{"id":154464,"date":"2014-07-21T17:40:47","date_gmt":"2014-07-21T20:40:47","guid":{"rendered":"http:\/\/revistapesquisa.fapesp.br\/?p=154464"},"modified":"2017-04-04T18:00:30","modified_gmt":"2017-04-04T21:00:30","slug":"every-taste","status":"publish","type":"post","link":"https:\/\/revistapesquisa.fapesp.br\/en\/every-taste\/","title":{"rendered":"For every taste"},"content":{"rendered":"

\"citrus\"L\u00c9O RAMOS<\/span>For habitual consumers of oranges, mandarins, lemons, and other citrus sold in supermarkets, the Sylvio Moreira Citriculture Center may hold a pleasant surprise. Its greenhouses of saplings and vast orchard of mature plants in the city of Cordeir\u00f3polis, state of S\u00e3o Paulo, are home to 1,700 different types of citrus. That includes almost 700 varieties of sweet oranges \u2013 those suitable for juicing or in natura consumption \u2013 and nearly 300 types of mandarins. Tasting the fruit of different trees at the Citriculture Center will reveal an astonishing wealth of flavors and textures. The research center is affiliated with the Campinas Institute of Agronomy (IAC), an agency within the S\u00e3o Paulo State Department of Agriculture. \u201cAll of the material used by the Brazilian citrus industry has passed through here at some point,\u201d summarizes agronomist Marcos Machado, researcher at the Citriculture Center and coordinator of the National Institute of Science and Technology of Genomics for Citrus Improvement (INCT Citros).<\/p>\n

Throughout the center’s 85-year history, researchers have crossbred different varieties, mainly in search of disease-resistant plants. Starting with traditional crosses, similar to the ones that resulted in the varieties of citrus sold in markets since their species were domesticated, the center has gradually enriched its arsenal of techniques as genetic information became available. Until now, this knowledge has focused primarily on the use of molecular markers to characterize different crosses, determining which descendants of a cross between two varieties (or species) had received the genetic material targeted by the researchers. But genomics has now come to the Citriculture Center, making way for new possibilities.<\/p>\n

\"Grafting

L\u00c9O RAMOS<\/span>Grafting scar: mandarin lime serves as rootstock for orange trees L\u00c9O RAMOS<\/span><\/p><\/div>\n

The first major breakthrough, which resulted in a paper published on the Nature Biotechnology website in June 2014, included some unexpected discoveries about the origin of present-day oranges and mandarins. Researchers already knew that citrus fruits are not natural species, but rather hybrids perfected by thousands of years of natural interbreeding. But there is no historical record of this Citrus domestication, which started in Southeast Asia. \u201cWe knew there were hybrids, but we had no details,\u201d says biologist Marco Takita, one of the authors of the paper.<\/p>\n

The researchers were surprised to discover that the genomes of some types of mandarin, thought to be variants of the ancestral species C. reticulata<\/em>, actually contain several genetic segments from C. maxima, a different species known as pummelo. Takita explains that the pummelo resembles a giant orange, weighs up to a kilogram (about 2.2 pounds), and is not usually consumed in Brazil. The species is used as a source of genetic diversity in plant breeding programs and, as researchers now know, it took part in the hybridizations that gave rise to the Ponkan mandarin. Because of the fruit’s commercial success in Brazil, the Ponkan genome was sequenced by the Citriculture Center with financial support from INCT Citros, which is funded by FAPESP and the National Council for Scientific and Technological Development (CNPq). \u201cIt is important to know that the pummelo served as a genetic source,\u201d says the researcher.<\/p>\n

The study also produced another unexpected finding. The Chinese mandarin variety known as Mangshan, thought to have the same origin as other mandarins and tangerines, is actually a separate species, C. mangshanensis<\/em>, which appears to be distantly related to C. reticulata<\/em>.<\/p>\n

Surprising new knowledge was also brought to light regarding the sweet orange, most commonly sold in Brazilian markets as laranja-pera, -ba\u00eda, or -lima. These varieties are all hybrids of C. reticulata<\/em> and C. maxima<\/em>, and much of their genome is genetically similar to mandarins like the Ponkan. The results revealed a very low level of genetic differentiation between sweet and mandarin oranges after branching off from their common ancestor. \u201cThe challenge now is to understand such things as why they are so genetically alike, but taste so different,\u201d says Takita.<\/p>\n

\"Germplasm

L\u00c9O RAMOS<\/span>Germplasm bank houses a wide variety of citrusL\u00c9O RAMOS<\/span><\/p><\/div>\n

The sour orange, used for making preserves, is also a hybrid of the species that gave rise to pummelos and mandarins. As if recreating the story from back to front, genomic research has enabled researchers to conclude that citrus fruits appeared in nature in Southeast Asia a few thousand years ago, before spreading across the globe.<\/p>\n

A consortium of citrus genome researchers began to be formed in 2005, with active participation from the researchers at the Citriculture Center. After nearly 10 years of work, during which the Center made progress in the sequencing of a Spanish clementine (a type of mandarin), a Chinese research group scored a coup and published the sweet orange genome in the journal Nature. Then, with similar results on hand, the international group decided to expand the study. \u201cWe sequenced an additional six genomes and produced a more elaborate discussion that actually questions some aspects of the Chinese study,\u201d says Machado.<\/p>\n

The results showed why the boundaries between citrus species are getting increasingly fuzzy. \u201cSome say there are 163 species of Citrus, while others identify no more than 16,\u201d says the researcher. \u201cLinnaeus classified six,\u201d he adds, referring to the 18th-century Swedish naturalist known as the father of taxonomy and creator of the binomial nomenclature system, which is used by scientists to this day.<\/p>\n

