Damping‐off of soybean in southern Brazil can be associated with different species of Globisporangium spp. and Pythium spp.

Abstract

Damping‐off of soybean is a common problem in some fields in southern Brazil. Frequently, Phytophthora sojae has been pointed out as the main causal agent. However, questions were raised as to whether other oomycetes could also be present. Hence, the objectives of this study were to isolate, identify, and determine the pathogenicity and aggressiveness of oomycetes isolated from soybean seedlings. Thirty‐three isolates were obtained from 13 fields. Isolates were identified based on morphology and molecular methods. Nine species were recovered: Pythium conidiophorum (n = 14, 42.4%), Globisporangium rostratifingens (n = 7, 21.2%), G. irregulare (n = 2, 6.1%), G. spinosum (n = 1, 3.0%), G. ultimum var. sporangiiferum (n = 2, 6.1%), Pythium acanthicum (n = 2, 6.1%), P. deliense (n = 1, 3.0%), P. inflatum (n = 1, 3.0%), and P. torulosum (n = 3, 9.1%). Pathogenicity and aggressiveness were determined with two soybean cultivars (DM57i52 and NEO530) in a seed rot assay and a root rot assay. All isolates were pathogenic to soybean with variable levels of aggressiveness in both assays. The range of seed disease severity index varied from 7.5 to 100 for DM57i52 and from 23.1 to 100 for NEO530. The mean root disease severity index of the soybean cultivars ranged from 29.4 to 92.8. This is the first official report of G. irregulare, G. rostratifingens, G. spinosum, G. ultimum var. sporangiiferum, P. acanthicum, P. conidiophorum, P. deliense, P. inflatum, and P. torulosum causing damping‐off of soybean in the state of Rio Grande do Sul in southern Brazil.

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

“…These species and isolates were chosen based on the results from a survey of soybean seedlings with symptoms in southern Brazil that revealed P. conidiophorum as the most frequent species recovered; in addition, G. irregulare and G. ultimum var. sporangiiferum were highly aggressive on soybean (Molin et al, 2021a). This information will be useful for breeding companies as well as growers that have reported problems with damping-off of soybean.…”

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Brazil is the largest soybean producer in the world (USDA, 2022). The area cultivated with soybean in the country is divided into macroregions due to the differences in environmental conditions (Kaster & Farias, 2012), which require cultivars adapted to each macroregion.Damping-off of soybean is a common problem reported by several growers in Macroregion 1 (Costamilan et al, 2013;Molin et al, 2021a), which includes the southern region of Brazil (Kaster & Farias, 2012). Symptoms of the disease include seed decay and root rot (Broders et al, 2007;Rojas et al, 2017), which can compromise seed germination, seedling emergence and initial establishment of

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“…In addition, other pathogens such as Rhizoctonia solani (Fenille et al, 2002), Fusarium spp. (Migliorini et al, 2018) and Globisporangium/Pythium complex (Molin et al, 2021a) have also been associated with the disease. There is some information on the reaction of Brazilian soybean cultivars to R. solani (Ben, 2015) and Fusarium (Gásperi et al, 2003); however, little is known about their reaction to Globisporangium/Pythium species.…”

Identification and Isolation Pattern of Globisporangium spp. from a Sanionia Moss Colony in Ny-Ålesund, Spitsbergen Is., Norway from 2006 to 2018

“…Globisporangium is the major genus of the oomycete segregated from the genus Pythium [23,24]. Globisporangium spp.…”

“…Globisporangium spp. are cosmopolitan, and many species of this genus can infect a variety of host species [24]. Some species of the genus cause snow rot disease in winter wheat and barley [25].…”