24 FLORIDA STATE HORTICULTURAL SOCIETY, 1963

my observation that it does not grow and pro that started to die by the time they were four or duce well on highly alkaline soils. five years old and none of them lived through their tenth year.

Rough Lemon The use of rough lemon as a rootstock for fresh fruit varieties on the Indian River will Rough lemon is tolerant to tristeza.It has soon destroy our reputation for producing quality a lower moisture requirement than all of the fruit. Furthermore, it could readily eliminate other commercial rootstocks. It grows well and the premium price we have enjoyed for so many produces high yields even on light sandy soils. years. If we are to protect this priceless repu Rough lemon, like sweet orange, is very sus tation it is the duty of each and every Indian ceptible to foot rot. Allthe precautions suggested River grower to use only those rootstocks which for sweet orange should also be observed for will produce fruit of the highest quality. this rootstock. Another serious objection to rough lemon is that it produces fruit of poor internal quality Future Rootstocks with all varieties. It is particularly undesirable to plant roughlemon on good land for the better Other rootstocks may soonbe in general use. the land the poorer the quality of the fruit. The Florida Citrus Budwood Registration Pro During wet years red grapefruit, and sometimes gram has now made available budwood of most even marsh seedless, grown on rough lemon may varieties which are free of psorosis and xyloporo- produce fruit with such low solids that it will sis and some varieties which are free of exocortis. never meet the maturity standards. This will permit the use of other promising root Trees on rough lemon, grown on alkaline soils, stocks such as trifoliata, Rangpur lime and prob have a comparatively short life. The more active ably others which are tolerant to tristeza. Plant the marl the shorter the life of the trees. I ob ings on these rootstocks are still too young to give served lemon rooted grapefruit planted on Palm us much information but so far they look quite Beach sand, which has a subsoil pH of about 8.4, promising.

A ROOTSTOCK TRIAL FOR TAHITI LIMES IN DADE COUNTY, FLORIDA

BURT COLBURN,1 F. E. GARDNER,2 AND The present experiment was initiated in order George E. Horanic2 to test the performance of Tahiti limes on a number of rootstocks under these unusual soil Introduction conditions. There were, in 1961, about 5700 acres of Ta Rootstock trials with citrus are generally con hiti (Persian) limes in Florida, the greater part sidered as long-term projects and to be of doubt of which (about 85%) were in Dade County. The ful value unless pursued for an extended period. remainder, chiefly in Polk and Highlands counties, With limes in Dade county, however, the vicissi was decimated by the freeze of December 1962. tudes of the weather such as hurricanes, floods, Limes in Dade County encounter soil problems and even occasional freezes, coupled with the not found in other areas of the State where citrus devastation caused by wood pocket disease, is grown. The oolitic limestone (Rockdale series) greatly curtail the period during which valid characteristically has a pH of about 8.0 and, records can be secured. Consolation is found, while porous in nature, may present problems of however, in thefact that lime trees grow rapidly, root penetration and extention. Because of fruit early in their life, and likewise decline these characteristics one might expect that the early so that they can be considered a short-term performance of some rootstocks, at least, would crop when compared to other citrus in other areas. be very different than in more conventional soils. However, the use of disease-free budwood, par ticularly that free from wood pocket disease,

l South Florida Growers Association, Goulds, Florida. should aid in prolonging the productive life of 2Crops Research Division, Agricultural Research Service, Tahiti lime trees. U. S. Department of Agriculture, Orlando, Florida. COLBURN, GARDNER, HORANIC: TAHITI LIME ROOTSTOCKS 25

