No. 610] 



LINKAGE IN LYCOPERSICUM 



609 



than spherical, but not constricted like the pear-shaped 

 fruit. The second generation gave the two parental types 

 of fruit shape together with the heterozygous fruit shape 

 in approximately the ratio of 1 : 2 : 1. The actual numbers 

 obtained are as follows : 114 plants with fruit shaped like 

 the Quarter Century parent, 208 plants with fruit shaped 

 like that of the Fj plants and 130 plants with pear-shaped 

 fruit. The shape of fruit was considered to be more 

 like that of the Quarter Century parent. Both types dif- 

 fered from the Yellow Pear shape by not having the con- 

 stricted neck. The non-constricted type is thus incom- 

 pletely dominant over the constricted. 



The cross therefore received one dominant factor from 

 one parent (standard vine) and two from the other (red 

 and non-constricted fruit). Any linkage between the fac- 

 tors for vine habit and shape of fruit would in this cross 

 be a case of spurious allelomorphism or repulsion accord- 

 ing to the English designation of this condition. 



The second generation segregated into 12 distinct cate- 

 gories according to the Mendelian expectancy for a tri- 

 hybrid where two factors show complete dominance and 

 one factor incomplete dominance. The actual results ob- 

 tained compared with the theoretical expectancies are 

 tabulated by Hedrick and Booth, and given here in Table I. 



TABLE I 



standard vine, Fruit Quarter Century shape, red 48 63 9/16 



yellow 16 213/16 



Fruit Hybrid shape, red 148 1271/8 



yellow 40 42 3/8 



Fruit Yellow Pear shape, red 98 63 9/16 



yellow* 29 213/16 



Dwarf vine, Fruit Quarter Century shape, red* 37 21 3/16 



yellow 13 71/16 



Fruit Hybrid shape, red 17 42 3/8 



yellow 3 14 1/8 



Fruit Yellow Pear shape, red 2 21 3/18 



yellow 1 7 1/16 



* Parental combinations. Total 452 452 



