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Document Type

Thesis - University Access Only

Award Date


Degree Name

Master of Science (MS)


Plant Science

First Advisor

Gub Liang Jiang


Soybean aphid (Aphis glycines Matsumura) has been an important pest of soybean (Glycine max (L.) Merr.) in the United States since 2000. Identification and genetic characterization of soybean aphid resistance in early maturing soybean germplasm will facilitate development of aphid-resistant cultivars in northern region. iv To identify new sources of soybean aphid resistance in early maturing soybeans, a total of 334 soybean genotypes including resistant and susceptible checks were tested in the greenhouse and field. Caged (no-choice) and non-caged tests were employed in greenhouse screening under artificia-1 inoculation of soybean aphid, and field evaluations were performed relying on natural aphid infestation with or without artificial aphid inoculation. In the greenhouse, four genotypes (Pl 603712, Pl 464911, Pl 430491, and Pl 6034328) of maturity group (MG) 0 or 00 exhibited low levels of aphid colonization similar to resistant checks, with 17-52 aphids per plant two weeks after inoculation; and three genotypes (Pl 6127598, Pl 200595, and Pl 603426D) of MG O were moderately resistant. In the field, however, only Pl 603712 and Pl 430491 exhibited a resistance reaction with fewer than 100 or 100-200 aphids per plant at peak infestation. Pl 603712 was only genotype which consistently exhibited resistance to soybean aphid in all tests, even higher than that of other known sources of resistance in the field. This suggests that Pl 603712 might be a new source of soybean aphid resistance. Preliminary polymorphism analysis using simple sequence repeat (SSR) markers also suggested that Pl 603712 might have unique locus (loci) or allele(s) different than previously identified genes of soybean aphid resistance. Further study is necessary and helpful to genetically characterize and effectively use its resistance. In addition, the relatively high levels of soybean aphid colonization on a Rag1 genotype (Pl 548663 or Dowling) in greenhouse tests suggest that the colony used in greenhouse tests might be virulent on Rag1 and thus might be biotype 2. High levels of soybean aphid infestation on Rag1 and Rag2 genotypes in field tests also imply that biotypes 2 and 3 may have been present in the eastern South Dakota field.

Library of Congress Subject Headings

Soybean -- Disease and pest resistance Aphids Soybean -- Germplasm resources


Includes bibliographical references (pages 47-60)



Number of Pages



South Dakota State University


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