Literature Review 38-10-14 registered by the Budwood Certification Program for freedom from tristeza, psorosis and The reported experimental work on rootstocks xyloporosis. In addition, no symptoms of exocortis for Tahiti limes is meager. Recently Campbell or wood pocket disease have appeared to date in and Lincoln (1) reported on the fruit yields this experimental planting. All trees were planted from 10 rootstocks planted in 1951. Shekwasha in the field on April 28, 1959 except those on Cit and own-rooted trees showed considerably higher rus macrophylla rootstock which were not planted yields than Rough lemon which was in third until 5 months later. place, followed by grapefruit, Cleopatra man The experimental planting design consisted darin, Sweet orange, Rangpur, Willow leaf man of 5 trees per plot for each of the 20 rootstocks darin, Sour orange, and Sweet lemon. The results randomized within each of 4 replications. Damage of this experiment were advanced cautiously be from Hurricane Donna in September of 1960 cause of frequent tree replacements occasioned necessitated replanting of some trees. Replants by frosts and hurricane winds, "probable high were eliminated as trees of record but otherwise incidence of virus diseases in the trees," and lack all performance records for statistical purposes of an experimental design which would lend itself are based on the average of 5 trees per plot in to statistical analysis of the data. Nevertheless each of the 4 replications.* their data show important differences in yields on The experimental block received adequate various rootstocks, some of which are probably and uniform cultural care over its entirety. An real. These authors cited earlier tests conducted 8-7-8 mixed fertilizer (30 percent organic N) at the Sub-Tropical Experiment Station at Home plus 4 percent Mgo was applied 5 times a year. stead and mentioned in the Florida Agricultural Nutritional sprays of Mn, Zn, and Cu plus Experiment Station Annual Reports as progress sulphur were applied in late December on early or interim reports. Necessarily these brief re January for minor element needs and for control ports are difficult to evaluate but tend to empha of melanose and rust mite or broad mite. Minor size the difficulties in conducting long-term Ta element dificiencies were fairly well controlled hiti lime experiments due to tree losses from by nutritional program program except for lime- storms and diseases. induced iron chlorosis which varied in degree de While these early experiments may have pending on the rootstock. yielded but little conclusive information on the Tree sizes, represented by centimeters of influence of rootstock on tree growth and fruit trunk circumference 2 inches above the bud union, production, they did provide opportunity for were taken August 15, 1962 and again on August much more precise data on fruit characteristics. 7, 1963, 4 years and 4 months after planting. In the course of his very comprehensive analyti Fruit yields were recorded in pounds of frr.it cal studies of the Persian lime, Lynch (3) ob for 3 separate periods, July 1 to August 17, and tained fruit quality data from Rough lemon, October 20 to December 30, 1962, and for the Willow leaf mandarin, Sour orange, Bitter Sweet, first half of the 1963 season up to July 16. The and Cleopatra mandarin rootstocks. He reported weights of picked fruits for these 3 periods were that Rough lemon produced larger fruits than combined into 1 value and expressed as average the other stocks in his study but that juice con pounds of fruit per tree. Because of the large tent, percent acid, and soluble solids were not number of small plots (80 within the experi appreciably different. Lincoln (2) carefully mental area) it was not feasible, using ordinary studied the juice content of Tahiti limes from picking crews, to secure reliable yield records 5 rootstocks and concluded that rootstock had over a complete season. It is believed, however, very little influence on percentage of juice. that the carefully-supervised partial yield records obtained are indicative of the relative fruitful- Materials and Methods ness of the various rootstocks. Fruit analysis. Samples of 25 fruits, 5 from Twenty rootstock varieties were selected for each of the 5 trees in every plot, were picked the field test. For the most part they were September 18, 1962, for determinations of average varieties which had performed relatively well as weight of fruit, percentage juice, total acid, total stocks in other areas with orange and grape soluble solids, and vitamin C. These were not fruit scions. The young seedlings were planted in tar paper pots in February 1957 and were *The assistance of E. James Koch of the Biometrical Services, ARS, Beltsville, Maryland on the statistical analyses subsequently budded with Tahiti lime clone LI is gratefully acknowledged. 26 FLORIDA STATE HORTICULTURAL SOCIETY, 1963 random samples but were, instead, carefully here were obtained with a refractometer rather selected for acceptable market maturity based on than a Brix hydrometer. This resulted in solids rind color. However, no conscious selection for readings widely different than those usually re size of fruit was exercised. A second and simi ported due to the relatively low refractivity of lar sample of 25 fruits was picked in October citric acid which comprises the bulk of the total from each plot and averaged with the fruit soluble solids in lime juice. However, these weights of the September picking, thus basing the procedures should afford valid relative compari mean weight per fruit on 50 fruits per plot. sons between rootstocks. Juice was extracted by means of an electric Results reamer and weighted for determination of per centage juice. Total soluble solids were deter For easy comparison, the mean values in the mined by refractometer readings, total acid by following tables are arranged in descending order titration with standard alkali, and vitamin C by of magnitude for each of the characteristics titration with 2,6-dichlorobenzenone indophenol. It studies: Tree size, yields, fruit size, percent juice, should be noted that percent of juice in limes as etc. Each rootstock carries the same number an official criterion of legal maturity is deter throughout all of the comparisons. The Duncan mined by expressing the juice with a hand ex multiple range technique, using letters of the tractor and basing the percentage on volume of alphabet following each mean, indicates which juice and fruit rather than on weight. This may means are statistically different from others at account for juice percentages at some variance odds of 19 to 1. with those reported by other workers. It should Fruit yields. The range in yields between also be noted that the total soluble solids reported rootstocks was pronounced (Table 1). Rangpur

