336 FLORIDA STATE HORTICULTURAL SOCIETY, 1970

Table 4. Total production in 1000 tons Table 5. Per capita fresh consumption

(estimateof 1971 crop) offruit in Israel in kgs.

Apples 65 Apples

Pears 40 Pears

Apricots 13 Apricots

European plums 4 Plums

Japanese plums 5 Peaches

Cherries 1 TOTAL

Peaches 17 areas above 2200 ft (mainly a sour cherry va TOTAL 145 riety: 'Chios'.) We have demonstrated that temperate zone deciduous fruits of acceptable quality can be (198/12) is one of our major peach varieties. grown in a subtropical climate of the Mediter Apricot culture is based practically on one ranean subtype, such as Israel's. Due to cold variety: 'Raanana', which is one of the best in storage facilities (mainly C.A.) there is a plen the world (it is suitable for fresh consumption, tiful supply of homegrown fruits throughout drying and canning). the year, tables 2, 3 and 4. There is no particular problem in growing Japanese plums. European plums are limited to areas at least 1800 ft above sea level. One LITERATURE CITED variety predominates: 'Sagiv' (probably iden 1. Weinberger, John H. 1969. The stimulation of dor mant peach buds by a Cytokinin. Horti-Science 4(2): 125- tical with 'Black Prince'). It lends itself also 126. to drying. Cherries are even more exacting in 2. Anon. 1969. Potassium nitrate (KNO3) a bud break ing spray. Volcani Institute for Agric. Research (Mimeo. their climatic requirements; they are limited to in Hebrew).

