Maxima ,04 CLIMATE EFFECTS ON GRAPEFRUIT AND LEMONS

wo PREVIOUS ARTICLES in California sour orange, and Cleopatra mandarin TAgricdture (November 1972 and had to be used during some seasons when April 1974) have repofled some climate trees on C, macrophylla were not avail- 60- 0 South Coast effects on oranges and mandarins. This able or had set too small a crop. The four A Limoneiro 56 - third and final report covers data ob- orchards involved in this study all re- 3 4 5 6 7 8 9 10 II I2 I 2 tained on Frost Marsh nucellar and Red- ceived good maintenance. Since recent MONTH blush nucellar grapefruit harvested over studies have indicated that climate is GRAPH 1. COMPARISON OF MONTHLY MEAN MAXIMUM a period of five crop seasons beginning the most important singIe factor influ- TEMPERATURES (1967-72) FOR THE FOUR FRUIT SAMPLING LOCATIONS with 1967-68. Eureka and Lisbon lemons encing variations in fruit maturity and were harvested over four seasons begin- quality within a variety, it is believed ning with 1968-69. that the differences shown here are OF As in the previous reports, fruit sam- largely climatic effects, even though it Minimo pling locations were the Limoneira Ranch was not possible to eliminate all other near Santa Paula in Ventura County, variables. 80- Thermal South Coast Field Station near Irvine in Graphs 1 and 2 compare temperature 76 - .4 Lindcove Orange County, Lindcove Field Station regimes for the five years of sampling o South Coast 72 - in Tulare County, and a commercial from the nearest weather station with A Lirnoneira 68 - citrus nursery near Thermal in the Coa- available records. chella Valley of Riverside County. The Fruit samples were collected at ap- Limoneira and South Coast locations rep- 60 proximately six-week intervals each sea- resent relatively cool coastal valley cli- son on or about October 30, December 7, 56 matic zones; Lindcove is in the hot January 23, March 9, April 19, May 29 Central Valley; and Thermal represents and July 30. Distances between orchards the very hot, interior low-elevation prechded picking all samples the same desert. day. Lemons were harvested at three 40 All grapefruit trees in this study were times, from late October to January; 36 - grapefruit were harvested on five dates, /,/,I/,, of the same scion budlines, on citrange 3 4 5 6 7 8 9 1011 12 I2 rootstock and were similar in age. Lemon from January to mid-July. MONTH trees were of the same scion budlines; Both grapefruit and lemons tend to GRAPH 2. COMPARISON OF MONTH.LY MEAN MlNlMlUM TEMPERATURES (1967-72) FOR TH'E FOUR SAMPLING they were mostly on C. macrophylla bloom and set fruit over an extended LOCATIONS. (Sources: Lindcove and South Coast Field rootstock but some trees on C. taiwanica, period of time in cool climates. To in- Station weather records; Climatological Data, U.S. Department of Commerce, Thermal Airport for Thermal a'nd Santa Paula for Limoneira.)

Eureka lemon fruit harvested in late October at Limoneira, South Coast, Redblush grapefruit harvested in late January at Limoneira, South Coast, Lindcove, and Thermal, from left to right. Lindcove, and Thermal, from left to right.

