{"id":547333,"date":"2025-05-09T15:57:26","date_gmt":"2025-05-09T18:57:26","guid":{"rendered":"https:\/\/revistapesquisa.fapesp.br\/?p=547333"},"modified":"2025-05-09T16:36:17","modified_gmt":"2025-05-09T19:36:17","slug":"new-compounds-to-be-tested-against-citrus-canker","status":"publish","type":"post","link":"https:\/\/revistapesquisa.fapesp.br\/en\/new-compounds-to-be-tested-against-citrus-canker\/","title":{"rendered":"New compounds to be tested against citrus canker"},"content":{"rendered":"

When the rainfall increases in the coming weeks, two biologists from S\u00e3o Paulo State are planning to take the compounds they have been developing over recent years to the orange groves. They\u2019ll be looking to see if these materials, used in outdoor conditions, can guard against the bacteria Xanthomonas<\/em> citri<\/em> subsp.<\/em> citri<\/em>, responsible for citrus canker, a long-standing disease in Brazilian cultivation, and present in some 20% of plantations.<\/p>\n

Andr\u00e9 Alexandrino, a partner in the startup BionFarm in S\u00e3o Carlos, SP, plans to evaluate the inhibitors that block an enzyme of this bacteria, without which the disease cannot propagate. Henrique Ferreira, of S\u00e3o Paulo State University (UNESP), Rio Claro campus, will deploy into the field with formulae based on eugenol, a dark-brown oil extracted from cloves (Syzygium aromaticum<\/em>). The two compounds demonstrated good results in the greenhouse and resulted in an integrated project between universities, companies, private investors, and citrus growers.<\/p>\n

A global issue, citrus canker takes the form of brown markings on all types of citrus fruits and leaves (oranges, tangerines, and lemons), with some varieties more susceptible than others. Other species of Xanthomonas<\/em> cause diseases in some 400 plant species, including those that produce grapes, passionfruit, tomatoes, cabbage, broccoli, and cauliflower.<\/p>\n

This canker was tackled in Brazil through elimination of blighted plants from 1957, the year in which it was identified in the country, to 2017, when eradication was replaced by other types of disease control, such as the planting of healthy seedlings and more resistant varieties, the use of windbreaks, and destruction of contaminated fruits. The bacteria, which propagates among the plants via rainwater, is also countered with copper-based pesticides; this, though, does not fully solve the issue.<\/p>\n

\u201cThe price of agricultural pesticides made with copper is still unbeatable, but we are preparing ourselves for when European consumers no longer wish to buy citrus fruits treated with copper,\u201d says Ferreira, of the Center for Research in the Biology of Bacteria and Bacteriophages<\/a>, one of the Research, Innovation, and Dissemination Centers (RIDCs) supported by FAPESP. Although efficient, this type of agrochemical can accumulate in the soil and plants.<\/p>\n

Ferreira saw this firsthand at the end of 2021, when an organic lemon exporter asked for an alternative to sodium hypochlorite (bleach) because a buyer in Europe no longer wanted it used to wash the fruits. Over two weeks at UNESP, he tested and validated the bactericide effect of a solution with 5% eugenol, previously accepted by importers; the solution was immediately applied to the washing of lemons prior to packaging, as detailed in a March 2021 article in Food Processing and Preservation<\/em><\/a>. The results led to eugenol\u2019s inclusion in products Ferreira was already testing against citrus canker.<\/p>\n

The tenacity of the disease drives research across several countries, among the most recent by a group from the Dr. Panjabrao Deshmukh\u00a0Krishi Vidyapeeth University in India, which in September 2023 wrote in the Journal of Plant Disease Sciences<\/em><\/a> that the extract of two plants used in Indian traditional medicine, the amla or Indian gooseberry (Emblica officinalis<\/em>), and the babchi (Psoralea corylifolia<\/em>), successfully eliminated X. citri <\/em>in a laboratory setting. One month later, a team from South China Agricultural University (SCAU) reported on eight compounds that inhibited the disease in citrus leaves in the Journal of Agricultural and Food Chemistry<\/em><\/a>.<\/p>\n

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L\u00e9o Ramos Chaves\u2009\/\u2009Pesquisa FAPESP<\/span>Leaves from orange trees with citrus canker, a long-standing blight for global citrus fruit cultivationL\u00e9o Ramos Chaves\u2009\/\u2009Pesquisa FAPESP<\/span><\/p><\/div>\n

