Crane • Lysenko's Experiments 



in 



I am often asked the question, what 

 are these "Mentors" and how do they 

 work? We have just read one account 

 of them in Soviet Biology, but Lysenko 

 says: "The best way for scientific 

 workers in various departments of bi- 

 ology to master the theoretical depths 

 of Michurin teaching is to study 

 Michurin's works, to read them over 

 again and again, and to analyze some 

 of them with a view to solving prob- 

 lems of practical importance." 



We will take Lysenko's advice and 

 refer to "The use of 'Mentors' in rais- 

 ing hybrid seedlings and examples of 

 definite changes induced in fruit tree 

 varieties by various external factors." 

 This was written by Michurin in 1916 

 and published in 1939. Here Michurin 

 says the "Mentor" method works as 

 follows: "Supposing we have a well- 

 developed six- or seven-year-old hybrid 

 seedling, which has not started fruiting, 

 we know that it will not start fruiting 

 before some ten years have elapsed 

 since in some cases the parent varieties 

 do not normallv start to fruit until their 

 twentieth year {sic). Yet by grafting 

 close to the base of the lower branches 

 of the crown several scions taken from 

 the fruitbearing tree which is known 

 to be of a high-yielding variety the 

 seedling can be induced to bear fruit 

 within two years." 



Further we are told: "In three 

 further instances the method was used 

 for the improvement of the quality of 

 hybrid fruits, namely, for development 

 of certain storage characters, for im- 

 provement in color of the fruits, for in- 

 crease in sugar content in fruit flesh. 

 In these instances the "Mentors" were 

 employed after the hybrids had already 

 fruited once"; and again: "It is quite 

 apparent that the method can be used 

 to effect various other changes in the 

 properties and characters of hybrid 



255 



varieties, such as the increase of fer- 

 tility, attainment of larger size fruits, 

 etc." 



Now I have had many families of 

 cherries in which the earliest seedlings 

 fruited in their fourth year and the 

 latest in their eighth year. These were 

 grown on their own roots without any 

 interference apart from ordinary' com- 

 mon-sense cultivation. Amongst tree 

 fruits pears are most delayed. A few 

 fruit in their eighth year, about 50 per 

 cent in their ninth vear and then there 

 is often a small proportion which have 

 not fruited until their fifteenth year. 

 The point is that as far as I can see 

 Michurin used no controls; indeed the 

 only way to get real control would be 

 to multiply an individual seedling vege- 

 tatively and use some as control and 

 some for experiment. Otherwise if ob- 

 servations are confined to a single or 

 very few trees one might mentor trees 

 which will fruit early and compare 

 them with others which normally fruit 

 late. 



In this country we are of course well 

 aware of certain root-stock effects, but 

 these, important as they are to com- 

 mercial growers, are indeed trifling 

 when compared with the claims of 

 Michurian mentors. 



We are also aware of the so-called 

 juvenile period of pears and other fruits 

 and of the practice of bark-ringing to 

 bring fruit trees into flower, but neither 

 these nor the root-stock effects are quite 

 as mysterious as "Mentors." Incidcn- 

 tallv, it is just conceivable that several 

 grafts at the base of branches might 

 have a similar effect to bark-ringing, 

 but Michurin does not make any such 

 suggestion. 



The claims of "Mentors" for im- 

 proving size, color, sweetness, fertility, 

 etc., are no more convincing than the 

 others. They are, however, ver\' re- 

 markable, the inferior seedlings de- 

 veloping fruit with qualities akin to 



