SEED INSPECTION 45 



Presence of Seed-Borne Diseases 



Germination of the seed used for variety studies of garden peas was recorded 

 from laboratory tests and also from duplicate lots planted in the field. Record of 

 the laboratory germination appears in the preceding table, but no field tests are 

 shown. Because of abnormally late planting, made necessary by the poor phy- 

 sical condition of the soil in the test plot, no fair comparison of results can be 

 made. However, the field planting for germination and the permanent planting 

 .for variety tests, as well as the germination tests in the laboratory, gave oppor- 

 tunity to observe the presence and efTect of seed-borne diseases upon field per- 

 formance. Professor O. C. Boyd, Extension Pathologist, gives the following 

 summary of his observations. 



Laboratory Germination Test 



1. Number of seed lots, 112; 200 seeds each. 



2. Number of lots which showed the following conditions: 



a. 8-25% of the seeds discolored, 15; 26-50%, 52; 51-75%, 33; 76-100%, 12. 



b. Deep cotyledonary lesions: 26. 



c. Soft rot of seeds: Light 16; medium 16; heavy 6. 



d. Mold contaminations: Light 51; medium 29; heavy 22. 



e. Blotch: Light 32; medium 18; heavy 12. 



3. Organisms isolated from shallow cotyledon stains and lesions: Slow growing yellow and white 



bacteria; Cladosporium sp.; Pencillium sp. 



4. Organisms isolated from deeper cotyledon lesions: Fusarium sp.; slow growing white and 



yellow bacteria; Ascochyta pisi (leaf and pod spotting fungus). 

 Field Germination Test 



1. Number of seed lots which showed the following diseases when the plants were from four to 



si.\ inches high: 



a. Root rots (Fusarium, Aphanomyces), 47; pronounced. 5. 



b. Wilts (Fusarium, et al.), 50; pronounced, 9. 



c. Mosaic, 8. 



2. Number of lots showing good stand, 38; medium, 25, poor. 46. 



3. Kinds of organisms isolated from diseased plants: Fusarium sp.; Aphanomyces sp.; Ascochyta 



pisi; Penicillium sp.; Pythium sp.; slow growing yellow and white bacteria. 

 Field Permanent Planting 

 I. Number of lots that showed the following diseases: 



a. Root rots (Fusarium, Aphanomyces), 26; pronounced, 8. 



b. Wilt, (Fusarium, et al.) 16; pronounced, 5. 



c. Undetermined blight, 9. 



d. Mosaic, 12. 



e. Leaf and pod flecking, 16; Ascochyta spot. 15. 



f. Bacterial leaf and pod spot and stem blight, 2. (3 & 3A) 



Relation Between Low Germination in Laboratory and Field Stand 



There was not a consistent or direct relation between field stand and laboratory germination; yet^ 

 80% of the lots that showed a germination of 70% or less in the laboratory also showed a corres- 

 pondingly low stand in the field tests. The reverse, however, was not consistently true. 

 Occurrence of Seed-Borne Diseases^ 



Lots from which were isolated the Ascochyta spot, Fusarium root-rot, and 

 bacterial pod and leaf spot organisms, also showed prominent symptoms of those 

 diseases in the field plantings. 



It is believed that the "Undetermined Blight" disease which was prevalent in 

 several lots of the permanent planting, may have been associated with one type 

 of seed-coat stain and cotyledon lesion. It does not correspond to any of the known 

 diseases of peas. 



The symptoms of the bacterial leaf and pod spot disease which were present 

 in two lots of the permanent planting were quite different from those of the well- 

 known bacterial blight caused by Bacterium pisi (SsTckett) EPS. It is believed 

 to be a seed-borne disease that has not been described in this country. 



The very characteristic "Blotch" spot on seed coats and cotyledons in the 

 laboratory germination test appeared to have some relation to the occurrence of 



' Isolations were made from only a few of each kind of disease observed in the laboratory and 

 field tests. 



