New Possibilities for

Rootstock Selections in the

21st Century

Richard Buchner, Joe Connell, Franz Niederholzer, Carolyn DeBuse, Cyndi Gilles, Ted DeJong, Sarah Castro and Chuck Fleck

What do roots do:

 Anchor trees to the soil

 Absorb water and provide mineral elements to the tree  Store carbohydrates and synthesize materials

 Determine scion growth and performance  Tolerance to soil types and conditions

 Resistance to soil borne diseases

 Must be graft compatible

Root structure is a branching system

 Main Roots

 Lateral Roots  Root hairs  Main uptake structures

 Need aeration  Low oxygen and high carbon dioxide reduce or stop root growth  Low soil moisture will stop root growth

 Low soil temperature will stop root growth

What are the rootstock choices

 Myrobalan

 Myrobalan 29C  Marianna 2624

 “M” Series – M40  Peach – Lovell, Nemaguard and Halford

 Almond

 Apricot

 2011 Planting

Selected characteristics of commonly used rootstocks for French Prune

Resistance or Susceptibility Pocket gophers and ROOTSTOCK Soil preferences Compatibility Anchorage Suckering mice Peach tree borer Myrobalan widely adapted to good for most good low suckering susceptible susceptible Seedling different soil types varieties mostly near and moisture crown conditions Myrobalan 29C widely adapted to good for most roots may be some susceptible susceptible different soil types varieties shallow the suckering near and moisture first 3 or 4 crown conditions years Marianna 2624 widely adapted to good for most roots may be some to high susceptible susceptible different soil types varieties shallow the suckering near and moisture first 3 or 4 crown and root conditions years Marianna 40 widely adapted to good for most more deeply low susceptible unknown; different soil types varieties rooted than probably and moisture Marianna susceptible conditions 2624 or Myro 29C Lovell well-drained, sandy good for most good low moderately highly susceptible loam soils best; varieties; not resistant sensitive to wet soil satisfactory for a conditions few including Robe de Sargeant and Suger Nemaguard well-drained, sandy probably same as good low moderately highly susceptible loam soils best; Lovell resistant sensitive to wet soil conditions

DISEASE RESISTANCE OR SUSCEPTIBILITY NEMATODE RESISTANCE Lesion (Root Knot Oak root fungus (Pratylenchus Meloidogyne Bacterial Canker Crown rot Crown Gall Brown line (Armillaria mellea) vulnus) spp.) Myrobalan variable, moderately variable, but susceptible susceptible susceptible many Seedling generally resistant generally less seedlings imparts susceptible than susceptible susceptibility peach

Myrobalan 29C imparts moderately more resistant susceptible a little more susceptible resistant susceptibility, resistant than seedling resistant than but less than Myrobalan seedling Marianna 2624 Myrobalan, but not so resistant as Marianna 2624 Marianna 2624 imparts high moderately more resistant resistant moderately susceptible resistant susceptibility resistant. than seedling resistant Myrobalan Marianna 40 unknown; early moderately unknown; unknown unknown; unknown; unknown; tests suggest it resistant probably similar probably similar probably probably imparts less to Marianna to Marianna susceptible susceptible susceptibility 2624 2624. than Marianna 2624 Lovell variable; but susceptible variable, but susceptible susceptible susceptible susceptible generally generally imparts less susceptible susceptibility than Nemaguard

Nemaguard generally susceptible unknown; susceptible susceptible susceptible resistant imparts less probably similar susceptibility Lovell than Marianna 2624

Note: Verticillium Wilt: Lovell and Nemaguard highly susceptible, plum less susceptible than peach. Ring Nematode: Myrobalan seedling, Myro 29C, Marianna 2624 and Marianna 40 are considered susceptible; Lovell and Nemaguard are moderately susceptible. Sources: Norton et.al. 1963 and M.V. McKenry, pers. comm.

