Scientists Crack The Genome of the Apple
- Richard Alleyne, Daily Telegraph (UK), Aug 29, 2010 http://www.telegraph.co.uk
'The complete genetic code of an apple has been mapped for the first time in a development that could lead to healthier and tastier varieties.'
The findings suggest that a major step in evolution of the fruit was caused by a catastrophic environmental event, possibly the same one that killed the dinosaurs.
The international team of scientists sequenced the DNA make up of the "Golden Delicious" apple and discovered why it is so different to other fruits
The breakthrough is expected to help farmers pinpoint what makes apples crispy, flavoursome and healthy. It could lead to new hardier varieties that can grow in harsher environments. The consortium also found that the apple, like the pear, has more than double the chromosomes than other fruits like raspberries and strawberries which could be why it has its distinctive features.
“Now we have the sequence of the apple genome, we will be able to identify the genes which control the characters that our sensory scientists have identified as most desired by consumers – crispness, juiciness and flavour, ” said Dr Roger Hellens, at New Zealand's Institute of Plant & Food Research.
The domesticated apple appeared in the Near East approximately 4,000 years ago. The apple crop is the main fruit crop of temperate regions and worldwide apple production now exceeds 60 million tons, or approximately 20 pounds of apples per year per person. It is the fourth most economically important fruit crop worldwide
The sequencing has revealed that large lengths of apple chromosomes are copied in other chromosomes. This duplication would explain why the apple, and closely related pear, genomes have 17 chromosomes, while all other plants in the Rosaceae family (including peach, raspberry and strawberry) have between 7 and 9 chromosomes.
Many of the genes in these duplicated areas are related to fruit development and this larger number compared with other fruit may have enabled the distinctive features seen in apple. The findings suggest that a major step in evolution of the fruit was caused by a catastrophic environmental event, possibly the same one that killed the dinosaurs.
Evolutionary analysis tracked the event to around 60 million years ago. It is thought to be a survival response to an event that caused mass extinctions of other species, including the dinosaurs.
Other well adapted plant species, such as poplar, have been shown to have undergone a similar evolutionary response at the same time. The research is published in the journal Nature Genetics.
The sequencing of the genome will assist scientists in identifying the genetic controls of characteristics that consumers desire in new varieties of apples, such as texture, taste and colour. Genetic markers developed from these key genes will be used to screen thousands of apple seedlings in conventional breeding programmes to preselect those with the right combination of traits for commercial success.
“It seems that at some point, around 50 to 65 million years ago, the apple ancestor separated from its Rosaceae cousins on the evolutionary pathway," said Dr Hellens.
By duplicating almost all of its genome, apples now have very different fruit characteristics to related plants, such as peaches, raspberries, and strawberries. The time frame for this evolutionary change coincides with similar events in other plants and mass extinctions of some species, including the dinosaurs. This suggests that a major environmental event forced certain species, including apple, to evolve for survival.”