Table 1.—Fruit yield, trunk circumference, and iron, chlorosis rating of Tahiti limes on various rootstocks

Rootstock Yield per Rootstock Trunk Rootstock Chlorosis No. Name tree No. circ. No. rating* (lb.) (cm.) (0-3) 1 Bangpur lime 156. k a 1 32.5 a 7 0 a 2 C. macrophylla 1U9.3 ab 8 31.9 ab k 0 a 3 Leonardy grft. 1UU.3 abc 7 31.6 a"b 2 0 a k Rough lemon 125.3 bed U 31.6 ab 11 0 a 5 Troyer citrange 119.5 cd 2 31.k ab 13 0 a 6 Watt tangelo 11U.5 de 12 30.9 ab 9 0 a 7 Own-rooted 113.9 de 11 30.3 ab Ik 0 a 8 Sampson tangelo 111.3 def 3 30.3 ab 1 .25 a 9 C. tiawanica 110. k def 13 29.5 abc 5 .25 a 10 Sunshine tangelo 106.1 def 6 29.^ abc 15 .25 a 11 Iran lemon 10U.U def 17 28.8 be 16 .38 ab 12 Orlando tangelo 88.3 efg 9 28.7 be 19 .50 abc 13 Cleopatra mand. 82.I+ fg 10 28.7 be 18 .88 bed Ik Sanfield citron 66.5 g 5 26.2 cd 6 1.00 cd 15 Citrangequat U8032 65.7 g Ik 23.9 de 8 1.13 d 16 Tavares limequat 63.6 g 20 23.6 def 3 1.25 d IT Seminole tangelo 63.3 g 15 22.2 ef 12 2.13 e 18 Uvalde citrange 6l.7 g 16 21.8 ef 17 2.38 e 19 Rusk citrange 61.6 g 18 21.6 ef 10 2.38 e

20 P. trifoliata — 19 20.5 f 20 3.00 f

Statistical significance: Means not followed by any letters in common are significantly different at odds of 19 to 1.

*Iron chlorosis ratings: 0 = no visible iron chlorosis. 1 = up to 10 percent of foliage with slight chlorosis. 2 = 10 to 50 percent of foliage more or less chlorotic. 3 = 50 to 100 percent of foliage chlorotic. COLBURN, GARDNER, HORANIC: TAHITI LIME ROOTSTOCKS 27

