Improved Grapevine Performance and Fruit Quality Through Gene Technology
Molecular biology provides a powerful new approach to understanding biological systems and is resulting in major technological advances in biology, agriculture and medicine. The application of these techniques to grapevines is providing new knowledge that will keep Australian grape and wine industries at the forefront of viticultural science in the future.
Australian scientists are using gene technology in research to advance our knowledge of how both microorganisms and grapevines function. These efforts form part of an ongoing, long-term program of scientific research and are not unique to Australia, or to the wine industry.
The Viticulture 2000 group identified the need for a strategic research program in this area and developed a program brief, following extensive consultation with the grape industries. The program includes projects aimed at improving resistance to pathogens and root pests to reduce reliance on chemical control and ensure security of supply; improving fruit quality; developing the tools for molecular breeding of grapevines and an integrated adoption and communication plan.
The introduction of genetically modified plants into our food supply is currently the subject of vigorous community discussion. No genetically modified grapes or yeasts are used in the production of Australian wines. The research in the CRCV is at an early stage and further development and testing is likely to take at least another 5-10 years.
Program Manager
Dr Simon Robinson
Dr Simon Robinson, PhD, BSc (Hons) (Adelaide) is a Project Leader with the Horticulture Unit of CSIRO Plant Industry at the Waite Campus of Adelaide University. In the first CRCV, Dr Robinson was the Program Manager for Grapevine Function and Genetic Improvement of Grape Quality and Low Chemical Input.
He has been actively involved in plant research for more than 25 years in Australia, the US and UK in areas covering plant physiology, biochemistry and molecular biology.
Dr Robinson's group recently isolated genes responsible for browning in fruit and vegetables and demonstrated that the browning reaction could be eliminated in potatoes by genetic modification to switch off the browning genes.
He has published more than 90 scientific papers and a number of International Patent applications and has received the Goldacre Award from the Australian Society of Plant Physiologists, a Queen Elizabeth II Fellowship and the William Culross Prize and the John Bagot Medal from Adelaide University.
program update (19/12/2005)
Our research in this program aims to improve the efficiency of production, vineyard sustainability and fruit quality through the application of gene technology. We are using molecular biology technologies to investigate grapevines and yeast and derive knowledge that will improve viticultural management and produce improved planting material in the future.
An aim of the program is to improve grape quality by developing a better understanding of the processes of berry development and ripening, sugar accumulation, organic acid metabolism, and the flavonoid pathway, which is responsible for the synthesis of anthocyanins, flavonols and tannins.
One of our most interesting findings in the past year is in relation to colour. We have found that white grapes are a result of mutations in the two genes that control colour in the berry skin. This mutation occurred thousands of years ago and originally all grapes would have been red. Rare and unrelated genetic mutations inactivated the two colour controlling genes in a red-berried parent vine, giving rise to seedlings with white berries. Through searching for these two genes that control colour, we have produced a marker that can be used in vine breeding to predict colour in the next generation of vines.
We have also gained greater insight into understanding the synthesis and accumulation of organic acids in grapes and significant new information about the nature of these acids has been obtained in the last twelve months.
We have found that there are two alternative pathways for the development of tartaric acid and have identified one of the key genes involved in this process. By looking at wild grapevine relatives that dont make tartaric acid, we were able to discover where to look using genomics tools. The identification of the gene has given us a much greater understanding of tartaric acid synthesis in grapes and how it could be manipulated.
In the area of genomics, one focus of our research has been in the area of flowering and fruit set important but not yet well understood processes. Management techniques such as pruning level can have an effect on yield but it is largely the interaction of environmental conditions and the genes in the plant that determine the degree of fruitfulness.
To gain a better understand of grapevine fruitfulness, key genes involved in grapevine flowering have been identified and investigated during latent bud development and after bud burst. The effect of the environment on the expression of the genes is also being studied. Some of the genes have a role in determining flowering time while other genes are involved in determining if a tendril or bunch will form while other genes are responsible for determining organ identity (anther and ovary development). By looking at many genes a grapevine flowering model is being developed to enable a better understanding of the importance of different genes in grapevine fruitfulness and their interrelationships.
