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Identifying New Sources of Resistance to Brown Stem Rot in Soybean
Author(s) -
McCabe Chantal E.,
Singh Asheesh K.,
Leandro Leonor F.,
Cianzio Silvia R.,
Graham Michelle A.
Publication year - 2016
Publication title -
crop science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.76
H-Index - 147
eISSN - 1435-0653
pISSN - 0011-183X
DOI - 10.2135/cropsci2015.08.0492
Subject(s) - biology , stem rot , germplasm , population , inoculation , pycnidium , horticulture , plant disease resistance , botany , gene , genetics , demography , sociology
Brown stem rot (BSR), caused by the fungus Phialophora gregata f. sp. sojae (Allington & D.W. Chamberlain) W. Gams (syn. Cadophora gregata ), causes yield losses up to 38%. Three dominant BSR‐resistant genes have been identified: Rbs1 , Rbs2 , and Rbs3 . Additional BSR resistance loci will complement breeding efforts by expanding the soybean [ Glycine max (L.) Merr.] genetic base. The objective of this research was to determine if PI 594637, PI 594638B, PI 594650A, and PI 594858B contained novel BSR resistance genes. The accessions were crossed to three genotypes with known BSR resistance genes and populations were developed for allelism studies. A minimum of 60 F 2:3 families tracing to individual F 2 plants in each population were used, and six seeds from each F 2:3 family were tested. Resistant and susceptible controls and parents were also included. The BSR symptoms were assessed under growth chamber conditions 5 wk after inoculation by measuring foliar and stem severities and recovery of P. gregata from stem sections. Allelism tests of F 2:3 plants from crosses of PI 594638B, PI 594858B, and PI 594650A with the resistant sources fit a 15:1 ratio, indicating that the resistant gene possessed by each of the PIs was nonallelic to Rbs1 , Rbs2 , and Rbs3 . The three PIs contain at least one novel BSR resistance gene and have the potential to serve as donors to elite germplasm, increasing stability of host resistance to P. gregata . Allelism tests of PI 594637 segregated in a 3:1 ratio and no significant difference was found between PI 594637 and the susceptible controls, indicating that PI 594637 is susceptible to BSR.