Ike was significantly better than Rough lemon varieties, so lacking in vigor under the conditions but not significantly ahead of C. macrophylla or of this test. In some, but not all instances, the Leonardy grapefruit. The top three stocks, Rang- poor vigor can be attributed to marked iron pur lime C. macrophylla, and Leonardy grape deficiency. The relationship of iron deficiency fruit all significantly out-yielded the own-rooted to rootstock performance is discussed later in trees. this report. The yield from the Poncirus trifoliata-rooted Fruit size. Differences in fruit size, as indi trees, was omitted from the statistical analysis cated by mean weight per fruit (Table 2) were because of* sparse, small, chlorotic fruit, which not significant between rootstocks except for the was totally worthless commercially. These fruits extremes of the column, although there was a were so atypical they were omitted also from considerable spread in fruit size between the the analytical studies which follow. However, tree extremes. High-yielding stocks—Rangpur lime, size on this stock has been included. C. macrophylla, Rough lemon and Troyer citrange Tree size, as indicated by trunk circumfer —are all high on the list for fruit size. However, ence, also shows a wide range on the various Uvalade citrange, the lowest-yielding stock, also stocks. (Table 1). As might be anticipated the produced large-sized fruit. largest trees, in general, produced the most fruit Percent juice. High juice content is obviously but these variables are not consistently corre an important criterion of quality in limes. The lated. The own-rooted trees were high in vigor spread in juice content between the lowest and but were well down the list of stocks in fruit the highest rootstocks was about 16 percent, production. This situation was also evident in although statistically significant differences be Sampson tangelo, frequently observed in other tween individual means could be established only rootstock tests (for oranges) to produce vigorous over rather wide ranges (Table 2). Rough lemon but low-yielding trees. On the other hand, Troyer resulted in significantly lower juice content than citrange and Leonardy grapefruit were more the majority of the other stocks, including most productive than their tree size would predicate. of those showing high fruit yields. It was surprising to find stocks such as Rusk Total soluble solids. For limes and lemons, to citrange and Tavares limequat, which have grown tal soluble solids has less significance as a cri vigorously on other soils and with other scion terion of quality than for other citrus fruits be-

Table 2.--Fruit size (weight), percent juice, and vitamin C of Tahiti limes on various rootstocks

Rootstock Weight per Rootstock Juice Rootstock Vitamin C No. fruit No. content No. (gm.) (percent) (mg./lOOcc.) Ik 35.8 a 5 Troyer citrange 108.9 a 13 62.0 a 3^.5 ab 18 Uvalde citrange 107.7 ab 3 61.5 ab 5 k 33.8 abc k Rough lemon 107.2 ab 12 61.3 ab 32.5 abed 2 C. macrophylla 106.1 ab 15 61.0 abc 13 32.3 abed 1 Rangpur lime 105.8 abc 1 60.8 abed 15 32.0 bed 12 Qrlando tangelo 105.2 abc 11 60.0 abede 7 1 32.0 bed 11 Iran lemon 10U.9 abc 7 59.0 abedef 11 31.8 bed 7 Own-rooted 10U.9 abc 19 59.0 abedef 58.8 abedef 18 31.8 bed 19 Rusk citrange 103.2 abc 2 6 31.8 bed 9 C. tiawanica 102.8 abc 17 58.8 abedef 10 31.5 bed 13 Cleopatra mand. 102.6 abc 10 58.3 abedef 2 31.3 bed 3 Leonardy grft. 102.3 abc 6 58.0 abedef 31.3 bed 6 Watt tangelo 101.k abed 8 57.8 bedef 9 31.0 bed 8 Sampson tangelo 101.2 abed 18 57.0 cdefg 19 30.8 bed 10 Sunshine tangelo 99.7 bed k 56.8 defg 17 3 30.3 cql 15 Citrangequat U8032 99.1 bed 9 55.5 fg 8 30.3 cd 16 Tavares limequat 97.1 cd Ik 55.3 fg 16 30.3 cd Ik Sanfield citron 93.6 d 16 55.0 fg 12 29.0 d 17 Seminole tangelo 93.6 d 5 53.3 g