Breeding for improvement<\/strong>
\nBased on the available information, Machado believes that the genomic approach is a way of \u201caiming high while staying grounded\u201d. By sequencing the genome of the Rangpur or mandarin lime, the Brazilian group has started studying the genealogy of limes, whose earliest ancestor is C. medica. The species was not selected at random: the mandarin lime can withstand drier environments, and therefore is used as root stock in 85% of all orange and mandarin plantations in the state of S\u00e3o Paulo. \u201cThe northern part of the state has the best characteristics for growing juice oranges, but its drier climate would require impracticable amounts of irrigation,\u201d Machado explains. Genomic research may help identify the genetic basis for the mandarin lime\u2019s drought resistance and pinpoint the genes associated with certain characteristics. This information could serve as a guideline for breeding decisions, and it might even help researchers achieve gene transfer in the laboratory. Experts call the gene transfer process cisgenics (which differs from transgenics in that it involves same-group species that can generate natural hybrids).<\/p>\n

\"Germination

L\u00c9O RAMOS<\/span>Germination in the laboratory: controlled genetic variationL\u00c9O RAMOS<\/span><\/p><\/div>\n

Given the economic importance of citrus, these studies are essential not only to meet the demands of the market and steer the search for new fruit varieties with improved flavor and other qualities, but also to fight disease. Two good examples of such afflictions for oranges are citrus variegated chlorosis (CVC), caused by the bacterium Xylella fastidiosa, and huanglongbing, or greening disease, first detected in Brazil 10 years ago and now a threat to this country’s citrus orchards. Mandarins are resistant to CVC, but susceptible to huanglongbing and Alternaria brown spot, a fungal disease that discolors leaves and fruit and causes leaf loss. The genetic homogeneity highlighted in the study published in Nature Biotechnology clearly shows why citrus are easy prey for crop-infesting microorganisms: if one tree falls victim to a disease, others of the same type will also succumb, because of their genetic similarity. For this reason, the Citriculture Center focuses much of its effort on producing varieties that can resist these diseases. \u201cSome hybrids of mandarin species produce fruit that have no direct value for consumers, but generate important genetic variability,\u201d explains agricultural engineer Mari\u00e2ngela Cristofani-Yaly. The results of the Citriculture Center researchers’ attempts to create new root stock and fruit varieties are described in recent publications, such as their papers published in the Journal of Agricultural Science and in Bragantia respectively in 2013 and 2014, .<\/p>\n

\u201cFirst we introduced resistance, and then we resumed our focus on fruit quality,\u201d says the researcher. To assess potential breeding options for producing new varieties of citrus used to make juice or eaten in natura, everyone at the Citriculture Center \u2013 researchers, students, and employees \u2013 serves as guinea pigs by taking part in sensory evaluation experiments to judge such characteristics as color, flavor, and ease of peeling, as described in the Journal of Agricultural Science paper published in 2013. The plants are also categorized by productivity, juice yield, and fruiting period, among other characteristics.<\/p>\n

Academic achievement is just one side of this research center in inland S\u00e3o Paulo State. Its other mission is contributing to the improvement of citrus, an industry in which Brazil stands out as the world’s leading producer of oranges and third largest supplier of mandarins, tangerines, and other varieties. China is the global leader in overall citrus production, but focuses mainly on mandarins. \u201cWith the new techniques, we can combine basic and applied knowledge, create a platform for new things,\u201d says Machado.<\/p>\n

But the Brazilian market is also a constraint. Much of the country’s orange harvest is used for making juice concentrate, which means that the industry has control over production. Its main objectives are to get more juice out of each fruit, and to pay less for them; this has triggered a crisis among orange growers. According to Machado’s calculations, about 10,000 citrus growers abandoned the business in the past decade. But he believes that the crisis may ultimately have positive consequences for consumers. If the researchers in Cordeir\u00f3polis are right, more citrus growers will agree to try planting the new varieties developed by the research center, and markets may start offering a wider variety of citrus meant for eating in natura. A mouth-watering prospect.<\/p>\n

Projects<\/strong>
\n1.<\/strong> Genomic platforms applied to citrus breeding (n\u00ba 08\/57909-2<\/a>); Grant mechanism<\/strong> Thematic Project; Principal investigator<\/strong> Marcos Antonio Machado (IAC); Investment<\/strong> R$ 3,533,624.89 (FAPESP).
\n2.<\/strong> Obtaining and evaluation of new varieties of scion and rootstock for citrus (n\u00ba 11\/18605-0<\/a>); Grant mechanism<\/strong> Thematic Project; Principal investigator<\/strong> Mari\u00e2ngela Cristofani-Yaly (IAC); Investment<\/strong> R$ 859,670.11<\/p>\n

Scientific article<\/em>
\nWU, G. A.\u00a0et al<\/em>.\u00a0Sequencing of diverse mandarin, pummelo and orange genomes reveals complex history of admixture during citrus domestication<\/a>.\u00a0Nature Biotechnology<\/strong>. On-line, 8 jun. 2014 (FAPESP).<\/p>\n","protected":false},"excerpt":{"rendered":"Research reveals origin and genetic diversity of citrus","protected":false},"author":3,"featured_media":0,"comment_status":"open","ping_status":"open","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":[159],"tags":[212,213,237],"coauthors":[1601],"class_list":["post-154464","post","type-post","status-publish","format-standard","hentry","category-science","tag-biotechnology","tag-botany","tag-genetics"],"acf":[],"_links":{"self":[{"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/posts\/154464","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\/3"}],"replies":[{"embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/comments?post=154464"}],"version-history":[{"count":0,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/posts\/154464\/revisions"}],"wp:attachment":[{"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/media?parent=154464"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/categories?post=154464"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/tags?post=154464"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/coauthors?post=154464"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}