infected and healthy 5-yr-old trees of Sicilian lemon 'Femminello', and shoot phenology on both lemon and 'Valencia' orange, both grafted onto 'Swingle' citrumelo, grown in southeastern São Paulo State, Brazil.

Early Population Dynamics of " Liberibacter asiaticus" in Susceptible and Resistant Genotypes After Inoculation With Infected Feeding on Young Shoots.

Huanglongbing is a highly destructive citrus disease associated with " Liberibacter asiaticus" (Las), a phloem-limited and non-culturable bacterium, naturally transmitted by the psyllid Although diverse approaches have been used to understand the molecular mechanisms involved in the pathogen-host interaction, such approaches have focused on already infected and/or symptomatic plants, missing early events in the initial days post-inoculation. This study aimed to identify the time course of Las multiplication and whole-plant colonization immediately following inoculation by infected psyllids feeding for 2 days. Thus, the experimental approach was to track Las titers after psyllid inoculation in new shoots (NS) of (susceptible), (partially resistant), and (fully resistant).

Protocol for Successful Transmission of ' Liberibacter asiaticus' from Citrus to Citrus Using .

A protocol to successfully transmit the huanglongbing (HLB) pathogen, ' Liberibacter asiaticus', between citrus plants by using the Asian citrus psyllid (ACP) and an alternative way to help growers control ACP are proposed. Best results were obtained when pathogen acquisition by adults reared on fully symptomatic ' Liberibacter asiaticus'-positive plants, latency, and inoculation occurred at ambient air temperatures ranging from 24 to 28°C and when a single infective adult ACP was confined for 7 days on soft, newly developing vegetative shoots (stages v2 to v4). No infection resulted from confinement of infective ACP adults on mature leaves (stage v6).

Modeling ' Liberibacter asiaticus' Movement Within Citrus Plants.

The phloem-limited ' Liberibacter asiaticus' (Las) causes huanglongbing, a destructive citrus disease. Graft-inoculated potted plants were used to assess Las speed of movement in phloem in the greenhouse, and the impacts of temperature on plant colonization in growth-chamber experiments. For assessment of Las speed, plants were inoculated at the main stem and assessed over time by quantitative PCR (qPCR) or symptoms at various distances from the inoculum.

Evidence That ' Liberibacter asiaticus' Moves Predominantly Toward New Tissue Growth in Citrus Plants.

' Liberibacter asiaticus' (Las) is an unculturable, phloem-limited, insect-transmitted bacterium associated with the Asiatic form of huanglongbing (HLB), the most destructive citrus disease. In Asia and the Americas, it is transmitted by the Asian citrus psyllid ( Kuwavama). Despite considerable research, little is known about the processes involved in plant infection and colonization by Las.

Optimization of sampling and monitoring of vegetative flushing in citrus orchards.

Citrus trees produce flushes throughout the year, but there are no criteria established for a precise shoot monitoring in orchards under tropical climate. Methods for quantification of flush dynamics would be useful for horticultural and pest management studies because different insect vectors feed and reproduce on flushes. We estimated the minimum number and distribution of trees for sampling and determined the flushing pattern over time in 'Valencia Late' orange trees grafted onto 'Swingle' citrumelo rootstock.

and as Short-Term Transient Hosts of ' Liberibacter asiaticus' and Implications for the Spread of Huanglongbing.

and are aurantioid hosts of the Asian citrus psyllid (ACP) , the principal vector of ' Liberibacter asiaticus' (Las). Las is the pathogen associated with huanglongbing (HLB), the Asian form of which is the most devastating disease of species and cultivars (Rutaceae: Aurantioideae). is a common ornamental and is grown as an ornamental, a citrus rootstock, and a hedgerow fence plant.

Citrus flush shoot ontogeny modulates biotic potential of Diaphorina citri.

The biology and behaviour of the psyllid Diaphorina citri Kuwayama (Hemiptera: Sternorrhyncha: Liviidae), the major insect vector of bacteria associated with huanglongbing, have been extensively studied with respect to host preferences, thermal requirements, and responses to visual and chemical volatile stimuli. However, development of the psyllid in relation to the ontogeny of immature citrus flush growth has not been clearly defined or illustrated. Such information is important for determining the timing and frequency of measures used to minimize populations of the psyllid in orchards and spread of HLB.

Seasonal Variation of 'Candidatus Liberibacter asiaticus' Titers in New Shoots of Citrus in Distinct Environments.

The major citrus area of Brazil occupies near 450,000 ha between the Triângulo Mineiro (TM) region of Minas Gerais State and the south of São Paulo State (SPS). Significant climatic variation occurs between regions which could affect huanglongbing (HLB) progress, which is lower in TM. To investigate this possibility, young sweet orange shoots were sampled periodically over 2 years to determine 'Candidatus Liberibacter asiaticus' titers in naturally infected trees in orchards in Analândia, central SPS, and Frutal and Comendador Gomes, within TM.