Identification of Quantitative Disease Resistance Loci Toward Four Pythium Species in Soybean

Abstract

In this study, four recombinant inbred line (RIL) soybean populations were screened for their response to infection by Pythium sylvaticum, Pythium irregulare, Pythium oopapillum, and Pythium torulosum. The parents, PI 424237A, PI 424237B, PI 408097, and PI 408029, had higher levels of resistance to these species in a preliminary screening and were crossed with “Williams,” a susceptible cultivar. A modified seed rot assay was used to evaluate RIL populations for their response to specific Pythium species selected for a particular population based on preliminary screenings. Over 2500 single-nucleotide polymorphism (SNP) markers were used to construct chromosomal maps to identify regions associated with resistance to Pythium species. Several minor and large effect quantitative disease resistance loci (QDRL) were identified including one large effect QDRL on chromosome 8 in the population of PI 408097 × Williams. It was identified by two different disease reaction traits in P. sylvaticum, P. irregulare, and P. torulosum. Another large effect QDRL was identified on chromosome 6 in the population of PI 408029 × Williams, and conferred resistance to P. sylvaticum and P. irregulare. These large effect QDRL will contribute toward the development of improved soybean cultivars with higher levels of resistance to these common soil-borne pathogens.

Breeding for disease resistance in soybean: a global perspective

“… 2000 ). Among the most damaging species, P. aphanidermatum , P. ultimum , P. irregulare , and P. sylvaticum have been used to screen potential sources of resistance for breeding efforts to reduce the impact of these pathogens (Ellis et al 2013b ; Scott et al 2019 ; Lin et al 2020 ; Clevinger et al 2021 ). Horizontal resistance is currently the only type of resistance identified for most Pythium species, except Rpa1 , which was identified from cv.…”

“…13) Rpa1 Satt510 and Satt114 (28,912,864–31,802,559 a2) Hypocotyl inoculation/isolate 64 F2:4 (86) R gene Archer Rosso et al ( 2008 ) Pythium irregulare MLG D1a (Chr. 1) - Satt515 (37,027,518 a2) Greenhouse test/isolates Br2-3–5, Cler1-4–1 F2:3 (192) 14.0% Weight, 17.7% Root rot PI424354 Ellis et al ( 2013b ) – Gm01_49641478_A_G (50,295,199–50,583,510 a2) Tray test/isolate Br2-3–5 SoyNAM RIL (116) 6.9% LG00-3372 Scott et al ( 2019 ) – Gm01_52253980_C_T (53,141,084 a2) Modified seed rot assay F9 (307) 6.6%SRS c , 7.4%ROTS d – Clevinger et al ( 2021 ) MLG D1b (Chr. 2) – Gm02_5035934_C_A (5,054,610–5,321,601 a2) Tray test/isolate Br2-3–5 SoyNAM RIL (91) 9.6% LD02-9050 Scott et al ( 2019 ) – Gm02_6529620_G_A (6,572,325–7,031,201 a2) Tray test/isolate Br2-3–5 SoyNAM RIL (91) 7.8% LD02-9050 Scott et al ( 2019 <...…”

Soybean cultivars adapted to southern Brazil differ in their reaction to Globisporangium irregulare, G. ultimum var. sporangiiferum and Pythium conidiophorum

“…oopapillum and P . torulosum (Clevinger et al, 2021). Moreover, four cultivars that were resistant to G .…”

“…oopapillum and P . torulosum (Clevinger et al, 2021), G . irregulare (Clevinger et al, 2021; Ellis et al, 2013) and G .…”

“…Genetic resistance of soybean to Globisporangium/Pythium can be conferred by either dominant genes (Rosso et al, 2008) or quantitative trait loci (QTLs) (Ellis et al, 2013;Klepadlo et al, 2019;Lin et al, 2018;Urrea et al, 2017). Some soybean cultivars have been reported in the United States as sources of resistance to P. aphanidermatum (Rosso et al, 2008;Urrea et al, 2017), P. sylvaticum, P. oopapillum and P. torulosum (Clevinger et al, 2021), G. irregulare (Clevinger et al, 2021;Ellis et al, 2013) and G. ultimum var. ultimum (Klepadlo et al, 2019;Rod et al, 2018).…”