Another project with an emphasis on fruit set is assessing the use of molybdenum sprays to improve fruit set and berry development in Merlot. A trial based at McLaren Vale is examining the short and long-term residual effects of molybdenum sprays on four Merlot varieties grown on different rootstocks and the mechanisms by which molybdenum is transported into the grapevine.
The course of grape berry growth and ripening depends on the complex interaction between viticultural practices, the prevailing environmental conditions and the genome of the grapevine. It is the differential expression of the various genes (each of which has a distinct function) in a timely manner and specific location which ultimately defines berry fate. Using the newly developed technology of DNA microarray analysis we can now measure the many changes that occur in the expression of thousands of genes during berry development, including the all-important process of berry ripening. Through the cooperative efforts of the international research community and the development of a commercial microarray chip we are now in a position to apply this technology to grapevine.
We have initially focused our study on the development of a detailed analysis of gene expression throughout berry development from flowering through to commercial ripeness. Our results show that grape berry gene expression alters dramatically both in the number of genes whose expression changes and in the frequency at which changes in expression occur. Both occur at a level that was not previously conceived. Many genes (our results indicate some 4,000 or so) change their expression during the transition into the ripening phase. Of these genes many have an identified function. In addition, there are other bursts of gene expression which occur at less expected times in development indicating that important events are occurring at times that have previously gone undetected. The investigation of changes in gene expression during berry development will provide essential baseline data to our further understanding and manipulation of berry growth and ripening.
We are also conducting field experiments where berries have been grown under different climatic (warm v cool) and viticultural conditions (altered pruning and irrigation) and we are identifying those genes whose expression changes and which may be indicators of, or essential to, a particular outcome or character in the fruit. By linking the data on gene expression with biochemical and wine sensory analysis we are completing the chain from gene to wine in an attempt to identify key genes that will provide indicators of the current berry state and predictors of fruit outcomes.
One of our major aims in this program continues to be isolating major resistance genes to powdery mildew. To do this, we need to establish the location of genetic markers on a physical map of the grapevine genome and isolate candidate genes using a bacterial artificial chromosome (BAC) library. Once candidate genes are identified, they can be transformed into susceptible grapevine cultivars and the transformed plants can be tested for resistance to powdery mildew.
The two main components of the research over the last 12 months have been to complete the screening and phenotyping of new mapping populations and to commence sequence analysis of BAC clones mapped to the location of the resistance gene locus. A number of promising candidate gens have now been identified from this sequencing effort and these will be tested over the next two years.
Another related project also focusing on powdery mildew is looking at the role of the host (grapevine) gene expression in the establishment of the disease. Such knowledge could be used to manipulate host gene responses to limit or restrict the development of feeding structures during the initial stages of infection and inhibit further fungal development.
Our research has identified specific changes in the expression of genes associated with host carbohydrate metabolism and transport during powdery mildew infection. Examination of the expression of five different grapevine hexose transporters has revealed that only one is specifically induced during powdery mildew infection. We have also identified a cell wall invertase gene that is specifically upregulated during powdery mildew infection.
In the past year we have also released a third brochure in the Gene Technology series that explains how we are using genomics to learn more about grapevine function. These brochures have been widely distributed and have been an important tool in providing accurate information about the use of this technology.
Current Program Three Projects:
Isolation of a major resistance gene to powdery mildew (3.1.1)
Mechanism of powdery mildew infection in grapevines (3.1.5)
Flavonoid pathway genes in grapes (3.3.1)
Role of growth substances in berry development (3.3.2)
The control of tartaric acid accumulation in grapevines (3.3.3)
Transformation of grapevines with berry quality genes (3.3.4)
Evaluation of sultanas with decreased browning (3.3.5)
Grapevine fruitfulness (3.4.1)
Grape genomics: grapevine gene discovery (3.4.2)
Grape genomics: genetic and physical maps of grapevine genes (3.4.3)
Understanding and improving quality through a genomics approach (3.4.5)
Role of Molybdenum in fruit set and berry development in Vitis vinifera cv. Merlot (3.4.6)
Completed Program Three Projects:
Modification of grape cluster architecture for control of fungal diseases (3.1.4)
Improved Resistance to Root Pests (3.2.1)
Auxins and pollen tube growth (3.3.6)
Identifying genes for wine yeast improvement (3.4.4)
Communication to the Grape and Wine Industries (3.5)
