- International Grape Genome Program
The International Grape Genomics Program (IGGP) is a collaborative
genome project dedicated to determining thegenome sequence of thegrapevine , "Vitis vinifera L." As the name suggests, it is a multi-national project involving research centers inAustralia ,France ,Canada ,Chile ,Germany ,Italy ,South Africa ,Spain and theUnited States .The project was initiated in on the premise that whereas the "Vitis" family provides the world's most economically important
fruit , itsbiology is still poorly understood. Many centuries ofviticulture have provided a large number of well-informed wine-producing centres throughout the world, yet exactly how a grapevine plant responds and interacts with the physical environment and deals withabiotic stresses, pests anddisease s is currently unknown.Agricultural technology surrounding "Vitis" has been traditionally based upon specificgenotypes , which in the main have relied on "vegetative multiplication" and control of growing conditions to improvequality and yield. While advances in quality have certainly been achieved, it has involved increased costs and is in danger of incurring unsustainable environmental overheads. The argument is that the relatively unknown biology of "Vitis" is capable of delivering desired viticultural improvements without the associated ongoing costs, and establishing its genome sequence will examine the role individual genes play inviniculture , improvinggrape characteristics and quality in a predictable way. [http://www.vitaceae.org/ website of the International Grape Genomics Program]Initial discoveries
As at March 2007, the project has mapped over half of the grapevine genome. In the course of their research, the
Cooperative Research Centre for Viticulture (CRCV), based at the CSIRO Plant Industry Horticulture Unit inAdelaide , Australia (one of the IGGP collaborating centres) discovered that white grapes only exist today as a result of a raregenetic mutation which took place thousands of years ago. White grapes are believed to have arisen due to the extremely rare and independent mutation of two similar and adjacent regulatorygenes , "VvMYBA1" and "VvMYBA2", in a red grape parent.Most grapevine cultivars can be divided into two groups - red and white - based on the presence or absence of
anthocyanin in the skin of the fruit, which the geneticists discovered to be controlled by these two genes. Although either can dictate colour, the "VvMYBA1" gene, which activates the anthocyaninbiosynthesis necessary to produce red grapes, was shown not to be transcribed in white grape berries. The white berryallele of "VvMYBA2" was inactivated by two mutations, one leading to anamino acid substitution and the other to aframeshift mutation. Tests showed that either mutation removes the ability of theregulator to switch on anthocyanin biosynthesis, and when both are switched off it results in a white cultivar. Sequence analyses of the "VvMYBA2" gene confirmed that all of the 55 whitecultivars tested contained the white berry allele, but not red berry alleles - and all displayed the exact same double mutation, pointing to a single, commonancestor . [http://www.blackwell-synergy.com/doi/abs/10.1111/j.1365-313X.2006.02997.x Amanda R. Walker, Elizabeth Lee, Jochen Bogs, Debra A. J. McDavid, Mark R. Thomas, Simon P. Robinson (2007)White grapes arose through the mutation of two similar and adjacent regulatory genesThe Plant Journal 49 (5), 772–785.] Assuming this to be true of all white cultivars, without this single parent vine there would be no white grapes today. White wine residues discovered inancient Egypt ian pottery remains suggest that this mutation occurred at least three thousand years ago, [http://www.a2mediagroup.com/?c=138&a=13871"First white wine was a happy accident" - article] although in lieu of testing against a known white grape genome, the possibility remains that the mutation could have occurred more recently. A similar dual mutation occurred during the last decade. Viticultor Jesús Galilea Esteban, of the vineyard Murillo de Rio Leza in Rioja, Spain, noticed a white grape mutation in someTempranillo grapevines growing on his estate. After the white vine was propagated and the mutation did not revert, the newvarietal was granted outline permission to apply for approved grape status by the Rioja D.O. and the first hectare of white Tempranillo was planted in the region in the year 2000. Both white and red vines share identical leaves, clusters and berry shape, as well as the short ripening cycles and sensitivity to pests and diseases typical of the red Tempranillo. The mutation is thought to have occurred as a result of environmental factors. [ [http://www.vinosalmundo.com/Ver_articulo.asp?id=272 Tempranillo en blanco y negro ] ]See also
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Genomics
* White TempranilloReferences
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