UC Riverside International Organization of Citrus Virologists Conference Proceedings (1957-2010)

Title Stubborn Disease Symptoms in Grafted Fruit of Citrus and Poncirus

Permalink https://escholarship.org/uc/item/3bg2q1fr

Journal International Organization of Citrus Virologists Conference Proceedings (1957-2010), 5(5)

ISSN 2313-5123

Author Olson, Edward O.

Publication Date 1972

DOI 10.5070/C53bg2q1fr

Peer reviewed

eScholarship.org Powered by the California Digital Library University of California PROCEEDINGS of the IOCV Stubborn Disease Symptoms in Grafted Fruit of Citrus and Poncirus E. 0. OLSON

THE TECHNIQUE (7) of grafting twigs USDA) 4475 citrumelo. Except for the bearing immature fruit into seedlings lemonquat, a hybrid of Texas origin, proved so useful in studying stub- the species and varieties have been born disease symptoms under con- described (7, 8). Fruiting twigs were trolled conditions that I pursued it taken mostly from virus-free nucellar further. Contrasted with the experi- trees; the Clementine mandarin tree ments in 1967-68, in which the test was infected with exocortis virus. conditions lacked uniformity and Madam Vinous sweet orange and emphasized comparisons between Duncan grapefruit seedlings, 30-45 normal and diseased fruit within va- cm tall and growing in 15-cm pots, rieties, the experiments of 1968-69, were grafted with single buds or side which are presented here, were con- grafts derived from plants infected ducted under reasonably uniform with stubborn virus. The usual virus conditions. They permitted better source in these trials was an 1 1-year- comparisons than the first trials. old Minneola tangelo nucellar seed- Tests were repeated with several ling tree severely affected by stub- varieties used in 1967-68, and 20 born disease. A few other stubborn- additional varieties were included. affected nucellar trees of recent origin also provided the virus. Inoc- Materials and Methods ulated seedlings showing the mot- Fruit-bearing twigs were obtained tled-leaf symptom of stubborn from the following: Moro, Pineapple, disease, a yellow and green blotch- Valencia, and Vaniglia Sanguigno ing differing from minor-element sweet orange; Redblush grapefruit; deficiencies (1, 5, 6, 91, were con- Owari satsuma; King mandarin; sidered to be infected. Changsha, Clementine, Dancy, and From late April to mid-July, 1968, ponkan mandarin; Minneola, Semi- twigs bearing young fruit of the dif- nole, and Thornton tangelo; Brazilian ferent varieties were collected and sour orange; chinotto; Rangpur grafted onto infected and normal lime; red shaddock; Eureka lemon; seedlings, with techniques previous- rough lemon; Mexican lime; karna; ly described (7). Grafts were consid- Palestine sweet lime; calamondin; ered successful if the fruit remained lemonquat; Rubidoux and Christian attached to the grafted stem for 30 trifoliate orange; Sacaton and CPB days. Fruit abscission occurring (Crops Physiology and Breeding, thereafter was attributed to the effect STUBBORN and RELATED DISEASES 7 of stubborn-virus infection unless absence of seed abortion. Only other causes were definitely impli- calamondin retained greened fruit cated. Observations and measure- in the absence of seed abortion ments include seed abortion, stylar- until harvest time; this variety was end greening, acorn shape, and the harvested in late October and may color of peel and albedo. Fruit of have been immature. each variety were harvested when Acorn-shaped fruit were common- normal fruit were well colored and ly found among mandarins on in- mature. fected plants; this symptom was All plants were grown in warm unusually well developed in the King glasshouses. Daily maxima of 32- variety. Someacorn-shapedand mal- 40°C prevailed for several hours, formed fruit were found in other se- and daily minima were mostly above verely affected varieties, and a trace 25OC except in the coldest months of acorn shape was seen in Eureka when the maxima were of shorter lemon. Blue albedo was observed duration and the minima were some- only in the peel of Thornton tangelo, times as low as 1 5-20 OC. Redblush grapefruit, and karna. On the basis of total symptoms, Results fruit of orange, grapefruit, tangelo, Results are summarized in Table 1 . and mandarin varieties were most Fruit grafted onto normal seedlings severely affected by stubborn dis- had typical numbers of good seed ease. The seed abortion, stylar-end and degreened normally, starting at greening, and acorn-shape symp- thestylarend of the fruit. The percent- toms were frequently combined in age of preharvest fruit drop of a mandarin fruit. given variety of fruit was often much Fruit of sour orange, shaddock, higher from infected plants than citrumelo, lemon, rough lemon, and from normal plants. The remaining lemonquat varieties, and of chinotto fruit on infected plants developed and karna, on infected plants showed stylar-end greening or failed to de- slight to severe seed abortion and green normally, and the seeds were often remained green instead of de- aborted. veloping normal peel color at matur- Complete seed abortion was the ity. They occasionally showed other most striking fruit symptom among symptoms of stubborn. varieties severely affected by stub- Symptoms of stubborn disease borndisease. Rarely, afew plump but were lacking in fruit of calamondin darkened seeds were found. Exces- and in the 3 lime and 2 trifoliate or- sive seed abortion also occurred in ange varieties, although fruit of some fruit varieties that did not show these varieties on infected plants well-marked external stubborn were smaller than those on healthy symptoms. Stylar-end greening de- plants. veloped less frequently than seed The time of grafting of fruit-bearing abortion; it was not found in the twigs affected the development of TABLE 1. PREHARVESTFRUIT ABSCISSION AND SEVERITY OF STUBBORN DISEASE IN FRUIT OF CITRUS AND PONCIRUS VARIETIES GRAFTED ONTO ORANGE OR GRAPEFRUIT SEEDLINGS WITH MOTTLED-LEAF SYMPTOM OF STUBBORN DISEASE^ Preha~e~t fruit abscission Grafted fruit harvested from infected plants

