banana genética

8/7/2019 banana gentica

1/6

370 Bananas

Condit, I. J. (1955). Fig varieties: a monograph. Hilgardia23, 323-538.

Ferguson, L., Michaldes, T. and Shorey, H. H. (1990).The California fig industry. Horl. Rei'. 12, 409-90.

Galil, J. and Neeman, G. (1977) Pollen transfer andpollination in the common fig (Ficus carica L.). Neli'Phytol. 79, 163-7l.

Serafimova, R. (1980) The fig o C. G. Danov, Plovdiv.Bulgaria. (Bulgarian with English sumrnary.)

Stagcr, L. E. (1985) First fruits of civilization. In 1. N. Tubb(ed.), Palestine in lhe Bronze and Iron Age: papasin honour o] alga Tufnell. Institute of Archacology.London, pp. 172-87.

Storey, W. B. (J975) Figs. In 1. Janick and 1. B. Moore(eds), Advances in [ruit breeding Purdue Univ. Press.pp.568-89.

Storey, W. B. (1976) Fig. In N. W. Simmonds (ed.),Evolution of crop plants. Longman, London, pp. 205-8.

Valdeyron, G. and Lloyd, D. G. (1979) Sex differencesand flowering phenology in the common fig Ficus carica.Evolution 33, 673-85.

Zohary, D. and Hopf, M. (1993) Domestication of plants inlhe O/d World, 2nd edn. Oxford University Press.

Zohary, D. and Spiegel Roy, P. (1975) Beginning of fruitgrowing in the Old World. Science 187, 319-27.

. .

72BananasMusa (Musaceae)

N. W. Simmonds9, Mclaren Road, Edinburgh.Formerly University of Edinburgh School ofAgriculture

Introduction. The bananas are large, stcoling, herbaceous perenniaJplants which are propagated vegetativcly by meansof corms. The basal corms are surmounted by'pseudostems' of leaf sheaths. Inflorescences areterminal and are initiated near ground leveI, beingthus thrust up the centre of the pseudostem byelongation of the true stem. Basal flower clustersare female and persist through growth to form thefruit bunch; distal flower clusters are male and theflowers and bracts that subtend them are commonJydeciduous.

The first ('plant') crop is taken about a year afterplanting; it is followed by the first ratoon and,thereafter, with regular pruning of excess suckers,cropping becomes more or less continuous. Fruitbunches are generally harvested unripe and ripenedunder cover or, in the case of exported fruit, aftermore or less prolonged refrigerated transport. Thebananas are tropical by origin and are intolerant offrost. In cultivation they are distributed throughoutthe warmer countries and hardly transgress 40 N andS latitudes. In the tropics proper they constitute amajor local foodstuff (e.g. in East Africa) as well asproviding the basis for an important export trade totemperate countries. World production is estimated tobe about 20 Mt of which about 15 per cent enters theexport trade. For general treatment of the bananas asa crop see Stover and Simmonds (1987).

Cytotaxonomic backgroundThe wild bananas are alI diploid and are distributedin Southeast Asia and the Pacific (Table 72.1, reviewin Simmonds, 1962). There are also a few (three to

- - - - - - - - - - - - - - ~ - - - - - - - - -


2/6

Bananas 371

Table 72.1 Classification of the bananas.Section Basic x RemarksEumusa 11 13-15 species, Southeast

Asia, including Musaacuminata andM. balbisiana, probably twosubgroups5-7 species, Southeast Asia5-7 species, New Guincaarea6--10 species, Southeast Asia

RhodochlamysAustralimusa

11!O

Callirnusa 10

five) more species of uncertain affinity of which twohave different chromosome numbers (2n = 2x = 14,18). The related Ensete has 2n = 2x = 18 and isdistributed in tropical Africa and Southeast Asia.Recent numerical-taxonomic study (Simmonds andWeatherup, 1990a) has suggested two subgroups ofEumusa, one of which is rather near systematicallyto Australimusa. More research is needed.

The vast majority of cultivated bananas (theEumusa cultivars) originated from Musa acuminataand M. balbisiana so have chromosome numbersbased on 11 (22, 33, 44). The small and unimportant(but extraordinarily interesting) Fe'i group of cultivarshad a quite independent origin from species ofAustralimusa and are diploid with 2n = 2x = 20(Stover and Simmonds, 1987, Ch. 5).

