Rootstocks and scions for raisin grapes

Matthew FidelibusUC Davis

Rootstocks and scions in California

• Despite the presence of Phylloxera and plant parasitic nematodes, most raisin vineyards in California are own-rooted ‘Thompson Seedless’

• The availability of newer, earlier-ripening scions, suitable for the mechanized dry-on-vine production method is leading to industry-wide changes in rootstocks and scions

• Most new vineyards are on rootstocks, with a scion that is not ‘Thompson Seedless’

Current rootstock situation in California

• Most raisin grapes are still own rooted, with the remainder on Freedom, Harmony, or 1103P rootstock

• Freedom and Harmony were released 45 years ago. Some strains of root knot nematode have evolved to overcome their resistance

• An increasing reliance on limited and, in some places poor quality, groundwater has increased interest in drought and salt-tolerant rootstocks

• Rootstock breeding and selection programs are attempting to produce and identify superior stocks for the future

Parentage & pest resistance of some common raisin rootstocks

Pest resistance

Rootstock Parentage PhylloxeraRoot knot nematode

Freedom 1613 (solonis x othello) x Dogridge low/medium high

Harmony 1613 (solonis x othello) x Dogridge low/medium medium/high

Salt Creek champinii high high

1103P berlandieri x rupestris high medium/high

Environmental suitability of some common raisin rootstocks

Environmental suitability

Rootstock Drought Salinity Lime soil texture

Freedom medium low/medium medium sandy to sandy loams

Harmony low/medium low/medium mediumsandy loams to loamy

sand

Salt Creek medium/high high medium sandy/infertile

1103P medium/high medium mediumdrought and saline

soils

Influence of common raisin rootstocks on scion mineral nutrition & growth

Mineral nutritionMacro nutrients Micro nutrients

Rootstock Vigor N P K Zn MnFreedom High High High High Low LowHarmony Medium/High Low Medium High Low/Medium Medium/LowSalt Creek High High High Medium/High Low Low1103P Medium/High Medium/High High Low/Medium Low/Medium High/Medium

Even the best possible rootstocks won’t benefit your vineyardif the scions are allowed to root!

Raisin varieties for tray-drying

• Most raisins in California are still dried on trays• Fruit may be laid onto trays with a machine

(“continuous tray”) or by hand• Thompson Seedless is by far the most

common variety used for tray-dried raisin production in California, followed by Fiesta

THOMPSON SEEDLESS

Thompson Seedless

• Approximately 66,900 ha of Thompson Seedless in California (2014). Most are for raisins, but approximately 4,451 ha were used for table grapes in 2012, and each year some go to juice and wine

• Normally achieves 21 Brix by the first week of September

• Average raisin yield is 4.5 MT/ha

FIESTA

Fiesta• Released in late 1973 as an early ripening

raisin grape for tray-drying (to avoid fall rains)• Ripens 1 to 2 weeks before Thompson

Seedless• High productivity• Highly susceptible to powdery mildew & other

common diseases• 4948 ha in California—second to Thompson

Dry-On-Vine (DOV) Varieties

• DOV is a newer production method suitable for mechanization

• Canes bearing mature fruit are severed, initiating the vine-drying process

• Drying proceeds more slowly on the vine than on trays since the temperature and fruit exposure to the sun are less for DOV

• Early-ripening varieties ensure drying without the use of drying emulsion

BLACK CORINTH (ZANTE CURRANT)

Black Corinth (Syn. Zante Currant)• Ancient origin• Many small clusters of very small berries• Gibberellic acid 3 to 5 days after full bloom

improves berry size and yield• Productive on spurs or canes, but cane-pruned

for DOV• Very susceptible to powdery mildew• Currently about 696 ha in California

FIESTA

DOVine

DOVine• Released in 1995 as first Thompson-type DOV variety • Ripens 2 to 3 weeks before Thompson Seedless• Extremely vigorous. Best-suited to cordon training

and cane-pruning• Low disease tolerance and prone to berry cracking• 229 ha in California

SELMA PETE

Selma Pete

• Released in 2001 as a superior Thompson-type DOV variety

• Ripens at least 3 weeks before Thompson Seedless

• Moderately vigorous, productive, and raisins are high quality

• Prone to zinc deficiency• 1,822 ha in California

SUMMER MUSCAT

DIAMOND MUSCAT

Fiesta DOVineThompson Seedless Selma Pete

All canes severed 8/14/01, pictured 9/10/01

Acknowledgements:CRMBAVFHal HuffsmithPeter CousinsStephen Vasquez