Statistical significance: Means not followed by any letters in common are 28 FLORIDA STATE HORTICULTURAL SOCIETY, 1963 cause the soluble solids are comprised mainly of of iron chlorosis (Table 1), but it is unlikely that acids which value, in itself, is of considerable a slight chlorosis, up to a visual rating of 1.0 importance. In this study, while the differences was a significant factor in the growth or fruit- in total solids bewteen rootstocks was not large, fulness of the trees. Above a rating of 1.0 iron there were many statistically significant differ chlorosis undoubtedly became increasingly sig ences (Table 3). Highest in total solids were the nificant as a limiting factor. It is interesting, trifoliate hybrids: Uvalde, Rusk, and Troyer however, that the Leonardy grapefruit made citranges. With the exception of Leonardy grape fairly vigorous trees and was in third place in fruit, all of the rootstocks with high fruit yields fruitfulness despite a chlorosis rating of 1.25. were low in total solids. These included Rangpur Orlando tangelo, with a rather high chlorosis lime, C. macrophylla, and Rough lemon. Thus rating (2.13), showed surprising tree vigor. Pon- Rough lemon maintained its reputation, gained cirus trifoliata, the stock most susceptible to in numerous tests with other citrus fruits, of chlorosis, was chlorotic to the point of partial resulting in low-solids juice. defoliation. Even the fruit was chlorotic and so Total acid. The range between the rootstock small as to be worthless. The tree growth, how showing the highest acid (5.98%) and the lowest ever, was no poorer than on several other stocks (5.34%) represented a difference of about 12 that exhibited only slight chlorosis. percent, a relatively narrow range (Table 3). Only between the extremes of the range were the Discussion differences of statistical significance. While the acid content of Tahiti limes can apparently be Rangpur lime topped the list of the 20 root influenced by rootstock, we would agree with stocks in this experiment in fruit yield, although Lynch's conclusion (3) that the effect is not statistical significance over the next 2 closest appreciable. stocks was lacking. The excellent performance of Vitamin C. The spread of vitamin C content Rangpur lime is dependent upon freedom from of juice between the highest and the lowest values exocortis and xyloporosis viruses. Neither Rang on the various rootstocks represented nearly 24 pur lime nor P. trifoliata (or any of its hybrids) percent, making this fraction the most sensitive showed any evidence of bark scaling characteristic of any of the juice constituents determined (Table of exocortis after 6 years from date of budding. 2). It might be commented, however, that limes, However, trees on Rusk and Uvalde citranges as with other citrus fruits, are not consumed were markedly stunted as though some other primarily because of their ascorbic acid value disease entity might be present. The Orlando but rather because of their taste appeal. tangelo rootstock, test plant for the presence of Iron chlorosis. Lime-induced iron chlorosis is xyloporosis, remained free of virus symptoms. a primary factor limiting the selection of root Own-rooted lime trees, developed by airlayer- stocks on the oolitic limestone soil. Only on 7 ing and first used commercially by the South of the 20 stocks were the trees completely free Florida Growers Association, have been known

Table 3.—Total soluble solids and total acids of Tahiti lime to compare favorably in vigor with trees on fruits 5 from various rootstocks Rough lemon roots. They have been observed, Rootstock Bootstock Name T.S .S. No. Acids however, to be more prone to develop symptoms (percent; Vpercent; of magnesium deficiency and also be be less tol 18 Uvalde citrange 8.35 a 8 5.98 a 19 Rusk citrange 8.27 ab 1U 5.90 ab erant of wet feet than trees on Rough lemon. The 8.10 abc 5.89 ab 5 Troyer citrange 19 yield data suggests that they may also be some 3 Leonardy grft. 8.07 abed 16 5.88 ab 13 Cleopatra mand. 8.06 abed 7 5.85 ab what less productive. The production of own- 1U Sanfield citron 8.02 bede 6 5.8U ab 15 Citrangequat 1*8032 7.99 bedef 17 5.83 ab rooted trees by Marcottage is described by Sutton 5.81 ab 16 Tavares limequat 7.99 bedef 9 (4). Seminole tangelo 7.89 cdef 1 5.80 ab Watt tangelo 7.86 cdefg 10 5.80 ab The choice of rootstocks for the high pH, oolite 10 Sunshine tangelo 7.86 cdefg 12 5.79 ab 1 Rangpur lime 7.83 cdefg 15 5.75 ab limestone soil is somewhat limited because of 12 Orlando tangelo 7.76 defgh 3 5.71+ ab lime-induced iron chlorosis. While this factor 8 Sampson tangelo 7.75 defgh 18 5.71 abc 9 C. tiavanica 7.71 efgh 11 5.69 abc no doubt surpressed the growth on certain of 5.69 abc 7 Own-rooted 7.69 fgh 5 the rootstocks in this test the data suggest that 11 Iran lemon 7.56 gh 2 5.65 be 1* Rough lemon 7.5U gh u 5.1*5 cd in some cases other factors were even more limit 2 C. "; 7.1*6 h 13 5.3U d ing. Despite the very chlorotic condition of trees on P. trifoliata, this stock produced trees as large Statistical significance; Means not followed by any letters in common are significantly different at odds of 19 to 1.- as on 4 other stocks, namely Citrangequat PI COHEN AND REITZ: VALENCIA AND RUBY RED ROOTSTOCKS 29

