Potential Rootstocks for "Redblush" Grapefruit in the Desert

Item Type text; Article

Authors Fallahi, E.; Rodney, R.; McDonald, H.

Publisher College of Agriculture, University of Arizona (Tucson, AZ)

Journal Citrus Research Report

Download date 02/10/2021 21:31:25

Link to Item http://hdl.handle.net/10150/215704 Potential Rootstocks For 'Redblush' Grapefruit In The Desert E. Fallahi, R Rodney, and H. McDonald

ABSTRACT

Effects of 12 rootstocks on yield, yield efficiency, bearing potential and quality of Redblush' grapefruitwere measured and potential rootstocks recommended for the arid climate of southwest Arizona. Trees on `Palestine' sweet lime and 'Volkamer' lemon produced high cumulative yield but small fruit.Trees on Macrophylla (Alemow)produced higher yields after 5 years of planting and had significantly higher mean yield efficiency than trees on other rootstocks.Thus, Macrophylla rootstock could be a good choice for 'Redblush'at the standard spacing and perhaps at high density spacing in southwest Arizona. Fruit of trees on ` Carrizo' and `Troyer' citranges were largest.Trees on `Savage' citrange had lowest yield thinnest peel and highest levels of total soluble solids and soluble solids /acid ratio. Fruit of trees on 'Swingle' citrumelo or C.P.B. 4475 rootstock consistently had higher percentage acid than those on other rootstocks.Considering yield and /or various quality factors,Vol/tamer' lemon, rough lemon ,'Palestine' sweet lime,'Oklawaha' sour orangeand particularly ' Carrizo' citrange are suitable for 'Redblush' grapefruitin the arid Southwest.'Savage' citrange, *hang' pummelo , `Cleopatra' mandarin , and `Swingle' were poor yielding rootstocks for 'Redblush ' grapefruit, and therefore undesirable for planting under the standard spacing of this experiment. 'Savage' and `Swingle' might be good choices at higher densities because they have yield efficiency, high maximum bearing potential and quality. INTRODUCTION

Yield,fruitquality,resistancetodiseases,andsoiladaptabilityaresomeofthe importantcriteriaforselectingrootstocks.Selectionforyield alone isanunsatisfactory strategytofollowinevaluatingscion /rootstockforfreshmarketfruit,asyieldandquality areofteninverselyrelated. Our objectivewastoevaluate long -term effects of 12 rootstocksonyieldandqualityof `Redblush'grapefruitgrowninArizona. Thislong -term evaluation enables us to identify potential rootstocks for the arid regions of the southwest. MATERIALS AND METHODS `Redblush' grapefruit was budded on 12 rootstocks. Trees were grown in the University of Arizona, Yuma Mesa Agriculural Center in 1966.The 12 rootstocks were: `Volkamer' lemon, Macrophylla,roughlemon,`Swingle' citrumeloorC.P.B.4475,'Carrizo'citrange,`Troyer' citrange,`Taiwanica',`Palestine'sweetlime,`Oklawaha'sourorange,`Cleopatra' mandarin, `Ichang' pummelo, and `Savage'citrange. Tree spacing was 7 x 7 m; thesoil was Superstitionsand,withthetop20cm mixedwithsilt(TypicCalciorthid,sandy,mixed, hyperthermic; 80% sand) with a pH of 8.0.Overall, tree spacing and cultural practices in the experimental block were similar to those in commercial groves.

Theexperimentaldesignconsistedofrandomizedcompleteblockswith4blocks (replications)perrootstockand 2treesper block(replication). Fruitfrom eachtreewas harvested in 30 kg boxes, and the yield was recorded for 14 years between 1971 and 1986. The number of fruit per tree was estimated by dividing totalyield per treeinto the average fruitweightin 8 years. Trunk cross -sectionalarea was measured annually. Yieldefficiency was calculated as yield (kg per tree) /cm2 trunk cross -sectional area for 14 years.

31 Maximum number of trees per hectare was predicted by the following procedures: 1) The number of treesunder the standard (commercial) spacing of this experiment was 202 per hectare(82treesperacre). Bearing potential per hectare was calculatedin1986(after20 yearsofplanting),bytheformula:cross- sectionalareain1986xcurrentstandardnumber of trees per hectare. 2) Rough lemon rootstock was considered as the standard rootstock sinceitisthe most widely used rootstock inthesouthwest Arizona. The bearing potentialof `Redblush'trees on each rootstock wassubtracted fromthatof thestandardrootstocktocalculatedeviation bearing potential of trees on each rootstock from the standard. 3)The deviationinstep 2 wasdividedintothecross- sectionalareaof eachrootstockin 1986 to calculate the number of trees per hectare that could be added to or subtracted from the current standard spacing. 4) The number in step 3 was added to or subtractedfrom the the current standard number of treesperhectaretocompute the maximum potential number of treesperhectareforeach rootstock.

