Metabolic Capacity Differentiates Plenodomus lingam from P. biglobosus Subclade ‘brassicae’, the Causal Agents of Phoma Leaf Spotting and Stem Canker of Oilseed Rape (Brassica napus) in Agricultural Ecosystems

Abstract

In contrast to the long-lasting taxonomic classification of Plenodomus lingam and P. biglobosus as one species, formerly termed Leptosphaeria maculans, both species form separate monophyletic groups, comprising sub-classes, differing considerably with epidemiology towards Brassicaceae plants. Considering the great differences between P. lingam and P. biglobosus, we hypothesized their metabolic capacities vary to a great extent. The experiment was done using the FF microplates (Biolog Inc., Hayward, CA, USA) containing 95 carbon sources and tetrazolium dye. The fungi P. lingam and P. biglobosus subclade ‘brassicae’ (3 isolates per group) were cultured on PDA medium for 6 weeks at 20 °C and then fungal spores were used as inoculum of microplates. The test was carried out in triplicate. We have demonstrated that substrate richness, calculated as the number of utilized substrates (measured at λ490 nm), and the number of substrates allowing effective growth of the isolates (λ750 nm), showed significant differences among tested species. The most efficient isolate of P. lingam utilized 36 carbon sources, whereas P. biglobosus utilized 60 substrates. Among them, 25–29 carbon sources for P. lingam and 34–48 substrates for P. biglobosus were efficiently used, allowing their growth. Cluster analysis based on Senath criteria divided P. biglobosus into two groups and P. lingam isolates formed one group (33% similarity). We deduce the similarities between the tested species help them coexist on the same host plant and the differences greatly contribute to their different lifestyles, with P. biglobosus being less specialized and P. lingam coevolving more strictly with the host plant.

Co‐inoculation timing affects the interspecific interactions between phoma stem canker pathogens Leptosphaeria maculans and Leptosphaeria biglobosa

“…Recent investigations have reported differences between L. maculans and L. biglobosa in terms of metabolic capacities. Leptosphaeria biglobosa is more efficient compared to L. maculans in terms of nutrient acquisition and utilisation of natural resources, 29,36 which is congruent with past reports indicating tissue colonisation by L. biglobosa occurs more rapidly compared to L. maculans 10,37 . The findings of this study further support this hypothesis since the mycelial growth rate coefficient of L. biglobosa was more than three times greater than that of L. maculans (Fig.…”

“…38,39 Additionally, one of the recent investigations of differences in metabolic capacity between Leptosphaeria species reported L. biglobosa to be less specialised, with L. maculans coevolving more strictly with the plant host. 36 Therefore, one of the hypotheses to explain the mechanisms of these interactions is that L. biglobosa utilised the resources more efficiently and potentially caused competitive exclusion of L. maculans by employing a resource-mediated (exploitative) competition strategy. 1 In return, L. maculans inhibited the growth of L. biglobosa dependent upon successful production of sirodesmin PL by employing an interference competition strategy.…”

“…Although both Leptosphaeria species were characterised to have hemi‐biotrophic lifestyles, differences between these two pathogens in terms of nutritional strategies were reported, with some even referring to L. biglobosa as a ‘necrotroph’ 38,39 . Additionally, one of the recent investigations of differences in metabolic capacity between Leptosphaeria species reported L. biglobosa to be less specialised, with L. maculans co‐evolving more strictly with the plant host 36 . Therefore, one of the hypotheses to explain the mechanisms of these interactions is that L. biglobosa utilised the resources more efficiently and potentially caused competitive exclusion of L. maculans by employing a resource‐mediated (exploitative) competition strategy 1 .…”

Microbial-Based Products to Control Soil-Borne Pathogens: Methods to Improve Efficacy and to Assess Impacts on Microbiome

“…Microplates (e.g., Phenotype MicroArray) can be used to compare the metabolism of multiple species in terms of potential niche overlap [ 66 , 67 ], i.e., to test individual strains in terms of carbon and nitrogen sources utilization [ 68 , 69 , 70 ]. Applying statistical or mathematical models to the data on metabolic dynamics, it is possible to predict the likelihood of two species competing once they are grown together.…”

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“…Several wild Brassicaceae (Descurainia, Sisymbrium, and Thlaspi) can also be infected with these fungi (West et al, 2001;Fitt et al, 2006;Zou et al, 2019;King, West, 2022). Plenodomus biglobosus and P. lingam differ from each other by micromorphological, cultural, physiological, biochemical and molecular phylogenetic features (Mendes-Pereira et al, 2003;Liu et al, 2014;Frac et al, 2022). It was considered that P. lingam is more aggressive than P. biglobosus and causes higher crop losses (West et al, 2001;Lob et al, 2013;Zou et al, 2019).…”