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ANA GERSCHENFELD Público 30/03/2016 - 08:36

É pouco conhecido do grande público. Mas foi o primeiro cientista a perceber que, para salvar a humanidade da fome, era imperativo conservar a biodiversidade genética das plantas cultiváveis do mundo inteiro em “bancos de sementes”. Ironicamente, morreu de fome na prisão durante o estalinismo.

Todos (ou quase) terão ouvido falar, nos media, do grande Cofre-Forte de Sementes Global de Svalbard, uma espécie de congelador gigante, de aspecto futurista, construído numa zona montanhosa do Árctico. Inaugurado em 2008, tem como objectivo proteger o maior número de espécies cultiváveis úteis do mundo – como feijões, arroz ou trigo –, contra as piores calamidades que possam acontecer, de forma a preservar o sustento alimentar da humanidade. Mas o que quase ninguém sabe é que essa ideia de preservação da biodiversidade agrícola nasceu há um século na cabeça de um cientista russo.

Foi precisamente em 1916 que Nikolai Vavilov, biólogo, geneticista, geógrafo, agrónomo e especialista do melhoramento das espécies vegetais partiu para a Pérsia (actual Irão) na sua primeira expedição, para recolher sementes cultivadas em regiões mais e menos “exóticas”. Essa sua actividade intensa de exploração dos quatro cantos do globo continuaria ao longo da sua vida e conduziria à criação, já em 1924 em São Petersburgo (então Leningrado), do primeiro banco de sementes do mundo.

“O sonho de Vavilov era acabar com a fome no mundo e o plano que tinha para o conseguir consistia em utilizar a ciência emergente da genética para gerar ‘super-plantas’, capazes de crescer em todos os locais e em todos climas – dos desertos de areia às gélidas tundras, durante secas ou inundações”, lê-se no site da cadeia global de televisão Russia Today. E para o poder fazer, o cientista precisava de trazer para o seu laboratório a diversidade genética global.

Coleccionador de plantas

Nikolai Vavilov nasceu em Moscovo a 25 de Novembro de 1887. O seu pai era um “próspero homem de negócios tornado milionário”, lê-se numa recensão de 1994, na revista Nature, da primeira da tradução em inglês (publicada em 1992) dos mais importantes trabalhos de Vavilov, coligidos sob o título de Origin and Geography of Cultivated Plants. Depois de acabar o curso no Instituto de Agricultura de Moscovo, Vavilov passou quase um ano, entre 1913 e 1914, no Reino Unido, no laboratório de William Bateson, pioneiro da genética moderna – e que cunhara aliás a palavra “genética” em 1901.

Quando estalou a Primeira Guerra Mundial, Vavilov regressou a Moscovo e, na Universidade de Saratov, (cidade situada a uns 700 quilómetros a sudeste de Moscovo, nas margens do rio Volga) começou a fazer investigações sobre a resistência das plantas às doenças, lê-se ainda na Nature, “virando-se depois para o estudo dos parentes selvagens das plantas cultivadas e formulando a ideia de que todas as plantas domesticadas tinham surgido em áreas de actividade humana na pré-história”. E foi para demonstrar esta hipótese que Vavilov organizou expedições “para sítios onde supostamente tinham assentado as povoações humanas mais antigas”. Identificou assim, primeiro cinco “centros de origem” das plantas cultiváveis. Mais tarde, esse número aumentou para sete ou oito (segundo as fontes).

A paixão de Vavilov pelas plantas vinha de longe. “Vavilov começou a coleccionar plantas durante a infância: tinha um pequeno herbário em casa”, escrevia em 1991 Barry Mendel Cohen (que fizera a sua tese de doutoramento sobre o cientista) num texto publicado na revista Economic Botany.

“Contudo”, prossegue Cohen, “a primeira verdadeira expedição destinada à recolha de plantas foi a sua viagem à Pérsia em 1916” – em plena Primeira Guerra Mundial. Vavilov não fora recrutado pelo exército por razões de saúde e o Ministério da Agricultura decidira então enviá-lo em missão à Pérsia.

Aquela expedição, que durou de Maio a Agosto, foi certamente uma aventura, salienta Cohen. “Primeiro, Vavilov ficou detido na fronteira durante três dias pelas autoridades russas, porque transportava com ele alguns manuais em alemão e mantinha um diário escrito em inglês” – um hábito que tinha adquirido durante a sua estadia no Reino Unido. Vavilov “foi acusado de ser um espião alemão e só foi libertado quando chegou a confirmação oficial da autenticidade dos seus documentos”, acrescenta Cohen.