Stubborn- With With Fruit-bearing Date Normal affected aborted stylar-end Development scion of plants plants Harvested seed greening of typical variety grafting (%) (%) (no.) (%) (%) peel color Sweet orange Moro June 10 delayed Pineapple July 3 delayed Valencia April 29 delayed Vaniglia sanguigno June 7 delayed Tangelo Minneola July 22 delayed Seminole July 23 delayedb Thornton July 22 delayed Mandarin Clementine June 10 Clementine July 10 delayed Changsha July 6 delayed Dancy July 6 delayed King July 10 delayed Owari satsuma July 10 delayed Ponkan July 8 delayed Miscellaneous Redblush grapefruit May 22 delayedb CPB 4475 citrumelo May 1 normal Sacaton citrumelo April 29 normal Chinotto July 16 delayed Brazilian sour orange July 16 delayed Red shaddock May 22 delayed Calamondin June 10 delayed, Rough lemon May 21 delayed, Rough lemon July 16 delayed Lemonquat July 10 normal Karna May 24 nor ma^^'^ Eureka lemon May 20 normal Mexican lime May 20 normal Palestine sweet lime July 16 normal Rangpur lime July 16 normal Christian trifoliate orange April 29 normal Rubidoux trifoliate orange May 1 normal a. Fruit harvested from normal seedlings showed no symptoms of stubborn disease. b. Blue albedo was common in peel of indicated variety. c. There were originally 37 fruit but all abscised; of the 21 fruit in controls, none abscised d. Fruit resembled poorly grown fruit, not sharply dist~nctfrom normal fruit. STUBBORN and RELATED DISEASES 9 stubborn symptoms and seemed to normal peel color at maturity, which influence fruit drop. All Clementine is reported asasymptom of greening mandarin fruit dropped long before disease, occurred in conjunction harvest from twigs grafted to infected with seed abortion in all varieties, with plants on 10 June. On fruiting twigs the questionable exception of cala- grafted a month later, a few fruit re- mondin. Excessiveseed abortion was mained until harvest on diseased associated with acorn-shaped and plants; they developed severe symp- malformed or lopsided fruit in man- toms of stubborn disease. Rough darin and other varieties. lemon fruit on twigs grafted to in- Blue albedo is probably not a spe- fected plants on 21 May developed cific symptom of stubborn disease a high percentage of seed abortion (3) and is often observed in field- and stylar-end greening. Those grown fruit in the absence of exces- same symptoms were almost ab- sive seed abortion. Nevertheless, sent from fruit on similar grafts bluealbedoisfrequentlyencountered made 2 months later. in field-grown fruit on stubborn-af- fected trees of grapefruit, orange, Discussion and tangelo. The principal fruit symptoms asso- The responses of 29 citrusvarieties ciated with stubborn disease of citrus to stubborn disease agree with, and can be induced experimentally in extend the results of, the earlier report many varieties under controlled on this work (7). Fruit of Dancy, glasshouse conditions. Excessive Changsha, King, and ponkan man- seed abortion, stylar-end green- darin developed incontestable symp- ing, acorn shape, delayed or erratic toms of stubborn disease; fruit drop greening, and blue albedo are con- was not excessive on infected plants. sidered to be important symptoms of The fruit of these varieties are of me- stubborn disease. The specificity of dium size and not too heavy to sup- fruit symptoms has not been fully port themselves well on grafted established, butexcessiveseed abor- twigs. They normally produce large tion in normally seedy varieties (2) numbers of good seeds so that ex- appears to be