RESUMO
BACKGROUND: Despite technical improvements in the citrus chain and leadership in orange production achieved in the past decades, premature fruit drop remains a major component of crop loss in São Paulo state citrus belt, the largest sweet orange production area in the world. The present study aimed to determine, during five consecutive seasons, the impact of the diseases and pests on premature fruit drop in the orange belt. RESULTS: Fruit drop due to the main diseases and pests averaged approximately 11.0%, which corresponded to approximately 63% of the annual fruit drop. The average fruit drop rate due to fruit borer and fruit flies combined was 4.0%, Huanglongbing (HLB) 3.3%, black spot 2.6%, leprosis 1.0% and citrus canker 0.3%. The average amount of fruit drop (million 40.8 kg boxes) and value of crop losses (million US$ dollars), in five seasons, were 12.7 and 66.2 for fruit borer/fruit flies, 11.0 and 57.9 for HLB, 8.1 and 42.2 for black spot, 3.1 and 15.6 for leprosis, and 0.9 and 4.9 for citrus canker, respectively. CONCLUSION: Fruit borer and fruit flies (combined), HLB, black spot, leprosis and citrus canker are, in this order, the main diseases and pests in the orange belt of São Paulo state. All of these causes significantly increased the overall fruit drop rate in the evaluated seasons. The results will contribute to the development of the Brazilian citrus industry, while showing to other citrus-growing regions the potential that diseases and pests have to jeopardize production. © 2022 Society of Chemical Industry.
Assuntos
Citrus sinensis , Citrus , Brasil , Frutas , Doenças das PlantasRESUMO
BACKGROUND: Mineral oil added to fungicide spray mixtures has been a frequently used strategy to control citrus black spot (CBS) worldwide. Although mineral oil may increase the efficacy of control, its use represents around 15% of the costs of a CBS spray program. This study aimed to assess the performance of different proportions of mineral oil added to a fungicide tank mixture for CBS control in young (less than 10 years old) and old (more than 12 years old) sweet orange orchards of early ('Hamlin'), mid-season ('Pera') and late-maturing ('Valencia') cultivars in São Paulo state, Brazil. The efficacy of 0.15%, 0.20% or 0.25% mineral oil added to a fungicide spray mixture was determined by assessing CBS incidence, severity and fruit drop in six orchards over two seasons. RESULTS: Fungicide programs with or without oil were effective in reducing 100% CBS symptom expression in both young and old 'Hamlin' orchards and in the young 'Pera' orchard. The lowest mineral oil rate tested (0.15%) showed a reduction in CBS intensity of around 90%, similar to the highest rate tested in the old 'Pera' orchard. The highest cost-benefit program to control CBS in the old 'Valencia' orchard was obtained with the mineral oil rate of 0.25%, commonly used in the São Paulo citrus belt, which reduced CBS severity by up to 97%. CONCLUSION: This study demonstrated that mineral oil rates for CBS control can be adjusted according to tree age and cultivar. These findings contribute to the establishment of more sustainable citrus production by reducing spray costs while maintaining the efficacy of CBS control. © 2021 Society of Chemical Industry.
Assuntos
Ascomicetos , Citrus sinensis , Citrus , Fungicidas Industriais , Brasil , Óleo Mineral , Doenças das Plantas/prevenção & controle , ÁrvoresRESUMO
Orange juice is a major agricultural product, and oranges are among the most widely sold fresh fruits in several countries. Citrus black spot (CBS), caused by the fungus Phyllosticta citricarpa, affects almost every species of citrus, causing a esthetic depreciation of the fruit and fruit drop, with consequent financial loss for its in natura commercialization. Fungicides are the major control measure for CBS, but have limited efficiency and high cost, and give rise to fungal strains resistant to these products. This work assayed the production of antifungal compounds by Bacillus spp. isolates and tested the potential of two isolates from B. subtilis (ACB-AP3 and ACB-83) for controlling CBS under field conditions with two previously untested orange varieties. A total of 15 isolates produced cell-free, thermostable or volatile compounds effective in suppressing P. citricarpa growth in vitro. It was possible to detect the production of two antibiotics (iturin and surfactin) by B. subtilis ACB-83. Additionally, B. subtilis isolates ACB-AP3 and ACB-83 displayed significant effects in controlling the disease under field conditions.