Mas as peripécias não se ficaram por aí. “A sua caravana percorreu áreas de deserto onde a temperatura ultrapassava os 40 graus Celsius à sombra e chegou a estar a entre 40 e 50 quilómetros da frente de guerra da fronteira russo-turca”, diz ainda Cohen.

A julgar pela lista dos destinos que visitou até ao início dos anos 1930, Vavilov não tinha medo das situações perigosas (fossem elas devidas à topografia, ao clima, aos conflitos ou simplesmente à vulgar criminalidade local) em que por vezes se via envolvido.

Visitou mais de 64 países e aprendeu 15 línguas para conseguir falar directamente com os agricultores. “Foi um dos primeiros cientistas a ouvir realmente os agricultores tradicionais, a gente do campo de todo o mundo, para saber por que é que achavam que a diversidade das sementes era importante nos seus campos ”, declarou em 2010, numa entrevista à rádio pública norte-americana, o ecologista e botânico Gary Paul Nabham, autor de uma biografia de Vavilov.

Depois da Pérsia, sempre a recolher espécies locais, Vavilov fez várias viagens aos Montes Pamir da Ásia Central; atravessou territórios nunca antes explorados do Afeganistão; percorreu países da zona mediterrânica, europeus (incluindo Portugal) e não só. No Sul da Síria, contraiu malária. Esteve na Palestina e, em África, foi até à Abissínia (na actual Etiópia), onde apanhou tifo. Também organizou expedições à China, Japão, Coreia, Taiwan, América do Norte, Central e do Sul. 

Diga-se ainda que, em 1921, foi convidado a assistir, com outro colega russo, ao Congresso Americano de Patologista dos Cereais – “um convite de histórica importância”, diz Cohen, “na medida em que foi o primeiro exemplo de cooperação científica entre os Estados Unidos e a recém-criada União Soviética”. O convite também mostra que o trabalho de Vavilov já era, naquela altura, reconhecido fora da Rússia.

Lisenko, inimigo mortal

A partir de 1920 e durante 20 anos, Vavilov dirigiu a Academia Lenine de Ciências Agrícolas da União (mais tarde rebaptizada Instituto Vavilov da Indústria Vegetal da União em sua honra), com sede em Leningrado. Criou 400 estações experimentais, espalhadas por toda a União Soviética e onde trabalhavam cerca de 20.000 pessoas. Publicou centenas de artigos de genética, biologia, geografia e selecção vegetal.

Ao longo de 16 anos de périplos, Vavilov e os seus alunos recolheram umas 200.000 amostras de sementes oriundas da União Soviética e do resto do mundo, que a seguir foram organizadas e estudadas nas diversas estações. “Foi assim que nasceu o primeiro banco mundial de genes de plantas do mundo”, lê-se ainda na já referida recensão da Nature, da autoria do norte-americano Valery Soyfer, da Universidade George Mason.

Mas a partir de 1935, aquele que seria o maior inimigo de Vavilov – e aliás da genética e das ciências da vida soviéticas – começou a ensombrar a vida pessoal e profissional de Vavilov: Trofim Lisenko (1898-1976).

Ao contrário de Vavilov, que era de família burguesa e portanto suspeito – Lisenko era de origem camponesa e tinha conseguido fazer um curso de agronomia. De facto, o próprio Vavilov começou por louvar e promover o trabalho de Lisenko por achar que ele era um digno “filho” da revolução bolchevique.

Em poucos anos, Lisenko tornou-se o “cientista” favorito de Estaline e o promotor de uma “genética soviética” que negava a própria existência dos genes e do ADN. Lisenko também fazia pouco da selecção natural, o processo basilar da teoria da evolução emitida por Darwin em meados do século XIX.

Como explicava Soyfer em 1989, num outro artigo na Nature, hoje ninguém duvida que as actividades de Lisenko tenham contribuído para a destruição das ciências agrícolas, biológicas e até médicas na União Soviética.