CITRUS CULTIVARS FOR THE TROPICS

A.H. KREZDORN not to geographical location. Undoubtedly, the most important climatic characteristic is tem Department of Fruit Crops IFAS perature. The lower limit for seed germination University of Florida and growth of citrus, the so-called vital tem Gainesville perature, is 55°F (15) ; however, it has been reported that it is doubtful whether an upper To discuss citrus cultivars limit is reached in the field (8). There are, of for the tropics, one must course, optimum temperatures that vary with define the term. Geographi the species and even with the cultivar (5, 6). cally, the tropics encompass Several researchers have related a heat index, the area of the world lying generally calculated by summing the mean tem between latitudes 23.5° peratures above 55 °F, to the performance of north and south of the equa various species and cultivars (1, 2, 15). Per tor. This definition is in formance has also been related to elevation adequate because there are because of its relation to temperature (14). many climates within the However, not only climate but also social cus geogpraphical tropics. Cul toms, taste preferences of different ethnic tivars respond to climate groups, and the intended use of the fruit must KREZDORN: TROPIC CITRUS CULTIVARS 337 be considered. It is within this framework that (anthocyanins) in blood oranges, so famous for varieties are discussed here. Conclusions are their quality in the Mediterranean, is inversely based primarily on limited literature and ob related to temperature (9). They do not de servations made in parts of the West Indies, velop the red pigmentation in the hot tropics northern South America, Central America and (14) or even in areas as cool as Florida. It is to a lesser extent some of the Pacific Islands. conceivable that cultivars of this group might find local areas of adaptation in the cool tropics The Grapefruit (C paradisi) but it is doubtful that they would achieve their peak of quality there. The grapefruit does well in both the hot, Navel oranges.—Cultivars in this group are humid and the hot, dry tropics, assuming1 appro very similar but selections vary appreciably as priate irrigation water is available in the latter. to date of maturity and fruiting. Quality is Its peak of quality is reached in such areas as superb; however, yields and quality are more Trinidad and Jamaica, which have long been greatly affected by climatic and soil features famous for the excellence of their fruit. The than any other sweet orange. Satisfactory yields quality of grapefruit is poor in the cool tropics are obtained only in the absence of severe physio but it is suitable for local consumption. logical stress. High temperatures and dry winds In some areas, unique conditions result in often result in severe fruit shedding (3, 5). mature fruit when there is no other fruit on the Fruiting is extremely poor because of Florida's major markets of the northern hemisphere. dry season, which includes the bloom and post- Grapefruit on the island of Dominica and at bloom periods. Navel oranges reach their zenith certain locations in Jamaica mature in the off in certain areas of California where the climate season summer months. Moreover, there are is cool and the moisture supply is adequate. several areas of the tropics where the bloom period could be regulated through irrigation and In the hot tropics, whether dry or humid, the off-season fruit produced. quality of the navel is atrocious. The peel is thick, the pulp dry and coarse, the color of both There are many grapefruit seedlings with peel and pulp very poor. However, in the cool, seedy fruit but excellent quality in the tropics; high elevations of the tropics, the quality is however, the seedless 'Marsh' does very well and superb and the color much better, even though should be the predominant variety of new plant ings. Various old varieties such as 'Silver Clus the deep orange peel color found in California is ter', including a seedless selection in Jamaica, not developed. It has long been suggested by observers in the tropics that navels should not be are grown in local situations, but with little justification. Few trees of red-fleshed grapefruit grown below an elevation of 1,000 meters. Re are found in the tropics; however, research has cently, data substantiating this has been re shown the development of red pigmentation ported (14). (lycopene) is enhanced by high temperatures (9, Even in those countries with low levels of 11). Thus, it would seem the red-fleshed grape income, the navels demand a high price on the fruit should do well in the hot tropics. local markets and they are highly recommended for the cool tropics. PUMMELOS OR SHADDOCKS (C. grandis) Round oranges.—Undoubtedly, the best round orange cultivar for the tropics is the 'Valencia'. The pummelos or shaddocks are found as Because of its high heat requirements, the 'Va seedlings throughout the tropics and they are lencia' matures prior to the development of a naturalized extensively in Jamaica. There is second crop in only the hottest regions (6). local utilization but a limited market. This Peel and flesh color is poor in the tropics, as with species attains its best quality in the hot tropics, all sweet oranges, although acceptable at higher and the introduction of some of the very fine elevations. It is doubtful that the 'Valencia' existing varieties, such as 'Pandan Wangi', could attain the natural peel color in the tropics 'Thong Dee' and 'Kao Phuang' (Siamese), that is required by major North American and should be made. European fresh fruit markets. However, the The Sweet Oranges (C. sinensis) fruit could be dyed, as are fruit of early matur ing cultivars in Florida and Texas. Also, the Blood Oranges.—The red pigmentation 'Valencia' attains a quality that is quite accept- 338 FLORIDA STATE HORTICULTURAL SOCIETY, 1970 able for processing. In Colombia, 'Valencia' commercial scale in Jamaica for many years oranges attain satisfactory quality from sea level where it colors well and withstands shipment to to 1,600 meters (14); however, observations in North American and European markets. dicate that at the warmer, lower altitudes qual 'Temple' is another natural hybrid from Ja ity is much inferior. Date of maturity varies maica that reaches its peak of quality in humid, greatly with temperature and in the tropics it subtropical Florida. It does not perform as well should be possible to maintain year-around pro in some of the drier areas although it is gen duction either through regulation of water or erally of acceptable quality. This variety also through planting at several elevations. merits widespread trial in the tropics. Early oranges, such as 'Hamlin' and 'Parson The 'Ugli' is a large mandarin hybrid occa Brown', which are low in sugar and acid even sionally shipped to the United States from Ja when at their best, do not do well in the tropics. maica. It is grown in Australia as 'Poormans The 'Pineapple', which is a selected seedling, does Orange' (3). It does best in the hot areas where reasonably well in the tropics and can be planted grapefruit is adapted. where an orange of this type is desired. Acid Citrus Mandarins (C. reticulata) Lemons (C. limon).—True lemons are not The mandarins are undoubtedly influenced planted widely in the tropics; however, they more by both temperature and humidity than should do well in both the hot and cool areas. any of the other species. Also, this group varies Lemons will grow better than most citrus in tremendously in shape, quality and date of ma cool areas, even though they are quite sensitive turity and might well be treated as several to frost; however, limited observation indicates species. that they also do extremely well in hot regions. The satsumas are perhaps the most important This species is very susceptible to the scab fun mandarin group because of the large number of gus (Elsinoe fawcetti) ; thus, it is likely that plantings in Japan. This excellent fruit is not production should be limited to dry areas in well adapted to the tropics but only to the north which scab is not prevalent. The standard varie ern part of the subtropics. Even in subtropical ties such as 'Eureka' and 'Lisbon' should do well. Florida, the fruit is of rather poor quality. How A few trees of the 'Meyer', a variety with a ever, fruit of passable quality is found in the wide range of climatic adaptation, is found in cool tropics. almost every tropical area. Trees of this variety The 'Ponkan' is undoubtedly the best quality should be removed immediately because they of tangerine for the hot tropics where it produces probably carry the tristeza virus and in some large fruit of excellent quality. However, the of the tropical areas tristeza is not found in peel of this fruit is so tender that it will not other cultivars. There are selections of 'Meyer' stand normal packinghouse handling and can be free of this disease that can be obtained from shipped only if carefully picked and handled. It Florida. 