Xanthomonas Albilineans Detection, Identification and Infectivity Titration in Sugarcane.

A PCR method with primers for t-RNA gene spacers was used for detection of Xanthomonas albilineans (Xa), the causal agent of leaf scald disease of sugarcane. A DNA segment of approximately 170 bp was amplified for Xa strains, but also for X. campestris pv. campestris, X. campestris pv. translucens and two sugarcane bacterial endophytes. Good agreement between PCR and isolation to detect Xa from sugarcane sap was observed. PCR was faster allowing pathogen detection in less than one day. Both methods resulted in low detection frequencies from asymptomatic plants, which may contain Xa below detection limits. The lowest limit for PCR was 26 cfus per reaction or 1.3\times10\sp4 cfu/ml. Adoption of procedures to concentrate and lyse a larger number of bacterial cells could increase the PCR sensitivity. DNA from 42 Xa isolates from four countries and seven other bacterial species was analyzed by rep-PCR with BOX and ERIC primers. Generated fingerprints of Xa were distinct from the other bacterial species. Within Xa, seven, nine and twelve groups were revealed by BOX, ERIC, and BOX and ERIC combined, respectively. Good agreement between group clustering and geographic origin and serovars was observed. Fingerprints were reproduced with cell lysate. Rep-PCR was faster and more reliable than Biolog or pathogenicity assay and could be used to identify and study diversity in Xa. Greenhouse experiments were conducted to determine the potential of infectivity titration to assess sugarcane cultivar resistance to leaf scald. Single-bud-cuttings were inoculated with three Xa inoculum concentrations. An ED\sb{50} for each cultivar was estimated based on probit analysis of cumulative infection frequencies. Different ED\sb{50} values allowed cultivar grouping into three classes which were in agreement with field observations. Good agreement between ED\sb{50} values and cumulative frequencies of death and recovery in symptomatic plants, and the frequencies of symptomatic plants observed at different evaluation dates for plants inoculated with 10\sp8 cfu/ml of Xa, also was observed. Greenhouse assays, using infectivity titration or just one inoculum concentration, could provide an alternative to field tests for assessing sugarcane resistance to leaf scald

Reação de cultivares de laranjeira doce que expressam o gene atacina A à infecção com 'Candidatus Liberibacter asiaticus'

The objective of this work was to evaluate the reaction of four sweet orange cultivars expressing the attacin A gene to 'Candidatus Liberibacter asiaticus' (Las) infection, a bacterium associated to huanglongbing (HLB) disease. Transgenic sweet orange plants of Hamlin, Natal, Pêra, and Valência cultivars, as well as nontransgenic controls received inocula by grafting budwood sections of HLB‑infected branches. Disease progression was evaluated through observations of leaf symptoms and by polymerase chain reaction (PCR) analysis, eight months after inoculation. A completely randomized design was used, with four experiments (one for each cultivar) performed simultaneously. Bacteria title was estimated by quantitative PCR (qPCR). HLB symptoms and Las titers were present in nontransgenic and transgenic plants expressing the attacin A gene of the four sweet orange cultivars, eight months after bacteria inoculation. Five transgenic lines (transformation events) of 'Pêra' sweet orange expressing the attacin A gene have significantly lower Las titers in comparison with nontransgenic plants of this cultivar.O objetivo deste trabalho foi avaliar a reação de quatro cultivares de laranjeira doce que expressam o gene atacina A à infecção por 'Candidatus Liberibacter asiaticus' (Las), bactéria associada à doença huanglongbing (HLB). Plantas transgênicas das cultivares Hamlin, Natal, Pêra e Valência, bem como controles não transgênicos, receberam inóculos, por enxertia, de seções de ramos infectados por HLB. A progressão da doença foi avaliada pela observação de sintomas foliares e por análise da reação em cadeia da polimerase (PCR), oito meses após a inoculação. Utilizou-se o delineamento inteiramente casualizado, com quatro experimentos (um para cada cultivar) realizados simultaneamente. A concentração bacteriana foi estimada por PCR quantitativo (qPCR). Sintomas de HLB e Las estavam presentes em plantas não transgênicas e em plantas transgênicas que expressaram o gene atacina A, nas quatro cultivares de laranjeira doce, oito meses após a inoculação. Cinco linhagens transgênicas (eventos de transformação) de laranjeira 'Pêra', que expressam o gene atacina A, apresentam concentrações de Las significativamente inferiores às das plantas não transgênicas desta cultivar

