GENE RECOMBINATION AND HETEROSIS 



311 



pairs (effective factors) differentiating the parents has been determined for 

 the Porter X Ponderosa hybrid populations only. 



In discussing the bearing the number of gene pairs differentiating the two 

 parents has upon gene recombination and heterosis, information concerning 

 phenotypic dominance of the characters for the hybrid populations is neces- 

 sary and will be derived by studying the means of the parental and hybrid 



TABLE 19.8 



MEANS FOR WEIGHT PER LOCULE AND NUMBER OF DAYS FROM SEED- 

 ING TO FIRST FRUIT RIPE WITH TYPE AND NUMBER OF GENE PAIRS 

 DIFFERENTIATING THE PARENTS FOR WEIGHT PER LOCULE* 



* For the hybrid populations of Danmark X Red Currant, Danmark X Johannisfeuer, Johannisfeuer X 

 Red Currant, and Porter X Ponderosa. 



t Pi is Red Currant, Johannisfeuer, Red Currant, and Porter, respectively. 

 t P2 is Danmark, Danmark, Johannisfeuer, and Ponderosa, respectively. 



populations given in Table 19.8. The means for weight per locule of tomato 

 fruits and number of days from seeding to first fruit ripe together with the 

 type and number of gene pairs differentiating the parents for weight per 

 locule for the hybrid populations of Danmark X Red Currant, Danmark X 

 Johannisfeuer, Johannisfeuer X Red Currant, and Porter X Ponderosa are 

 given in Table 19.8. 



The first two hybrid populations were grown at Cheyenne, Wyoming, in 

 1938, the third hybrid population at the same location in 1939, and the last 

 hybrid whose means are listed in the extreme right hand column of Table 

 19.8 was grown at Woodward, Oklahoma, in 1941. The means of this table 