8 CALIFORNIA AGRICULTURE, MARCH, 1975 and Lindcove locations in January, about 10 months after set, This illustrates the 5oo size problem associated with growing E. M. NAUER grapefruit near the coast. 400- J. H. GOODALE Fruit shape was also influenced by cli- mate. Grapefruit produced at Thermal k5 300- L. L. SUMMERS were longer (rounder) from button to v, stylar end compared to diameter, while A’ Grapefruit WALTER REUTHER .Thermol were shorter (flatter). 0 South Coos1 .-Py A Limoneiro The climatic zones compared appeared 100- 4 / A’i‘ernow A’i‘ernow sure that all fruit in a sample originated in the same bloom, young fruit of the -. .. .. - . . normal spring set were tagged just after posite sides of the same fruit than were the “June drop,” and only these tagged shown between locations, except that in fruit were sampled for analysis. January, fruit from Thermal showed the 126 At each sampling, 48 fruit of each best color, and smaller fruit from Li. variety (24 per tree) at each location moneira the least color. There was also were analyzed. Fruit and extracted juice little change in Marsh grapefruit rind were weighed; length, width, and rind II.0r color as the season progressed from Jan- 0 thickness were measured. Color of rind uary to July. Redblush rind color was G 10.6- and flesh was visually rated by matching best developed in the warmer interior each fruit with color chart standards. locations. The greatest color change in Rind texture was rated by eye, com- Redblush occurred between late May paring each fruit with a series of six and late July in fruit grown at Lindcove; photos of fruit ranging from smooth to during this period reddish rind color 82 coarse and pebbly. Flesh texture was deepened considerably, so that in late A Limoneiro rated as fine, medium, or coarse. Grape- MID-LATE EARLY MID- LATE JULYLATE July the rind of Lindcove fruit was a JbN MARCH APRIL MAY fruit juice was tasted and rated for pala- much deeper red than that from the GRAPH 4. FLESH COLOR RATINGS SHOWING RED tability on a scale of 70 = acceptable, 80 = PI GM ENTATl ON DEVELOPMENT IN RED BLUSH other locations. Grapefruit grown at GRAPEFRUIT good, 90 = excellent. Concentrations of Lindcove exhibited considerable rind total soluble solids, citric acid, and as- stipple on many fruit, particularly fruit r corbic acid (vitamin C) were assayed. growing on the outside of the tree. This The photographs illustrate typical dif- type of rind blemish was very slight or 8ot ferences in Redblush grapefruit picked in lacking at the other locations. late January and Eureka lemons picked Both grapefruit and lemons from all in late October. With both grapefruit and climatic zones were of acceptable rind lemons, differences between major cli- texture for marketing. Grapefruit grown matic zones were greater than differences at Lindcove were the coarsest, while between seasons for most of the measure- fruit grown at the two coastal locations 50 - ments taken. were the smoothest. Thermal grapefruit Thermol With the exception of rind and flesh were intermediate in texture. A Lindcove color, results with Marsh and Redblush 40- 0 South Coost Rind thickness varied according to A Limoneira grapefruit were similar. Differences be- fruit size and between seasons, as well as tween Eureka and Lisbon lemons were between climatic zones. In general, both 30 MID-LATE EARLY MID- LATE JAN MARCH APRIL MAY JULY much less than differences between major varieties of grapefruit produced fruit GRAPH 5. TRENDS IN GRAPEFRUIT TASTE RATINGS climatic zones. In general Eureka fruit with the thickest rind at Lindcove, the IN THE FOUR LOCATIONS was slightly larger than Lisbon fruit, and thinnest rind at the two coastal locations, less elmgate than Lisbon fruit except at and intermediate rind thickness at Ther- 90 Thermal. Eureka lemons, except at Ther- mal. Average Marsh grapefruit rind mal, yielded a slightly higher percentage thickness in mm for all samplings in all of juice and had a slightly higher sugar- seasons was 7.5 at Limoneira, 7.3 at acid ratio than Lisbons at all locations. South Coast, 11.1 at Lindcove, and 9.1 Other fruit quality criteria showed no at Thermal. Average Redblush rind differences between Eurekas and Lisbons. thickness was 6.9 at Limoneira, 7.0 at Grapefruit size, shape, rind South Coast, 9.3 at Lindcove, and 8.5 at Thermal. Average fruit size is shown in graph 3. O’ O’ Marsh Gropefruit A LlndCove As with oranges and mandarins, grape- Flesh characteristics 0 South Coast fruit produced larger fruit in the warmer Marsh grapefruit grown at Thermal 20 Lemons ALimoneiro climatic zones. Grapefruit grown in the exhibited a slightly darker internal color k==q 12 ’ LATE EbRLI MID-LATE EARLY MID LATE LATE cool Limoneira location were smaller in than fruit from the other climatic zones OCT DEC JAN MARCH APRIL MAY JULY July, 16 months after set, than were through the May sampling; by July GRAPH 6. TRENDS IN TOTAL SOLUBLE SOLIDS TO ACID RATIO FOR LEMONS AND MARSH GRAPEFRUIT GROWN grapefruit grown at the warmer Thermal Thermal fruit were too granulated to IN FOUR DIFFERENT CLIMATIC ZONES