Porém, no início da sua ascensão, Lisenko conseguiu uma aparente vitória contra a fome que alastrava na URSS devido à colectivização forçada da terra. E em 1929, anunciou que uma técnica da sua invenção, dita de “invernalização”, iria permitir fazer florescer em pleno inverno o trigo que normalmente só desabrochava na Primavera. O método não foi validado e acabou por não cumprir as promessas de Lisenko de aumento da produção. Mas ele não estava disposto a arcar com a responsabilidade do falhanço e o culpado escolhido seria Vavilov, o homem que tanto contribuíra para o celebrizar. Lisenko tinha-se tornado o seu inimigo mortal.

Assim, após o seu regresso do México, em 1933, Vavilov foi proibido de empreender novas viagens. E a partir de 1934, Lisenko fez dele “o bode expiatório pelas desastrosas políticas agrícolas de Estaline”, lia-se na revista Science em 2008.

Quando Vavilov percebeu o que estava a acontecer, começou a criticar a “ciência” de Lisenko, numa controvérsia que culminaria com a “vitória” do pseudo-cientista Lisenko – e com uma tragédia: a detenção de Vavilov a 6 de Agosto de 1940 pela polícia secreta soviética.

“Vavilov estava a recolher amostras de plantas na Ucrânia” quando foi detido, escrevia em 2008 na Nature Jan Witkowski, geneticista do Laboratório de Cold Spring Harbor (EUA), a propósito da publicação de um livro sobre o assassínio de Vavilov. Transferido para Moscovo, foi submetido a um terrorífico interrogatório durante 11 meses. Em Julho de 1941, Vavilov e dois dos seus colegas foram condenados à morte. Os colegas foram fuzilados, mas a sentença de Vavilov acabou por ser comutada em 20 anos de prisão… na cadeia de Saratov, aquela mesma cidade onde tinha iniciado a sua carreira 26 anos mais cedo. Sobreviveu dois anos numa cela subterrânea e sem janelas, em condições tais que contraiu escorbuto.

Vavilov morreu de fome em Saratov a 26 de Janeiro de 1943, aos 55 anos de idade. Nem a própria mulher, que voltara a residir em Saratov, sabia que o marido estava ali tão perto.

Vavilov só seria parcialmente reabilitado – e Lisenko definitivamente desacreditado – em 1965 pelo então presidente da URSS Leonid Brejnev, sob a pressão de dissidentes russos como o físico Andrei Sakharov e o escritor Alexandre Soljenitsyne, explica ainda Barry Mendel Cohen.

A ausência de Vavilov não passou despercebida a nível internacional. O próprio Winston Churchill fez vários apelos a Estaline para saber o que tinha acontecido a Vavilov. E, numa carta publicada na revista Science a 21 de Dezembro de 1945, Karl Sax, da Universidade de Harvard (EUA), perguntava: “Onde está Vavilov, um dos maiores cientistas da Rússia e um dos maiores geneticistas do mundo? Vavilov fora eleito presidente do Congresso Internacional de Genética, que decorreu em Edimburgo em 1939, mas não apareceu e desde então não temos tido notícias dele. Recebemos agora a informação da nossa Academia Nacional das Ciências de que Vavilov morreu. Como morreu e porquê?”

Alguns colegas de Vavilov já tinham tido o mesmo destino trágico do que ele – não na prisão, mas no cerco de Leningrado pelas tropas nazis, de 1941 e 1944, que matou à fome dezenas de milhares de cidadãos.

Numa outra carta publicada na Science em 2003, apelando a Vladimir Putin para salvar a preciosa colecção do Instituto de Leningrado (que esteve à beira de ser demolido por promotores imobiliários), três antropólogos norte-americanos resumiam o que acontecera àqueles cientistas: “Apesar de sofrerem eles próprios de subnutrição grave e apesar de trabalharem a poucos metros de uma vasta reserva de alimentos sementes, tubérculos e fruta, os cientistas preferiram morrer a empobrecer a herança genética do país”, que “percebiam ser indispensável para o futuro da agricultura” soviética. Oito morreram em 1942 e “pelo menos um deles (…), um especialista em amendoins, morreu sentado à sua secretária”, escrevem os autores.

Mas foi o seu gesto, mais do que heróico, que permitiu que o banco de genes do Instituto Vavilov seja, ainda hoje, um dos maiores do mundo.

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ScienceDaily (Sep. 27, 2011) — Most of what we have come to think of as our daily fruits, vegetables, and grains were domesticated from wild ancestors. Over hundreds and thousands of years, humans have selected and bred plants for traits that benefit us -- traits such as bigger, juicier, and easier-to-harvest fruits, stems, tubers, or flowers. For short-lived, or annual, plants, it is relatively easy to envision how such human-induced selection rapidly led to changes in morphology and genetics such that these plants soon become quite different from their wild progenitors.

