MONOPLOIDS IN MAIZE 



391 



MONOPLOIDS IN MAIZE 



It has been known for some time that monoploids occur naturahy in maize 

 in measurable frequency. Data of Randolph (Randolph and Fischer, 1939) 

 and of Einset (1943) suggest that monoploids occur spontaneously at a rate 

 of about one per thousand. Data of Stadler (unpublished) indicate a rate of 

 about one per hundred in a genetic stock. At the start of the studies reported 



* Desired homozygous individual, j of gametes and ,'4 of zygotes. 



Fig. 25.1 — Efficiency of Monoploid Method Compared with Selfing to Si for Obtain- 

 ing Homozygous Individual AAbbCC from Heterozygous Parent AaBbCe. 



here it was assumed that naturally occurring monoploids would furnish a suf- 

 ficient supply at a rate of occurrence of the order of one in one or two thou- 

 sand plants of a progeny provided the bulk of the diploids could be screened 

 out by some simple device during the seed or seedling stages. This has proven 

 feasible. 



It was also assumed that some method for inducing doubling of the mono- 

 ploid chromosome complement would have to be developed. Though this still 

 appears desirable and possible, artificial induction of chromosome doubling 

 has not been necessary in order to obtain diploid self progeny from a portion 

 of the monoploids. The reason for this is that the fertility of the plants is in- 



