440 



E. J. WELLHAUSEN 



slightly higher double cross yield, but should have no effect on yields of 

 the F2. 



As shown in Table 27.10, the F2 generation progeny of the better double 

 cross hybrids with Si lines retained a substantial advantage in yield (12 to 

 20 per cent) over the open-pollinated variety Celaya. Hybrid No. 1 with S2 

 lines was included to see if it would actually show a greater drop in yield 

 between Fi and F2 than the others. 



From Table 27.11 it is evident that the F2 or F3 yields of the double 



TABLE 27.10 



YIELDS OF Fi, F,, AND F3 GENERATION PROGENY OF 



SEVEN DOUBLE CROSS HYBRIDS IN PER CENT 



OF THE VARIETY CELAYA 



No. 



1. 

 2. 

 3. 

 4. 

 5. 

 6. 

 7. 

 8. 



Pedigree 



(Gto61-5-4XAg. 172-2) X(M30-6O-3XC 243-2-2) 



(C 1 23 X C 90) X(C 243 XAg. 172) 



(C123XM30-60)X(C90XC243) 



(C 123XC 90)X(C 243XM30-60) 



(C 123XC 90)X(C 243XAg. 32) 



(C 123XC 90)X(Ag. 32XAg. 172) 



(C 123XC 243) X(L II 67 XL II 90) 



Celaya 



101 



111 



101 

 100 



L.S.D. = 12.5% 



TABLE 27.11 

 YIELD OF Fi, F2, AND F3 PROGENIES IN PER CENT OF Fi 



crosses with Si lines was consistently about 80 per cent of the yield in Fi, 

 whereas the F2 of the double cross with S2 lines was 87 per cent of the Fi. 

 This is not significantly higher, but also not significantly lower as one might 

 expect on the basis of the lower yields of the S2 lines. 



The few F3 yields available were not greatly different from those of the F2. 

 The assumption that in general, barring selection, there is no further reduc- 

 tion in yield beyond Fo has been adequately supported by experimental 

 data. Sprague and Jenkins (1943) tested the Fi, Fo, F3, and F4 of one 24 line 

 and four 16 line synthetics in various districts in Iowa. There was little dif- 