2011 Planting

 Deseret Farms in Butte County (replicated) 4/28/11 and 2/10/12  Miki Orchards Yuba County (replicated) 6/3/11 replanted  Wolfskill location (non-replicated) 1/19/11

French Prune as the scion Conventional culture – long pruning for tree training

Experimental Design

 R C B design

 15 rootstocks with 5 replicates  75 plots x 6 trees/plot = 450 trees (replicated)

 18 rootstocks at Wolfskill: 3-10 trees/plot = 99 trees

Replicated Rootstocks

 Myro seedling  Empyrean 2

 Myro 29C  Citation

 Marianna 2624  Krymsk 86

 Lovell peach  Krymsk 1

 M40  Rootpac – R (Yuba only)

 M30  Viking (Dave Wilson) 2012

 M58  Atlas (Dave Wilson) 2012

 HBOK 50 (Duarte)

Wolfskill Rootstocks

 Empyrean 1  Imperial California  Empyrean 3  Controller 9  WRM 2 (Doyle, myro type)  HBOK 10  Fortuna  HBOK 27

 Speaker  HBOK 32  Puente  Own rooted  Krymsk 2  Marianna 2624  Krymsk 99  Lovell  Ishtara  Myro 29C

Rootstock Pedigree (scientific) Pedigree (Common) Other names Trial Interest to CA P. persica (Nemaguard) x (Prunus dulcis Nemagaurd x(almond x Bac canker Atlas Grower x Prunus blierianna) (apricot x plum)) resistant? P.persica x (P. amygdalus x P. blireiana Nemagaurd x(almond x Bac canker Viking Grower (P.ceresifera x P.Mume) (apricot x plum)) resistant?

Citation Prunus salicina x Prunus persica Red Beaut plum x peach 4-G-816 Grower

European prune (OP seedling Empyrean 2 Prunus domestica Penta Grower small tree of 'Imperial Epineuse')

nematode HBOK 50 Prunus persica Harrow Blood X Okinawa Grower resistant? Krymsk 1 Prunus tomentosa x Prunus cerasifera Plum x plum VVA1 Grower grown in Europe Krymsk 86 Prunus cerasifera x Prunu spersica Plum/peach hybrid Kuban 86 Grower anchorage M30 Prunu cerasifera x Prunus munsoniana Plum x wild plum Grower M40 Prunus cerasifera x Prunus munsoniana Plum x wild plum Grower Less suckering M58 Prunus cerasifera x Prunus munsoniana Plum x wild plum Grower smaller tree?

Myrobalan Prunus cerasifera Myrobalan seedlings Grower control seedling

Rootpack R Prunus cerasifera x prunus dulcis Plum/almond hybrid Replantpac Grower

Grower/ Lovell Prunsus persica peach seedling control Wolfskill

Marianna Grower/ M2624 Prunus cerasifera x Prunus munsoniana Plum x wild plum control 2624 Wolfskill Grower/ Myro 29C Prunus cerasifera Myrobalan clone control Wolfskill

Rootstock Pedigree (scientific) Pedigree (Common) Other names Trial Interest to CA Controller 7 Prunus persica Harrow Blood X Okinawa HBOCK 32 Wolfskill Controller 8 Prunus persica Harrow Blood X Okinawa HBOCK 10 Wolfskill Controller 9 Prunus salicina X Prunus persica Plum/peach hybrid P30-135 Wolfskill

Peach x Chinese wild peach. Empyrean 1 Prunus persica x P. davidana Barrier Wolfskill Venice, Italy

European prune (seedling of Empyrean 3 Prunus domestica Tetra Wolfskill sensitive to ORF Regina Claudia Verde)

Fortuna Prunus cerasifera x Prunus persica Plum/peach hybrid Wolfskill HBOCK 27 Prunus persica Harrow Blood X Okinawa Wolfskill