Fruitweight,juicevolumeperfruit,percentagejuice(perfruitweight),specific gravity, peelthickness,totalsolublesolids, percentagetitratableacid, andtotalsoluble solid /acidratio were measuredinearly February for 8 years between 1976 and1986. Ten fruitper tree were sampled randomly for quality evaluation in each testing year. Fruit were weighedandcutinhalf. Peelthickness,juicevolume,specific,totalsolublesolids,and totalacids(aspercentageciticacidperjuice),and totalsolublesolidstoacidsratio were measured.

RESULTS AND DISCUSSION

Yield

Trees on Macrophylla were more precocious than those on allother rootstocks. Trees onMacrophyllaalso had significantlyhigheryieldefficiency (yield /trunk crosssection) thantrees onallotherrootstocksoverthe14 -year period(Table1). Trees on `Cleopatra' mandarinand`Taiwanica'hadlowproductionuntil9yearsafterplanting. Treeson `Volkamer'lemon,roughlemon,'Carrizo'citrange,`Okiawaha'sourorangeand`Palestine' sweetlimewereinthehighcumulativeyieldinggroup,whiletreeson`Savage'citrange, Icharg'pummelo,`Cleopatra'mandarin,and`Swingle' citrumelowereinthe low - yielding category (Table 1).

Trees on'Swingle' and `Savage' hadsmallcanopies. Thesetrees, however, had relativelyhigheryield efficiencythantreesonmostotherrootstocks,calculatedeither by formulayield /trunkcrosssection(Table1)or by yield /canopy volume(datanotshown). Ourpredictionshowedthat alargernumberoftreesperhectarecanbeplantedif Macrophylla,`Savage'citrangeand`Swingle'rootstocksareused. Maximumpotentialyield was predictedto be highfortrees on Macrophylla,`Swingle',and `Palestine'lime,and low for trees on `Cleopatra' mandarin rootstocks (Table 1). These predictionswere made based on the assumption that tree volume is proportional with the cross -sectional area.

Fruit size

Fruitsof trees on'Carrizo' and `Troyer'citranges were largerthanfruitfromthe otherrootstocks,(Table2). Treeson'Carrizo'citrangeproducedthelargestmeanfruit sizeover8years(Table2).Theirtotalcumulativeyieldover14years wasstatistically equaltothatoftrees on `Volkamer'lemon, which numerically had thehighesttotalyields (Table1). This leads us to suggest thattrees on 'Carrizo' produce optimal yields(size and number)whentotalyieldaloneistheparameterofinterest. Minordifferenceswere observedinlength /diameterratio(L/D)or"sheep nose shapemeasurementoffruitfrom differentrootstocks. None oftherootstocksproducedtreeshavingfruitwithalength-to- diameterratioof more than0.95,indicatingthat"sheepnose" was notasignificantquality deterrent.

32 Peel thickness

FruitinourexperimenthadgenerallythickerpeelthanthoseinTexas(1,2,3), perhapsbecauseof highertemperaturesinYuma. Fruitfromtreeson`Taiwanica', Macrophylla,sourorange,and `Ichang'hadsignificantlythicker peelthanthosefrom `Savage'citrange(Table2). Fruitfromtreeson`Swingle',`Troyer',and`Cleopatra'had the same thickness (Table 2); this data agrees with Wutscher and Dube (3). Juice volume per fruit and percent juice by weight

Fruit from trees on 'Carrizo' citrange had significantly higher volumeof juiceperfruitthantreeson sourorange and`Taiwanica'(Table2).Percentage juiceinfruitfromtreeson`Palestine'sweetlimeand Macrophylla wassignificantlyhigher thanthepercentageofjuiceinfruitfromtreeson`Swingle'citrumelo,`Taiwanica',sour orange, `Cleopatra' mandarin, and `Ichang' pummelo (Table 2). Total soluble solids

