R L and R D Gaskalla 994 Commercial citrus inventory 994 Flor free, ;;\gncultural Statistics Service, 222 Woodward St, Orlando, FL icla R J 986 The influence of tree size control and plant density on citroductivity Acta Hort 75249254 PCj and R P Muraro 982 Effect of tree spacing on fruit produc00 0 and net returns of Pineapple oranges Proc Fla State Hort Soc u<> 952933 t V K 987 High density planting and dwarf roots tocks in citrus a ref au, J MaharashtraAgric Univ 2(2)8994 c7bana S, S Morioka, and S Nakai 987 Effect of planting density on Ta froit yield under diffeent cultural treatments in Satsuma mandarin tree J Japan Soc Hort Sci 5695 \\"liaton T A, W S Castle, D PH Tucker, andj D Whitney 978 Higher clensicv plantings for Florida citrus concepts Proc Fla State Hort Soc 9 2733,i;heaton, T A, W S Castle,] D Whitney, D PH Tucker, and R P Muraro I990 A high density citrus planting Proc Fla State Hort Soc 035559 Hucron Wheaton, T A,] D Whitney, W S Castle, and D PH Tucker 986 Tree spacing and rootstock affect growth, yield, fruit quality, and freeze damage of young Hamlin and Valencia orange trees Proc Fla State Hort Soc 992932 Wheaton, T A,] D Whitney, D PH Tucker, and W S Castle 984 Cross hedging, tree removal, and topping affect fruit yield and quality of citrus hedgerows Proc Int Soc Citriculture 094 Wheaton, T A,] D Whitney, W S Castle, R P Muraro, H W Browning, and D P H Tucker 995 Citrus scion and rootstock, topping height, and tree spacing affect tree size, yield, fruit quality, and economic return J Amer Soc Hort Sci 2086870 Whitney,J D, A Elezaby, W S Castle, T A Wheaton, and R C Littell 99 Citrus tree spacing effects on soil water use, root density, and fruit yield Trans Amer Soc Agr Engo42934 Whitney,J D, T A Wheaton, W S Castle, and D PH Tucker 994 Optimizing orange grove factors for fruit production and harvesting Trans Amer Soc Agr Eng 3736537 Proc Fla State Hort Soc 086973 995 "A 6YEAR COMPARISON BETWEEN 6 ROOTSTOCKS BUDDED WITH HAMLIN SWEET ORANGE" CHARLES 0 YOUTSEY Florida Department of Agriculture & Consumer Services Division of Plant Industry Bureau of Citrus Budwood Registration 3027 Lake Alfred Road, Winter Haven, Fl3388438 ORIE LEE, LEE AsSOCIATES 5005 Lillian Lee Road St Cloud, Fl 3477 Addittonal index words Citrumelo, citrange Abstract Yields, juice quality, and tree size were recorded from one Hamlin orange (C sinensis (L} Osbeck} clone on O unnamed citrumelo (Citrus paradisi Macf x Poncirus trifoliata} and 3 unnamed citrange ( C sinensis x P trifoliata} rootstocks, Sour orange (Citrus aurantium}, Swingle citrumelo and Norton citrange Trees were planted in November 986, spaced 4 x 22 feet in 6 replications of 3 tree plots Cumulative yields were hiighest for trees on citrumelos F/803, F/88, W2, F/802, and sour orange, and lowest forcitrange F/80, citrumelo F/809 and F/807 Cumulative pounds soluble solids per acre were highest for citrumelo F/803, F/88, F/802, F/808, and sour orange They were lowest for citrange F/80, citrumelo F/809, and F/807 Tree size was calculated by measuring the effective height of fruiting Citrumelo F/802,W2, F/88, sour orange, F/803 and F/806 were the largest trees When Swingle was assigned an index of 00, there were trees on seven rootstocks that produced fruit higher in the tree than Swingle Using Swingle as an index for production of pounds soluble solids per tree in seasons 99293 & 99394, only trees on F/802, F/88, sour orange, and F/803 rootstocks out produced trees on Swingle Tests for Citrus Tristeza Virus (CTV) in December 992 on all trees on sour orange rootstock showed that 277% of these trees were identified with severe isolat s of CTV By August 993, five trees on sour orange rootsock were declining Reiire d Proc Fla State Hort Soc 08 995 Introduction In 955, Dr Mortimer Cohen, then a pathologist with the State Plant Board in Gainesville, made controlled pollinations among selected trees in the University of Florida horticultural grove on Archer Road as part of his interest in horticultural characteristics of nucellar citrus seedlings Fruits from these pollinations were harvested in January and March of 956 and seed was planted Many of these nucellar and zygotic seedlings were subsequently planted in 960 at the Division of Plant Industry Budwood Foundation Grove located near US 27 and