254 



GENETICS AND PLANT BREEDING 



and fruits, this tomato plant docs not 

 stand out as a ver\' wonderful happen- 

 ing. In my own work with tomatoes I 

 have had a fruit partly red and partly 

 yellow and it is only a small step from 

 this to wholly red and wholly yellow 

 fruits on one plant. 



In L)'senko's Heredity and its Vari- 

 ability translated by Dobzhansky 

 (1946) it appears that the yellow to- 

 mato used in the grafting experiments 

 was the double recessive rryy. Plants 

 are also mentioned where the fruits 

 were pale yellow or slightly reddish. In 

 The New Genetics in the Soviet Union 

 by Hudson and Richens (1946) to- 

 mato fruits pale yellow with pink 

 stripes are described. Since such fruits 

 may appear new and unusual I will 

 point out that these descriptions ap- 

 pear to correspond to the fruits of a 

 variety named "Blood Orange" which 

 has been known in England for ten 

 years or more. In this variety individ- 

 ual fruits var)'. At one extreme the 

 fruits appear almost wholly yellow and 

 at the other they are appreciably red- 

 dish. Between these extremes fruits 

 with intermediate amounts of red oc- 

 cur, i.e., yellow with irregular blotches 

 or stripes of red. 



II 



The so-called "Mentors" elaborated 

 by Michurin receive much attention. 

 Lysenko tells us I. V. Michurin not 

 only recognized the possibility of ob- 

 taining vegetative hybrids, but he 

 elaborated the Mentor method. This 

 method consists in the following: by 

 grafting scions (twigs) of old strains 

 of fruit trees on the branches of a 

 young strain, the latter acquires prop- 

 erties which it lacks, these properties 

 being transmitted to it through the 

 grafted twigs of the old strain, lliat is 

 why I. V. Michurin called this method 

 "Mentor." We are also told: "When 



grafted, organisms which have not 

 reached the stage of full development, 

 i.e., have not completed their cycle of 

 development, will always change their 

 development as compared with the 

 plants which have their own roots. In 

 the union of plants by means of graft- 

 ing the product is a single organism 

 with varying strains, that of the stock 

 and that of the scion. By planting the 

 seeds from the stock or the scion it is 

 possible to obtain offspring, individual 

 representatives of which will possess 

 characteristics not only of the strain 

 from which the seed has been taken, 

 but also of the other with which it has 

 been united by grafting." 



I have been profoundly interested 

 in the growing, breeding and grafting 

 of plants and trees for nearly fifty years, 

 and have raised thousands of fruit trees 

 from seed; grown many both on their 

 own roots and on the roots of others. 

 I have also grafted twigs of an old 

 variety on a young seedling on its own 

 roots and also twigs of young seedlings 

 on to old varieties. I have raised peach 

 seedlings from peaches growing on 

 plum roots; plum seedlings from 

 Prunus domestica growing on P. cerasi- 

 fera roots; pear seedlings from pears 

 growing on quince, on pear-stocks, and 

 also on their own roots. In the same 

 way I have used as parents apples grow- 

 ing on widely different root-stocks. In 

 all these there has not been the slight- 

 est indication of the different roots 

 having had any influence on the seed- 

 lings. That is to say in my experi- 

 ence no vegetative hybridization oc- 

 curred. 



I have also compared numerous 

 seedlings on their own roots with the 

 same individuals grafted, at an early 

 stage, on other roots. Tliose which 

 were good on the grafted tree were also 

 good on their own roots and those 

 which were inferior on the one were 

 also inferior on the other. 



