288 



BREEDING CROP PLANTS 



report of a recent study at the Minnesota Station (Olson, Bull, and 

 Hayes, 1918), which contains experimental evidence together 

 with a review of other experiments in relation to score card 

 characters and yield, show no correlations between individual 

 characters 'such as trueness to the ideal score card ear type and 

 subsequent yield of these ears. 



Artificial self-fertilization in corn isolates homozygous types 

 which are less vigorous than normally cross-pollinated plants. 

 All other evidence seems to show that too close a purity of 

 type corn tends to a reduction in vigor. The grower whose 

 method of selection is based upon ear type is certainly obtaining 

 no gain in yield of shelled corn per acre. The detrimental 

 results of too close selection to type may not be very apparent and 

 may be more than counterbalanced by the extra attention from a 

 cultural standpoint, for an interest in ideal ear types certainly 

 stimulates the farmer to produce better corn. It is not, however 

 an increase due to better breeding but to better cultural practice. 



The present purpose is to outline methods of seed selection. As 

 there is no apparent relation between score card characters for 

 type of ear planted (within a particular variety) and resultant 

 yield, even though such selection may be constantly practiced, we 

 may pay little attention to those characters as far as our breeding 

 plan goes. The grower should, of course, produce corn of one 

 variety which is pure, judged by easily evident characters, such as 

 color of seed and cob. Abnormalities, such as very large butts, 

 badly flattened cobs, or very irregularly rowed ears, should not 

 be used as foundation stock. Aside from these there is no need 

 of paying much attention to type. Ability of a variety to 

 mature under the conditions, is very important and needs much 

 attention. 



Two methods of work are outlined here, either of which may be 

 of considerable value in increasing yield. 



METHOD OF BREEDING CORN FOR SPECIAL BREEDERS 



Nearly all discussions of corn breeding are based on the ear-to- 

 row method. Such a method takes considerable time and can be 

 carried out only by the breeder or occasional seed specialist. 

 The ear-to row test is commonly understood. It consists of 

 growing the seed of a certain number of ears in individual rows 

 and determining the better yielding ones. Each ear saved is 