I4 in Polk County After extensive evaluation by personnel from the Citrus Budwood Registration Office, nucellar selections of Pineapple, navel, Valencia and Redblush grapefruit were released as budwood for use by the Florida Industry beginning in 972 and have become popular scions commonly used in the Florida industry (Bridges 973) (Bridges&Youtseyl974) (Norman 964) (Pieringer et al 978) Certain of the zygotic seedlings from Cohens work were fruited and from 968 through 973, many seedling stands were established for evaluation of uniformity, vigor, germination, and disease susceptibility Several of the more uniform and vigorous selections were identified for trial as rootstocks in 973 when the Budwood Foundation Grove was moved to a new location near Dundee, Florida, and in other trials by USDA and IFAS research scientists (Wutscher et al 988) (Youtsey and Bridges 979) Because of increased interest in the potential for use of citranges and citrumelos, this study was undertaken to determine the performance of these controlled pollination seedlings used as rootstocks for Hamlin sweet orange in comparison with standard commercial rootstocks Materials and Methods In the fall of 983, seeds were harvested and sown for 0 citrumelo, ( C paradisi cv Duncan grapefruit x P trifoliata) and 3 citrange (csinensis cv Parson Brown x P trifoliata and 69
one cv Pineapple x P trifoliata) seedling trees, and for Swingle citrumelo, Norton citrange, and Sauvage sour orange Uniform seedlings were lined out in Nov 984 and budded injuly 985 Budwood was taken from the H4XE mother tree maintained under screen at the DPI Citrus Budwood Foundation grove in Dundee The budwood source was free of citrus tristeza virus (CTV) as well as psorosis, xyloporosis/ cachexia, exocortis, and other detectable viroids Subsequent serological tests for citrus blight did not show the presence of blight specific markers (Derrick et al 990) Other visible symptoms of citrus blight in the mother tree have not been observed Trees were planted in Nov 986 at St Cloud, Florida, in soil consisting predominately of Myakka fine sand Tree spacing was 4 x 22 feet The experimental design was a randomized complete block with 6 replications of 3tree plots Trees of the citrumelo F/803 were containergrown in a commercial greenhouse (budded in September 985) and were originally set in an adjacent trial, but later moved by tree spade into this planting in November For the first crop in the 987988 season, fruit were counted from individual trees; thereafter yields were determined for each 3tree plot in standard 0box tubs by measuring the depth of fruit with a calibrated stick inserted through a crossbar placed over the rim of the tub Each box equals approximately 90 pounds Approximately 40 fruit were collected from each of 3 replications for juice analysis prior to harvest Analysis was done by the Dept of Citrus using commercial extractors at CREC Tree size was measured in July 989 and height of fruiting was measured in November 994 Grove nutrition and pest control were managed to produce fruit for processing Irrigation was supplied as needed from a microsprinkler system without fertigation Only minor hand pruning was done until 994 when annual hedging began The data were examined by analysis of variance and means compared by least significant difference as appropriate The trial was injured in a December 989 freeze Visual assessments of tree damage were made in April 990 Results and Discussion,3 Trees on F/803 (cmtainer grown) averaged 8 f tree 2 years after plantug Trees on Swingle, F/808, FruitJ F /807 averaged 29 fruit per tree Average fruit yieldll roots tocks was 24 per tree Trees began bearing a com 0 f] crop at 3 years of age and varied from /2 to 2 bo erg trees on citrumelo F/803 rootstock led, or equaled stocks in annual yields and led sour orange and s t % and 46%, respectively, in cumulative yields (TI Yields of scions on sour orange were reduced in the rn, cent 2 years due to CTV decline affecting 6 of the 8 tre ost nual yields of citrumelo F/88 were comparable Wits l orange except in the 992993 and 994995 season s9lt were comparable to or greater than Swingle in all seasons mulative yields were less than % greater for F/88 vs s ; orange, but 88% better than Swingle Trees on citran so 80, citrumelo