Questions are being asked globally about the long-term stability of grape phylloxera resistance in commercial rootstocks. That’s why the work of the CSIRO Rootstock Breeding program, led by Harley Smith, has caught the attention of the biosecurity world.
The program is utilising next generation genetic and molecular tools for developing new rootstocks with long-term resistance to phylloxera, as well as root knot nematode, using DNA marker-assisted selection1.
Given that phylloxera is the major endemic biosecurity threat to the Australian wine industry, the use of resistant and/or tolerant rootstocks is an essential vineyard management tool for safeguarding vineyards from this devastating insect pest1.
Phylloxera can feed on both the roots and leaves of Vitis species depending on the genotype of the host and insect2. Root-feeding phylloxera cause the most economic damage to Vitis vinifera and are therefore the greatest group of concern in Australia, given that approximately 70% of vines are planted on own roots nationally.
On Vitis vinifera, these phylloxera strains feed on mature roots, resulting in swellings called tuberosities, which ultimately lead to vine death. Phylloxera feeding can also occur on young feeder roots, resulting in the formation of characteristic nodosities. These nodosities alone may affect the vigour and longevity of the vine, but rarely result in plant death3. Their presence on resistant rootstocks has been widely reported and, importantly for Australia, can lead to spread to highly susceptible own-rooted vines.
“Studies have shown that in Europe and California, there is a grape phylloxera strain that appears highly adapted to feeding on rootstocks with Vitis riparia parentage4,5,6,7,“ Harley said.
“While it’s not clear if a similar strain exists in Australia, studies in Europe and California infer that phylloxera is evolving and becoming better adapted to Vitis riparia rootstocks, which includes Teleki 5C, SO4 and 101-14. In these cases, a high level of feeding on young roots produces numerous nodosities rather than tuberosities, which appears to reduce root function and vine performance under abiotic stresses.”
Rootstocks currently used in commercial vineyard production are derived from North American Vitis species that have co-evolved with phylloxera and, as a result, they typically display varying levels of resistance to this insect pest1. This resistance is based on the ability of these rootstocks to prevent the development of vine killing tuberosities6. However, these rootstocks are derived from a limited number of Vitis riparia, Vitis rupestris and Vitis berlandieri selections6. This low genetic diversity is being recognised as a concern, as the source of phylloxera resistance in these rootstocks is likely similar. The ability of these rootstocks to combat a changing climate and pest pressure is now being questioned4, given a breakdown in this resistance would severely limit the options for replanting of infested vineyards.
“In the natural world, as pests evolve and climate changes, vineyard management tools must be continually modified,” Harley said.
The CSIRO Rootstock Breeding program is selecting phylloxera and root knot nematode resistance traits from the wild North American grape species including Vitis cinerea8,9 to further increase the genetic diversity of commercial rootstocks.
“To breed long-term resistance, Vitis cinerea is being crossed with other North American Vitis species and hybrids harbouring other phylloxera resistance traits1. By combining two resistant traits into the same rootstock, it’s extremely difficult for phylloxera to evolve and break two different resistance traits simultaneously. Progeny derived from these crosses containing two resistance traits for phylloxera will be selected using DNA markers. We’re not only using this strategy for phylloxera but also for root knot nematode resistance,” Harley said.
The outcome of this work is the production of next generation rootstocks with increased genetic diversity and long-term resistance to phylloxera and root knot nematode for Australian conditions.
In Australia, our 83 known phylloxera strains have been genetically grouped into six distinct families, with individuals in each family likely sharing similar traits10. These families are represented in testing by strains G1, G4, G7, G19, G20 and G30.
“The Vitis cinerea phylloxera resistance trait mapped at CSIRO provides complete resistance to the most prevalent endemic phylloxera strains, G1 and G4, which are highly adapted to feeding on the roots of Vitis vinifera wine grape cultivars8,” Harley said.
In collaboration with Dr Catherine Clarke at Agriculture Victoria, the CSIRO team is evaluating whether Vitis cinerea can also provide resistance to other phylloxera strains including G7, G19, G20 and G30.
“We’re collaborating with Agriculture Victoria’s phylloxera research program to ensure that the rootstocks we are developing will provide effective resistance to a wide range of phylloxera strains,” Harley said.
To read more about the CSIRO rootstock breeding programs click here.
References
1. Dunlevy J., Clingeleffer P., and Smith H. (2019). Breeding next generation rootstocks with durable pest resistance using DNA marker-assisted selection. Wine & Viticulture 3: 40-44.
2. Powell, K.S. and Clarke, C.W. (2018). A Scientific Basis for Risk Analysis of Grape phylloxera Daktulosphaira vitifoliae Fitch. Wine Australia.
3. Benheim, D., Rochfort, S., Robertson, E., Potter, I., & Powell, K. S. (2012). Grape phylloxera (Daktulosphaira vitifoliae) – a review of potential detection and alternative management options. Annals of Applied Biology, 161(2), 91–115.
4. Kocsis L., Granett H., Walker M. A. (2002). Performance of Hungarian phylloxera strains on Vitis riparia rootstocks. Journal of Applied Entomology. 126: 567-571.
5. Kocsis L., Granett J., Walker M. A., Lin, H. and Omer, A. D. (1999). Grape phylloxera populations adapted to Vitis berlanieri x V. riparia rootstocks. American Journal of Enology and Viticulture 50:101-106.
6. Riaz S., Pap D., Uretsky J., Laucou V., Boursiquot J. M., Kocsis L. and Walker M. A. (2019). Genetic diversity and parentage analysis of grape rootstocks. Theoretical and Applied Genetics 132: 1847-1860.
7. University of California Cooperative Extension Newsletter (2012). http://cenapa.ucanr.edu/newsletters/Vineyard_Views_Newsletter_-_Events43564.pdf.
8. Smith, H.M., Clarke, C.W., Smith, B.P., Carmody, B.M., Thomas, M.R., Clingeleffer, P.R. and Powell, K.S. (2018b). Genetic identification of SNP markers linked to a new grape phylloxera resistant locus in Vitis cinerea for marker-assisted selection. BMC Plant Biology 10:360.
9.Smith, H.M., Smith, B.P., Morales, N.B., Moskwa S., Clingeleffer, P.R. and Thomas, M.R. (2018a). SNP markers tightly linked to root knot nematode resistance in grapevine (Vitis cinerea) identified by a genotyping-by-sequencing approach followed by Sequenom MassARRAY validation. PloS One 13:e0193121.
10. Umina P. A., Corrie A. M., Herbert K. S., White V. L., Powell K. S. and Hoffmann A. A. (2007). The use of DNA markers for pest management: clonal lineages and population biology of Grape phylloxera. Acta Horticulturae. 733: 183-195.