Variation of Apples

Inheritance versus environment

The quality and characteristics of an apple will depend on two factors: the genetic inheritance of the apple and the environment in which the apple was grown.

1. Imagine two identical apple trees. One is in a sheltered orchard with fertile soil, well-cared for and easily pollinated because there are lots of bees and other apple trees nearby. The other tree, although of the same type, stands alone, on poor soil, perhaps on a cold and wind swept hill. It is not fertilized or cared for. Which apple tree do you think yields more apples? Which apples will be larger and healthier?

2. The second factor influencing the characteristics of an apple is its genetic make-up, its particular variety. Go into any food shop and you will find a number of different apple varieties. Some are green, some red, some sweet, some tart. Genes pass characteristics from one generation to the next.

What species of plant is the apple tree?

Classification of Plants

(with kind permission of Gerald Dawe)

Different varieties of apple

apple tree - variety Lizzy

Apples are used not only for eating but also for cooking, baking and making juice, cider and vinegar. Not every variety of apple is suited to all the demands made by these various processes. That is why there is no such thing as the “ideal apple”. You can’t make cider out of dessert apples and you certainly would not want to eat a cider apple! Over the years a number of varieties have been created to satisfy the needs of the consumer and producer.

As long as 4000 years ago people were growing apples in the Middle East. It was the Romans who brought apple trees to Britain. Since then a number of varieties have been imported into the UK at different times. The National Fruit Collection with over 30 acres of orchards and the largest collection of apples in the world with more than 2100 distinct varieties is in Brogdale, Kent. [Visits can be arranged: Brogdale Horticultural Trust, info@brogdale.org.uk]

Until the last hundred years or so, apple growers selected trees that were successful. If a naturally occurring apple had the qualities a grower wanted, he chose to propagate it. If you were lucky a chance seedling would do particularly well in your orchard.

It is only since the discovery of the rules of genetics and the biology of variation that serious apple breeding has been able to develop.

Questions: Which two factors influence the quality and characteristics of an apple? When were the first apple trees planted in Britain? How many different varieties of apple are in the National Fruit Collection? Why do we need different varieties of apple?

 

How are new apple varieties cultivated?

Apples are flowering plants (see plant classification) and have flowers containing reproductive organs. Pollen is carried from one tree to another by insects (bees or bumble bees) or the wind. To aid in the pollination process colonies of bees are often brought into orchards.

The pollen grains germinate on the stigma, send a tube down into the ovary and fertilize it. However, the fertilized flowers can only produce apples if other conditions are met. During the blossom period apple farmers hope for warm weather. The most successful orchards are situated in a sheltered position and sometimes even windbreaks are built.

Another problem is that some apple varieties will fertilize by their own pollen, whilst others need pollen from a different variety. That is why orchards contain trees of different varieties. (Also, having trees that crop at different times can help with the harvest and storage of the apples, but pickers must be careful if some apples have to be picked separately. Mechanical picking becomes very difficult if there are too many different varieties in the same row. The same applies to the pruning process)

I. Variation through Mutation

Mutations can occur naturally at random. Radiation, such as x-rays and gamma rays, and some chemical exposure can also cause mutations.

Traditionally apple varieties were bred from naturally occurring mutations. However, as we will see further on, some pomologists are experimenting with mutation created through irradiation.

New apple varieties created by mutation are called “mutant” or “sports”. The apple variety Cox’s Orange Pippin, for example, has more than ten sports (Cherry Cox, Cox Red Sport, Crimson Cox, King Cox…) Often the sport is merely a better colour than the parent, but sometimes there can be a real improvement in other characteristics as well.

II. Variation through Selective Breeding

Seedlings

The second way of creating new varieties is with specially selected and grown seedlings. This kind of research was conducted by LARS (Long Ashton Research Station), which unfortunately has now had to close due to lack of funding. Liz Copas and colleagues created a whole series of new cider apple seedlings.

