The apple. Apples are members of the rose family (Rosaceae) and are of very ancient origin in Eurasia. The wild progenitors are either extinct or unknown. Pliny the Elder (23-79AD), listed twenty two varieties of apple known to the ancient Romans.
Today, apples are probably the most popular fruit, with oranges or, perhaps, bananas being second. The apple is self-incompatible and bees are necessary for pollination. Hand pollination is easy, but the main difficulty in breeding is the very large number of seedlings that have to be screened in order to produce one new cultivar. Cultivated apples are normally grafted on to seedling rootstocks. An old apple orchard can be useful for testing promising scions in a breeding program, because an old tree can carry some fifty or more grafts.
The story of Johnny Appleseed suggests a technique for amateur plant breeders. His real name was John Chapman, and he travelled westward, in the early 1800s, into Ohio, Indiana, and Illinois. As he went, he planted hundreds of apple seeds that he had obtained from cider presses in Pennsylvania. Most of his seedlings would have produced aberrant types, but some were very useful. In any event, these early settlers wanted apples mainly for making applejack, as this was the only source of alcohol they had. His activities helped to make the Ohio Valley a major apple producing area, and North America soon had a greater variability in apples than Europe. He was ultimately responsible for the phrase "As American as apple pie".
In Canada (and elsewhere, no doubt) passengers eating an apple on a train would often throw the core out of the window. Many of these train tracks are now abandoned, and have been converted into hiking trails. Numerous apple trees grown from those unwanted apple cores line these tracks and they merit investigation as a possibly useful, and readily available, population for selection purposes. It should be remembered that each core would normally produce several trees that are genetically very different from each other, even though they seem to grow as one tree that is apparently branched near the ground. Mammalian toxicity
Before being released to growers, new crop protection chemicals have to be tested for their mammalian toxicity. This is usually measured in milligrams of the chemical, per kilogram of mammalian body weight, required to kill 50% of the test population. This lethal dose is called the LD50. These tests, of course, are made on laboratory animals, usually rats or mice. Manchineel
See: Hippomane manchinella.
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