Performance of Peach Rootstocks Propagated as Seedlings vs. Cuttings

T.G. Beckman and A.P. Nyc'zepirSE Fruit and Tree Nut Research LabUSDA-Agricultural Research ServiceByron, GeorgiaUSA

S.C. MyersDept. of Horticulture and Crop ScienceOhio State UniversityColumbus, OhioUSA

Keywords: Prunus persica, clonal propagation, peach tree short life. PTSL

AbstractFollowing the release of 'Guardian'(BY520-9) peach rootstock in 1993,

nurseries experienced significant problems with seed germination when fall-planteddirectly into the nursery. Rooted cuttings were proposed as a possible alternative.'Cresthaven' peach trees budded onto 'Nemaguard' seedlings, 'Guardian' cuttingsand seedlings, and 'Lovell' cuttings and seedlings were established in 1997 in a highdensity orchard and trained to a 2-arm open center system. Through 2003, trees on'Nemaguard' seedlings displayed the highest vigor when measured as trunk cross-sectional area (TCSA). Trees on 'Lovell' seedlings displayed the smallest TCSA.There was no significant difference in the TCSA observed in trees propagated on'Guardian' cuttings vs. 'Guardian' seedlings. Through three harvest seasons, treeson 'Guardian' cuttings produced the largest cumulative yield but were notsignificantly different from that observed on 'Guardian' or 'Lovell' seedlings. Treeson 'Lovell' cuttings had the smallest cumulative y ield. Trees on 'Lovell' seedlingsdisplayed significantly higher cumulative yield efficiency than all other rootstocktreatments. Trees on 'Nemaguard' seedlings displayed significantly lowercumulative yield efficienc y than all other rootstock treatments except 'Lovell'cuttings. There was no significant difference iii the cumulative yield efficiency oftrees on 'Guardian' cuttings and those on 'Guardian' seedlings. There appears to beno clear horticultural advantage or disadvantage to the use of 'Guardian' cuttingsover 'Guardian' seedlings at this time.

INTRODUCTION'Guardian' IN (BY520-9) peach rootstock was introduced for commercial trial in

1993 as a rootstock with superior performance on peach tree short life (PTSL) sites (Okieet al., 1994). Because the original mother tree was lost during the evaluation process,'Guardian' has been distributed as a bulked seedlot. This bulked lot has been collectedfrom a subset of the 69 plus surviving seedlings from the field trial in which 'Guardian'was identified (Beckman et al., 1997). Initial seed germination was very poor when fall-planted directly into the nursery, ranging from 28% to 41% (Beckman et al., 1997).Efforts were undertaken to identify lines with superior seed germination so that inferiorlines could he dropped from the bulked lot. One of the first 'Guardian lines with superiorseed germination to be identified was SC'3-17-7. Nevertheless, the initial poor seedgermination gave impetus to the possibility that rooted cuttings might provide analternative means of propagation. The primary purpose of this experiment was todetermine if rooted 'Guardian' cuttings would provide satisfactory horticulturalperformance compared to 'Guardian' seedlings.

MATERIALS AND METHODSTrees of 'Cresthaven' budded onto rooted cuttings of 'Guardian' (SC3-17-7

selection) and 'Lovell', and seedlings of 'Guardian' (SC3-17-7 selection). 'Lovell' and'Nemaguard' were planted in March, 1997 at a spacing of 6.1 in (between rows) by 1.83in (within row) at the Byron location. Guard trees were planted at the ends of the rowsand in adjacent flanking rows. Soil type was a Greenville fine sandy loam, a clayey,kaolinitic, thermic, typic Rhodudult, representative of soils typically utilized for peach

Proc. 6" Intl. Peach Symposium 289Ed. R. InfanteAda Hon. 713. ISHS 2006

production in the middle Georgia area. Trees were trained to a 2-arm open center systemand maintained according to standard commercial recommendations (Myers, 1989). Aweed flee zone ca. 2.4 m wide, centered on the tree row was maintained with herbicides.No supplemental irrigation was provided. Each spring, trees were judged to be at fullbloom when ca. 70% of flowers had opened (based oil inspection). Fruit wereharvested in the years from 2001 to 2003 at 3- to 4-day intervals at a commerciallymature stage, i.e. as ground color changed from green to yellow. No attempt was made tosort cullage hence, weights reported are gross yields. Trunk diameter was measured 30cm from the soil surface shortly after planting and each fall thereafter followingdefoliation (typically late November). Diameters were converted to trunk cross sectionalarea for analysis. Plot design was a randomized complete block with 12 single-treereplicates of each of the rootstock treatments. Data were analyzed by the General LinearModels (GLM) program of the Statistical Analysis System for personal computers (SAS.2003). Mean separation was performed by Wailer-Duncan k-ratio t tests.

