Gene technology is being used to speed up the identification of positive genetic traits, that can then be used to more quickly screen vines for sodium and chloride tolerance bred through traditional methods.
This is achieved using a common soil microorganism called Agrobacterium, which in the wild, infects plant tissues by inserting a special piece of DNA into the genome of the host plant. This fragment of DNA then sets to work, reprogramming the plant’s cells to multiply; effectively providing a safe haven for the bacterium to replicate.
Now, uniquely in Australia, scientists in Adelaide’s CSIRO Agriculture and Food team are using the bacterium as a vector to genetically transform grapevines, by inserting desirable pieces of DNA into their genome. The method has been used over many years to introduce foreign genes into various other plant species, including important crops.
‘The DNA constructs we are introducing into grapevine cells using Agrobacterium are designed to reduce the activity of a specific target gene. We then see what impact this has on grapevine growth and development, thereby giving us more knowledge about how important that particular gene is’, explained Dr Mandy Walker, CSIRO Adelaide Research Team Leader in the Agriculture and Food Laboratory.
‘These constructs, or bits of DNA, are integrated into the genome of a single cell of the grapevine and then this cell multiplies to become an embryo and eventually a small plant, which we can replicate.’
Research a laborious process
In the current phase of their research, supported by Wine Australia, Dr Walker’s team is testing nine different genes in Shiraz, focusing on candidate genes suspected to be involved in controlling abiotic stressors, for example sodium and chloride exclusion.
Unfortunately, transformation of grapevine has proven to be challenging. Dr Walker concedes the procedure is long (about 12–24 months), difficult and with a very low rate of success.
However, the end result could be an important investment for future grapevine development – and put Australian grape and wine research, and CSIRO’s Agriculture and Food Lab in particular, on the world stage.
‘Understanding gene function allows us to design DNA markers to assist in breeding rootstocks with the best possible combinations of important genes to withstand stress or pests.’
‘There are probably only about 10 laboratories around the world that can do grapevine transformation. We are the only laboratory in Australia and probably more successful than most of the rest of the world’, Dr Walker said.
From previous projects funded by Wine Australia – and in collaboration with the University of Adelaide – the team had identified several genes that are important in determining how effective different rootstocks are at dealing with salt and in restricting the movement of chloride or sodium to the shoots and berries.
‘Some of the genes were identified by examining the expression of genes (which is often used as an indicator of activity) in a rootstock that take up a lot of chloride (such as K51-40) and compared to a rootstock that doesn’t (such as 140 Ruggeri)’, explained Dr Walker.
The candidate genes were then typed by looking at the DNA sequence and comparing that sequence to information about salt exclusion genes in other plant species. This helped the team narrow down the list of genes to test.
‘From our previous work and that of others, we’ve found that there doesn’t seem to be one class of gene involved in chloride exclusion – and our work with the transgenic plants confirms this’, Dr Walker said.
However, Dr Walker said the current project has been able to identify a key sodium exclusion gene – and has allowed the team to test several others believed to be involved in chloride and sodium exclusion.
‘We used transformation technology to reduce the expression of a gene called hkt1.1 in Shiraz and were able to definitively demonstrate that this gene is very important for sodium exclusion. Hence this sodium exclusion trait is simpler than the more complex chloride story.’
The project’s final report can be downloaded here.
