R0s.(Heter.J»l<^ 



TABLE 3 



Ratios of resistant to susceptible plants in crosses 

 of resistant S. a ndipe n u i ns 



Number of Type of 

 Parentage Seedlings Cross 

 Resistant : Susceptible 



Expected Number of Seed- 

 Ratio lings Expected 



Resistant : Susceptible 



HU X Hii 



( 70 



( 



( 291 



( 119 



nh X ( 565 

 S. tubero sum ( 



( 215 



varieties 



H3 X 



S. tuberosiun 



varieties 



Susceptible Kb 

 X S. tuberosum 



9U 



From Toxopeus and Huijsman 1953 



25 

 51 



193 



263 



311 

 129 



KL X 



0x0 



1:3 



0:00 



101.2 303.7 

 All susceptible 



H3 X 



S. tuberosum 83 



varieties 



B. Tests made in Cambridge 



99 H X 1:1 

 KKL X 5:7 



91 91 

 75.8 106.2 



HI X 



S. tuberosum 



17 



13 



Susceptible H3 



X Susceptible 



C.P.G. 1U70 



50 



0x0 



0:0 



All susceptible 



Possible alternative ratios (in brackets). It is now clear that only a 

 single gene (H) is responsible for resistance, and the alternative KL 

 system does not obtain. 