48032, Uvalde citrange, Tavares limequat, and Rangpur lime, C. Macrophylla, and Leonardy Rusk citrange (ref. table 1), all of which ex grapefruit in that order topped the list of 20 hibited only very minor iron chlorosis. The seem- • stocks in fruit production although the differences ing lack of adaptation of these 4 stocks in this between their performance and those of their experiment apparently cannot be attributed to closest competitors were not statistically signi- iron deficiency. cant. Rangpur lime significantly outyielded Routh lemon while all of the top 3 produced more Summary fruit than own-rooted (marcotted) trees. In addition to fruit production and tree size, data is also presented on size of fruit, juice con A field test of registered Tahiti limes (Clone tent, total soluble solids, total acid, vitamin C, LI-38-10-14) on 20 rootstocks in a randomized and relative degree of iron chlorosis as influenced block design with 4 replications of 5 trees each by rootstock. was planted in April 1959 in Rockdale soil, Dade County, Florida. The calcareous soil, with a pH of about 8.0, LITERATURE CITED resulted in varying degrees of lime-induced iron 1. Campbell, C. W. and F. B. Lincoln. A comparison of rootstocks for Tahiti lime on Rockdale soils in Florida. chlorosis and limited the growth on a number of Proc. Fla. State Hort. Soc. 75: 61-63. 1962. 2. Lincoln, F. B. The juice content of Tahiti limes rootstocks. P. trifoliata, was particularly sus produced on various rootstocks. Proc. Fla. State Hort. Soc. ceptible to to iron chlorosis. Factors other than 72: 361-362. 1959. 3. Lynch, S. J. Some analytical studies of the Persian iron chlorosis appear to have markedly limited lime. Fla. Agr. Exp. Sta. Tech. Bull. 368. 1942. 4. Button, Norman E. Marcotting of Persian limes. the performance of certain stocks. Proc. Fla. State Hort. Soc 67: 219-220. 1954.

ROOTSTOCKS FOR VALENCIA ORANGE AND RUBY RED GRAPEFRUIT: RESULTS OF A TRIAL INITIATED AT FORT PIERCE IN 1950 ON TWO SOIL TYPES

Mortimer Cohen and Herman J. Reitz Methods University of Florida The trial described here is unique in that it Florida Citrus Experiment Station provides a comparison of the behavior of similar Lake Alfred rootstocks on two different soil types in areas about 200 feet apart. All 4 of the experimental The influence of citrus rootstocks on growth blocks were planted on the same day in December and production of different scion varieties has 1950 at the Indian River Field Laboratory at Fort been the subject of numerous articles in Florida Pierce. They consist of 2 plantings of Valencia and elsewhere, but often these are speculative or oranges and 2 of Ruby Red grapefruit. One plot based on only a few observations. Actual reports of each variety is found on Leon soil, an acid soil of comparative studies of randomized and repli underlain by organic hardpan; the other plot is on cated plantings of trees on different stocks grow Parkwood soil, a relatively fine-textured soil near ing under comparable conditions' are relatively neutral at the surface and underlain by marl. few, even for the more common rootstocks. Some This is a soil on which a large portion of the older of the more recent treatments of aspects of this citrus trees in the Indian River area are grown. field are those of Bitters (1), Moreira et al (4) The plots on Parkwood soil each contain six and Gardner and Horanic (2). This is a report rootstock varieties: Cleopatra mandarin, Parson on the first 13 years of a rootstock experiment Brown sweet orange, Rangpur lime, Rough lemon, under Indian River conditions comparing, pri sour orange and trifoliate orange. Trees on the marily, stocks of commercial importance. same six rootstocks were planted at the same time on Leon soil but, in addition, the Valencia plot on Florida Agricultural Experiment Stations Journal Series Leon soil has trees on Sampson tangelo and the No. 1767.