'Meyer' is not a true lemon and if used will not tolerate ethylene degreening. for lemon concentrate, peel oil of the true lemon The 'Dancy' has been observed doing well in must be added to give it the appropriate flavor. the hot tropics where it appears to color better The 'West Indian' lime (C. aurantium), also than most tangerines, provided it receives suffi called 'Key' and 'Mexican', is a true lime grown cient light. widely in the tropics and requires heat to develop There are also some mandarin hybrids that good fruit size. Large quantities of this fruit are well suited to certain parts of the tropics. are grown on the island of Dominica and in The 'Ortanique' originated in Jamaica as a certain parts of Mexico. The 'West Indian' lime chance seedling and is an outstandingly good is very susceptible to withertip (Gloeosporium fruit. It is easy to distinguish between 'Ortani- limetticoleum), which is much worse in humid que' and 'Temple' trees; however, the fruit of than dry climates. these 2 cultivars are very similar. The 'Ortani The 'Tahiti' (C latifolia) lime is a very large que' is a much better fruit than the 'Temple' in fruit of excellent quality. The 'Tahiti' is grown the cool areas of the Jamaican highlands. The primarily in Florida where it is better adapted 'Ortanique' should certainly be tested in all of than the 'West Indian' lime. It is not susceptible the cool tropics because it has been grown on a to withertip and only moderately susceptible to KREZDORN: TROPIC CITRUS CULTIVARS 339 citrus scab (Elsinoe fawcetti). It is adapted to ized for cooking purposes in much of Latin both the hot and cool tropics and can be grown America. The sour orange produces extremely better in very humid areas than can the 'Key' woll throughout both the hot and cool tropics. lime. It was once thought that the peel oil of Virtually no efforts have been made to select this cultivar was inferior to that of the 'West improved types and fruit from chance seedlings Indian' lime but recently buyers have been are found throughout tropical markets. Varia accepting 'Tahiti' peel oil in large quantities. bility is great and superior cultivars could One of the major reasons for the successful undoubtedly be selected. development of a 'Tahiti' lime industry in Flor Citron (C. medica).—Citrons reportedly will ida has been selection of budwood free of lime not withstand excessive heat (5); but this refers blotch, a genetic disorder. Lime blotch is noted more to exposure to the sun's rays than throughout the tropics and any commercial heat itself. Seedlings and cuttings of citrons are plantings should be based on wood obtained from found fruiting well in many areas of the tropics sources known to be free of this difficulty. but they appear particularly well adapted to the cool areas. Processing and marketing pose sep arate problems but production is feasible. The Acidless Citrus 'Corsican' is the citron of commerce and should The sweet lime (C. limettioides) is so insipid be tested along with other clones from the Med it is unappealing to North American palates but iterranean. the taste is pleasing to Arabic, Indian and Latin American populations. The Indian or Palestine Cultivar Improvement sweet lime is an important fruit and rootstock Plant breeding has resulted in tremendous in the near east and India. Seedlings of this species are very uniform and found throughout improvement in the yield and quality of many crops, such as wheat, rice and various vegetables. Central America in door yards, around cow pens and in some cases as escapes. There is a clonal In more recent years, even tree fruits such as selection, the 'Columbian' sweet lime, but no dis peaches and nectarines have been tremendously improved through classical breeding programs. tinct advantage has been noted for it. However, the combination of the prevalence of A very similar fruit which is often seen in Central America and the northern part of South nucellar embryony and juvenility in citrus has America is classified by some as C. limetta and limited plant breeding as a tool for improving grouped with the lemons (5). However, it is citrus. Improvement has been made primarily difficult to see how this fruit can be separated through the use of monoembryonic parents such from the sweet limes because of the many sim as 'Clementine', 'Temple' and the pummelos. ilarities. The limettas, also called sweet lemons, Several hybrids with 'Clementine' parentage have are grown in the Mediterranean area to some obtained commercial significance (12, 13) and an extent where some selections have apparently appreciable number of monoembryonic hybrids been made. In much of Latin America, this fruit resulting from pummelo x grapefruit crosses is known as limetta limon and thought to have have been developed (4). The latter might well therapeutic value. It grows very well at ex serve as sources of genetic material for further tremely high elevations. All of the sweet limes hybridization. or sweet lemons grow well throughout the hot A review of the origin of citrus varieties and cool tropics. shows quite clearly that most of those in exist It is doubtful that sweet limes will ever attain ence today have arisen either as selected chance prominence on the North American or European seedlings or mutations (5). In Japan, careful markets but they certainly are in demand in selection of satsuma mutants has resulted in a markets of tropical areas. series of satsuma cultivars varying as to date of ripening, quality and color. Mutations have also played an important role in the development Fruits Utilized for Their Peel of grapefruit and other grapefruit cultivars S our orange (C. aurantium).—The sour have been selected from chance seedlings. orange is grown widely as a rootstock but the All of Florida's important commercial orange fruit is seldom used in the United States. The varieties, except 'Valencia', have been obtained peel makes a superior marmalade and it is util from the thousands of acres of seedling 340 FLORIDA STATE HORTICULTURAL SOCIETY, 1970 citrus planted by early settlers. The navel 20 million citrus trees were lost (10). However, oranges, the original of which probably arose as the virulence of this disease in these areas seems a mutant, produces a large number of small to be related at least in part to an efficient vector, naveled mutants and numerous selections have the black aphid (Toxoptera citricidus). One sees been made on the basis of date of maturity and little if any evidence of tristeza in the Caribbean, fruitfulness. Less has been done with the 'Va Central America and the northern part of South lencia' which produces numerous mutants and America. Moreover, in areas such as Florida chimeras that could well be used in a program of where the virus is widespread, it has done only cultivar improvement. minor damage. Thus, sour orange must still be It would appear that, even though there is the recommended variety for much of the Ameri now much more monoembryonic citrus material can tropics and in Florida it has become more for use in plant breeding programs, the imme important than ever. Currently, there is no root- diate hope for cultivar improvement in the stock that will adequately substitute for sour tropics is through the careful selection of mate orange in tropical areas. rial from the many thousands of acres of sweet In subtropical areas the trifoliate orange orange seedlings growing as shade for coffee or (Poncirus trifoliata) and the citranges, hybrids in the wilds of the American tropics. Many of sweet oranges and trifoliate orange, show thousands of seedling sweet oranges and numer much promise as substitute stocks. However, the ous seedling grapefruit and mandarin trees were trifoliate orange grows poorly as a rootstock in noted in a trip down the Escondido River of the tropics. Nicaragua. It was obvious that there was an The 'Rangpur' lime (C. limonia), also known appreciable amount of variability in the fruit as 'Cravo' lemon in Brazil, grows well even in from the various trees. These differences in the presence of tristeza and merits further trial. cluded dates of maturity, color, fruit size and It does not produce fruit with as good quality even the occurrence of navels. The same is true as the sour orange but it is somewhat better than of trees being grown for shade in coffee planta that produced on rough lemon, which cannot be tions. However, careful trials must be developed recommended because of the poor quality fruit for it is extremely easy to mistake variation due it produces and its susceptibility to Phytophthora. to environment for true genetic differences. This However, 'Rangpur' is very sensitive to exocortis has been well demonstrated in studies of alleged and xyloporosis viruses. differences in red grapefruit selections where a Cultivars on 'Cleopatra' mandarins fruit too number of such selections were found to be poorly for general consideration. However, it might prove satisfactory for some of the man identical (7). darin hybrids. Fruit yields improve greatly after There are numerous pummelo trees on some islands of the Caribbean and there appear to be trees are 15 to 20 years of age. a number of natural hybrids growing as seed Nematode problems have not been thoroughly lings. This undoubtedly accounts for the de studied but, strangely, the tropical nematode velopment of such varieties as 'Ugli' in Jamaica. Radopholous similis, which caused spreading de In fact, the 'Temple' and 'Ortanique' could easily cline of citrus when introduced into Florida, ap be pummelo x mandarin hybrids. One also finds parently does little harm in the tropics. At least, trees declining in a manner similar to those in local varieties such as the 'Grenadine* in Granada Florida are not evident. Nevertheless, nematode that apparently arose in a similar fashion. resistance is a factor to be considered in select ing rootstocks. Rootstocks The rootstock problem is by no means solved One cannot completely discuss scion cultivars and successful growth of citrus in the tropics without taking rootstocks into account. Were it will depend upon the development of satisfactory not for the threat of the tristeza virus, sour rootstocks as well as the selection of appropriate orange would be the only reasonable rootstock for scion varieties. the American tropics. Cultivars budded onto this rootstock are of superior quality and the LITERATURE CITED root system is tolerant of Phytophthora. Tristeza 1. Bain, F. M. 1949. Citrus and climate. Calif. Citro- devastated citrus trees on this stock in Argen graph 34(9):382; (10):426. 2. Barnard, C. 1946. Climate and distribution of citrus. tina, Brazil, Paraguay and Uruguay. Reporterly, Jour, of the Australian Inst. of Agr. Sci. p. 134-138. SHEPHERD: BANANA CULTIVARS 341