Assuntos
Antifúngicos/isolamento & purificação , Antifúngicos/farmacologia , Ascomicetos/efeitos dos fármacos , Bacillus/isolamento & purificação , Bacillus/metabolismo , Citrus/microbiologia , Ascomicetos/crescimento & desenvolvimento , Ascomicetos/patogenicidade , Frutas/microbiologia , Fungicidas Industriais/metabolismo , Fungicidas Industriais/farmacologia , Doenças das Plantas/microbiologia , Esporos FúngicosRESUMO
Terpene volatiles play an important role in the interactions between specialized pathogens and fruits. Citrus black spot (CBS), caused by the fungus Phyllosticta citricarpa, is associated with crop losses in different citrus-growing areas worldwide. The pathogen may infect the fruit for 20-24 weeks after petal fall, but the typical hard spot symptoms appear when the fruit have almost reached maturity, caused by fungal colonization and the induction of cell lysis around essential oil cavities. d-Limonene represents approximately 95% of the total oil gland content in mature orange fruit. Herein, we investigated whether orange fruit with reduced d-limonene content in peel oil glands via an antisense (AS) approach may affect fruit interaction with P. citricarpa relative to empty vector (EV) controls. AS fruit showed enhanced resistance to the fungus relative to EV fruit. Because of the reduced d-limonene content, an over-accumulation of linalool and other monoterpene alcohols was found in AS relative to EV fruit. A global gene expression analysis at 2 h and 8 days after inoculation with P. citricarpa revealed the activation of defence responses in AS fruit via the up-regulation of different pathogenesis-related (PR) protein genes, probably as a result of enhanced constitutive accumulation of linalool and other alcohols. When assayed in vitro and in vivo, monoterpene alcohols at the concentrations present in AS fruit showed strong antifungal activity. We show here that terpene engineering in fruit peels could be a promising method for the development of new strategies to obtain resistance to fruit diseases.
Assuntos
Citrus sinensis/metabolismo , Citrus sinensis/microbiologia , Frutas/metabolismo , Frutas/microbiologia , Engenharia Genética/métodos , Liases Intramoleculares/metabolismo , Monoterpenos/metabolismo , Monoterpenos AcíclicosRESUMO
Phyllosticta citricarpa is the epidemiological agent of Citrus Black Spot (CBS) disease, which is responsible for large economic losses worldwide. CBS is characterized by the presence of spores (pycnidiospores) in dark lesions of fruit, which are also responsible for short distance dispersal of the disease. The identification of genes involved in asexual reproduction of P. citricarpa can be an alternative for directional disease control. We analyzed a library of mutants obtained through Agrobacterium tumefaciens transformation system, looking for alterations in growth and reproductive structure formation. Two mutant strains were found to have lost the ability to form pycnidia. The flanking T-DNA insertion regions were identified on P. citricarpa genome by using blast analysis and further gene prediction. The predicted genes containing the T-DNA insertions were identified as Spindle Poison Sensitivity Scp3, Ion Transport protein, and Cullin Binding proteins. The Ion Transport and Cullin Binding proteins are known to be correlated with sexual and asexual reproduction in fungi; however, the exact mechanism by which these proteins act on spore formation in P. citricarpa needs to be better characterized. The Scp3 proteins are suggested here for the first time as being associated with asexual reproduction in fungus. This protein is associated with microtubule formation, and as microtubules play an essential role as spindle machinery for chromosome segregation and cytokinesis, insertions in this gene can lead to abnormal formations, such as that observed here in P. citricarpa. We suggest these genes as new targets for fungicide development and CBS disease control, by iRNA.
Assuntos
Agrobacterium tumefaciens/fisiologia , Ascomicetos/fisiologia , Regulação Fúngica da Expressão Gênica , Interações Microbianas , Mutação , Reprodução Assexuada/genética , Transformação Genética , Citrus/microbiologia , DNA Bacteriano , Ordem dos Genes , Genes Reporter , Mutagênese Insercional , Doenças das Plantas/microbiologiaRESUMO
The citrus industry is severely affected by citrus black spot (CBS), a disease caused by the pathogen Phyllosticta citricarpa. This disease causes loss of production, decrease in the market price of the fruit, and reduction in its export to the European Union. Currently, CBS disease is being treated in orchards with various pesticides and fungicides every year. One alternative to CBS disease control without harming the environment is the use of microorganisms for biological control. Diaporthe endophytica and D. terebinthifolii, isolated from the medicinal plants Maytenus ilicifolia and Schinus terebinthifolius have an inhibitory effect against P. citricarpa in vitro and in detached fruits. Moreover, D. endophytica and D. terebinthifolii were transformed by Agrobacterium tumefaciens for in vivo studies. The transformants retained the ability to control of phytopathogenic fungus P. citricarpa after transformation process. Furthermore, D. endophytica and D. terebinthifolii were able to infect and colonize citrus plants, which is confirmed by reisolation of transformants from inoculated and uninoculated leaves. Light microscopic analysis showed fungus mycelium colonizing intercellular region and oil glands of citrus, suggesting that these two new species are capable of colonizing citrus plants, in addition to controlling the pathogen P. citricarpa.