Microcera pseudaulacaspidis Feng Liu & C.L. Yang, sp. nov.

Liu, Feng, Deng, Yu, Wang, Fei-Hu, Jeewon, Rajesh, Zeng, Qian, Xu, Xiu-Lan, Liu, Ying-Gao & Yang, Chun-Lin, 2023, Morphological and molecular analyses reveal two new species of Microcera (Nectriaceae, Hypocreales) associated with scale insects on walnut in China, MycoKeys 98, pp. 19-35 : 19

Microcera pseudaulacaspidis Feng Liu & C.L. Yang, sp. nov.

Fig. 3

Etymology.

In reference to the generic name of scale insect from which it was isolated.

Holotype.

SICAU 22-0161.

Host.

Pseudaulacaspis pentagona ( Diaspididae , Homoptera )

Habitat.

On the trunk of Juglans regia .

Sexual state.

Undetermined.

Asexual state.

Stromata byssoid, well-developed, bright orange to orange-red, formed directly on the margin of host scales or their covers with 1-7 sporodochia. Sporodochia 250-900 μm long, 400-860 µm wide, (x-= 620 × 570 μm, n = 50), conical, orange-red, upright masses on margin of host scales. Macroconidia 70-120 µm long × 4.2-10.5 µm wide (x-= 95.7 × 6.5 μm, n = 50), hyaline or jasmine, cylindrical, slightly curved, slender towards each end, 3-10 septate, mostly 7-9 septate, difficult to distinguish apical cell and basal cell. Microconidia and chlamydospores were not observed.

Material examined.

China, Sichuan Province, Neijiang City, Dongxing District, Paifang Village walnut industrial base (29°48′15″N, 105°06′44″E, alt. 340 m), on scale insect Pseudaulacaspis pentagona , 16 April 2022, Feng Liu, LF 202204001, (SICAU 22-0161, holotype), ex-type culture SICAUCC 22-0163 .

Culture characters.

Colonies from a single macroconidium on PDA grow slowly and reach approximately 2 cm in diameter after 12 days at 25 °C, circular, flat, producing masses of macroconidia in the centre of the colony, measuring 76-125 µm long × 5.3-7.6 µm wide (x-= 91.2 × 6.3 µm, n = 50), smaller than those in nature, white mycelium on the surface and the back of colonies is dark orange.

Notes.

Based on multi-gene phylogenetic analyses, Microcera pseudaulacaspidis is closely related to M. kuwanaspidis (Fig. 1 ). However, we observed significant differences in the DNA sequence data, including base-pair differences and gaps, with values of 1.45% (0 gaps), 17.67% (17 gaps), 3.22% (2 gaps), 1.53% (2 gaps), 1.70% (1 gap) and 3.82% (1 gap) in the ITS, LSU, tef 1-α, tub 2, cmd A and his 3 genes, respectively. The PHI test also showed that no significant recombination events between M. pseudaulacaspidis and closely phylogenetically-related species occurred (Fig. 2 ). Based on a comparison of their morphological characteristics, M. pseudaulacaspidis can be distinguished from M. kuwanaspidis by shorter macroconidia (95.7 × 6.5 µm vs. 107 × 7.3 µm) with more septa (7-9-septate vs. 5-7-septate) ( Xu et al. 2021). Given the morphological dissimilarities, distinct nucleotides at various sites and the well-supported lineage in our phylogeny, we have sufficient evidence to establish M. pseudaulacaspidis as a new species.

Figures

Figure 1. Phylogram generated from RAxML analysis, based on combined ITS, LSU, tef 1 - α, rpb 1, r pb 2, a cl 1, act, tub 2, cmd A and his 3 sequence data of Microcera isolates. Bootstrap support values from Maximum Likelihood (MLBS, left) higher than 75 % and Bayesian posterior probabilities (BIPP, right) equal to or greater than 0.95 are indicated at the nodes, respectively. The sequences from ex-type strains are in bold. The newly-generated sequence is in red.

Figure 2. The result of the pairwise homoplasy index (PHI) test of closely-related species using both LogDet transformation and Splits decomposition. PHI test results (Fw) <0.05 indicate significant recombination within the dataset.

Figure 3. Microcera pseudaulacaspidis (SICAU 22 - 0161) a, b stromata and sporodochia on host substrate c-e conidiophore with developing macroconidia f germinated conidium g-o Macroconidia o, p colonies on PDA after 30 days. Scale bars: 200 µm (a, b); 20 µm (c-e); 10 µm (f-n).