3. Bowman, F. T. 1956. Citrus Growing in Australia. fruit and 'Ruby' blood oranges. Proc. First Int. Citrus Angus and Robertson, Sydney. 311 pp. Symp. 1:271-275. 4. Furr, J. R. 1969. Citrus breeding for the arid south 10. Moreira, S. and A. A. Salibe. 1969. The contribu western United States. Proc. First Int. Citrus Symp. 1: tions of research for the progressive changes in citrus 191-198. rootstocks. Proc. First Int. Citrus Symp. 1:351-364. 5. Hudgson, R. W. 1967. Horticultureal varieties of 11. Purcell, A. E., R. H. Young, F. F. Schultz, Jr. citrus. Chap. 4 in The Citrus Industry, Vol I, History, and F. I. Meredith. 1968. Influence of age on lycopene con World Distribution, Botany and Varieties. Ed. by W. Reu- centration in colored fruit. Proc. Amer. Soc. Hort. Sci. ther, H. J. Webber and L. D. Batchelor, Univ. of Calif., 92: 170-178. Div. of Agr. Sci., Berkeley, Calif. 12. Reece, P. C. and F. E. Gardner. 1959. 'Robinson', 6. Jones, W. W. 1961. Environmental and cultural fac 'Osceola' and 'Lee'—new early maturing tangerine hy tors affecting the chemical composition and physical char brids. Proc. Fla. State Hort. Soc. 72:48-51. acters. Chapt. 2 in The Orange — Its Biochemistry and 13. , C. J. Hearne and F. E. Gardner. 1964. Physiology. Ed. by W. B. Sinclair, Univ. of Calif., Div. 'Nova' tangelo — and early ripening hybrid. Proc. Fla. of Agr. Sci., Berkeley, Calif. State Hort. Soc. 77:109-110. 7. Krezdorn, A. H. and N. P. Maxwell. 1959. Fruit 14. Reuther, W. and D. Rios-Castano. 1969. Comparison quality study of eight strains of red eshed grapefruit on of growth maturation and composition of citrus fruit in two rootstocks. Jour, of the Lower Rio Grande Valley subtropical California and tropical Colombia. Proc First Hort. Soc. 13:54-58. Int. Citrus Symp. 1:277-300. 8. Mendel, K. 1969. The influence of temperature and 15. Webber, H. J. 1948. Plant characteristics and light on the vegetative development of citrus trees. Proc. climatology. Chapt. 1 in The Citrus Industry, Vol. I, His First Int. Citrus Symp. 1:259-265. tory, Botany and Breeding. Univ. of Calif. Press, Berkeley, 9. Meredith, F. I. and R. H. Young. 1969. Effect of Calif. temperature on pigment development in 'Red Blush' grape

