Resistance of the SoyNAM Parents to Seed and Root Rot Caused by Four Pythium Species

Abstract

<jats:p> Some Pythium spp. cause damping off and root rot in soybeans and other crop species. One of the most effective management tools to reduce disease is host resistance; however, little is known about resistance in soybean to Pythium spp. The soybean nested associated mapping (SoyNAM) parent lines are a set of germplasms that were crossed to a single hub parent to create recombinant inbred line populations for the purpose of mapping agronomic traits. The SoyNAM parents were screened for resistance to Pythium lutarium, Pythium oopapillum, Pythium sylvaticum, and Pythium torulosum in separate assays to evaluate seed and root rot severity. Of the 40 SoyNAM parents, only ‘Maverick’ was resistant to the four species tested; however, 13 were resistant to three species. Other lines were resistant to two, one, or none of the species tested. Correlations between seed and root rot severity for the lines assessed were weak or insignificant. Results indicate that mechanisms of resistance to seed and root rot caused by Pythium spp. may not necessarily be the same. </jats:p>

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

“…Archer is a cultivar that was identified with resistance to G. ultimum, G. irregulare, P. aphanidermatum and P. vexans (Bates et al, 2008). Additionally, Maverick is a soybean cultivar characterized as resistant to P. lutarium, P. oopapillum, P. sylvaticum and P. torulosum (Lerch-Olson et al, 2020).…”

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

“…Several studies have measured resistance toward different Pythium species (Rod et al, 2018;Lerch-Olson et al, 2020) and have identified QDRL, mostly minor, in RIL populations of soybean (Ellis et al, 2013;Stasko et al, 2016;Urrea et al, 2017;Klepadlo et al, 2019;Lin et al, 2018Lin et al, , 2020Scott et al, 2019). Almost all of the studies have shown partial resistance aside from one study by Rosso et al (2008) showing monogenic resistance.…”

“…AGERM was calculated as the number of germinated seeds that were inoculated/number of germinated seeds that were non-inoculated. There was a strong negative correlation between ROTS and AGERM, which was also seen in Lerch-Olson et al (2020). Therefore, AGERM data were not used for identifying QDRL.…”

“…All disease screenings were conducted at Iowa State University in 2018 in a growth room without light (Lerch-Olson et al, 2020). Each of the four populations was evaluated for resistance to two or three Pythium species (Table 1) in a modified seed rot assay (Zhang and Yang, 2000;Broders et al, 2007).…”

“…Five seeds from each RIL were placed on 4-day-old Pythium colonized plates and the plates were incubated in the dark for 7 days at 15 • C (P. oopapillum and P. torulosum) or 23 • C (P. irregulare and P. sylvaticum). The cultivar "Sloan" was used as a susceptible check (Lerch-Olson et al, 2020). Previous work identified "Sloan" as susceptible to multiple Pythium species (Broders et al, 2007;Matthiesen et al, 2016).…”