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

IntroductionThe severe Asian form of huanglongbing (HLB), a vascular disease associated with the phloem-limited bacterium ‘Candidatus Liberibacter asiaticus’, is transmitted by the Asian citrus psyllid (ACP) Diaphorina citri. Disease impacts are known for sweet oranges and acid limes but not lemons.MethodsIn 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. HLB severity (percentage of tree canopy area with HLB symptoms) was assessed every 3–4 months, fruit yield and quality in May (2017 to 2019) or June/July (2020-2021), and vegetative and reproductive shoots fortnightly on 50-cm-long branches. The development of ACP on one-year-old seedlings of five lemon varieties, ‘Tahiti’ acid lime, ‘Valencia’ orange, and orange jasmine was evaluated.ResultsSymptoms increased from 11% in 2017 to 64% in 2021, and a monomolecular model estimated 10 years for symptoms to occupy >90% of the tree canopy. On average, production of trees with symptom on 20%, 50% or 80% of the canopy respectively dropped by 18%, 38%, and 53% compared to healthy trees. Fruits of symptomatic branches of lemons were 4.22% lighter and the number of dropped fruits did not correlate with symptom severity. Flushing on symptomatic branches started earlier by 15 to 55 days as compared to the healthy branches of lemon and orange. On diseased trees, vegetative and reproductive shoots respectively increased by 24.5% and 17.5% on lemon and by 67.2% and 70.6% on sweet orange, but fruit set was reduced by 12.9% and 19.7% on lemon and orange trees, respectively. ACP reproduced similarly on all tested plants.DiscussionThe fast symptom progress, significant yield reduction, and earlier flushing on diseased trees, providing conditions highly favorable for the pathogen to spread, reinforce the need of prompt diseased tree removal and frequent ACP preventive control to manage HLB in lemons as in any other citrus crop

The direction of UNESP (São Paulo State University) in terms of the Solidarity Economy

This paper aims to report on the University extension activities based on the principles of the Solidarity Economy, developed by teachers and students from several campuses of UNESP, in partnerships with other institutions and the communities involved. In addition to a brief history of the Solidarity Economy in Brazil, and the opportunities and challenges of Technological Incubators for Popular Cooperatives (ITCPs), the paper presents important considerations for an Institutional Program aimed at strengthening and expanding the role of such Incubators at UNESP

A trajetória da UNESP no contexto da Economia Solidária

This paper aims to report on the University extension activities based on the principles of the Solidarity Economy, developed by teachers and students from several campuses of UNESP, in partnerships with other institutions and the communities involved. In addition to a brief history of the Solidarity Economy in Brazil, and the opportunities and challenges of Technological Incubators for Popular Cooperatives (ITCPs), the paper presents important considerations for an Institutional Program aimed at strengthening and expanding the role of such Incubators at UNESP.En este trabajo damos cuenta de las experiencias de extensión universitaria basadas en los principios de la Economía Solidaria que han sido desarrolladas por profesores y estudiantes de diferentes sedes de la UNESP, en colaboración de otras instituciones y comunidades. Además de una breve historia de la Economía Solidaria en Brasil y reflexiones sobre las oportunidades y desafíos de las Incubadoras Tecnológicas de Cooperativas Populares (ITCPs), son presentados los elementos más importantes de un programa institucional para el fortalecimiento y la expansión de las Incubadoras en la UNESP.No presente trabalho, relatam-se experiências de extensão universitária fundamentadas nos princípios da Economia Solidária desenvolvidas pelos servidores docentes, servidores técnico-administrativos e discentes de várias Unidades da Universidade Estadual Paulista “Julio de Mesquita Filho” – UNESP, em parceria com outras instituições e com as comunidades envolvidas. Além de um breve histórico sobre a temática da Economia Solidária no Brasil e das oportunidades e desafios das Incubadoras Tecnológicas de Cooperativas Populares (ITCPs), apresentam-se importantes subsídios para uma proposta de Programa Institucional de fortalecimento e de expansão das Incubadoras na UNESP

