Inoculum potential of Sclerotinia sclerotiorum sclerotia depends on isolate and host plant

Abstract

The soilborne fungus Sclerotinia sclerotiorum infects many important crop plants. Central to the success of this pathogen is the production of sclerotia, which enables survival in soil and constitutes the primary inoculum. This study aimed to determine how crop plant type and S. sclerotiorum isolate impact sclerotial production and germination and hence inoculum potential. Three S. sclerotiorum isolates (L6, L17, L44) were used to inoculate plants of bean, carrot, lettuce, oilseed rape (OSR) and potato, and the number and weight of sclerotia per plant quantified. Carpogenic germination of sclerotia collected from different hosts was also assessed for L6. Production of sclerotia was dependent on both crop plant type and S. sclerotiorum isolate, with OSR and lettuce supporting the greatest number (42–122) and weight (1.6–3.0 g) of sclerotia per plant. The largest sclerotia were produced on OSR (33–66 mg). The three S. sclerotiorum isolates exhibited a consistent pattern of sclerotial production irrespective of crop type; L6 produced large numbers of small sclerotia while L44 produced smaller numbers of large sclerotia, with L17 intermediate between the two. Germination rate and percentage was greatest for larger sclerotia (4.0–6.7 mm) and also varied between host plants. Combining sclerotial production data and typical field crop densities suggested that infected carrot and OSR could produce the greatest number (3944 m−2) and weight (73 g m−2) of S. sclerotiorum sclerotia, respectively, suggesting these crops potentially contribute a greater increase in inoculum. This information, once further validated in field trials, could be used to inform future crop rotation decisions.

Automated image processing framework for analysis of the density of fruiting bodies of Leptosphaeria maculans on oilseed rape stems

“…The technical difficulty of estimating fruiting body numbers on a large quantity of debris has slowed down this research. Direct enumeration can be achieved for large sclerotia of Sclerotinia sclerotiorum (Taylor et al , ) but it becomes impractical for microsclerotes, such as those of Ramolispora sorghi (Brady et al , ). Similarly, some authors have been able to estimate perithecia of Mycosphaerella fijiensis on leaves (Burt et al , ) or pseudothecia of Leptosphaeria maculans on stubble (Lô‐Pelzer et al , ), but without automated phenotyping methods, the observation time and tediousness limit the number of samples that can be processed.…”

Application of pimaricin against potato white mould

“…For example, contrary to the isolates 2 and 3, carpogenic germination of isolate 1 was completely inhibited at the concentration of 2.5 mg/L. It is reported that different isolates of S. sclerotiorum show a variety of reactions to ecological situations, non‐chemical and biocontrol agents (Wu & Subbarao, 2008; Ojaghian, 2011, Ojaghian et al, 2015, Ojaghian et al, 2016; Taylor et al., 2018).…”

Inhibitory effect of natamycin against carrot white mold caused by Sclerotinia sclerotiorum

“…4). It is reported that different isolates of S. sclerotiorum show a variety of reactions to ecological situations, nonchemical, and biocontrol agents (Wu and Subbarao 2008;Ojaghian 2011;Ojaghian et al 2015Ojaghian et al , 2016bTaylor et al 2018).…”