Rootstocks stronglyinfluencedtotal solublesolids ofscion fruit (Table 2). ` Redblush'on`Savage'citrangeandsourorangerootstockshadthehighestsolublesolids; fruitfrom trees on `Volkamer' lemon, rough lemon, and Macrophyllawere among thelowest (Table2). Differencesinsolublesolidsbetweentreeson`Volkamer'lemon and`Savage' citrange may be due totheiryielddifferences. Trees on `Savage' had thelowest, and those on `Volkamer'lemon had thehighest number offruitpertree(Table1). More of the carbohydrate resources of trees on `Savage' may have been partitionedinto the smaller number offruit,resultingintheobservedhighlevelsoftotalsolublesolids. Fruitfromtrees on sour orange had high soluble solids (Table 2) in spite of their high yield (Table1). Fruit from treeson`Savage' citrange, sourorangeand `Swingle' citrumelo had significantly highersolublesolidsthanthoseonMacrophyllarootstock(Table2). Specificgravityof fruitfromtreesonallrootstocksweregenerallyproportionaltotheirsolublesolids(data not shown). Total acids

Fruitfromtreeson' Swingle' citrumelohadsignificantlyhighertotalacids,while fruitfromtreeson Macrophyllarootstock had thelowestacids(Table2). ` Redblush'fruit on `Volkamer' lemon, rough lemon, and `Palestine'sweet lime rootstocks were also among the low acid fruit (Table 2). Soluble solids /acid ratio

Fruitinthisexperimentgenerally had a highersolublesolids /acidratiothanthose from Texas(1,2,3). ` Redblush'fruit on `Swingle'citrumelo, rough lemon,`Taiwanica',and `Volkamer'lemon hadthelowestratio.'Redblush'fruiton`Savage'citrange,Macrophylla, ` Carrizo' citrange, `Troyer'citrange,sour orange, and `Cleopatra' mandarinhadthe highestmeansolublesolids /acidratio(Table2). Hightotalsolublesolidsinfruitfrom treeson'Savage'citrangeismainlyresponsibleforthehighsolublesolids /acidratioin thisrootstock,whereasthehighacidcontentoffruitfromtreeson`Swingle'citrumelo results in a low soluble solids /acid ratio (Table 2).

CONCLUSIONS In our long -term study,trees on `Volkamer' lemon and Palestine' sweet lime had high yield,but poorfruitquality,when grown on sandysoilandinaridclimaticconditionsof southwest Arizona. Although trees on `Volkamer' lemon produced high yield,large canopy volumeand /orlargetrunkcross -sectionalareaoftreesonthisvigorousrootstockresulted intheirhavingthesame orloweryieldefficiencythantreeson slowergrowingrootstocks

33 (Table1). However,`Volkamer' lemon and Palestine'sweet limearedesirablerootstocks for `Redblush'at standard spacing when yieldis the primary goal of the growers. Trees on Macrophyllarootstockwere precocious,hadrelativelyhighcumulativeyield, significantly higher yield efficiency, and predictedpotentialyield per acrethantrees onother rootstocks(Table1). `Redblush'fruitonthisrootstockhadahighsolublesolids /acid ratiothatallowedfruittoreach theminimumsolid /acidstandardforharvestingearlier thanthoseonotherrootstocks. Becauseofthesedesirablecharacteristics,Macrophylla couldbea goodchoiceforplantingatstandardspacingorhigherdensitiesinsouthwest Arizona. Trees on sour orange had high yield and fruit quality (Tables 1 and 2).Sour orange is resistanttofootrot;consideringyieldandqualityparameters,itmay be a goodrootstock for`Redblush' on the sandysoilareasof southwest Arizona. Trees on rough lemon were vigorousandfruitqualitywaspoor. However,roughlemonissuitableforplantingin Arizonabecause`Redblush'treesonthisrootstockproducehighyieldsandare drought - tolerant due totheirextensiveroot system on sandy soil(Table1). Trees on'Carrizo' rootstockhadhighyields,withlargerandjuicierfruitthanthoseonotherrootstocks. This rootstock can also be recommended for planting on the sandy soil of southwest Arizona.

`Redblush'treeson `Savage'citrange,Ichang'pummelo,`Cleopatra'mandarin,and `Swingle'citrumelohadrelativelylower yieldthanthoseonotherrootstocks(Table1). Therefore,theserootstocksarenotsuitablefor`Redblush'atthespacingusedinthis experiment. However,`Savage'citrangeand `Swingle'citrumelo might be goodchoicesfor plantingathigherdensities,becausetheyincreasedyieldefficiencyandquality.Also,it was predicted that `Redblush' trees on these rootstocks would have highproduction on a per hectare basis.

REFERENCES

1. Wutscher, H.K. and A.V.Shull. 1972. Performance of 13citruscultivarsasrootstocks for grapefruit. J. Amer. Hort. Sci. 97(6): 778 -781.

