First Report of Diaporthe ueckerae Causing Stem Canker on Soybean (Glycine max) in Colombia

Abstract

In October 2018, soybean plants displaying elongated black to reddish-brown lesions on stems were observed in a field planted to the cv. BRS Serena in the locality of Puerto López (Meta, Colombia), with 20% incidence of diseased plants. Symptomatic stems were collected from five plants, and small pieces (∼5 mm2) were surface sterilized, plated on potato dextrose agar (PDA) and incubated for 2 weeks at 25°C in darkness. Three fungal isolates with similar morphology were obtained, i.e., by subculturing single hyphal tips, and their colonies on PDA were grayish-white, fluffy, with aerial mycelium, dark colored substrate mycelium, and produced circular black stroma. Pycnidia were globose, black, occurred as clusters, embedded in tissue, erumpent at maturity, with an elongated neck, and often had yellowish conidial cirrus extruding from the ostiole. Alpha conidia were observed for all isolates after 30 days growth on sterile soybean stem pieces (5 cm) on water agar, under 25ºC and 12 h light/12h darkness photoperiod. Alpha conidia (n = 50) measured 6.0 – 7.0 µm (6.4 ± 0.4 µm) × 2.0 – 3.0 µm (2.5± 0.4 µm), were aseptate, hyaline, smooth, ellipsoidal, often biguttulate, with subtruncate base. Beta conidia were not observed. Observed morphological characteristics of these isolates were similar to those reported in Diaporthe spp. by Udayanga et al. (2015). DNA from each fungal isolate was used to sequence the internal transcribed spacer region (ITS), and the translation elongation factor 1-α (TEF1) gene, using the primer pairs ITS5/ITS4 (White et al. 1990) and EF1-728F/EF1- 986R (Carbone & Kohn, 1999), respectively. Results from an NCBI-BLASTn, revealed that the ITS sequences of the three isolates (GenBank accessions MW566593 to MW566595) had 98% (581/584 bp) identity with D. miriciae strain BRIP 54736j (NR_147535.1), whereas the TEF1 sequences (GenBank accessions MW597410 to MW597412) had 97 to 100% (330-339/339 bp) identity with D. ueckerae strain FAU656 (KJ590747). The species Diaporthe miriciae R.G. Shivas, S.M. Thomps. & Y.P. Tan, and Diaporthe ueckerae Udayanga & Castl. are synonymous, with the latter taking the nomenclature priority (Gao et al. 2016). According to a multilocus phylogenetic analysis, by maximum likelihood, the three isolates clustered together in a clade with reference type strains of D. ueckerae (Udayanga et al. 2015). Soybean plants cv. BRS Serena (growth stages V3 to V4) were used to verify the pathogenicity of each isolate using a toothpick inoculation method (Mena et al. 2020). A single toothpick colonized by D. ueckerae was inserted directly into the stem of each plant (10 plants per isolate) approximately 1 cm below the first trifoliate node. Noncolonized sterile toothpicks, inserted in 10 soybean plants served as the non-inoculated control. Plants were arbitrarily distributed inside a glasshouse, and incubated at high relative humidity (>90% HR). After 15 days, inoculated plants showed elongated reddish-brown necrosis at the inoculated sites, that were similar to symptoms observed in the field. Non-inoculated control plants were asymptomatic. Fungal cultures recovered from symptomatic stems were morphologically identical to the original isolates. This is the first report of soybean stem canker caused by D. ueckerae in Colombia. Due to the economic importance of this disease elsewhere (Backman et al. 1985; Mena et al. 2020), further research on disease management strategies to mitigate potential crop losses is warranted.

New polyketides from the liquid culture of Diaporthe breyniae sp. nov. (Diaporthales, Diaporthaceae)

“… Diaporthe ueckeri (syn. D. miriciae , Gao et al 2016 ) has been reported in Australia, Colombia and the USA, on Cucumis melo ( Cucurbitaceae , Cucurbitales ), Glycine max ( Fabaceae , Fabales ) and Helianthus annuus ( Asteraceae , Asterales ) ( Thompson et al 2015 ; Udayanga et al 2015 ; López-Cardona et al 2021 ). Diaporthe thunbergiicola has been only isolated from Thunbergia laurifolia ( Acanthaceae , Lamiales ) in Thailand ( Liu et al 2015 ).…”

Current understanding of the Diaporthe/Phomopsis complex causing soybean stem canker: A focus on molecular aspects of the interaction

“…are able to infect a range of other plants when artificially inoculated (Li et al, 2010). This is the case for D. caulivora, D. longicolla, D. gulyae, D. miriciae, D. cucurbitae and D. helianthi, which were able to cause stem canker in soybean and sunflower upon inoculation assays (Floyd & Malvick, 2022;López-Cardona et al, 2021;Mathew et al, 2018;Mena et al, 2020).…”

“…gulyae and D . miriciae were also detected in SSC symptomatic soybean plants in North Dakota, United States, and in Meta, Colombia (López‐Cardona et al., 2021; Mathew et al., 2018). Recently, D .…”

“…cucurbitae and D . helianthi , which were able to cause stem canker in soybean and sunflower upon inoculation assays (Floyd & Malvick, 2022; López‐Cardona et al., 2021; Mathew et al., 2018; Mena et al., 2020). Survival and perithecia development of D .…”

Development of rapid DNA extraction and PCR amplification methods for fungi and parasitic plants

“…Puccinia thaliae, Athelia rolfsii, Talaromyces siamensis, Neoscytalidium dimidiatum, Nigrospora sphaerica, Nigrospora aurantiaca, Colletotrichum siamense, Lasiodiplodia theobromae, Neopestalotiopsis cubana, Epicoccum sorghinum, Fusarium oxysporum, Diaporthe ueckerae, Hypoxylon hypomiltum, Fusarium proliferatum, Daldinia eschscholtzii, and Macrophomina phaseolina, and parasitic plants, viz. Cuscuta australis and Cassytha filiformis, are the common pathogens that have been reported to cause plant disease (Rattan, 2005;Li et al, 2015;Ghuffar et al, 2018;Lee et al, 2019;Elahi et al, 2021;López-Cardona et al, 2021;b;c;g;i;j;. To identify and detect the pathogens, the PCR is used to target the specific regions in pathogens' genomic DNA (Lau, Botella, 2017).…”