Two other members of the group are of someeconomic importance. First Manila hemp, long asource of marine cordage, derives from the sheathfibres of abaca, M. textilis. This species, a memberof Australimusa with 2n = 2x = 20, is native to andwas cultivated in the Philippine Islands and Borneo.It has been but little bred and there is no evidencethat cultivars are significantly removed from their wildprogenitors. The crop is now virtually extinct. Second,Ensete ventricosum, native to upland East Africa, haslong been cultivated in the highlands of Ethiopiafor pseudostem starch and fibre. Again, though theagriculture is an ancient one, there is no evidencethat the species has evolved in cultivation. But it is afascinating and beautiful crop (reviews in Simmonds,1958; and Taye Bezuneh and Asiat Felleke, 1966).

The rest of this chapter is devoted to the fruit-bearing Eumusa cultivars.

Early historyThe key to the understanding of banana evolutionlies in the analysis of parthenocarpy and sterility inthe edible diploids. Wild banana fruits are trilocularberries in which the seeds are surrounded by a massof sweetish-acid. starchy, parenchymatous pulp. Ifunpollinated, ovaries generally swell slightly andremain a persistent empty shells. Fruit growthis propoitiohal to seed content and it is clearthat the growth of pulp depends upon a stimulusfrom the developing seeds. By contrast, in ediblebananas, the stirnulus to pulp growth is autonomous;seeds are unnecessary (though, if present, theydo further stimulate fruit growth). Genetic studiesshow that the autonomous stimulus that culminatesin vegetative parthenocarpy is due to several (atleast three) cornplementary dominant genes whichare present (though of unknown distribution) inwild forms of M. acuminata. They also show that itis possible to have thinly parthenocarpic fruits whichare (more or less) edible if unpollinated but heavilyseeded if pollinated. The typical seedless ediblebanana is therefore a product of two evolutionaryprocesses: parthenocarpy and sterility, both essential.

Sterility in the edible diploids is basically geneticfemale sterility, as inferred (though not preciselyanalysed) from breeding experiments. Thus manyfernale-sterile but male-fertile edible diploids, naturaland experimental, are known. In addition, gameticsterility, manifest in both ovules and pollen, is oftensuperimposed; it has been caused by the carryingover from wild ancestors and the accumulation duringclonal existence of structural chromosome changes(inversions and translocations).

Edibility evolved first in wild M. acuminata. Thespecies is very variable and taxonomic evidenceindicates that the primary centre was the Malaypeninsula (possibly including closely neighbouringterritories). With high probability, several subspeciescontributed and human selection favoured partheno-carpy, structural heterozygosity and seed sterility,leading to the production of edible seedless fruits,followed by male sterility consequent upon structuralheterozygosity. Edible diploids are still widely but


3/6


4/6

Bananas 373

Fig. 72.2 Evolutionary geography of the bananas, Musa.and the Pacific islands. They are diploids with2n = 2x = 20 (so far as is known) and, pheno-typically, clearly belong in Australimusa, with thewild New Guinea species M. maclayi as a very likelyprogenitor. An independent origin of edibility mustbe inferred.

Recent historyBy the end of the sixteenth century, bananas werewidely spread throughout the tropics. Relatively fewclones had moved out of the centre of origin inSoutheast Asia and this pattern persists today;diversity declines in the sequence Asia-Africa-America.

The banana export trades developed mainly intropical America in the later nineteenth centuryand have depended for 100 years on remarkablyfew clones, ali triploids (AAA), namely: Gros Micheland various mutant members of the Cavendish group.These are well adapted to large-scale cultivation andocean transport to distant markets, but are susceptibleto certain diseases (review inWardlaw, 1961). Indeed,bananas constitute one of the best examples in thehistory of agriculture of the pathological perils ofmonoclone culture,

Gros Michel is susceptible both to Panama disease(banana wilt) caused by Fusarium oxysporum f.cubense and to leaf spot (Sigatoka) caused byMycosphaerella musicola which appeared in the

