The integrative taxonomy of Beauveria asiatica and B. bassiana species complexes with whole-genome sequencing, morphometric and chemical analyses

Abstract

Fungi are rich in complexes of cryptic species that need a combination of different approaches to be delimited, including genomic information. Beauveria (Cordycipitaceae, Hypocreales) is a well-known genus of entomopathogenic fungi, used as a biocontrol agent. In this study we present a polyphasic taxonomy regarding two widely distributed complexes of Beauveria: B. asiatica and B. bassiana s.lat. Some of the genetic groups as previously detected within both taxa were either confirmed or fused using population genomics. High levels of divergence were found between two clades in B. asiatica and among three clades in B. bassiana, supporting their subdivision as distinct species. Morphological examination focusing on the width and the length of phialides and conidia showed no difference among the clades within B. bassiana while conidial length was significantly different among clades within B. asiatica. The secondary metabolite profiles obtained by liquid chromatography-mass spectrometry (LC-MS) allowed a distinction between B. asiatica and B. bassiana, but not between the clades therein. Based on these genomic, morphological, chemical data, we proposed a clade of B. asiatica as a new species, named B. thailandica, and two clades of B. bassiana to respectively represent B. namnaoensis and B. neobassiana spp. nov. Such closely related but divergent species with different host ranges have potential to elucidate the evolution of host specificity, with potential biocontrol application. Citation: Kobmoo N, Arnamnart N, Pootakham W, et al. 2021. The integrative taxonomy of Beauveria asiatica and B. bassiana species complexes with whole-genome sequencing, morphometric and chemical analyses. Persoonia 47: 136-150. https://doi.org/10.3767/persoonia.2021.47.04.

Keywords: Beauveria; chemotaxonomy; population genomics; taxonomy.

Fig. 1

Population genomics analyses. a. A circular NJ tree based on whole-genome SNPs, the red asterisks represent the type strains of Beauveria asiatica (ARSEF4850) and B. bassiana (ARSEF1564), thick branches correspond to those supporting 100 % bootstrap; b. principal component analysis (PCA) for total sampling; c. Bayesian clustering for total sampling; d. Bayesian clustering for B. asiatica; e. PCA for B. bassiana; f. PCA for B. asiatica.

Fig. 2

A Bayesian phylogenetic tree based on concatenated 1 034 genes in Beauveria species. The red dots represent the nodes supported by 1.00 posterior probability. The highlighted clades are supported by Bayesian concordance factors with 95 % confidence interval.

Fig. 3

Morphometric analysis. a. Boxplots representing the distribution of the length and the width of phialides and conidia between Beauveria asiatica and B. bassiana. The red asterisks denote significant difference between the two species; b. boxplots representing the distribution of the length and the width of phialides and conidia between the clades within B. asiatica (left panel) and within B. bassiana (right panel).

Fig. 4

Statistical analyses of secondary metabolite profiles resulting from liquid chromatography-mass spectrometry (LC-MS). a. Euclidean distance-based NJ tree; b. principal component analysis (PCA) for total sampling (top panel) and for the clades within Beauveria asiatica and B. bassiana (bottom panel).

Fig. 5

The presence/absence of secondary metabolites gene clusters among Beauveria species. The isolates were ordered from left to right according to a binary distance-based clustering.

Fig. 6

Beauveria namnaoensis. a–d. Fungus on the hosts; e. colony obverse on PDA after 10 d; f. colony reverse on PDA after 10 d; g. colony obverse on PDA after 20 d; h. colony reverse on PDA after 20 d; i–j. phialides and conidia; k. conidia. — Scale bars: a, e–h = 10 mm; b–d = 5 mm; i = 10 μm; j–k = 5 μm.

Fig. 7

Beauveria neobassiana. a–h. Fungus on the hosts; i. colony obverse on PDA after 10 d; j. colony reverse on PDA after 10 d; k. colony obverse on PDA after 20 d; l. colony reverse on PDA after 20 d; m–n. phialides and conidia; o. conidia. — Scale bars: a–b, d–h = 5 mm; c, i–l = 10 mm; m = 10 μm; n–o = 5 μm.

Fig. 8

Beauveria thailandica. a. Stromata on host (Coleoptera larva); b–g. fungus on the hosts; h. fertile head; i. perithecia; j. asci; k. asci with asci caps; l. ascospore; m. part-spores; n. colony obverse on PDA in 10 d; o. colony reverse on PDA in 10 d; p. colony obverse on PDA in 20 d; q. colony reverse on PDA in 20 d; r–s. phialides and conidia; t. conidia. — Scale bars: a, n–q = 10 mm; b–g = 5 mm; h = 1 mm; i = 200 μm; j, l = 50 μm; k, r–t = 5 μm; m = 10 μm.