‘Next generation’ rootstocks with long-term resistance to phylloxera and root knot nematode – and optimised for Australian conditions – are a step closer.
CSIRO research scientist Harley Smith told delegates at the recent Australian Wine Industry Technical Conference that the CSIRO Rootstock Breeding Team had identified and genetically mapped resistance traits for grape phylloxera and root knot nematode from the wild North American grape species Vitis cinerea.
The finding is significant, because standard commercial rootstocks currently used in wine grape production are derived from a limited number of North American Vitis species cultivars and have a narrow genetic base.
‘This low genetic diversity is a major problem, as the sources of phylloxera resistance are likely similar in the commercial rootstocks. Therefore, a breakdown in their resistance to grape phylloxera would limit the options for replanting of infested vineyards’, Harley explained.
One way around this problem is to combine two or more diverse non-redundant resistance traits in one rootstock – if resistance to one is broken, the other is still functional.
Harley said, however, that it was not feasible to effectively combine resistance traits using traditional breeding approaches, which is why the CSIRO Rootstock Breeding Team has taken a different approach.
‘Our team genetically mapped the grape phylloxera and root knot nematode resistance traits and identified DNA markers tightly linked to these resistance traits.’
He said having the linked DNA markers allowed the team to screen hundreds to thousands of plants at the seedling stage using a simple procedure.
‘As a result, we were able to effectively identify individuals with multiple grape phylloxera and root knot nematode resistance traits in progeny produced during the breeding process.’
Harley said the phylloxera resistance trait provides complete resistance to the G1 and G4 grape phylloxera strains, which are highly adapted to feeding on Vitis vinifera wine grape cultivars.
In collaboration with Dr Catherine Clarke at Agriculture Victoria, the team now plans to evaluate whether Vitis cinerea can also provide resistance to other grape phylloxera strains including G7, G19, G20 and G30.
The team also found that the root knot nematode resistance trait provides complete resistance to Meloidogyne javanica ‘pt 1103P’, an aggressive nematode strain that effectively feeds and reproduces on 1103 Paulsen. This root knot nematode resistance trait also provides complete resistance to strains of Meloidogyne arenaria and Meloidogyne incognita.
‘Therefore, the Vitis cinerea root knot nematode resistance trait appears to provide complete resistance to all three major root knot nematode species,’ he said.
Harley said the next generation rootstocks would have a distinct genetic base from the commercial rootstock varieties.
‘With the development of genotyping-by-sequencing techniques and the application of new genetic mapping programs, we now have the tools to develop new rootstocks with durable resistance to these soil pests.’
He said the planned crosses for next generation rootstock development would combine the newly identified phylloxera and root knot nematode resistance traits with other phylloxera and root knot nematode resistance traits in order to achieve long-term resistance to these vineyard pests.
Harley was named a Fresh Science Winner at the Australian Wine Technical Conference in 2019.
