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ARS Home » Midwest Area » Ames, Iowa » Corn Insects and Crop Genetics Research » Research » Publications at this Location » Publication #318875
Title: Identifying new sources of resistance to Brown Stem Rot in Soybean

Author
item MCCABE, CHANTAL - Iowa State University
item SINGH, ASHEESH - Iowa State University
item LEANDRO, LEONOR - Iowa State University
item CIANZIO, SILVIA - Iowa State University
item Graham, Michelle

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/29/2016
Publication Date: 7/1/2016
Citation: McCabe, C.E., Singh, A., Leandro, L., Cianzio, S., Graham, M.A. 2016. Identifying new sources of resistance to Brown Stem Rot in Soybean. Crop Science. doi: 10.2135/cropsci2015.08.0492.

Interpretive Summary: Breeding for resistance to diseases and pests is important for protecting soybean yields. In 2010, 14 percent of total soybean yield, valued at $5.6 billion, was lost to disease or insect pests. Brown stem rot (BSR), caused by the fungus Phialophora gregata, can cause yield losses up to 38 percent. To date, few sources of resistance have been identified. In order to identify new sources of resistance, researchers screened the US germplasm collection. In this screen, four lines were identified with high levels of resistance to BSR. In this study, we used genetic testing to determine if resistance found in these lines was novel and could be used for breeding soybean with enhanced resistance to BSR.

Technical Abstract: Breeding for resistance to diseases and pests is an important objective to improve and protect soybean yields. In 2010, 14.4 percent of total soybean yield, valued at $5.59 billion, was suppressed by pathogenic diseases caused by fungi, microbes, and nematodes. Brown stem rot (BSR), caused by the fungus Phialophora gregata, may cause yield losses up to 38 percent. To date, three dominant BSR resistant genes have been identified: Rbs1, Rbs2, and Rbs3. However, additional loci in the soybean genome could contribute to BSR resistance. This research was conducted to determine if soybean accessions PI 594858B, PI 594637, PI 594638B, and PI 594650A contain novel BSR resistance loci and their mode of inheritance. The four accessions were individually crossed to the three known sources of BSR resistance. BSR severity was assessed in growth chambers five weeks after inoculation based on three measurements: plant vigor, incidence of discoloration, and recovery of P. gregata. Allelism tests with F2:3 plants from PI 594638B, PI 594858B, and PI 594650A fit a 15:1 segregation ratio, indicating non-allelism to Rbs1, Rbs2, and Rbs3. Therefore, these PIs contain at least one novel gene conferring resistance to the fungus. Crosses between these three lines will be needed to determine the number of novel genes identified. Progeny from PI 594637 segregate in a 3:1 ratio, indicating that PI 594637 is susceptible to BSR. These new sources of resistance have the potential to serve as donor genes in elite germplasm thereby increasing the stability of host resistance to P. gregata.