SEED INSPECTION 57 



Laboratory and Field Germination Tests of Sweet Corn 



Seed Laboratory, Departments of Botany and Vegetable Gardening Cooperating 



The following summary marks the end of three successive years' work, during 

 which comparative laboratory and field tests of sweet corn have been conducted 

 in an endeavor to find the efi'ect of various seed-borne organisms on germination. 



The purpose of the germination tests and the methods followed throughout 

 were essentially the same as those described for 1933. This year, however, in 

 addition to the laboratory and field germination work, a seed treatment test 

 was conducted. Several lots of seed that showed pronounced contamination or 

 infection by common seed-borne fungi in the laboratory germinator, as well as 

 a few comparatively disease-free lots, were included in order to determine the 

 effect of two common seed disinfectants upon normal germination in the field. 

 The Seed Laboratory had direct charge of the germination work in the labora- 

 tory; the Vegetable Gardening Department supervised planting of the field 

 tests; and O. C. Boyd, Extension Plant Pathologist, made disease readings 

 with interpretations in all three tests. 



The laboratory germinations were run during April and May, and the field 

 plantings were made in June. The field tests were located on moderately 

 heavy, well-drained soil, and weather and soil conditions were considered very 

 favorable for germination and subsequent growth of plants. 



This year 196 lots or sources of seed, representing 83 varieties, were germ- 

 inated in the laboratory; and 175 of the corresponding lots in the field. A 

 summary of the results, together with interpretations is given below. A more 

 detailed discussion of the results for the three year's project will appear at a 

 later date in another publication. 



1. Germination in the laboratory (average of all lots): Per Cent 



a. Total germination (range of 66.5-100) 92.6 



b. Abnormal due to seedling infection (0-56) 17.5 



c. Abnormal due to other causes (0-8) 0.9 



d. Normal germination (33-99) 74.2 



2. Germination in the field (average of all lots) : 



a. Total emergence (range of 23.5-99.5) 79.4 



b. Abnormal plants (only stunted plants were pulled and 

 examined) : 



(1) With infected mesocotyl or root (0-27) 10.9 



(2) Not diseased; undersized only (0-6) 0.9 



c. Normal germination (18.5-97.5) 67.6 



In general the results were similar to those for 1933. Again the average 

 total emergence in the field test fell far below the average total germination in 

 the laboratory, but was only slightly higher (5.2%) than the average normal 

 germination in the laboratory series. Perhaps the most outstanding difference 

 between the above summary and the one for 1933 is the higher percentage of 

 abnormal seedlings this year in both the laboratory germinators and the field 

 planting. Seed-lot contamination and seedling infection by Rhizopus and 

 Penicillium in particular, as well as kernel decay and seedling infection by 

 Diplodia, were more noticeable in the laboratory test this year than in 1933. 

 It may be that weather conditions prior to and during harvest of the seed were 

 particularly favorable for contamination and infection by those fungi. 