A SURVEY OF MAJOR BANANA CULTIVARS

K. Shepherd In the main stream of cultivars, it seems certain that the most ancient ones were diploid Banana Breeding Research Scheme, forms of the wild M. acuminata (2n=22). Many Banana Board, Jamaica such clones still exist in banana cultures but only one, 'Sucrier' or 'Honey' or 'Pisang mas' (Sim- A banana cultivar for monds 1966) has a worldwide tropical distribu the purposes of this review tion and a popularity on many local markets for is defined as a clone bearing its extreme sweetness. parthenocarpic, normally Three other major factors have contributed to seedless fruits, which are the diversity of the present day, of which the edible in greater or lesser first in order of importance is that early diploid degree. The fruits may be cultivars were not necessarily totally sterile but considered edible when ripe set at least some seeds by natural pollination. and raw or they may be On experimental evidence with existing cultivars eaten only after cooking, and breeding lines, a very small proportion of in either the green or ripe any plants arising from such seeds would be state (or they may even be triploids. This is the likeliest origin of the fermented). Further, there is a recent trend in triploid cultivars which, over the course of many some countries to use bananas as raw materials centuries, have come to predominate in most if for processed food products, although the culti not all banana cultures. vars involved have other, more direct uses. The second factor was hybridisation of early The cultivars of the world are very numerous cultivars with another wild species, M. balbis- and as yet so poorly studied and compared that iana, giving rise not only to hybrid diploids it is impossible even to make a good guess at the which are now rare but ultimately to hybrid total number of distinct clonal stocks in exist triploids by the process already mentioned. For ence. Important centres of diversity include East convenience, we can classify cultivars as com Africa, India, Malaysia and Indonesia, New binations of haploid chromosome sets A=M. Guinea and the Philippines. acuminata and B=M. balbisiana. Hence the Parthenocarpic forms have arisen in two re diploid and triploid M. acuminata cultivars are mote sections of the genus Musa, but those allied respectively AA and AAA, the hybrids are AB, to Musa textilis (Manila hemp) are of minor im AAB and ABB. Another species, M. schizocarpa portance and will not be further discussed. has also intervened in New Guinea (Hutchison