The Genetics and Breeding of Fruit Trees

Abstract

The following quotation is the author's summary taken from a paper presented by M. B. Crane in 1952 at the 13th International Horticultural Congress in London:

"Breeding experiments with fruit trees have been mainly carried out in the search for new forms of commercial value, and usually the families raised for this purpose have been small. Large families are, however, desirable both for practical results and for genetic study. Their genetic complexity, maintained by vegetative reproduction, and the length of time which elapses from seed to maturity and from one generatioq to another, make the breeding of fruit trees prolonged. But apart from this the impact of genetics on fruit tree breeding has not been so profound as expected by early geneticists. This is mainly because their most important characters, such as resistance to pests and diseases, size, shape, colour and quality of fruit, are quantitatively inherited and our knowledge of the inheritance of such characters has been limited. In the diploid fruits, many characters are discontinuous and simply inherited, but as a rule, even in these, the inheritance of those characters which go to make up fruit quality is complex. In the polyploid fruits continuous variation is almost the rule, and results from the cumulative action of a number of genes. Study of the inheritance of such characters, polygenic characters as Mather has called them, is further complicated by variability being dependent on both genotype and environment; in fruit trees, environment both natural and cultural such as the use of different rootstocks, etc., has profound effects. With such characters as size and shape of fruit it is common to find in the progeny a pronounced shift towards the characters of the wild type. Although selection for desirable characters in fruits has been going on for centuries, it has been much slower than in crops normally raised from seed, and in some ways it has been further impeded by vegetative reproduction."