a key symptom of stub- cessive seed abortion is conspicu- born disease and to have some influ- ous in affected fruit. These charac- ence on other fruit symptoms. Field teristics suggest that further trials observationsonexcessiveseedabor- should be made to test mandarin tion indicated that this condition was varieties as indicators of stubborn not associated with 6 other citrus disease; they are reported to be viruses, and it occurred in the present affected by most of the stubborn tests in the absence of other viruses and stubbornlike diseases of citrus (2). In experiments reported here, (4). stylar-end greening occurred only Time of grafting seemed to influ- in the presence of excessive seed ence fruit drop and development of abortion. Delayed development of symptoms of stubborn in Clementine 10 PROCEEDINGS of the IOCV mandarin and rough lemon fruit. The rapid indexing for this virus and in behavior of the varieties and earlier other studies of stubborn disease. observations (7) indicate that grafting The technique may enable further offruit-bearingtwigsshould be timed comparisons of the apparently re- to achieve good fruit retention and lated stubborn, greening, little leaf, maximum development of , symp- leaf mottling, and likubin (4). In all toms. Varietal differences in fruit re- these, the fruit develop one or more tention may influence the selection of of the symptoms associated with experimental materials. stubborn disease. This technique Grafting of fruit-bearing twigs onto may be valuable in studies on im- other plants to obtain fruit responses pietratura (lo), in which damage to to stubborn disease within a single fruit is a response to virus infection. season offers new possibilities in the Literature Cited 1. CALAVAN,E. C., and CHRISTIANSEN,D. W. citrus trees showing various symptoms 1966. Effects of stubborn disease on of stubborn disease, p. 1413-20. In H. various varieties of citrus trees. Israel J. D. Chapman led.), Proc. 1st Intern. Botany 15: 121-32. Citrus Symp. Vol. 3. Univ. Calif., River- 2. CARPENTER,J. B., CALAVAN.E. C., and side. CHRISTIANSEN.D. W. 1965. Occur- 7. OLSON,E. 0. 1969. Symptoms cf stubborn rence of excessive seed abortion in cit- disease in Citrus and Poncirus fruit rusfruitsaffected with stubborn disease. grafted onto virus-infected seedlings. Plant Disease Reptr. 49: 668-72. Phytopathology 59(2): 168-72. 3. CARPENTER,J. B., and HIELD, H. Z. 1958. 8. REUTHER,W., WEBBER,H. J., and BATCH- Accentuation of blue albedo in Marsh ELOR. L. D. (eds.). 1967. The citrus in- grapefruit by sizing sprays with 2,4,5-T. dustry.Vol. 1. History,world distribution, Plant Disease Reptr. 42: 63-64. botany and varieties. Univ. Calif. Div. ~.CHILDS,J. F. L. (ed.). 1968. Chapter 5:Stub- Agr. Sci., Berkeley. born, greening, and related diseases, 9. SALIBE, A. A., and CORTEZ,R. E. 1966. p. 105-76. InJ. F. L. Childs (ed.), Proc. Studies on the leaf mottling disease of 4th Conf. Intern. Organization Citrus citrus in the Philippines. FA0 Plant Pro- Virol. Univ. Florida Press, Gainesville. tect. Bull. 14(6): 141-44. 5. MCCLEAN.A. P. D., and OBERHOLZER.P. 10. SCARAMUZZI.G., CATARA.A. A,, and C. J. 1965. Greening disease of the CARTIA,G. 1968. Investigations on sweet orange; evidence that it is caused impietratura disease, p. 197-200. In J. by a transmissible virus. S. African J. F. L. Childs led.), Proc. 4th Conf. Intern. Agr. Sci. 8: 253-76. Organization Citrus Virol. Univ. Florida 6. OLSON.E. 0. 1969. Mottled-leaf symptom Press, Gainesville. on index plants graft-inoculated from