Nearly every one of us who is fond of growing tropical fruits is equally fond of eating them. With few exceptions, most of us have our favourites. (Tom Economou from Miami, who has been a regular presenter to the Tampa Bay RFCI, claims his favourite is whichever one is at hand.) Within each of our favourite fruit types there is often a particular variety, which we choose over all others.
This favorite variety is propagated vegetatively. If it were not for the ability to produce new plants via cuttings, air layering, tissue culture, and especially, grafting, there would be no favourite varieties of a given fruit, only a hodgepodge of trees all belonging to the same species but distinct from each other in one or more characteristics, often including the quality of their fruits.
But where do these cherished varieties come from? There are 2 main ways in which they develop: through bud sports and from seedlings.
Bud sports arise from established trees, when a branch appears bearing fruit (or other characteristics, e.g., leaf size, shape or colour, thornlessness) different from the remainder of the tree. This occurs when a bud meristem cell undergoes a genetic mutation which is passed on to all of its descendent cells which, in turn, produce the new branch. If these new characteristics are deemed superior to the old ones, then the aberrant branch is used to propagate new plants vegetatively.
Bud sports occur in all types of fruiting trees, but are more commonly encountered in some than in others. A good example of trees which frequently produce bud sports is citrus. Thus, on an orange, lemon, lime, or grapefruit tree of standard variety, a limb may appear which has variegated leaves, thornless limbs, cold resistance or fruit which is larger, sweeter, acidless, seedless or different in colour. The naval orange was discovered as a bud sport on a seeded orange tree, and the car car (red navel) was a bud sport of a standard naval.
However, most new fruit varieties are produced by growing seedlings, and selecting those of the best quality. Sometimes these seedlings are produced through a concerted effort of breeding varieties together and then selecting those having the most desirable characteristics. The Arkin carambola was developed in this way. A breeding effort may even involve the hybridization of two or more different species. Probably the best examples are again found in citrus: thus we have many varieties of tangelos (=tangerine x grapefruit), tangors (=tangerine x orange), limequats (=lime x kumquat), citrangequat (=citron x orange x kumquat), to name a few. Another example is the atemoya (=sugar apple x cherimoya), which many favour as the best of the annonas.
When species are successfully hybridized, the offspring may show a huge diversity of characteristics ranging from all of those of one parent, through various combinations of both parents, to all of those of the other parent. Thus, a cross of tangerine and grapefruit has produces tangelos as different as very different from what is desired. (A college biology professor relayed a story to me of an attempt by a Russian geneticist to produce the perfect food crop in which the entire plant is edible. He crossed a cabbage with a potato, expecting to get a plant which was cabbage above ground and potato below ground. He did succeed in his cross, but the offspring he obtained was potato above ground and cabbage below ground! As this was anecdotal rather than referenced, I don't know if the story was based in fact, but it illustrates my point well.)
Many excellent fruit varieties have been produced through the chance production of seedlings which may appear under or near an established tree from rotting fruit, or after fruit consumption by an animal, including humans. A little old lady in Australia through an apple core in her yard and a few seedlings grew there. One of those seedlings produced the first Granny Smith apple!
Herein lies the main message I wish to convey to you. Whenever you are enjoying a bounty of fresh exotic fruit,
Reserve a place in your yard for growing seedling trees. Share the extra seedlings with your friends and neighbours. Give them to other RFCI members. You may produce the next "Arkin Carambola" or "Granny Smith Apple"!
In our yard, we have an orange tree which produces large, juicy, sweet oranges which are nearly seedless. We use the fruit to make gallons of delicious, beautifully-coloured juice as good as that of Valencia oranges. And the fruit ripens nearly two months sooner than our Valencias do. This tree grew from a seedling I found growing next to a campsite in the woods about 20 years ago.
To grow fruit from seedlings takes a good deal of patience. A citrus seedling may take 10 years or more to bear fruit. However, there are exotic fruits, which don't take anywhere near that length of time. Cashews often flower within a year, papayas a little longer. Most of the Eugenia species, passion fruits and annonas, among others, take only three to four years to bear fruit. The rewards can be well worth your patience.
Growing seedling trees doesn't require as much room as you would need for the varieties you favour. You can grow them in relatively crowded conditions. Since many won't meet your expectations they would only be grown until they begin fruiting, and then can be removed, while those you wish to keep growing and producing can be moved to a permanent location.
There is something extremely satisfying about eating a fruit picked from a tree you have nurtured since germination. Besides, wouldn't it be great if everyone favoured a fruit variety named after you?
DATE: August 1999
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