A trajetória da UNESP no contexto da Economia Solidária

This paper aims to report on the University extension activities based on the principles of the Solidarity Economy, developed by teachers and students from several campuses of UNESP, in partnerships with other institutions and the communities involved. In addition to a brief history of the Solidarity Economy in Brazil, and the opportunities and challenges of Technological Incubators for Popular Cooperatives (ITCPs), the paper presents important considerations for an Institutional Program aimed at strengthening and expanding the role of such Incubators at UNESP.En este trabajo damos cuenta de las experiencias de extensión universitaria basadas en los principios de la Economía Solidaria que han sido desarrolladas por profesores y estudiantes de diferentes sedes de la UNESP, en colaboración de otras instituciones y comunidades. Además de una breve historia de la Economía Solidaria en Brasil y reflexiones sobre las oportunidades y desafíos de las Incubadoras Tecnológicas de Cooperativas Populares (ITCPs), son presentados los elementos más importantes de un programa institucional para el fortalecimiento y la expansión de las Incubadoras en la UNESP.No presente trabalho, relatam-se experiências de extensão universitária fundamentadas nos princípios da Economia Solidária desenvolvidas pelos servidores docentes, servidores técnico-administrativos e discentes de várias Unidades da Universidade Estadual Paulista “Julio de Mesquita Filho” – UNESP, em parceria com outras instituições e com as comunidades envolvidas. Além de um breve histórico sobre a temática da Economia Solidária no Brasil e das oportunidades e desafios das Incubadoras Tecnológicas de Cooperativas Populares (ITCPs), apresentam-se importantes subsídios para uma proposta de Programa Institucional de fortalecimento e de expansão das Incubadoras na UNESP

Ineffectiveness of pruning to control citrus huanglongbing caused by Candidatus Liberibacter americanus

The huanglongbing (HLB) disease of citrus trees, caused by Candidatus Liberibacter asiaticus and Ca. Liberibacter americanus, was first reported in Brazil in March, 2004. The presence of the disease has caused serious concerns among growers. Pruning experiments were conducted to determine if removal of symptomatic branches or the entire canopy (decapitation) would eliminate infected tissues and save HLB-affected trees. Pruning was done in five blocks on a total of 592 3- to 16 year-old 'Valencia', 'Hamlin' or 'Pera' sweet orange trees showing no symptoms or with two levels of symptom severity. Ten decapitated trees per block were caged and all trees were treated with insecticides to control the psyllid vector, Diaphorina citri. Mottled leaves reappeared on most symptomatic (69.2%) as well on some asymptomatic (7.6%) pruned trees, regardless of age, variety, and pruning procedure. Presence of the pathogen (Ca. Liberibacter americanus) in all symptomatic trees was confirmed by PCR. In general, the greater the symptom severity before pruning the lower the percentage of trees that remained asymptomatic after pruning

Vegetative shoot flush dynamics of ‘Pera’ sweet orange on three rootstock cultivars

The dynamics and intensity of new shoot flushes of ‘Pera’ sweet orange scions [Citrus × sinensis (L.) Osbeck] grafted onto ‘Rough’ lemon (Citrus × limonia var. jambhiri Lush.), ‘Swingle’ citrumelo [Citrus × aurantium var. paradisi x Poncirus trifoliata (L.) Raf.] and ‘Sunki’ mandarin (Citrus reticulata ‘Sunki’) rootstocks were evaluated in the field at a citrus farm located in a northern region of the state of Sao Paulo, Brazil. Every 20 days for 16 months, new shoots were counted within a square frame of 0.25 m2 set on the central portion of the canopy and classified based on their phenological stages. Trees on ‘Swingle’ rootstock produced a lower area under the flush shoot dynamics curve (AUFSD) and mean number of new shoots than trees on ‘Rough’ lemon or ‘Sunki’ mandarin. For trees on all three rootstocks, new shoot intensities varied significantly over time with the greatest number of new shoots developing during late spring and early summer. Increases in minimum air temperature and available soil water were important indicators of overall emergence of new shoots.&nbsp

Reaction of sweet orange cultivars expressing the attacin A gene to 'Candidatus Liberibacter asiaticus' infection

The objective of this work was to evaluate the reaction of four sweet orange cultivars expressing the attacin A gene to 'Candidatus Liberibacter asiaticus' (Las) infection, a bacterium associated to huanglongbing (HLB) disease. Transgenic sweet orange plants of Hamlin, Natal, Pêra, and Valência cultivars, as well as nontransgenic controls received inocula by grafting budwood sections of HLB-infected branches. Disease progression was evaluated through observations of leaf symptoms and by polymerase chain reaction (PCR) analysis, eight months after inoculation. A completely randomized design was used, with four experiments (one for each cultivar) performed simultaneously. Bacteria title was estimated by quantitative PCR (qPCR). HLB symptoms and Las titers were present in nontransgenic and transgenic plants expressing the attacin A gene of the four sweet orange cultivars, eight months after bacteria inoculation. Five transgenic lines (transformation events) of 'Pêra' sweet orange expressing the attacin A gene have significantly lower Las titers in comparison with nontransgenic plants of this cultivar