DEVELOPMENT OF THE HETEROSIS CONCEPT 



59 



In these studies the usual method of predicting combining ability of a 

 double cross gave excellent agreement between both predictions and the 

 actual double cross yield. 



The studies of the performance in early and later tests of F2 to F4 lines 

 from L317 X A116 when crossed with (A334 X A340) in comparison 

 with A357(A334 X A340) were carried out by Payne and Johnson. The 

 methods of comparing combining ability in different generations were 

 adapted by the writer, who alone is responsible for the conclusions drawn. 

 The lines were first placed in +1, — 1, etc. X L.S.D. at the 5 per cent point 

 with the performance of A357(A334 X A340) as 0. Classes for performance 

 of individual lines were made by adding the yield class of a line to its moisture 

 class with the sign of the latter changed. 



The F2 and F3 crosses were both grown the same year, the F3 and F4 were 

 grown in different years, and the F4and the top crosses were grown the same 

 year (see Tables 3.10, 3.11, 3.12). 



In these studies no new lines seemed markedly superior to A357 in com- 



TABLE 3.10 



COMBINING ABILITY RELATION OF F2 AND F3 LINES 



OF (L317XA116) IN CROSSES WITH (A334XA340) 



GROWN IN SAME TRIAL IN 1947 



o 

 •-t 



o 



+2 +1 -1 -2 -3 -4 -5 

 F2 crosses, performance classes 



Total 

 1 

 6 



5 

 6 

 7 

 4 



2 

 2 



3i 



TABLE 3.11 



COMBINING ABILITY RELATION OF F3 AND F4 LINES 



OF (L317XA116) IN CROSSES WITH (A334XA340) 



F3 GROWN IN 1947, F4 IN 1949 



Total 



o 



o 



en 



+2 +1 -1 -2 -3 -4 

 F4 crosses, performance classes 



1 

 6 



5 

 6 

 7 

 4 

 2 

 2 



33 