But what about longer-lived, perennial crops, such as fruit or nut trees? How do these long-lived species respond to short-term selection processes, and will this information be helpful in predicting responses to rapid climate changes?

Dr. Allison Miller (Saint Louis University, MO) and Dr. Briana Gross (National Center for Genetic Resource Preservation, USDA-ARS, Fort Collins, CO) are interested in the diversity of plant genomes in domesticated crops and the evolution of their breeding systems under domestication. They undertook an extensive review of perennials, primarily long-lived tree crops, comparing their morphology and genetics in response to human selection pressures to that of natural tree populations and annual crops, which is something we know a lot about. They published their findings in the September issue of the American Journal of Botany.

"Since their origins roughly 10,000,000 years ago, agricultural societies have been based primarily on annual grains and legumes such as corn, wheat, rice, common beans, and lentils," notes Miller. "The importance of these crops is without question; however, every agricultural society has also domesticated perennial plants and these are less well-known than the annuals."

In their article, Miller and Gross point out that one of the challenges to domesticating long-lived species is that they have especially long juvenile phases. This imposes limits on farmers because they have to wait years before they can evaluate, select, and cultivate fruits, in contrast to annuals that can be grown from seed every year. Moreover, like many trees in nature, perennial tree crops are often obligate outcrossers, requiring pollination from another individual. Farmers have gotten around these "obstacles" by clonally propagating individuals with desirable traits.

While clonal propagation may seem like it would result in lower genetic variation, the authors observe that clonal propagation and a long juvenile phase means perennial tree-crops have actually gone through fewer sexual cycles since domestication and thus have remained closer, genetically, to their wild progenitors. Indeed, perennial fruit crops retain an average of 95% of the (neutral) genetic variation found in their wild counterparts, compared with annual fruit crops which retain about 60%.

Interspecific hybridization is very common in tree species in nature, and this ability to readily hybridize is an important trait in domestication -- once a hybrid is formed, it can become the basis for an entire new variety through clonal propagation. Thus, clonal reproduction can also result in rapid rates of change in domesticated systems because individuals with desirable traits can be reproduced exactly and extensively.

"The evolution of perennial plants under human influences results in significant changes in reproductive biology," notes Miller, "and in many cases, perennial crops have reduced fertility in cultivation."

While many annual crops were domesticated from self-compatible wild ancestors, few perennial crops were derived from selfing wild populations. Thus, domesticated perennials often encounter mate limitation barriers when one or just a few clones are planted across a geographic region. However, plants in these agricultural systems have responded by evolving alternative strategies to ensure fruit production. For example, grapes have shifted from having unisexual to bisexual flowers and to having self-compatible fertilization.

Genetic bottlenecks in cultivated populations occur when only a subset of wild individuals are brought under cultivation -- over time, the genetic base narrows as superior individuals are selectively propagated, resulting in elite cultivars that can be genetically depauperate. However, the authors found that many domesticated tree crops are derived from multiple areas, where seeds and cuttings were removed from geographically distinct wild populations. Moreover, many perennial species are highly heterozygous and clonal propagation maintains this heterozygosity at the individual level. Thus, perennial tree crops tend to have a much broader genetic bottleneck than annuals.

In light of the growing concern over monocultures and the loss of genetic diversity in our domesticated crops, Miller and Gross' review of perennial long-lived crops highlights the importance of maintaining long-lived perennials which may have lower environmental impacts as well as higher genetic variability within their populations.

"Understanding how basic evolutionary processes associated with agriculture (e.g., domestication bottlenecks, selective cultivation) impact plant species is critical for crop breeding and for the conservation of crop genetic resources," concludes Miller.

Scientists are also interested in how climate change might impact agriculture. In this framework, Miller is interested in exploring how perennial crops withstand heterogeneous climates over multiple years. "Little is known about the genomic basis of adaptation to climate in perennial plants, or how gene expression patterns may vary from year to year based on climatic conditions in a given location," she notes.



Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by American Journal of Botany, via EurekAlert!, a service of AAAS.