New World in 1933. It is, however, rather tolerantof (maybe not resistant to) the burrowing nematode,Radopholus similis. The Cavendish group of cultivarsis resistant to most Fusarium isolates but verysusceptible to leaf spot and nematodes. Leaf spotcan be controlled by spraying and nematodes byfumigation. Panama disease is uncontrollable in asusceptible variety and this fact provided the stimulusfor banana breeding. In recent decades, the diseasesituation has worsened with the spread of bacterialwilt (Pseudomonas solanacearum), black leaf streak orblack Sigatoka (Mycosphaerella fijiensis) and bananabunchy top virus, as well as of nematodes and newstrains of Fusarium.

Banana breeding began in Trinidad and Jamaica inthe early 1920s and has continued in the Caribbeanever since, with the development of a strongprogramme in Honduras from about 1960. This workwas ali directed towards export clones and, thoughcommercially unsuccessful, laid the necessary basesof scientific understanding. Reviews will be found inRowe and Richardson (1975), Rowe (1984), Stoverand Simmonds (1987), Rowe and Rosales (1993).

Essentially, the approach ultimately developed hasbeen first to breed edible diploids (AA) which werevigorous, productive, female sterile , male fertile anddisease resistant. These are crossed as males onto the disease-susceptible but otherwise acceptableGros Michel (AAA). Gros Michel is, if pollinated,very slight1y seed fertile and, -with much labour anddifficulty, progenies can be built up. About one-third


5/6

374 Bananas

Heptaploids6A'+Aandaneuploidsdisearded

Potentialsting I ~ eommereialclones

Wild acuminata t------,AA

I Edibl~~plOidS

Primarytetraploids3A'+A

Seeondary Itriploids t---~Selection and te2A'+A .Fig. 72,3 Summary of banana breeding.

of the seedlings are tetraploid (AAAA), the productsof female restitution (33 + 11); miscellaneous aneu-ploids, heptaploids (33 + 33 + 11 = 77) and otherhigh polyploids are discarded. In practice, tetraploidsfrom Gros Michel are toa large and, since about1960, its semi-dwarf mutant Highgate has beensubstituted for it. Fortunately, the mutation behavesas a dominant with good penetrance in tetraploidprogeny, so attractive semi-dwarfs result.

Early results (1930s and 1940s) were unpromisingin that, though disease-resistant clones with quitegood bunches were produced in some .iurnbers, theywere not good enough and none was successful.The move (1940s onwards) to improve the maleparents resulted in better bunches but worse diseaseresistance. From the 1970s onwards, some reallyoutstanding diploid male parents were produced by

." the Honduras programme and knowledge of diseaseresistance improved greatly (Rowe and Rosales,1993). But disease problems have grown and demandson the breeder have increased. ln the longer run, theultra-conservative trades will probably have to changetheir habits and grow new clones if they are to surviveat all; they used to say that they could not growCavendish dones! Some day, the need to reinstateserious commercial banana breeding programmes(not mere 'projects') will become apparent.

Hybrid clonesAAB, ABB, etc.

Complexerossingsystems

Highgate, GrosMichel A' A' A'

New cookingbananas

eomplex AIBhybrids

An important recent event, with implications forlonger-term banana evolution, was the foundationof the lnternational Network for the lmprovementof Bananas and Plantains (INIBAP, 1984). INIBAPis devoted to research on bananas as an importanttropical food crop and a substantial commitment tothe breeding of hybrid (AAB, ABB and 4X) clonesis thereby implied (Fig. 72.3 and see Persley andDe Langhe, 1987). Thanks to the earlier breedingstudies, the scientific bases of such breeding are fairlyclear. Rowe (in Jarret, 1990) gives a good accountof the current 'state of the art' and the prospectspresented by Rowe and Rosales (1993) seem evenmore attractive. There is a substantial food cropprogramme being developed at the Internationallnstitute for Tropical Agriculture (IIT A) Nigeria.

ProspectsGenetic resource conservation of the crop has beenpursued fairly vigorously for many years and quitegood collections are in hand, spread over severaltropical sites (Williams, in Persley and De Langhe,1987, review). As indicated above, banana breedinghas already enhanced banana evolution by theaddition of a new group (AAAA) and undoubtedly.