CALIFORNIA AGRICULTURE, MARCH, 1975 9 judge internal color. Marsh grapefruit Lemons grown in the interior climatic from Lindcove, South Coast, and Limon- zones were more yellow, while coastal BUD FA11 eira were very similar in flesh color grown fruit was greener at each picking through May, but by July fruit from date. Color break from green to yelloM Lindcove was darker than fruit from the was rapid and continuous from late Oc coastal locations. tober to mid-late January ; lemons growr Redblush grapefruit from both interior at Thermal changed color more rapidlj locations was well colored throughout the from late October to early Decembei season, while only very pale red colora- than during the following six weeks. tion developed at the coastal locations Rind texture of lemons varied only (graph 4). Redblush developed the dark- slightly between climatic zones. As with est red pigmentation of flesh at Lindcove grapefruit, lemons from Lindcove wen in July. With grapefruit there were no coarsest, and those from the coastal cli. apparent flesh texture effects of climate matic zones were smoothest. except for granulation by July at Lemon rind thickness was strongly in. Thermal. fluenced by climate. Fruit grown at the two coastal locations had the thickesi Grapefruit juice composition rind, with South Coast lemons having Throughout most of the season, juice thicker rind than Limoneira fruit. Lem- percentage of grapefruit varied only ons from Thermal had the thinnest rind, Noninfectious bud failure (BF) affects certain slightly between climatic zones: between while Lindcove lemons were intermediate almond varieties and has become increasingly 41 and 46% for Redblush, and hetween between desert and coastal fruit in rind 39 and 47% for Marsh. Highest juice thickness. Average lemon rind thickness widespread in recent years. percentage was at Thermal with Red- in mm for all samplings in all seasons Symptoms are produced by failure of vege- blush and at South Coast with Marsh; was 4.9 at Limoneira, 5.5 at South Coast, tative buds (particularly on middle and ter- second highest was at South Coast with 4.5 at Lindcove, and 3.7 at Thermal. minal portions of shoots) to grow in the Redblush and at Thermal with Marsh. spring. This is followed by vigorous wide- Flesh characteristics Lowest juice percentage with Marsh was angled growth from surviving buds. In some at Lindrove; Redblush juice content was Lemon flesh color varied only slightly trees, particularly when other symptoms are between climatic zones. Lemons produced about the same at Lindcove and Limon- severe, bands of roughened bark appear on eira. In July juice percentage of grape- at the two coastal locations were lightest in flesh color; Thermal lemons were the some branches. As this pattern of bud failure fruit at Thermal dropped to an average develops, BF trees develop wild, disoriented of 25% as the fruit became badly gran- darkest ydlow color internally, while growth patterns and hence the disorder is ulated. Lindcove fruit was intermediate in flesh frequently called “crazytop.” Thew was little difference in taste color. There were no observed effects of ratings between Marsh and Redblush. climatic differences on flesh texture of Early work on the BF problem developed lemons. Average taste ratings for both varieties the concept of increased BF incidence with combined are shown in graph 5. Results Lemon juice composition successive vegetatively propagated genera- indicate that superior juice quality can- Juice percentage of lemons increased tions. At that time BF was attributed to a not bp attaincd at the two cooler climatic from coast to interior. Average juice per- ienetic disorder with unstable characteris- zones. By July, grapefruit from Thermal centages for all harvests in all seasons tics. Since then, observations suggest that was exressively overripe and granulated. were 31.2% for Limoneira, 33.2% for mvironmental conditions affect the stability Solids-acid ratios for Marsh grapefruit South Coast, 38.4% for Lindcove, and md expression of BF. Vegetative propagation are shown in graph 6. Solids-acid ratios 43.2% for Thermal. This trend may be s done on the premise that plants propa- for Redblush were almost identical to caused, at least in part, by the tendency Zated from a common parent remain the those for Marsh. of coastal fruit to have thicker rind than same, but this premise is not fulfilled in the Ascorbic acid (vitamin C) content of interior grown lemons. 3F disorder. In other cases where variations grapefruit juice did not vary greatly be- Solids-acid ratios for lemons are shown lave occurred after vegetative propagation, tween climatic zones. Coastal grown in graph 6; figures for the two lemon :he problem has most often been attributable grapefruit contained slightly larger quan- varieties have been combined, since dif- tities of ascorbic acid. ferences between these varieties were :o environmental influences, virus infections The results of these studies show that, not significant. Lemon juice from coastal )r mutations. However, variability of nonin- except for pigmentation, Marsh and Red- lemons contained more ascorbic acid ‘ectious BF cannot, at present, be directly ac- blush grapefruit are commercially iden- (vitamin C) than interior grown lemons. :ounted for by any one of these factors. This tical in physical and chemical character- ;eries of articles adds further information on istics. E. M, Nauer is Specialist; J. H. Good- he nature of BF and discusses selection for ale is Senior Nurseryman; L. L. Summers Lemon size, shape, rind reedom from BF within the Nonpareil variety. is Staff Research Associate ; and Walter t documents the impact of environment on Like the other varieties studied, lemons Reuther is Professor of Horticdture and potential and expression and provides produced larger fruit in the warmer cli- Horticulturist, Department of Plant Sci- 1F lata on yield reduction due to BF. Finally, it matic zones, as shown in graph 3. Lem- ences, University of California, River- ons also tended to be slightly more elon- side. R. L. Blue, D. C. Elfving, Jan iutlines a system of management decisions gate when grown in the warmer interior Moore, C. N. Roistacher, and R. L. Wag- or orchardists faced with almond trees af- climatic zones. ner assisted with this research. ected with BF.

10 CALIFORNIA AGRICULTURE, MARCH, 1975