Apple varieties have always had interesting names (such as Granny Smith, Prairie Spy, Polka, Monarch, Mollie’s Delicious, Fairie Queen, Leatherjacket, Red Army, Winter Peach…), so it was fun to find out how the research team decided to name their new varieties. They primarily opted for the first names of people involved in the project, such as “Gilly”, “Vicky”, “Willy”, “Angela”, “Jean”, “Fiona”, “Debbie”... The only two exceptions were “Prince William” and “Hastings”. The latter because the tree was number 66 in row 10 (Battle of Hastings 1066!)

variety Prince William	variety Lizzy	variety Vicky

What are some of the criteria pomologists (apple scientists) look for when developing a new variety?

• Taste and flavour

• Texture

• Yield

• Cropping period (an apple grower would have trouble with man power if all his apples were ripe at the same time)

• Appearance (unfortunately many retailers choose to promote attractive looking apples over ones that actually taste good.

• Shape and vigour of tree

• Length of storage life

• Resistance to diseases: ( there is an increasing demand for organically grown fruit )

• Resistance to pest: pesticides are expensive

Early research into cider apple varieties:

In the mid-19^th Century the Royal Horticultural Society started awarding prizes to encourage the creation of new apple varieties. It was soon realized, however, that individual growers had to concentrate on production and specialist fruit growing research stations were started.

It takes a long time to develop a successful new variety of apple. You have to develop a sophisticated method of observation and propagation. (If you want to read more about the growing and propagating of apple trees click onto the following link: …)

Variety Trials:

Until the 1930s cider apple growers did not normally apply insecticidal and fungicidal sprayings. It was noted that the yields were far lower for cider apples than for eating apples grown by commercial growers with the aid of agro-chemicals. The researcher C.Savidge observed numerous apple trees in an experimental orchard in Burghill, Herefordshire. He wanted to study the cropping periods of a number of common cider apply varieties and their resistance to disease and pests.

He had planted 25 varieties in a specially laid out orchard and very systematically applied a number of different disease and pest control techniques. He observed this orchard for a period of 30 (!) years and published his findings in an article in 1938. (“An Investigation into the behaviour of certain cider apple varieties”, Journal of the Ministry of Agriculture, C. Savidge, 1938.)

Obviously soil type and climate come into the equation, but research like that helps to isolate the most successful varieties with regard to the factors studied. It is very important that the grower plants the right kind of trees as an orchard keeps producing for several decades and is a huge financial investment. Orcharding is not like potato growing where you can change the variety of potato from one year to the next.

But other qualities, apart from disease and pest resistance are important too:

In the 1950s the Long Ashton Research Station identified a list of varieties that could be grafted to bush rootstocks, which would reduce the planting distances between trees and make mechanical harvesting easier. 

Organic Apple Orchards:

Variety trials for organic growers have not been going on long enough in Britain to be of use to local growers. For apples to be considered organic, many chemical insecticides and fertilizers are forbidden. It is therefore extremely important that organic growers choose varieties that are resistant or show tolerance to pests and disease (especially scab and powdery mildew). They should also have a flowering period to avoid frost, cope well with competition for nutrients and water and have good eating and storage qualities.

The latest research methods:

The latest research methods involve highly sophisticated laboratory work in sterile conditions. There is much debate whether some of these methods are ethical or desirable.

Micropropagation:

Plant tissue culture is a method of cloning plants. A cutting is taken from a suitable plant, sterilised in bleach solution and transferred to a jelly (agar) containing nutrients and hormones. Roots and shoots develop and you get a new genetically identical plant. This new plant can then be grown on in compost.

This method is used to produce virus free apple trees. The virus moves about in the sap stream, but takes longer to reach some parts of the tree. In most virus infected trees there is one tiny part that remains free of the virus. This part, a micro cutting from the main stem, is taken and rooted in a nutrient jelly. The trees grown by this method all have the same variety of apple, which is another benefit, as identical new trees can be grown more quickly and distributed to plant nurseries. They can also be grown all year round.