Integrated project<\/strong>
\nFerreira says that eugenol and other essential oils, such as that of oregano (Origanum vulgare<\/em>) and lemongrass (Cymbopogon spp<\/em>.), which also presented good results in the greenhouse, constitute the second generation of compounds that he began to test against X. citri<\/em> some 15 years ago. Gallate, derived from an acid deployed by the plant against insect attacks, represents the first generation and has proven effective in keeping bacterial multiplication in check, as detailed in Frontiers in Microbiology <\/em>in April 2015.<\/p>\n

In addition, Ferreira developed other compounds with colleagues from two universities in the Netherlands, and is working on the formula with specialists from Santa Clara Agroci\u00eancia, a company producing agrochemicals in Ribeir\u00e3o Preto, in the interior of S\u00e3o Paulo State. \u201cWe have more than 15 formulae tested and validated in the greenhouse, and undergoing economic feasibility studies,\u201d he says.<\/p>\n

Alexandrino is optimistic and says that the enzyme inhibitors could compete with copper in terms of price. The efficacy of the two types of compound has been demonstrated to be equal in greenhouse testing, as reported in the journal Microbiology Spectrum <\/em><\/a>in May this year. In partnership with his brother Daniel, he successfully gained the support of two investors, and a large-scale citrus producer is set to provide them with an area for testing.<\/p>\n

Development of these inhibitors began around 2009. Looking for relevant X. citri<\/em> proteins in the evolution of the disease, chemist and pharmacist-biochemist Maria Teresa Marques Novo Mansur, of the Federal University of S\u00e3o Carlos (UFSCar), identified the enzyme phosphomannose iseromase\/GDP-mannose pyrophosphorylase (GDP stands for guanosine diphosphate), also known as XanB.<\/p>\n

Described in detail in the Journal of Proteomics <\/em>in 2017, this enzyme helps to produce xantham gum, which facilitates the bacteria\u2019s interaction with the plant. During his doctoral work at UFSCar, concluded in 2020, Alexandrino examined the gene that produces XanB. \u201cAfter genetic analyses and in vivo<\/em> testing, we saw that without this enzyme the bacteria didn\u2019t cause the disease in citrus fruits,\u201d says Mansur.<\/p>\n

One of her team, chemist Mariana Barcelos, liaised with chemist Carlos Henrique Tomich Paula da Silva, of the University of S\u00e3o Paulo (USP) School of Pharmaceutical Science at Ribeir\u00e3o Preto, to design molecules capable of inhibiting the enzyme. Over the course of two years, using molecule bases and computer modeling, Tomich and Barcelos, during her master\u2019s work with him, modeled the three-dimensional structure of the enzyme and found the points of connection with other molecules, known as attachment sites.<\/p>\n

They then selected the most promising inhibitors, all derived from carbohydrates\u2014three are amino-sugars, and the fourth a phenolic glycoside\u2014which block the interaction of the bacteria with the plant. As these were already in commercial production for other purposes, it was possible to import them, and Alexandrino evaluated them: \u201cWe now have some 15 molecules, but not all are feasible because of the production cost.\u201d<\/p>\n

The field testing should go on for two years. \u201cThe efficacy of the new compounds tends to be lesser than when tested in the greenhouse, because wind and rain facilitate the entry of bacteria into plants, and the sun can speed up the degradation of applied defenses,\u201d warns agricultural engineer Franklin Behlau, of the Brazilian Fund for Citrus Protection (FUNDECITRUS), who is participating in the two lines of research.<\/p>\n

Though satisfied with the results to date, Behlau has a concern over the efficacy of the compounds: \u201cIt\u2019s not enough to act against the bacteria only when the compounds are applied just before it arrives. In the citrus grove, the effect has to linger for a number of weeks between one application and another. Copper is good at this, even in the wind and rain.\u201d<\/p>\n

If testing is successful when concluded, the formal evaluations required by official regulators, for registration and authorization for the sale of new products, should begin.<\/p>\n

The story above was published with the title “The quest for alternatives to copper<\/strong>” in issue 344 of October\/2024.<\/p>\n

