CONFERENCE 10 MARCH 2006
LATEST TECHNICS TO IMPROVE THE MONITORING OF GRAPEBERRY
RIPENING
|
|
|
|
I – Modern approaches of ripening physiology |
|
|
|
|
|
|
|
Berry quality, yield, water
use efficiency and disease resistance are just a few examples of traits
controlled by genes present in the grapevine genome. Discovering these
genes and linking them to specific traits can be achieved by using a
genomics approach. Over the last 5 years there has been significant international research activity in grapevine gene discovery. As part of an international collaboration through the International Grape Genome Program (IGGP) many research groups have submitted gene sequences to public databases as a means of sharing data and encouraging further research. This approach has proved very successful and if we assume that grapevine has approximately 25,000 genes then nearly half of all grapevine genes have now been discovered. This is a significant achievement in such a short time. An extension of this gene discovery research is the use of the sequence information for gene expression studies using microarrays. The advantage of microarrays is that it can be used to look at the expression of thousands of genes at a time instead of the traditional approach of investigating one gene at a time. In Australia we are using grapevine microarray technology to advance our understanding of berry development and quality. The growth of the berry is the result of complex interactions between the environment, the imposed management regime and the genotype (genes) of the cultivar. An extensive body of knowledge exists, built up over more than a hundred years, which describes the best environment for growing grapevines and appropriate viticultural management techniques. In contrast, very little is known about the genes that are responsible for berry development and quality. Microarray technology has the potential to greatly advance our knowledge in this area and also provide insight into how the genes responsible for berry growth respond to environmental and viticultural management treatments. An extensive study is being conducted in Australia using microarrays to investigate berry development of Cabernet Sauvignon over 3 seasons grown in 3 different regions (Clare, Willunga and Mildura) that range from mild to hot growing conditions. Different management treatments are also being investigated and include cane verus spur pruning and normal irrigation compared to partial deficit irrigation. The study has found that berry development is far more complex than initially thought. In addition to thousands of genes changing their level of expression at veraison, with many being turned on or off, additional stages both pre and post-veraison have been identified where significant gene expression changes are occurring. As a result of this research key genes and processes involved in berry development have been identified. One of these new findings is that grapes are on steroids. Brassinosteroids (BR) are a class of plant steroidal hormones not previously implicated in fruit development. The research has shown that brassinosteroids have a role in berry development. Gene expression analysis of these genes during berry development revealed gene transcript accumulation patterns that were consistent with a dramatic increase in endogenous BR levels observed at the onset of fruit ripening. Application of BRs to grape berries promoted ripening, while brassinazole, an inhibitor of BR biosynthesis, delayed fruit ripening. The use of gene expression studies to investigate fruit with differing quality characteristics may also provide clues as to what genes are responsible for berry quality characters or off flavours. For example, the levels of some compounds important to flavour are present at extremely small levels and are difficult to measure. Microarray technology offers the possibility of monitoring their synthesis via gene expression analysis. It is clear that the study of genes will lead to a better understanding of berry development. Future application of this knowledge may lead to better vineyard management decision support systems and development of new varieties with improved fruit quality. References Symons GM, Davies C, Shavrukov Y, Dry IB, Reid JB, Thomas MR (2006) Grapes on steroids. Brassinosteroids are involved in grape berry ripening. Plant Physiology 140: 150-158 Acknowledgements The research was supported by CSIRO Plant Industry, the Cooperative Research Centre for Viticulture and the Grape & Wine Research Development Corporation. |
|