Genetic Engineering:

There is a huge debate going on as to the safety and desirability of GM foods. [GM foods are foods which have new genetic material implanted into their cells with the aid of specialised enzymes in order to give the plant advantages such as increased yields or resistance to disease.]  Many researchers swear by the benefits of this type of work. In apples, for example, some crab apple varieties carry genes which render them less susceptible to the fungus disease, scab and mildew. Can the disease resistant characteristics of this wild apple be transferred to new varieties of edible apples via genetic modification without the edible apple losing its taste etc.?

Biotechnology companies would argue that these apple trees would be more environmentally friendly as they would not require so many sprayings of pesticides and as a result the apples would also be cheaper. Others, however, would question the safety of GM foods. Do these new gene combinations have effects that are so far unknown? Biodiversity and the farming structure might also be affected by growing GM crops. Fewer varieties of apple trees would be grown and small growers might increasingly be forced out of the market place. 

Irradiation:

If you apply radiation to existing apple tree varieties you can create mutants. One-year-old shoots are exposed to gamma radiation from a Cobalt 60 source. The radiation alters the characteristics of the chromosomes. The argument for this kind of work is that you can alter certain characteristics without losing others as might happen if you cross breed varieties in the traditional way.  Long Ashton Research Station tried some experiments with irradiation in the 1970s and early 80s, the aim being to make more easily managed trees.  For example to reduce the growth of some trees like Bramley and increase others, e.g. the cider apple Yarlington Mill.  The results were reasonable, but not good enough to continue.  The most successful irradiation work was to produce a self fertile Cox tree. 

Hormone Treatment:

A huge amount of research has being undertaken into synthetic hormones that are sprayed onto the trees during the blossom period to stop natural pollination and to fertilize flowers chemically. This method is already being used widely with grapes and satsumas – that’s how you get seedless ones!  Nothing useful as regards cider apples came out of the research though eating apples and pears can be 'set' (i.e. the young fruit just formed after flowering is encouraged to grow). 

Hormonal Growth Regulators are also being developed to reduce the rate of growth of the tree without losing the fruiting capacity. In wet summers, the branches can grow at the expense of the apples.  When the hormone growth regulator is applied, the shoots grow  shorter but the number of leaves and buds remains the same. There would be less need for mechanical pruning as well.  Regalis is a hormone growth regulator used to shorten growth of branches without reducing the leaves, this brings young cider apples into production earlier.  It is the only hormone spray regularly used by cider growers, as all the others are too expensive.

Questions: How could you clone an apple tree? What is Genetic Engineering? What are thought to be the advantages and disadvantages of GM food? Why might you want to subject an apple tree to gamma rays? How could you get a seedless apple?

 

apple tree - variety Vicky

Some popular varieties of cider apples and their origins:

• Ashton Bitter: a seedling raised from a Dabinett / Stoke Red cross by G.T. Spinks, the Long Ashton Fruit Breeder in 1947.

• Breakwell’s Seedling: a seedling of the Foxwhelp type introduced by George Breakwell, Monmouth.

• Major: a common variety in South Devon

• Nehou: a French variety introduced into Herefordshire early 20^th century

• Reine des Hatives: a French variety introduced into Herefordshire early 20^th century

• Stembridge Jersey: a seedling from the Kingsbury Episcopi area of central Somerset, introduced by W.J. Stuckey and named after the local village of Stembridge.

• Taylor’s: a seedling raised near Kingsbury Episcopi in Somerset.  

• Tremlett’s Bitter: a Devon variety from the Exe Valley

• White Jersey: widely grown in the orchards of south east and north Somerset.

Further Reading:

Cider and Juice Apples: Growing and Processing, Ed. R.R.Williams, University of Bristol Printing Unit.

The Apple Book, Peter Blackburne-Maze, Collingridge, 1986.

The Book of Apples, Joan Morgan and Alison Richards, Ebury Press, London, 1993.

The Apple Grower: A Guide for the Organic Orchardist, Michael Phillips, Chelsea Green Publishing Company, 2005.

Organic Apple Production – pest and disease management, HDRA Publishing, 2001.

Biology for You, Gareth Williams, Nelson Thornes, 2006.

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