RESULTS AND DISCUSSIONThrough 2003, 'Cresthaven' trees oil seedlings displayed

significantly larger trunk cross-sectional area (TCSA) than all other rootstock treatmentsexcept those oil cuttings as shown in Table 1. Trees oil seedlings hadthe smallest TCSA though this may have been due, in part, to their significantly smallersize at planting. There were no significant differences in the TCSA of 'Cresthaven' treeson either 'Guardian' cuttings or 'Guardian' seedlings during the course of thisexperiment.

Through three harvest seasons, 'Cresthaven' trees on 'Guardian' cuttingsdisplayed the highest cumulative yield, but were not significantly different from thatobserved on 'Guardian' or 'Lovell' seedlings as shown in Table 2. Trees of 'Cresthaven'grafted on 'Lovell' seedlings displayed significantly higher cumulative yield efficiencythan all other rootstock treatments, as shown in Table 3. Trees on 'Nemaguard' seedlingsdisplayed the lowest cumulative yield efficiency. There was no significant difference inthe cumulative yield efficiency of 'Cresthaven' trees on 'Guardian' cuttings compared tothose on 'Guardian' seedlings.

Rootstock effects oil average harvest date (Stembridge and Gambrel],1974) were small and variable as shown in Table 4. Average fruit weight of all treatmentswould have been deemed marketable in all three seasons as shown in Table 5. It has beenour experience that 90-100 g fruit will typically meet the 57 mm (2.25 in) diameter gradeand 125-150 g fruit will meet the 62 mm (2.50 in) diameter grade (Beckman, unpublisheddata). Differences in the suckering tendencies of the rootstocks were generally small asshown in Table 6. However, of some potential interest is the smaller number of rootstocksuckers produced by 'Guardian' cuttings compared to 'Guardian' seedlings and thesimilar pattern observed with 'Lovell' cuttings compared to 'Lovell' seedlings.

CONCLUSIONSThe results of this trial indicate that there is no clear horticultural advantage or

disadvantage in the use of 'Guardian' cuttings vs. 'Guardian' seedlings. Both rootstocksprovide similar vigor and yield. 'Guardian' cuttings appear to provide a small advantagein regards to reduced suckering when compared to 'Guardian' seedlings. Since 1993 the'Guardian' selections being used to construct the bulk commercial lot have changedconsiderably, due in large part to seed germination considerations. At this time the bulked'Guardian' seed distributed to nurseries is dominated by one line, SC3-17-7. Recent seedgermination has been deemed satisfactory, ranging from 60-80% over the past 3 years(Beckman, unpublished data). Hence, interest in the use of rooted cuttings has waned,especially considering the likely higher per unit cost associated with clonal propagation.Moreover, one critical issue not addressed in this trial is any possible difference in thelongevity of peach trees budded to 'Guardian' cuttings vs. 'Guardian' seedlings whenplanted on a peach tree short life (PTSL) site. This area needs to be addressed before any

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recommendation for the use of 'Guardian' cuttings over 'Guardian' seedlings, or vice-versa, can be made.

ACKNOWLEDGEMENTSThe authors gratefully acknowledge the technical assistance of Roger Laster,

Deborah Mooney, Amy Savelle and Madelis Valdes in the establishment andmanagement of this project.

Literature CitedMyers, S.C. (ed.). 1989. Peach Production Handbook. Georgia Extension Handbook No.

I. 221 p. Coop. Ext. Serv., Univ. of Georgia, Athens, Ga.Beckman, T.G., Reighard, G.L., Okie, W.R., Nyczepir, A.P., Zehr, E.I. and Newall, W.C.

1997. History, current status and future potential of Guardian' 1 (BY52-9) peachrootstock. Aeta Hort. 451:25 1 -258.

Okie. W.R., Beckman, T.G., Nyczepir, A.P., Reighard, G.E., Newall. W.C. and Zehr, E.I.1994. Guardian (BY520-9), a peach rootstock for the southeastern United States thatincreases scion longevity. llortScience 29:705-706.

SAS Institute, Inc. 2003. SAS for Windows. Version 9. 1, SAS Institute. Inc., Cary NC.Stembridge, G.E. and Gambrel], C.E., Jr. 1974. Measuring peach thinning and maturation

responses. I-TortScienee 9:29-30.

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Tables

Table I Rootstock treatment effects on trunk cross-sectional area (TCSA) ofCresthaven' peach scions (1997-2003, Byron, Ga).