Journal Reference:

  1. A. J. Miller, B. L. Gross. From forest to field: Perennial fruit crop domestication. American Journal of Botany, 2011; 98 (9): 1389 DOI: 10.3732/ajb.1000522

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A new domain of life

 

Plenty more bugs in the sea

 

LIFE, like Caesar’s Gaul, is divided into three parts. The Linnaean system of classification, with its prescriptive hierarchy of species, genus, family, order, class, phylum and kingdom, ultimately lumps everything alive into one of three giant groups known as domains. The most familiar domain, though arguably not the most important to the Earth’s overall biosphere, is the eukaryotes. These are the animals, the plants, the fungi and also a host of single-celled creatures, all of which have complex cell nuclei divided into linear chromosomes. Then there are the bacteria—familiar as agents of disease, but actually ecologically crucial. Some feed on dead organic matter. Some oxidise minerals. And some photosynthesise, providing a significant fraction (around a quarter) of the world’s oxygen. Bacteria, rather than having complex nuclei, carry their genes on simple rings of DNA which float around inside their cells. The third great domain of life, the archaea, look, under a microscope, like bacteria. For that reason, their distinctiveness was recognised only in the 1970s. Their biochemistry, however, is very different from that of bacteria (they are, for example, the only organisms that give off methane as a waste product), and their separate history seems to stretch back billions of years. But is that it? Or are there other biological domains hiding in the shadows—missed, like the archaea were for so long, because biologists have been using the wrong tools to look? That is the question asked recently by Jonathan Eisen of the University of California, Davis, and his colleagues. They suspect there are, and in a paper just published in the Public Library of Science, they present an analysis which suggests there might indeed be at least one other, previously hidden, domain of life. What I did on my holidays The data from which this conclusion was drawn were collected between 2003 and 2007 on one of the most scientifically productive holidays in history. This was a round-the-world cruise taken by Craig Venter on his yacht, Sorcerer II, which studied the diversity of micro-organisms in the Atlantic, Pacific and Indian oceans. Dr Venter was working out his frustrations after having been fired in 2002 from Celera Genomics, a company he helped set up in 1998 with the specific aim of sequencing the human genome faster and better than the public Human Genome Project was managing at the time. In that, it succeeded. In the wider aim of turning such knowledge into hard cash, however, it was nowhere near as successful as its financial backers had hoped. Dr Venter therefore found himself with more time on his hands than he had been planning. His killer app in Celera’s assembly of the human genome was a technique called shotgun sequencing. This first shreds a genome into pieces small enough for sequencing machines to handle, then stitches the sequenced pieces back together by matching the overlaps using a computer. In principle, he realised, that trick could be used on mixed DNA from more than one organism. A good enough program would stitch together only fragments from the same type of creature. This would allow you to see what was living in a sample without having to culture anything. And since a huge majority of micro-organisms (by some estimates, 97%) cannot be cultured, that sounded like a great idea. Metagenomics, as the new technique is known, has vastly extended knowledge of what bugs live in the sea—and in many other places, from hot springs to animals’ guts. It is not perfect. In practice a lot of what emerges are fragments of genomes, rather than complete assemblies. But it has been enormously successful at identifying previously unknown individual genes. Dr Eisen wondered if it could be pushed still further. He started combing through the data from the cruise to look for new forms of genes that have, in the past, proved useful in distinguishing bacteria, archaea and eukaryotes from each other, to see if there are any other domains of life out there. After a false start pursuing what are known as ribosomal RNA genes—which are involved in protein synthesis and are believed by some people to be the genetic core around which the rest of life accreted—he lighted on two genes called RecA and RpoB. RecA is involved in DNA recombination. RpoB is involved in translating DNA into RNA. Both, like the genes for ribosomal RNA, are old and ubiquitous. And lo, when he drew trees that tracked the evolutionary relationships between all the RecAs and all the RpoBs found on the cruise, he discovered parts of the trees that did not fit with the pattern established by known versions of these genes in the public genetic databases. Some of these novel branches were, nevertheless, similar enough to known branches to be accounted for as known unknowns. But both RecA and RpoB had one branch that really was an unknown unknown. Neither of these branches fits in the existing tree of life. And that is a mystery. It may be that they belong to some as-yet-uncharacterised group of viruses (entities classified outside Linnaeus’s system, since there is no agreement about whether they are alive or not). Or it may be that they belong to a fourth domain of living organism. Either way, it suggests a profound lacuna in biologists’ understanding of the world. The question is, is it a big lacuna as well as a deep one? Is the new group an important part of the biosphere? That is hard to say at the moment. The genes concerned are rare in the overall metagenomic analysis, so creatures carrying them may not be abundant. On the other hand, those creatures might just be too small to be caught easily by the filters used to winnow life from water for analysis in the first place. As to importance, when originally identified as distinct, the archaea, too, were regarded as marginal—yet their methane-generating properties are now a factor in climate-change calculations. If the new domain is real, it must have been around for several billion years, and must thus have something going for it. What that something is remains to be seen. from the print edition | Science and Technology