Projects<\/strong>
\n1.<\/strong> Sustainable citrus farming through controlled release of antibacterial compounds from microgel-based formulations (n\u00b0 21\/10839-4<\/a>); Grant Mechanism<\/strong> Thematic Project, agreement with the Dutch Research Council (NWO); Principal Investigator<\/strong> Henrique Ferreira (UNESP); Investment<\/strong> R$2,962,257.89.
\n2.<\/strong> Center for Biology Research on Bacteria and Bacteriophages (n\u00b0 21\/10577-0<\/a>); Grant Mechanism <\/strong>Research, Innovation, and Dissemination Centers (RIDC); Principal Investigator<\/strong> Shaker Chuck Farah (USP); Investment<\/strong> R$28,895,915.64.
\n3.<\/strong> Differential proteomic analysis in Xanthomonas axonopodia: Proteins and genes of biotechnological interest (n\u00b0 07\/50910-2<\/a>); Grant Mechanism <\/strong>Young Investigator Award; Principal Investigator <\/strong>Maria Teresa Marques Novo Mansur (UFSCar); Investment <\/strong>R$990,036.24.
\n4.<\/strong> Functional analysis of the xanB and xylA genes potentially involved in the pathogenicity of Xanthomonas citri <\/em>subsp. citri<\/em> (n\u00b0 20\/05529-3<\/a>); Grant Mechanism <\/strong>Regular Research Grant; Principal Investigator <\/strong>Maria Teresa Marques Novo Mansur (UFSCar); Investment <\/strong>R$314,088.22.
\n5.<\/strong> Planning and biological activity of phosphomannose isomerase (PMI) inhibitors of Xanthomonas sp. for treatment and prevention of citrus canker (n\u00b0 23\/01921-4<\/a>); Grant Mechanism <\/strong>Regular Research Grant; Principal Investigator<\/strong> Carlos Henrique Tomich de Paula da Silva (USP); Investment <\/strong>R$172,698.26.<\/p>\n

Scientific articles<\/strong>
\nALEXANDRINO, A. V. et al<\/em>. GDP-mannose pyrophosphorylase is an efficient target in Xanthomonas citri<\/em> for citrus canker control<\/a>. Microbiology Spectrum<\/strong>. Vol. 12, no. 6. May 9, 2024.
\n<\/strong>BATTAGIN, T. S. et al<\/em>. Syzygium aromaticum (clove) essential oil: An alternative for the sanitization of citrus fruit in packinghouses<\/a>. Food Processing and Preservation<\/strong>. e15496. Mar. 27, 2021.
\n<\/strong>CARNIELLI, C. M. et al<\/em>. Xanthomonas citri<\/em> subsp. citri<\/em> surface proteome by 2D-Dige: Ferric enterobactin receptor and other outer membrane proteins potentially involved in citric host interaction<\/a>. Journal of Proteomics<\/strong>. Vol. 151, pp. 251\u201363. Jan. 16, 2017.
\n<\/strong>KR\u00d3L, E. et al<\/em>. Antibacterial activity of alkyl gallates is a combination of direct targeting of FtsZ and permeabilization of bacterial membranes.<\/a> Frontiers in Microbiology<\/strong>. Vol. 6. Apr. 28, 2015.
\n<\/strong>MORE, K. K. et al<\/em>. Evaluation of plant extracts against Xanthomonas citri<\/em> causing citrus canker<\/a>. Journal of Plant Disease Science<\/strong>. Vol. 18, no. 1. Aug. 8, 2023.
\n<\/strong>WANG, X. et al<\/em>. Innovative strategy for the control of citrus canker: Inhibitors targeting the type III secretion system of Xanthomonas citri<\/em> Subsp. citri<\/em><\/a>. Journal of Agricultural and Food Chemistry<\/strong>. Vol. 71, no. 43. Oct. 13, 2023.<\/p>\n","protected":false},"excerpt":{"rendered":"Farmers are turning to copper to stop one of the oldest pests in Brazilian citrus farming","protected":false},"author":17,"featured_media":547338,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"_exactmetrics_skip_tracking":false,"_exactmetrics_sitenote_active":false,"_exactmetrics_sitenote_note":"","_exactmetrics_sitenote_category":0,"footnotes":""},"categories":[169],"tags":[1637],"coauthors":[5968],"class_list":["post-547333","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-technology","tag-agriculture"],"acf":[],"_links":{"self":[{"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/posts\/547333","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/users\/17"}],"replies":[{"embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/comments?post=547333"}],"version-history":[{"count":2,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/posts\/547333\/revisions"}],"predecessor-version":[{"id":547348,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/posts\/547333\/revisions\/547348"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/media\/547338"}],"wp:attachment":[{"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/media?parent=547333"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/categories?post=547333"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/tags?post=547333"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/coauthors?post=547333"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}