F/809, and citrumel? F /807 yid/ xft d fo the?year period Sour orane had better yields thq,; ;;;l most years, but CTV will cause a reduction in fy Pounds soluble solids per acre generally followed yiel per tree, except for ctrumelo W2 which was slightly bette ;;, cumulative yields thn Swingle, but produced less soluble ids per acre than Swingle (Table 2) Trees on rootstock F 3 led all other rootstocks in production of pounds of solubi}i solids per acre each of the six years, except F /802 in 993; and produced more cumulative pounds solids per acre th; sur orange and Swingle by % and 204% respectiveiy0! Citrumelo F/88 and F/02 produced pounds soluble so) ids per acre comi>arable with s<;>ur orange, while producing ;l 8 7% and 58% higher than Swmgle respectively Citrumeli; F/803 prodced 2% more pounds of soluble solids peti ; acre than Swingle, but only % more than the CTV affect g) ed sour orange oer the 6year period Rootstocksyroducini the least cumulauve pounds sohds per acre were cltranges F/? 80,2,3, Norton, and citrumelo F/809, F/807 \ JD ;sqi I },, Table Average annual and cumulative yields (boxes/tree) of Hamlin trees on 6 rootstocks, j 993994 994995 989990 99099 99992 992993 Citrum F/803 Citrum F/808 Citrum W2 Citrange F/82 Citrange F/83 Sour Orange Citrum F/88 Norton Citrange Citrange F/80 Swingle Citrum Citrum F /809 Citrum F/808 Citrum F /807 Citrum F/804 Citrum F/806 Citrum F/802 22 08 08 04 29 8 23 24 9 3 23 8 22 9 3 27 33 37 32 29 28 29 3 68 58 5 70 67 5 58 44 53 59 57r 57 36 4 46 48 89 66 64 73 83 70 76 62 74 67 77 87 Mean 5 72 LSD" 03 Roots tocks Cumulative Yield/Tree y; ;\i 3 2 2 222 j 226 i 269 27l 2 69 2 87 238 204 23 242 259 ;,j ;, 238 Box =90 lbs r3 declining trees 6 declining trees wleast significant difference 5 replications only 70 Proc Fla State Hort Soc 08 995
Table 2 Annual and cumulative yields in pounds of solids per acre of Hamlin trees on 6 rootstocks ; Rootsrock awrn F/ 803 Citrurn F/ 808 CitnUJ w2 Ciu<Jnge F/82 Citrange F/8 3 Sour Orange CitrWll F/ 88 Norton Citrange Ciuang F/8 0 Swingle Citrum Ci(nmi FI 809 Citrrn F/808 CilflHll F/807 CilrtllTI F/804 Gtrum F/806 Cimn F/802 nual Mean, /30 989 /7 990 2/5 99 4700 5544 4452 4704 4774 5 4788 4 67 60 3766 3654 78 5726 34 2758 558 5974 6 0626 046 2068 074 3608 4 6986 2334 66 332 8582 928 9548 968 09463 29232 22904 27 96 24066 27608 23464 2384 4966 296 5736 22736 544 2672 2364 22988 27464 The only tree lost in this plantingwas caused by CTV and occurred on sour orange rootstock Five additional trees on sour orange have declined in the past 2 years from infection that has apparently spread from nearby plantings Tree decline caused by Phytophthara has not been observed in this trial nor was Phytophthara found in a survey conducted in an adjacent trial (Castle, personal communication) One tree each on F/807, and 4, appear to be declining from citrus blight, as determined by wateruptake tests (Lee et al 984) Several /4993 2/l 993 2/4 994 Cum Total Each R/S 47586 4442 42882 4692 39424 53508 52962 38234 328 454 35560 4790 3460 496 47334 49966 430885 47936 42728 38584 38808 403 46200 40670 39368 28070 462})8 3438A 38486 40 394 40852 438 404373 6274 59248 57358 45892 49 53060 60970 505 37268 494 473 536 3972 5744 552 6246 5242 27602 85682 75658 668 67978 966 96462 66936 26826 80698 43402 73404 4688 72466 77758 9282 trees on Norton citrange have zinc deficiency symptoms and had high wood accumulation of zinc in tests performed in 99 (Wutscher et al 977) but no visible decline symptoms are presently found in trees on this stock Trees on Norton rootstock were removed from an adjacent USDA trial after blight symptoms appeared (Wutscher et al 995) Injury from the December 989 freeze was assessed in April 990 using a visual rating of to 5 where l=little or no damage to limbs and twigs, and 5=a dead tree (Fig ) No 355 35 = Oil 5 00 803 808 W2 82 83 = No Dead Wood S/O 88 NOR 80 SWG 809 808 807 804 806 802 5 =Dead Tree Figure Freeze injury ratingapril 24, 990 Proc Fla State Hart Soc 08 995 7