2. Wutseher, H.K. and A.V.Shull. 1975. Yield,fruitquality,growth,andleafnutrient levelsof14-year -oldgrapefruit,CitrusparadisiMac.,treeson21rootstocks. J.Amer. Soc. Hort. Sci. 100(3): 290 -294.

3. Wutscher, H.K. and D. Dube. 1977. Performance of young nucellargrapefruiton 20 rootstocks. J. Amer. Soc. Hort. Sci. 102(3): 267 -270.

34 Table 1. Influence of rootstock on yield and bearing potential in 'Redblush' grapefruit Yield Predicted Predictedmaximum Rootstocksz Cum.yield(kg /Tree)14 Years (kgefficiency /cm2) 14 Yrs.mean Avg.of 8 Yrs Numberfruit ofper tree in 1986(cm2)potentialBearing fromDiviation Std.(cm2) potentialof bearing perorbeTrees added hectar to (A) dropped(D) potentialper Hectarnumber trees percum.potential Nectaryield (MT) MacVol 2620bc2972a' 0.95a0.69cde 527ab591a 108,272ab65,246d -33,333+ 9,696 103A 18D 305184 799547 CitRle 2303d2686abc 0.82b0.70cde 530d511ab 74,134d98,576b -24,442 -0- -0-67A 269202 620543 TroCar 2366cd2660abc 0.66efd0.64efg 429d502abc 106,656ab95,142bc -+ 3,4348,080 15D 7A 209187 494497 PalTai 2687abc2630bc 0.74bcd0.56g 511ab492c 122,412a81,406cd -17,170+23,836 43A39D 245163 658429 CleOso 2257d2796ab 0.59fg0.58fg 413d545ab 111,302ab123,422a +12,726+24,846 41D23D 179161 404450 SayIch 1781e2056de 0.77bc0.73bcde 371e359e 80,194cd71,912d -26,-18,382 664 75A46A 277248 493510 y zMesa Abbreviations: separation within the columns by Duncan's Multiple Range Test, 5% level. OsoCarVol: - 'Volkamer''Oklawaha' lemon;sour orange; Mac - C.cle macrophylla; - 'Cleopatra' Rle: mandarin; Rough lemon; Ich - ' Cit 'Ichang'Carrizo' - 'Swingle' citrumelo; citrange; Tro - 'Troyer' citrange; Tai - C. taiwanica; Pal - 'Palestine' sweet lime; pummelo; Sav - 'Savage' citrange Table 2. Influence of rootstock on fruit quality of 'Redblush' grapefruit- Juice Percent soluble Total Total Volt' Fruit weight 357bx (g) Peel thickness 7.8abc (mm) (ml /fruit) 161abvolume (% of Fruit Wt.) 46.5abc juice (solids °Brix) 8.8e (% in Juice)Total acid 1.36e Soluble solids /total acid 6.6cRatio AleMac 367ab363ab 7.8abc7.9ab 166aó165ab 46.6abc47.1ab 8.9e 1.36e1.28f 6.6c7.0a CarCit 381a374ab 7.6bc7.5bc 171a164aó 46.5abc45.6cd 10.2bc 9.9c 1.43cd1..61a 7.Oa6.4d TaiTro 368aó380a 8.1a7.5bc 160b168ab 45.Od45.9bcd 9.4d9.9c 1.42cd1.45c 6.6c6.9ab OsoPal 366ab354b 7.9ab7.6bc 160ó162aó 45.4cd47.3a 10.4ab 9.3d 1.52b1.39de 6.9ab6.7bc IchCle 373ab 7.9ab7.8abc 161ab165ab 44.8d45.7cd 10.Oc 9.9c 1.S0b1.44c 6.7bc6.9ab zSav Each value in 366ab the table is the mean of 8 years of data with 4 replications per year and 2 trees per replication.7.4c 164aó 46.4abc 10.6a 1.52b 7.1a xY MeanAbbreviations: separation within columns by Duncan's Multiple Range Test, 5% level. OsoCarVol - -'Oklawaha' sour orange; Cle - 'Cleopatra' mandarin; Ich -' 'Ichang'Carrizo' pummelo;citrange;Volkamer' Sav Tro - 'Troyer' lemon; Maccitrange; - C. macrophylla; Tai - C. Taiwanica; Rle - Rough Pal lemon; Cit - 'Swingle' citrumelo; - 'Palestine' sweet lime; - 'Savage' citrange.