Imperial Prunus domestica plum R/S Italian Origin Wolfskill California (P. cerasifera x P.salicina)X (P. peach/plum hybrid (complex Ishtara Ferciana Wolfskill cerasifera x P. persica) hybrid selected by INRA) Krymsk 2 Prunus incana x Prunus tomentosa wild cherry x Manchu cherry VSV 1 Wolfskill

Plum/Plum hybrid (Sand cherry Krymsk 99 P. besseyi x P. salicina Wolfskill x Japanese plum)

Own rooted Prunus domestica European prune Wolfskill French

Puente Prunus cerasifera Plum (from Spain) Adara Wolfskill Sharpe Prunus angustifolia x unknown plum Plum x plum Wolfskill Speaker No idea scientific name Plum/peach hybrid Spicer Wolfskill Red leaf myroblan type (found WRM #2 Prunus cerasifera Wolfskill growing in the Willamette river)

Scientific and common pedigree for the Butte, Yuba and Wolfskill prune rootstock experiments

Rootstock TCSA 11/22/13 TCSA 11/6/14

1 HBOK 50 10.86 18.97 a

2 M58 17.79 28.40 a 3 Citation 16.18 28.61 a 4 Empryrean #2 17.64 29.39 a 5 Krymsk #1 18.85 29.78 a 6 Marianna 2624 18.85 31.90 bc 7 Krymsk #86 17.79 32.01 bc 8 Myrobalan 18.85 32.29 bc 9 M40 20.58 35.21 bcd 10 Lovell 23.24 39.29 bde

11 Viking 23.07 41.22 de 12 M30 26.23 45.09 ef 13 Atlas 25.87 45.89 ef 14 Myro 29C 32.37 51.96 f

Trunk Cross Sectional Area (TCSA) in cm2 for the Butte County Prune Rootstock comparison. Stat Graphics Multiple Range Test with statistically significant differences at the 95% confidence level. Trunk circumference measured 12 inches above graft union.

Average Fruit Count Rootstock TCSA 2013 (cm2) TCSA 2014 (cm2) 2014 HBOK 10 13.70 34.16 1.00 Krymsk 2 26.21 40.53 59.00 HBOK 32 20.94 44.10 8.60 Imperial CA 20.67 44.23 0.25 HBOK 27 23.89 46.36 8.00 Ishtara 31.63 53.55 5.40 Speaker 30.25 54.21 38.00 Controller 30.50 56.01 12.00 Own Root 27.39 56.82 5.00 Empyrean 3 24.24 56.90 4.80 Marianna 2624 36.06 58.70 22.80 Krymsk 99 31.91 65.09 30.33 Lovell 42.32 69.53 30.40 Puente 41.17 74.51 18.67 Myro 29C 45.37 82.10 11.40 WRM 2 58.46 95.27 40.00 Fortuna 59.52 112.14 86.40 Empyrean 1 65.69 120.33 24.83

Trunk cross sectional areas in cm2 and average fruit count for the Wolkskill rootstock selections. Average fruit count represents the counted sum of all fruit divided by the number of trees in the plot.

Figure 4. Prune trees growing in the Butte County prune rootstock experiment. Photo taken 12/15/14.

What about Krymsk 86??

 Too soon to tell, work in progress

 Origin – Krymsk Experimental Breeding Station,

Krasnodar Region, Russia

 Parentage – Prunus cerasifera x Prunus persicia plum/peach hybrid

 Compatibility – looks ok so far

 Vigor – looks ok so far

 Anchorage – probably good  Suckering – probably low

Soil Pathogens

 Nematode – probably susceptible

 Bacterial canker – unknown

 Oak root fungus – unknown  Phytophthora – unknown

 Crown Gall – probably susceptible

In Summary

 30 new rootstocks under evaluation

 Three test sites (Butte, Yuba and Wolkskill)

 After only 2 year growth looks good  2 years experience with Krymsk 86

In conclusion…

The prune industry will have many rootstock selections in the st 21 century which will provide the basis for new and very productive prune production