00,_ 9 00 95 97 93 90 85 ;; \, 5 00 u ", ljim J J[ 803 808 " W2 82 ; 83 4 [, ",, [ ; h ii u S/O 88, NOR 80, SWG, >, t, " 809 ",, 804,,,,, HI 807 ; 808 _ o; li<i, ;, I,, ;, lib t\l, ; \ ; 0 ;, r 8 0 T m t Er//I, 65, lm i },, ;,, f, li ;\ x H,; ; rn,, tmr 79 7 8 6 ; im, IL \ fl },tz 89!,, " ", 90 77 ;c 35 8J ;, f;tl I\ 79 _,, ; 8 i I 92 7 65 60 92, Q,j Q,j 82 9,4 92 85 70 96 9 9 96 8;] 00!, ; 806 < " 802 Rootstock Figure 2 Tree height and width in feetjuly 3, 989 $, trees were killed Trees on citrange F/80, 2, 3 citrumelo ed from several flatwoods plantings on citrumelo F/ 803 and[ W2 had injury into larger limbs and were the most severely F/808 with at least one instance traceable to infected tree; damaged Citrumelo F/807 suffered the least damage with from the nursery and 2 occasions from close association with, fire ant injury Screening tests of F /807,8, and 8 to deter ll little or no dead wood Average height and width of all trees was measured in July mine susceptibility to Phytophthora have been rated intermedi 989 (Fig 2) Trees on citrumelo F/803 and W2 were the ate to susceptible (Graham, personal communication) F/80 largest and citrumelo F/807 and 9 were the smallest Fruiting height was measured in November 994 after the trees had filled the inrow spaces (Table 3) Visual measure Table 3 Average fruiting height measured /0/94 on 3 replications (9 ; trees) ments recorded the average height of fruit in the tree for 3 replications (9 trees each rootstock), to determine if any rootfrt Ht Indexr Yield Index Average Feet Rootstocks stock might produce acceptable yields at a lower height which 060 066 could result in more favorable harvesting costs Swingle root Citrum F/803 9 985 34 Citrum FI 808 stock was assigned a value of 00 and the fruiting height and Citrum W2 9 03 average yield in pounds soluble solids per tree for the most re Citrange F/82 870 9 29 8 904 23 Citrange F/83 cent two years were compared 066 Seven rootstocks produced trees that bore fruit higher in Sour Orange 0 096 Citrum F/88 the tree on average than did Swingle Trees on citrumelo FI Norton Citrange 870 000 36 802 bore fruit higher than Swingle by 27% however the Citrange F/80 660 779 000" 000" 36 yield was only 4% higher in pounds soluble solids per tree In Swingle Citrum 760 934 27 contrast, trees on sour orange bore fruit only 6% higher in Citrum F/809 900 05 38 Citrum F /808 the tree than swingle, yet the yield was 2% more in pounds Citrum F/807 7 890 soluble solids per tree Yield was directly related to tree size, Citrum F/804 8 985 34 9 except for trees on F/806 and W2 which were larger than Citrum F/806 059 44 lo to 53 Citrum F/802 Swingle but produced less pounds soluble solids per tre A number of commercial plantings containing some of Index Pounds solid per tree for 9293 & 9394 these citrumelo rootstocks have been established in Florida in rindex Maximum fruit height different soil types and under various cultural practices Tree Average maximum fruit height per tree losses from Phytophthora footrot and rootrot have been report "Indexes are computed with Swingle at 00 72 Proc Fla State Hort Soc 08 995
r I 3 was ranked with Swingle as more tolerant (Graham et al 993) Few problems related to Phytophthorahave has been re ported in plantings of these rootstocks on well drained soils of the ridge Citrus Blight has been reported in plantings of F/803 while F/ 808 has not sustained severe losses (Youtsey and Rosenthal 986) It remains to be seen to what extent that Citrus Blight will occur in this trial From observations to date it would seem that few of these rootstocks are superior overall to Swingle, but citrumelo FI 88 and F/802 may be acceptable rootstocks for further tria plantings with Hamlin orange scions because of increased yields offruit per tree and pounds soluble solids per acre Citrumelo F/803 should also be included due to the outstanding yield performance, however, care should be taken that nursery stock should be free of Phytophthora and careful attention should be given to control of fire ants in the planting Acknowledgments The authors wish to recognize Jim Baldwin for his valuble assistance with statistical analysis and Tommy Long for juice analysis Literature Cited Bridges, GD and C 0 Youtsey 974 Yield variations among citrus nucellar seedling clones at the Florida State Foundation Grove, Proc Florida State Hort Soc 98588 Derrick, K S, R F Lee, R H Brlansky, L W Timmer, B G Hewitt, and G A Barthe 990 Proteins associated with citrus blight Plant Dis 74 6870 Graham,] H and W S Castle 993 Screening citrus genotypes for tolerance to phytophthora