4 BULLETIN" 1062, TJ. S. DEPARTMENT OF AGRICULTURE. 



With increased starchiness a number of factors operate toward 

 increasing the number of ear infections. Immature seed ears are 

 characterized by starchiness. Some of the starchy ears may come 

 from the normally late-maturing strains, in which case the ear is 

 exposed to weather conditions more favorable for infection by the 

 root-rotting organisms during the period of ripening. Because of 

 their high moisture content, such immature ears afford a good me- 

 dium, even after harvest, for the development of these organisms 

 when introduced from external sources. It has already been ob- 

 served, however, that larger percentages of ear infection occur in 

 the starchy groups of seed ears from strains with practically the 

 same length of growing season. Field observations indicate that 

 such seed ears are obtained from stalks suffering from an unbal- 

 anced food supply. Perhaps the main contributing factor is a root- 

 rotted condition of the parent stalk itself. These factors merely 

 furnish additional argument in favor of the practice of selecting 

 seed ears from the stalk in the field. 



RELATION OF KERNEL STARCHINESS TO PATHOLOGICAL 

 PERFORMANCE. 



As starchy seed ears are more frequently infected with root-rot 

 organisms than the more horny ears, it has seemed important to de- 

 termine the relation of kernel starchiness to pathological perform- 

 ance in the field. Decreased stands and yields follow the planting 

 of kernels from infected seed ears, as has been determined by the 

 writer and by Duddleson and Hoffer 2 (unpublished data) and pre- 

 viously reported in the course of these investigations by Hoffer and 

 Holbert. 3 



Because of the larger proportion of infections in the starchy seed 

 ears, the planting of seed from these two groups without regard to 

 the germination records would be expected to show superior yields 

 from the more horny seed. In the study of the field effects of ear 

 infection during the seasons of 1918, 1919, and 1920, approximately 

 equal numbers of infected and of disease-free ears from the horny 

 and the starchy groups were used in ear-to-row experiments. All 

 rows were 75 hills in length. Only ears giving 100 per cent germina- 

 tion in the laboratory were used for seed. 



The data from these plats have been summarized in Table 2 on 

 the basis of starchiness of kernels. In this table the field perform- 

 ance of the horny groups of ears in each experiment has been taken 

 as 100 per cent. The figures represent the percentage of decrease 

 incurred through the use of the starchy seed ears. In all but one 



2 Duddleson, B. H., and Hoffer, G. N. The improved rag-doll germinator for the 

 elimination of diseased seed corn. (Manuscript.) 



3 Op cit. 



