434 



E. J. WELLHAUSEN 



Si line of Urquiza (Urq. 54) and an Si line of Chalqueno (Hgo. 3-5) as the fe- 

 male parent, with a very vigorous first generation selfed line Mex. 37-5 also 

 from Chalqueno as the pollinator. This hybrid involving one Urquiza line 

 and two Chalqueno inbreds has been one of the best combinations to date 

 of Urquiza and Chalqueno lines. In general, hybrids of inbred lines from 

 Chalqueno and inbred lines of Urquiza have been disappointing in comparison 

 with the yield of the variety V-7, although the Chalqueno lines in the crosses 

 were selected on the basis of combining ability with the variety Urquiza, 

 and Urquiza lines on the basis of their combining ability with a variety of 

 Chalqueno. None of the hybrids, including H-1, approached very closely the 



TABLE 27.5 



RELATIVE YIELDS IN PER CENT OF CHALCO FOR THREE 



LONG SEASON VARIETIES AND HYBRIDS 



IN 1948 AND 1949 



yield, ear size, and depth of grain of the best 10 per cent of the plants in the 

 variety V-7. 



If a hybrid could be made in which 80-90 per cent of the plants ap- 

 proached the yield of the best 10 per cent of the plants in the variety V-7, 

 it would be an excellent hybrid. If such a hybrid is to be obtained, another 

 line of approach seems warranted. The best approach to this immediate ideal 

 is probably through the recombination of lines from V-7 or other varieties 

 within the race Chalqueno rather than bringing in outside germplasm, since 

 no race or variety has as yet been found which in Fi crosses with V-7 has 

 been as good as V-7. The question of selecting the proper tester for use in 

 isolating the high-combining genotypes, inter se, needs further study. Per- 

 haps a tester made up as a double cross or as a synthetic of the most vigorous, 

 most agronomically desirable, highest yielding, and best combining Chalque- 

 no lines would be the one to use. Against this nucleus of concentrated adapted 

 germplasm, other lines from V-7 or lines from other varieties of Chalqueno, 

 regardless of vigor, could be tested for their combining ability. Those that 

 increased the yield of the tester could then be pooled, and this pool could be 