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http://www.sciencedaily.com/releases/2011/02/110224201859.htm

ScienceDaily (Feb. 24, 2011)The Svalbard Global Seed Vault (SGSV) celebrated its third anniversary February 24 with the arrival of seeds for rare lima beans, blight-resistant cantaloupe, and progenitors of antioxidant-rich red tomatoes from Peru and the Galapagos Islands. The arrival of these collections, including many drought- and flood-resistant varieties, comes at a time when natural and human-made risks to agriculture have reinforced the critical need to secure all the world's food crop varieties.

The seeds arriving for safekeeping in the depths of an Arctic Mountain on Norway's remote Svalbard Archipelago included major deposits from genebanks maintained by the Consultative Group on International Agricultural Research (CGIAR), which is the largest single contributor of seeds to the Seed Vault.

Among the shipments is a Peruvian desert lima bean variety on the verge of extinction that was rescued by the Colombia-based International Center for Tropical Agriculture (CIAT), as well as other lima beans and relatives that grow in very dry or high-altitude locations. In total, CIAT's new shipments include 3,600 bean and forage samples collected from 94 countries, including Afghanistan, Nepal, Yemen, Vietnam and Zimbabwe.

Thousands of other cereal and bean varieties are being deposited by the International Center for Agricultural Research in the Dry Areas (ICARDA). The International Livestock Research Institute (ILRI) in Addis Ababa, Ethiopia is depositing forage crops. In Arizona, a Navajo ceremony was held to bless seeds of rare desert legumes from the University of Arizona before they began their long journey to Svalbard.

The new accessions, which will be added to the more than 600,000 already stored at Svalbard, include Agricultural Research Service-US Department of Agriculture (USDA) donations of soybeans collected by USDA researchers in China in the 1920s.

The USDA's shipment also includes seed collections of Solanum chilense and Solanum galapagense, wild relatives of the tomato whose genetic material was used by breeders at USDA and the University of California, Davis, to create tomatoes high in lycopene (an antioxidant) and beta-carotene (a source of Vitamin A). Other US shipments included seeds for important disease-resistant varieties of spinach, maize and cantaloupe.

"The optimism generated by the arrival of this incredible bumper crop of contributions is tempered by the threats that seem to emerge almost daily to seed collections around the world," said Cary Fowler, Executive Director of the Global Crop Diversity Trust, which manages the Seed Vault in partnership with the Norwegian government and the Nordic Genetic Resources Center in Sweden. "As the threats to agriculture escalate, the importance of crop diversity grows."

A vivid example of some of the threats facing genebanks is when unrest in Egypt led to the looting of the Egyptian Desert Gene Bank in North Sinai. At the Desert Gene Bank, home to a prized collection of fruit and medicinal plants, looters stole equipment, destroyed the facility's cooling system, and ruined data that represented more than a decade worth of research. Meanwhile, the Global Crop Diversity Trust continues to fight plans to bulldoze the field collections at Russia's Pavlovsk Experimental Station, Europe's most important collection of fruits and berries, to make way for a housing development.

The Norwegian vault's third anniversary also brings reminders of natural threats to crop diversity and the food security it maintains.

Dr. Tony Gregson, a grain farmer from Victoria's Wimmera region, which has been alternately baked and flooded recently, accompanied Australia's first contribution to the seed vault, which has travelled further than any other seeds that have come to Svalbard.

Gregson, who sits on the board of the Crawford Fund, which supports international agriculture research, noted that virtually all Australian food crops come from outside the country. Coupled with the country's recent bouts of extreme weather, this makes Australia's farmers particularly sensitive to the importance of global crop diversity.

"Australian farmers have recently had to deal with both droughts and floods. This is not only terribly difficult for farming communities, but also affects food prices worldwide -- harsh reminders of the need to find crop varieties that will help adapt to these changing conditions," Gregson said.

