SEED INSPECTION 45 



a final reading was made 3 days after the usual 5-day count, thus allowing some 

 slow seedlings to be included in normals; and third, conditions in the field test 

 happened to favor the activity of molds and other seed-borne organisms which 

 caused more kernel decay during and before germination in the field than occurred 

 in the laboratory. 



Summary of the Mold and Disease Readings 



1. The most common molds that occurred in the laboratory germinations 

 were species of Rhizopus, but Mucor, Penicillium, Aspergillus, and Cladosporium 

 were also present. 



2. Molds were observed in 92.7 per cent of the lots tested in the laboratory; 

 and Scutellum Rot, caused largely by Rhizopus and other molds, in 96.5 per cent. 



3. Molds (mostljf Rhizopus) caused root infection in the laboratory trials 

 in a larger number of lots than any other single fungus, such as Fusarium, Gibber- 

 ella, Diplodia ; and in nearly as many lots as those three types of fungi combined. 

 Although injury to the seedlings appeared not necessary for infection by any of 

 those organisms, yet Penicillium infection occurred mostly at breaks in both the 

 roots and shoots. 



4. There appeared to be no definite relation between the amount of molds 

 in a rag-doll and the amount of seedling infection caused by molds. Some lots with 

 heavA' mold contaminations showed little or no seedling infection; while others 

 with light molds may have shown marked infection. Perhaps the variety was an 

 important factor. 



5. In the laboratory the presence of molds in the germinator, together with 

 prominent Scutellum Rot, appeared to have little effect upon germination. For 

 example: 50 lots that were selected for light-to-very-light molds averaged only 

 3.6 per cent higher normal germination than 50 lots that showed heavy-to-very- 

 heavy mold contamination. This difference might well be accounted for by the 

 slightly greater amount of seedling infection in the heavy-mold series. 



6. On the other hand, in the field emergence test, the same series of low-mold 

 lots averaged 22.3 per cent higher normal germination than the heavy-mold lots. 

 Furthermore, the low-mold series averaged almost as high germination in the field 

 as in the laboratory, being only 3.5 per cent lower in the field ; whereas, in the heavy 

 mold series there was a difference of 21.3 per cent in favor of laboratory over field 

 germination. 



7. It is believed that the greater depressing effect of molds on normal germi- 

 nation in the field test was due to kernel decay before and during germination. 

 In the laboratory, kernel decay by the molds had not progressed bej'ond the Scu- 

 tellum Rot stage at the time the final readings were made. 



8. In the laboratory test, kernel discolorations due to such seed-borne 

 disease fungi as Fusarium, Gibberella, Diplodia, Alternaria, Hormodendron, 

 Cephalosporium, and Basisporium, were attended by only slight reduction in 

 normal germination, and the same was true in the field test. For example: 77.5 per 

 cent of the lots germinated in the laboratory showed " pink " kernels, varying from 

 1 to 42 per cent of the kernels in a lot, and caused by species of Fusarium, Ceph- 

 alosporium, and Gibberella; yet 50 lots which contained from none to 3 per cent 



