title: Pyramided QTL underlying tolerance to Phytophthora root rot in mega-environments from soybean cultivars 'Conrad' and 'Hefeng 25'.
abstract: Phytophthora root rot (PRR) of soybean (Glycine max (L.) Merr.) is the second most important cause of yield loss by disease in North America, surpassed only by soybean cyst nematode (Wrather et al. in Can J Plant Pathol 23:115-121, 2001). Tolerance can provide economically useful disease control, conditioning partial resistance of soybean to PRR. The aims of this study were to identify new quantitative trait loci (QTL) underlying tolerance to PRR, and to evaluate the effects of pyramided or stacked loci on the level of tolerance. A North American cultivar 'Conrad' (tolerant to PRR) was crossed with a northeastern China cultivar 'Hefeng 25' (tolerant to PRR). Through single-seed descent, 140 F2:5 and F2:6 recombinant inbred lines were advanced. A total of 164 simple sequence repeat (SSR) markers were used to construct a genetic linkage map. The percentage of seedling death was measured over 2 years (2007 and 2008) in the field at four naturally infested locations in Canada and China following additional soil infestation and in the greenhouse following inoculation with Phytophthora sojae isolate. A total of eight QTL underlying tolerance to PRR were identified, located in five linkage groups (F, D1b+w, A2, B1, and C2). The phenotypic variation contributed by the loci ranged from 4.24 to 27.98%. QPRR-1 (anchored in the interval of SSR markers Satt325 and Satt343 of LG F), QPRR-2 (anchored in the interval of Satt005 and Satt600 of LG D1b+w), and QPRR-3 (anchored in the interval of Satt579 and Sat_089 of LG D1b+w) derived their beneficial allele from 'Conrad'. They were located at chromosomal locations known to underlie PRR tolerance in diverse germplasm. Five QTL that derived beneficial alleles from 'Hefeng 25' were identified. The QTL (QPRR-1 to QPRR-7) that were detected across at least three environments were selected for loci stacking and to analyze the relationship between number of tolerance loci and disease loss percentage. The accumulation of tolerance loci was positively correlated with decreases in disease loss percentage. The pyramid of loci underlying tolerance to PRR provided germplasm useful for crop improvement by marker-assisted selection and may provide durable cultivar tolerance against the PRR disease.
authors.affiliation: Soybean Research Institute, Key Laboratory of Soybean Biology in Chinese Ministry of Education, Northeast Agricultural University, 150030 Harbin, China.
authors.forename: Xiuping
authors.initials: X
authors.lastname: Li
authors.forename: Yingpeng
authors.initials: Y
authors.lastname: Han
authors.forename: Weili
authors.initials: W
authors.lastname: Teng
authors.forename: Shuzheng
authors.initials: S
authors.lastname: Zhang
authors.forename: Kangfu
authors.initials: K
authors.lastname: Yu
authors.forename: Vaino
authors.initials: V
authors.lastname: Poysa
authors.forename: Terry
authors.initials: T
authors.lastname: Anderson
authors.forename: Junjie
authors.initials: J
authors.lastname: Ding
authors.forename: Wenbin
authors.initials: W
authors.lastname: Li
mesh_terms: D000222:Adaptation, Physiological / Q000235:genetics*; D000483:Alleles; D004777:Environment; D008040:Genetic Linkage; D007178:Inbreeding; D010641:Phenotype; D010838:Phytophthora / Q000502:physiology*; D010935:Plant Diseases / Q000235:genetics* / Q000382:microbiology; D018517:Plant Roots / Q000235:genetics / Q000382:microbiology*; D040641:Quantitative Trait Loci / Q000235:genetics*; D013025:Glycine max / Q000235:genetics / Q000382:microbiology*
references.citation: Crop Sci. 2002 Jan;42(1):271-277
references.pmid: 11756285
references.citation: Annu Rev Phytopathol. 2002;40:381-410
references.pmid: 12147765
references.citation: Proc Natl Acad Sci U S A. 1993 Dec 1;90(23):10972-6
references.pmid: 8248199
references.citation: Genetics. 1994 Nov;138(3):963-71
references.pmid: 7851788
references.citation: Nature. 2000 Aug 17;406(6797):718-22
references.pmid: 10963595
references.citation: Theor Appl Genet. 2003 Aug;107(4):745-50
references.pmid: 12783169
references.citation: Theor Appl Genet. 2004 Jun;109(1):122-8
references.pmid: 14991109
references.citation: Genomics. 1987 Oct;1(2):174-81
references.pmid: 3692487
references.citation: J Hered. 2002 Jan-Feb;93(1):77-8
references.pmid: 12011185
references.citation: Theor Appl Genet. 2002 Feb;104(2-3):294-300
references.pmid: 12582700