--------------------------------------------~


6/6

has the potential to go much further along the sameline , to add new triploids (AAA) and imrneasurablyto enhance the supply of vigorous. discase-resistant.polyploid. hybrid (A/B) clones for local food pro-duction. In the not-so-long run, even the bananatrade will have to change its habits and the fact thatthe international agricultural research system at lastrecognizes bananas as a vcry important food crop iscncouraging.

References.larret, R. L. (cd.) 1990) Idcntification of genctic diversitv

in lhe genlls Musa . INIBAP, Montpellier , France.Persley, G. J. and De Langhe, E. A. (eds) 1987) Banana

and plantain breeding strategies . AClAR. Canberra ,Austrlia .

Richardson, D. L., Hamilton, K. S. and Rowe, P. R.(1965) Notes on bananas 1. Natural edible tetraploids.Trop. Agric. Trin. 42, 125-37.

Rowe, P. R. (1984) Breeding bananas and plantains. PlantBrdg. Revs. 2, 135-55.Rowe, P. R. and Richardson, D. L. (1975) Breeding bananasfor disease resistance, [ruit quality and yield, SIATSA, LaLima, Honduras, BulI. 2, pp. 41.

Rowe, P. R. and Rosales, F. E. (1993) Bananas andplantains. ln J. L. Janick and J. E. Moore , (eds),Advances in [ruit breeding ; 2nd edn , in preparation.Portland, OR o

Shepherd, K. (1957). Banana cultivars in East Africa.Trap. Agric., Trin. 34, 277-86.

Simmonds, N. W. (1958) Ensete cultivation in the southernhighlands of Ethiopia; a review. Trap. Agric. Trin.35,302-7.

Simmonds, N. W. (l962) The evolution o] lhe bananas,London.Simmonds, N. W. and Weatherup, S. T. C. (1990a)

Numerical taxonomy of the wild bananas. New Phytol,115, 567-71.Simmonds, N. W. and Weatherup, S. T. C. (1990b)

Numerical taxonomy of the cultivated bananas. Trap.Agric. Trin. 67, 90--2 (and erratum slip in same journal,67,287, 1990).

Stover, R. H. and Simmonds, N. W. (1987) Bananas, 3rdedn. London.Taye Bezuneh and Asiat FeIleke (1966) The production and

utilization of the genus Ensete in Ethiopia. Econ. Bot.20,65-70.

Wardlaw, C. W. (1961) Banana diseases, London.

"'mli ...

73CloveSvzygium aromaticum (Myrtaceae)

N. BermawieRcscarch Institute for Spices and Medicinal Crops,Bogor. IndonesiaandP. A. PoolLondon, England

IntroductionThe cloves of commerce are the dried unopenedftower buds of the clove tree. These are used whole,shredded or ground as a spice for f1avouring food.C10ve oils, obtained by distillation of the driedftower buds, flower bud stems or leaves, are usedin the pharmaceutical and perfume industries, and inmicroscopy. C10ve oil was formerly used to produceartificial vanillin, but this is now obtained from othersources.

However, mostcloves produced today are used inkretek cigarettes, which contain tobacco mixed with30-40 per cent by weight of dried and shredded c1oves.Production and consumption of kretek cigarettes areparticularly associated with Indonesia, and the steadygrowth of the kretek industry has made lndonesiaboth the world's largest producer and the world'slargest consume r of cloves. lndonesia began a majorclove replanting programme in the 1960s in orderto achieve self-sufficiency and this, combined with adecline in production in Zanzibar and the MalagasyRepublic, has moved Indonesia from third to firstplace among clove-producing countries.

The decline of clove production in Zanzibar maybe attributed to politically inspired changes and alsoto sudden death disease (Purseglove et al., 1981).A different problem, Sumatra disease, has killedthousands of clove trees in Indonesia and causesannual losses estimated at f25 million. In 1986,world annual production of cloves was estimatedto be 55,000-60,000 t, Indonesia's annuaI productionwas.estimated to be 35,000-40,000 t and Indonesia'sannual consumption was estimated to be 45,000-

i,~"

"i:1 ;1. !

banana genética

Documents

Transcript of banana genética