rootrot in chlamydosporeinfested soil IV World Congress of the International Soc of Citrus Nurserymen Lee, R F, LJ Marais, L W Timmer, and] H Graham 984 Syringe injection of water into the trunk a rapid diagnostic test for citrus blight Plant Dis 68553 Norman G G 964, Old and nucellar lines in the foundation grove of the Div of Plant Ind Proc Fla State Hort Soc 77776 Pieringer, A P, GD BridgeS!nd C 0 Youtsey 978, Comparison of yield and internal quality of 25 navel orange selections, Proc, Fla State Hort Soc 92225 Wutscher, HK, M Cohen, and RH Young 977 Zinc and watersoluble phenolic levels in the wood for the diagnosis of citrus blight Plant Dis Rptr 6572576 Wutscher, HK and L L Hill 995 Performance of Hamlin orange on 6 Rootstocks in East Central Florida HortScience 30()443 Wutscher, HK andf W Bistline 988 Performance ofhamlin orange on 30 citrus rootstocks in Southern Florida ] Amer Soc for Hort Soc 3(4)493397 Youtsey, C 0 and G D Bridges 979 Yield and growth comparisons of one oldline and eight nucellar Washington navel budlines in a demonstration planting on ten rootstocks Proc Florida State Hort Soc 922022 Youtsey, C 0 and FJ Rosenthal 986 Incidence of citrus blight in Floridas citrus budwood foundation grove Florida State Hort Soc 99773 ridges, G D 973 The Florida citrus budwood program Proc, st Interna tional Citrus Short Course, p 335 Proc Ra State Hort Soc 087377 995 TREE SURVIVAL IN LONGTERM CITRUS ROOTSTOCK FIELD TRIALS WILLIAM S CAsTLE AND JAMES C BALDWIN University of Rorida,!FAS Citrus Research and Education Center 700 Experiment Station Road Lake Alfred, FL 33850 Additional index words Blight, citrus tristeza virus, Phytophtlwra Abstract Tree losses caused by blight, citrus tristeza virus (CTV) or Phytophthora foot rot were recorded periodically in four formal rootstock experiments and one grower trial The f ve trials, located throughout Florida, were planted between 968 and 978 The scion cultivar was either Valencia or Hamlin sweet orange [Citrus sinensis (L) Osb] with rough lemon (C jambhiri Lush), Volkamer lemon (C volkameriana en & Pasq), sour orange ( C aurantium L), Cleopatra mandarin (C reshni Hort ex Tan), Carrizo citrange [ C sinensis x Poncirus trifoliata (L) Raf], and Swingle citrumelo ( C paradisi Florida Agricultural Experiment Stationjournal Series No N054 We grateuy acknowledge the support for these projects received from Becker Hokling Corp, Alcoma Packing Co, Talquin Corp, Via Tropical Fruit Co, One Lee, C Elton and Robert Crews and Gene Swearingen, Congen Inc and ck Neitzke, the Berry Corp, Florida growers through a Citrus Production Fesearch AdVisory Council grant (Project 92827), and L W Timmer and R lee,for disease assays Proc Fla State Hort Soc 08 995 Macf x P trifoliata) rootstocks common to most trials A broad range of other rootstocks were included in the experiments Early losses were caused by site conditions, cultural practices and Phytophthora foot rot Overall, few trees were lost to the latter except for trees on sweet orange rootstock where generally < 50% survived Blight was the primary cause of loss among older trees except for CTV decline in trees on sour orange Trees on commercial stocks survived blight according to prior experience, ie, high survival among those on Swingle citrumelo, sweet orange, and sour orange(> 80%) and lower survival (< 50%) for those on rough lemon with other rootstocks having intermediate losses The survival results between trials were sufficiently consistent to suggest that longterm field trials are, and continue to be, the only current means to conduct blight evaluations Among noncommercial and new rootstocks, tree survival was > 75% for those on English Small trifoliate orange, C amblycarpa, Koethen sweet orange x Rubidoux trifoliate orange, Chinotto, a pummelo, and 808 citrumelo Blight, Phytophthora diseases, and citrus tristeza virus (CV) continue to be among the principal causes of tree loss in the Florida citrus industry In searching for rootstocks tolerant or resistant to these diseases, new plant material is fre; quently screened in controlled tests before field evaluation These tests function well to identify the usually small number of plants with desirable traits among the much larger original population; however, these tests also have certain disadvan 73