While crop diversity is critical to adapting agriculture to climate change, it is also at risk of being lost due to rapid changes in climate and farm environments. For example, in February, the Trust announced a partnership with potato farmers in Peru to duplicate and deposit in the Seed Vault seeds from 1,500 varieties of potatoes still found in the Peruvian Andes, where some varieties are threatened by climate change. To keep pace with rapid changes in the global climate, the Global Crop Diversity Trust is also moving to collect wild relatives of domesticated drops. With the support of a US$50 million grant from the government of Norway, the Trust is participating in a global search to locate and conserve wild relatives of wheat, rice, bean, potato, barley, lentils, chickpea, and other essential food crops that could contain valuable genetic traits.

Cary Fowler commented, "As we celebrate the third anniversary of this remarkable Vault, it is thrilling to see yet another fantastically diverse shipment of seeds arrive. The scale of the challenges facing agriculture can be overwhelming, yet the knowledge that over 600,000 samples are now guaranteed to be safe and available to help farmers gives me great hope for our common future."

 

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Engenharia Genética

por papinto, em 20.01.11

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ScienceDaily (June 22, 2010) — Research led by the University of Bath has discovered that plants, like animals, also have a battle of the sexes when it comes to raising their offspring.

Their findings could open new avenues to increase crop yields and improve food security for an ever-growing global human population.

Since mothers give birth to young, they must invest more of their resources into producing offspring than fathers.

For mothers, it's a balance between giving enough resources to keep their babies healthy, but still making as many babies as they can. In contrast, it benefits fathers to have young that are as large as possible and more likely to survive.

The researchers, from the Universities of Bath, Exeter and the Albrecht von Haller Institute for Plant Sciences in Germany, have now shown that this parental struggle also exists in plants.

The study, funded by the Natural Environment Research Council (NERC) and the Biotechnology & Biological Sciences Research Council (BBSRC), and published in the Proceedings of the Royal Society B, shows for the first time that male plants can influence the size of seeds.

Using the model plant Arabidopsis, they bred female plants with a variety of different male plants and measured the size of seeds produced with each pairing.

They found that crossing the female plant with a specific strain, or genotype, of male plant produced bigger seeds, allowing the father to have more healthy offspring at the cost of the mother.

Dr Paula Kover, Senior Lecturer at the University of Bath, explained: "Seed size can make a huge difference to whether a seedling is likely to survive, so you would imagine that there would be an optimum seed size for mothers to produce, balancing the likelihood of survival with the cost in energy of producing them.

"However, we see a lot of variation in seed size. The reason for this is a long-standing debate.

"Previously it was thought that seed size was controlled solely by the mother's genes, but for the first time we've shown clearly that genes passed on from the father plant can also have an effect on seed size.

"The next step will be to identify the specific genes that influence seed size. Previously plant breeders only considered the mother's genes in the breeding process, so this study could open the door on a whole new group of genes that could increase crop yield."

Dr Clarissa House, from the University of Exeter, added: "Relatively few studies have been able to distinguish between the influence of paternal genotypes for offspring fitness and maternal effects. Our study clearly shows that paternal genes are important."

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The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of Bath.

Journal Reference:

  1. C. House, C. Roth, J. Hunt, P. X. Kover. Paternal effects in Arabidopsis indicate that offspring can influence their own size. Proceedings of the Royal Society B: Biological Sciences, 2010; DOI: 10.1098/rspb.2010.0572

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 in: www.cap.pt
19-Jan-2010

Um consórcio internacional de investigadores acaba de publicar na revista Nature uma sequenciação completa do genoma da soja.


Esta descoberta poderá contribuir para identificar os genes relevantes para as propriedades agronómicas desta planta. Os investigadores identificaram mais de 46 mil genes, dos quais mil e cem estão associados ao metabolismo dos lípidos.


Estes genes são responsáveis pelo facto de a soja ter mais ou menos óleo e poderão ser modificados para obter mais óleo de soja quer para fins alimentares quer para aumentar o seu uso na produção de biodiesel. Os investigadores acreditam que, por esta via, poderá ser possível obter plantas de soja que produzam mais 40% de óleo.


Nesta investigação participaram 18 instituições, entre as quais o Serviço de Investigação Agrária e o Departamento de Energia dos Estados Unidos da América, assim como a Universidade da Carolina do Norte.

 


 

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