TCSA'(cm')RootstockTyp&19972000200120022003'Nemaguard'Sdlg0.46 a42.5 a58.2 a85.9 a98.7 a'Guardian'Cutt0.52 a32.5 ab47.6 ab60.9 ab82.9 ab'Guardian'Sdlg0.37 a33.7 ab39.9 b47.7 be61.2 be'Lovell'Cutt0.43 a24.7 b35.7 be4.0 be52.7 c'Lovell'Sg0.12 h12.7 c22.1 c27.2 c40.6 cMSDX 0.16 11.2 14.4 29.7 29.3

'Calculated from trunk diameter measurements at spring planting, 30 cm from soil line. All other yearstrunk diameter was measured following fall leaf abscission.Sdlg = open-pollinated seedling. Cutt hardwood cutting\1 SI) -= Mini mum Significant Di fhrcnce, Waller Duncan k-ratio / Test (k-ratio- 100)

1 able 2. Rootstock treatment effects on annual and cumulative total gross yield of'Cresthaven' peach scions (1997-2003, Byron, Ga).

Yield (kg/tree)RootstockType'200120022003'Nemaguard'Sdlg3.04.915.3 h'Guardian'Cuti5.08.128.3 a'Guardian'Sdlg4.07.924.9 a'Lovel]'Cutt3.2 5.214.7 b'Lovell'Sdlg3.25.125.0aMSDYnsns8.3'dl g = open-pollinated seedling. Cult = hardwood culling\ll)\lininium Siciiilicaiii l)illicn, \\ilIcr l)iriicun k-Tatio i I ei f k IxioDO)

Cumulative23.2 h41.3 a36.9 a22.4 b33.3 ab

11.0

I able 3. Rootstock treatment eliects nit annual and cumulative y ield efficiency of'Cresthaven' peach scions (1997-2003, Byron, Ga).

Yield efficiency (kg/cm2)l/notstockType'200120022003Cumulative'semaguard'Sdlg0.060.10 b0.18 d0.26 d(juardian'Cutt0.110.13 ab0.34 be0.50 be(ivardian'Sdlg0.120.18 a0.43 h0.65 hI ovell'Cutt0.080.11 ab0.27 ed0.40 cd1 ovell'Sdlg0.150.20 a0.64 a0.84 a

\IS]Y ns0.100.140.19di -- open-pollinated seedlin g , ( ' itlihurdu ood cutting

\iH)\gIHIII.IIId j d Jiui:IL. \\,[i)iiuiiiIi!

Table 4. Rootstock treatment effects on weighted average harvest date of 'Cresthaven'peach scions (1997-2003. Byron, Ga).

Weighted average harvest date'

RootstockTyp&2001 2002 2003

'Nemaguard'Sdlg190 a 202 196 cGuardian'Cult198 ab 201 198 ab

'Guardian'Sdlg189 ab 201 199 a

'Love!!'Cult188 ab 201 197 c

'Lovell'Sdlg187b 201 197 bc

MSD - 1.4'Julian day calculated per Stcmhridgc and Gambrell, 1974. HortSeicnce 9:29-30.

Sdlg open-pollinated seedling, Cult hardwood cuttingNISD Minimum Significant Dilference, Waller Duncan k-ratio (Test (k-ratio- IOU)

Table 5. Rootstock treatment effects on average fruit weight of 'Cresthaven' peach trees(1997-2003, Byron. Ga).

Average fruit weight (g)RootstockType'2001 20022003

'Ncmaguard'Sdlg185a 126 173a'Guardian'Cutt175 ab 143 157 ab'Guardian'SdIg191 a 128 137b'Lovell'Cutt167 ab 132 161 ab'Lovell'Sdig142b148170aMSDY34 ns 33Sdlg open-pollinated seedling. Cutt = hardwood cuttingMSI) = Minimum Significant Difference, Walter Duncan k-ratio! Test (k-ratio= 100)

Table 6. Rootstock treatment effects on rootstock suckering of 'Cresthaven' peach trees(1997-2003. Byron, Ga).

Rootstockstickers(number/tree)RootstockType'2001 2002 2003

'Nemaguard'Sdlg0.5 A1.0 1.8 ab'Guardian'Cutt0.0 b 0.1 0.2 b'Guardian'Sdlg1.1 a 1.4 1.3 ab'Lovell'Cutt0.0 b 0.0 0.1 b'Lovell'Sdlg1.0 ab 1.3 3.3 a

KIS DY1.1 n 2.2Sdlg = open-pollinated seedling, Cutt = hardwood cuttingMSD = Minimum Significant Difference. Walter Duncan k-ratio! Test (k-ratio--tOO)

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