The Use of Induced Mutations for the 

 Improvement of Vegetatively Propagated Plants 



I 



NILS NYBOM 



Balsgard Fruit Breeding Institute, 

 Fjalkestad, Sweden 



f we look at lists of new fruit varieties, a great many will be found 

 to constitute spontaneous mutations. A glance at a rose nursery 

 catalog will tell us the same thing, and we also know that much of 

 the variation in form and color among flower bulbs and other orna- 

 mental plants goes back to spontaneous mutations that have been 

 taken care of and have been cultivated as new and more attractive 

 varieties. In orange trees, potatoes, strawberries, and many other 

 clonal plants there are often said to occur different "races", some of 

 which may be claimed to be better keeping, better yielding, or 

 deviating in other respects from the original types (65, 72, 77, 92, 

 100). 1 



For several reasons, these sports seem to have been of special 

 importance among the vegetatively propagated plants. Their greater 

 constancy, preserved through clonal propagation, permits the detec- 

 tion of even slight phenotypical changes. Thanks to the vegetative 

 mode of reproduction, practically all such changes may be propa- 

 gated, even such that would lead to complications and perhaps rapid 

 elimination in a seed-propagated plant. 



The vegetatively propagated plants often have a long period of 

 sexual reproduction. They usually turn out to be highly heterozy- 

 gous, and our knowledge of their genetical relationships is still very 

 imperfect. All this has made improvements by means of the classical 

 methods, involving crossing, recombination and selection, time- 

 consuming and dearly bought. To a considerable extent this may 

 also have favored the use of spontaneous mutations in these plants. 



Towards the end of the twenties, means were found for the arti- 

 ficial induction of mutations, as it seemed of the most varying kinds 

 and in unlimited amounts. No wonder that plant breeders tried to 

 apply this possibility in their work. I am not going to relate this story 

 in detail here as it has been dealt with elsewhere (46, 49, 50, 86, 104). 



^ee References, page 285. 



252 



