THE INHERITANCE OF DEFECTIVE 

 SEEDS IN MAIZE^ 



P. C. Mangelsdorf 

 CoiniccticKt Agricnltural Rxpcvijucnt Station. Ncxc Haven. 



DEFECT1\'E seeds are heritable 

 variations in maize in which the 

 endosperm is lacking or is in- 

 complete or abnormal in its develop- 

 ment. These characters were first 

 reported in the Journal of Heredity by 

 Jones,' who observed them in several 

 varieties of corn that had been self- 

 fertilized for the first time. Crosses 

 made by him. and later generations 

 classified by the writer have shown that 

 there is more than one type of this 

 abnormality, and the first four de- 

 fectives studied have been found to be 

 genetically distinct. 



In the past few years many experi- 

 ment stations have begun projects for 

 the imi^rovement of corn by selection 

 in self -fertilized lines. Altogether, 

 more than six thousand strains of corn 

 have been inbred for this purpose. 

 This inbreeding has brought to light 

 many recessive variations, previously 

 covered up by the remarkable heter- 

 ozygosity which exists in the average 

 variety, and among these recessive 

 variations there have been a large 

 number of defective seed types. De- 

 fective seeds have appeared in all the 

 so-called sub-species of maize with the 

 possible exception of tunicata and in 

 more than thirty representative Ameri- 

 can A^arieties as well as in several 

 varieties from Spain and one from 

 Peru. During the summer of 1922 

 crosses were made between many of 

 these defectives and the four types 

 originally tested at the Connecticut sta- 

 tion in order to determine, if possible. 

 the number of distinct genetic factors 

 involved. Between fifty and sixty 



crosses have been made and in only 

 one of these have the results been such 

 as to indicate that the two defectives 

 which entered the cross were genetical- 

 ly alike. It appears, then, that there 

 are many different factors involved 

 which cause defective seeds in maize. 

 A brief description of several charac- 

 teristic types follows : 



Classification of Defectives 



The defectives show varying degrees 

 of development. There are types 

 ranging from those which consist of 

 only a transparent, empty, pericarp 

 with scarcely a trace of endosperm 

 tissue, to others in which the develop- 

 ment is but slightly less than nonrial. 

 There are others, even more extreme, 

 in which the seed develops almost nor- 

 mally but fails to go into the rest- 

 ing stage and germinates on the ear. 

 Between these two extremes are all 

 gradations, and within each type is 

 a certain amount of variation, so that 

 it is often impossible to separate two 

 such types when they occur on the 

 same ear. 



The defectives may be roughly clas- 

 sified into three groups as follows : 



1. Complete defectives; those in 

 which the development of the ovule is 

 arrested shortly after fertilization. 



2. Partial defectives; those in 

 which development proceeds until a 

 certain amount of endosperm tissue 

 has been laid down. 



3. Germinating seeds ; those in 

 which the mature seed fails to go into 

 the resting stage. 



^ Contribution from the Bussey Institution, Harvard University. 



^JoNES, D. F. Heritable Characters of Maize; Defective Seeds. Journal of Heredity, 

 vol. xi. No. 4. 1920. 



119 



