Topic 5 - Rootstocks, hybrids and grapevines of the future

Question 1

What are rootstocks?

Answer 1

Grapevine species (or hybrids) other than Vitis vinifera used for establishing the root system whereon a scion variety (Vitis vinifera) is grafted

Question 2

What is a hybrid grapevine?

Answer 2

A cross between two grapevines of different species, carrying a specific trait such as disease resistance or tolerance to an environmental constraint.

Question 3

What species are most rootstocks?

Answer 3

Most rootstocks are either native North American Vitis species or hybrids of two or more of these species, including Vitis riparia, Vitis berlandieri, and Vitis rupestris.

Question 4

Different rootstocks have different characteristics concerning how they contribute to adapting to certain environmental limitations - what are these environmental limitations, and what is a rootstock that is suitable for adapting to each limitation?

Answer 4

o Drought resistance: (Richter 110, Ruggeri 140)
o Resistance to soil salinity: (Ramsey, Ruggeri 140)
o Sites with poor drainage: (Dog Ridge, Schwarzmann)
o Acidic soils: (Richter 110, Ruggeri 140)
o Alkaline soils: (Ruggeri 140, Richter 110)
o Nematodes: (Dog Ridge, Ramsey)
o Poor soils (low vigour): (Dog Ridge, Ramsey)
o Fertile soils (high vigour): (101-14 Mgt, Schwarzmann)

Question 5

Why are rootstocks used for pest and disease resistance?

Answer 5

• Vitis vinifera grapevines are highly susceptible to two soil-borne pests, phylloxera and plant parasitic nematodes.
• Rootstock varieties derived from other grapevine species and hybrids are often resistant to these pests and may be used as rootstocks with Vitis vinifera varieties grafted on them.

Question 6

Resistance by rootstocks to pests, in general, can be conferred by various means, including:

Answer 6

1. Non-preference: The rootstock possesses characteristics that are unattractive to pests for reproductions, feeding or shelter.
2. Antibioses: The pest can establish feeding on the rootstock; however, the rootstock adversely affects the growth and reproduction of the pest.
3. Tolerance: The rootstock supports a pest population; however, the rootstock can live and thrive, suffering minor permanent damage.

Question 7

What two types of resistance to phylloxera can grapevine rootstocks have?

Answer 7

1. Resistance by tolerance. Rootstock forms a layer of cork tissue (periderm) around the root lesion. The cork layer limits the spread of decay into the root or may cause abscission of all or part of the lesion.
2. Resistance by repulsion of the insect. With this resistance, the rootstock possesses a certain trait, unattractive to phylloxera, and the insect won’t feed on the roots. This form of resistance is found in Muscadinia grapevines (for example, in the Muscadinia rotundifolia species).

Question 8

What are nematodes? What are the most common nematodes affecting grapevines?

Answer 8

1) Nematodes are microscopic roundworms, often causing substantial grape yield losses in affected vineyards.

2) The most common nematodes affecting grapevines are Rootknot nematodes, Dagger nematodes, Citrus nematode, Root-lesion nematode and Ring nematodes.

Question 9

What is the most significant nematode pest in Australia?

Answer 9

Rootknot nematodes are Australia’s most significant nematode pest and may cause up to 60% yield loss when they affect a vineyard.

Question 10

Why are dagger nematods particularly destructive?

Answer 10

Dagger nematodes are particularly destructive as they can spread a number of viruses which may be detrimental to the health of grapevines.

Question 11

How is resistance to nematodes achieved?

Answer 11

Resistance to nematodes is thought to be largely achieved through a tolerance mechanism by resistant rootstocks, such as Ramsey.

These rootstocks will therefore somewhat support a population of nematodes, with very little or no considerable damage to the roots.

Question 12

How are rootstocks used towards optimised site and soil adaption?

Answer 12

• The American Vitis species from which most rootstocks are derived, often display adaption to certain soil types and conditions.
• Some rootstocks tolerate adverse soil conditions better than other rootstocks.
• Rootstocks do not necessarily, however, tolerate some soil conditions better than ungrafted Vitis vinifera grapevines.
• Rootstocks are sometime used on sites even where phylloxera or nematodes are not a considerable issue, purely to improve tolerance towards certain pre-existing soil conditions.

Question 13

How do hybrid grapevines emerge?

Answer 13

• A hybrid grapevine emerges when pollen from the male part of a flower of one vine species is transferred to the female part of a flower of another vine species and fertilisation occurs.
• Hybrids can occur naturally or can be bred by humans.
• Breeding programs are often followed in order to develop hybrids with improved features, such as enhanced resistance to diseases and pests.

Question 14

Many hybrid varieties have been developed by crossing which grapevine species?

Answer 14

Many hybrid varieties have been developed by crossing a Vitis vinifera grapevine with an American species, as the American species had natural resistance to diseases and pests such as powdery mildew and phylloxera.

Question 15

What is the main use of hybrids today?

Answer 15

The main usage of hybrids today, is as rootstocks.

