Association of Diaporthe longicolla with Black Zone Lines on Mature Soybean Plants

Abstract

In 2014, during a survey for soybean (Glycine max L.) diseases in Illinois, Indiana, Iowa, Michigan, and South Dakota, zone lines were observed on the lower stems of soybean plants. The survey was performed by sampling two to three fields per state. In each field, at least five plants exhibiting zone lines were collected. Isolations were made from the zone lines by plating 1-cm pieces on potato dextrose agar. A total of 90 isolates producing black stromata in concentric patterns and alpha conidia were tentatively identified as Diaporthe longicolla (Hobbs) Santos, Vrandecic and Phillips. DNA was extracted from the mycelia of 10 representative isolates and the identity was confirmed by sequencing the internal transcribed spacer (ITS) region. Additionally, phylogenetic analysis combining translation elongation factor-1a and actin sequences was performed and the ten isolates grouped with the D. longicolla ex-type cultures in a well-supported clade (94% bootstrap support). A pathogenicity test was performed in the greenhouse by inserting D. longicolla-infested toothpicks into the lower stems of the soybean plants. To complete Koch's postulates, D. longicolla was re-isolated from the zone lines of the inoculated plants and the pathogen identity was confirmed by sequencing the ITS gene. Accepted for publication 23 August 2015. Published 28 August 2015.

Soybean Stem Canker Caused by Diaporthe caulivora; Pathogen Diversity, Colonization Process, and Plant Defense Activation

“…This is consistent with recent results obtained by Ghimire et al (2019). D. longicolla has been previously isolated from SSC lesions (Gebreil et al, 2015;Mathew et al, 2015); it has been associated to black zone lines on the lower stems of soybean plants (Olson et al, 2015), and it causes soybean stem blight (Cui et al, 2009). D. longicolla causes also Phomopsis seed decay leading to a reduction in seed germination of up to 90% and seed FIGURE 9 | Defense-related genes expression levels in soybean stems after Diaporthe caulivora inoculation.…”

Diaporthe pseudolongicolla: The new pathogen on soybean seed in Serbia

“…However, D. longicolla has long been described as a fungus without the teleomorph stage whose pycnidia have very long necks that release only alpha conidia. Recent studies revealed new details on this fungus such as atypical symptoms on stems in the field, pycnidia with beta conidia and the ability to form teleomorph (Santos, Vrandečić, Ćosić, Duvnjak & Phillips, 2011;Vidić et al 2013;Olson et al 2015).…”

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

“…aspalathi and D . caulivora in having larger pycnidia, and longer conidiophores with alpha‐ and beta‐conidia (Olson et al., 2015; Santos et al., 2011; Vidić et al., 2013). Some isolates of D .…”

“…Recently, D . longicolla has been associated with stem canker lesions, and inoculation assays performed under field and laboratory conditions confirmed that this species causes SSC (Gebreil et al., 2015; Ghimire et al., 2019; Mathew, Castlebury, et al., 2015; Mena et al., 2020; Olson et al., 2015). Field losses due to SSC can reach levels of 80%–100% (Backman et al., 1985; Krausz & Fortnum, 1983).…”