Question 16

What is an example of a hybrid used for reasons other than rootstocks?

Answer 16

• American hybrids were bred to counter the harsh growing conditions of eastern United States.
• These hybrids are mainly crosses between Vitis vinifera and Vitis labrusca (for example, the hybrid varieties Concord, Catawba and Delware).
• Hybrids derived from Vitis labrusca often have ‘foxy’ characters, which many wine consumers consider an undesirable attribute.
• Nevertheless, these hybrids are commonly used for grape juice, wine, table grapes, preserves and food additives in parts of the United States.

Question 17

The changing climate will be the largest determinant of how grapevines are developed for the sustainability of the wine industry.

What are two approaches the wine industry can take to mitigate against climate change?

Answer 17

1) Move viticulture to cooler, non-traditional winegrowing regions

2) Use breeding and/or genetic modification (and additional methods) as tools to improve the resilience and sustainability of grapevines under hotter and drier conditions.

Question 18

Why will breeding towards disease resistance likely contribute considerably to what we will see in the grapevines of the future?

Answer 18

The reduction of the usage of spray chemicals will be crucial for the future as societies across the world are becoming more aware of the health and environmental impacts of some of these chemical.

Question 19

Why are regions most likely suitable for wine grape growing moving toward the North Pole and South Pole?

Answer 19

Mean growing temperatures of traditional viticulture regions are raising too high, which impacts vine growth and berry metabolism.

Question 20

What issues is climate change having on vitaculture?

Answer 20

• Higher temperatures are causing compressed harvests as grape ripening times are accelerated.
• Wineries are often unable to cope with the intake of too many varieties concurrently.
• Climate change can also cause grape juice sugar levels to become excessive, resulting in wines with higher than optimal alcohol levels.

Question 21

What mitigations/ strategies can be taken to ensure the sustainability of the wine industry facing climate change?

Answer 21

1) Move to traditionally cooler regions, essentially creating new viticulture regions.

2) Growers in traditional regions will need to find more ways to adapt to an even hotter and drier climate. These adaptions would include very careful selections of planting material and design of vineyards. Irrigation control will also become even more crucial, while canopy architecture will need to be managed to allow sufficient canopy shade and bunch protection from direct sunlight.

3) o Substitution of current Vitis vinifera varieties in these regions may have to take place to introduce better suited varieties and clones. This aspect is where breeding strategies may play a particularly important role in determining the development of vines for the future.

Question 22

How can breeding be employed asa strategy to ensure sustainability of the wine industry? What is an example where breeding is being used to produce better adapted grapevines?

Answer 22

• Conventional breeding, genetic modification and marker-assisted breeding could be used to produce better adapted grapevines.
• Conventional cross-breeding can be utilised to produce completely new varieties.
• The major reason for using cross-breeding today, it to generate varieties with disease and virus resistance.
• By using parent varieties that display natural resistance to major diseases and viruses (such varieties are often non-vinifera species), and crossing them with Vitis vinifera varieties, new varieties (often hybrids) are produced that can be grown with less or no chemical spray treatments.
• A breeding program at the CSIRO has recently produced the 1st generation of powdery and downy mildew resistant grapevines bred for Australian conditions.

Question 23

What are transgenic grapevines?

Answer 23

Transgenic grapevines are identical to the parent varieties, however, they have one or more ‘extra’ genes.

Considerable research especially in the early 2000s was focussed on creating GM grapevines with disease resistance or other traits.

• If (or when) GM grapevines become a commercial possibility, one can expect common varieties, for example, Shiraz or Chardonnay, with traits such as disease resistance or improved tolerance to warmer and drier climates. Pathogen and abiotic stress resistance, as well as fruit quality traits and high yielding potential, would likely be common qualities of new GM grapevines in the future.

Question 24

What new technologies may we see play a role in vineyards in the future?

Answer 24

In addition to commonly used automation technologies, such as mechanical harvesting and pruning, precision viticulture techniques, for example, variable rate irrigation systems and remote sensing will become more accessible to growers.

In addition to precision viticulture, smart phone applications and robotics are being developed and will play a role in the management of vineyards in the future.

Question 25

Which of the following is not a common reason for using rootstocks when establishing a vineyard?
A. To prevent phylloxera-related damage
B. To combat soil salinity
C. To alter the terroir
D. To inhibit nematode infection

Answer 25

C. To alter the terroir

Question 26

You want to plant a vineyard site with high soil fertility and where root-knot nematodes are present. Which of the following rootstocks would most likely be suitable to use?
A. Schwarzmann
B. Ramsey
C. Dog Ridge
D. Paulsen 1103

Answer 26

A. Schwarzmann

Question 27

Which of the following statements is most accurate?

A. Hybrid grapevines are created through transgenic modification
B. Hybrid grapevines always exhibit increased resilience to climatic extremes
C. Hybrid grapevines are created through crossbreeding two species
D. Hybrid grapevines are phylloxera resistant

Answer 27

C. Hybrid grapevines are created through crossbreeding two species