Nigrospora weininensis M.L. Liu & Z.F. Yang, 2024

Nigrospora weininensis M.L. Liu & Z.F. Yang , sp. nov. ( Fig. 1 View FIGURE 1 )

Mycobank number: MB856315.

Etymology:— The name reflects the location, Weinin county, where the fungus was first isolated.

Sexual morph: Not observed. Asexual morph: Sporulates on OA, after 2 weeks of incubation in the dark at 25 °C. Hyphae branched, septate, hyaline to pale brown, thick-walled. Conidiophores reduced to conidiogenous cells. Conidiogenous cells 3–5.6 × 2–3.6 μm (x̅ = 4.8 × 2.9 μm, n = 15), discrete, solitary, monoblastic, determinate, ampulliform to subglobose, straight or curved, olivaceous to pale brown. Conidia discrete on aerial mycelia on OA, 3.2–7.2 × 3.4–7.5 μm diam. (x̅ = 5.4 × 6.4 μm, n = 30), initially pale brown, becoming black when mature, globose to subglobose, shiny, smooth, aseptate.

Distribution:— Guizhou Province, China.

Type:— CHINA. Guizhou Province: Weining County, nematode cysts in the potato field, 9 July 2020, Zaifu Yang , HGUP 23-0017 (holotype) ; ex-type GUCC 23-0144 .

Hosts:— Cysts of PCN.

Other materials examined:— CHINA. Guizhou Province: Weining county, cysts of PCN in the potato roots ( Fig.2 a,b View FIGURE 2 ), 9 July 2020, Zaifu Yang, living cultures, GUCC 23-0145, and GUCC 23-0146.

GenBank numbers:—

ITS: PP729081, PP729082, PP729083

tef 1-α: PP731561, PP731562, PP731563

β-tubulin: PP737836, PP737837, PP737838

Notes:— The sequence data of ITS, β-tubulin, and tef 1-α of our collections (GUCC 23-0144, GUCC 23-0145, and GUCC 23-0146) provided species in Nigrospora as the closest matches in NCBI. The phylogenetic analysis ( Fig. 2 View FIGURE 2 ) showed that our collections were genetically close to N. osmanthi but distinct, forming a clade with MP/BI = 100%/1.00 statistical support. However, in morphology, our taxon differs from N. osmanthi by cylindrical, solitary conidiogenous cells and small conidia, while N. osmanthi has globose to ampulliform conidiogenous cells aggregated in clusters on hyphae and large conidia (3.2–7.2 × 3.4–7.5 vs 9–11.5 × 12.5–14.6 μm diam.) ( Wang et al. 2017). Therefore, we introduced our collections as a novel taxon, Nigrospora weininensis sp. nov.

Nematicidal activity of the N. weininensis (GUCC 23-0144) fungal fermentation filtrate

The corrected mortality rate of A. besseyi was more than 80% but less than 100% after treating it with the fermentation filtrate of N. weininensis for only 12 h ( Fig. 3a View FIGURE 3 ). Between 12 and 24 h, the corrected mortality rate reached 100%. The original fermentation filtrate was diluted five times (i.e. to 20% fermentation filtrate). Within 72 h of treating A. besseyi , the corrected mortality rate reached 100%. When the original fermentation filtrate was diluted ten times (10% fermentation filtrate), the corrected mortality rate did not exceed 20%.

The corrected mortality rate of B. xylophilus was 100% after only 12 h treating with the fermentation filtrate stock solution of N. weininensis ( Fig. 3b View FIGURE 3 ). When treated with 20% fermentation filtrate the mortality rate of B. xylophilus was less than 20%. After 72 h, the corrected mortality rate of B. xylophilus treated with 10% fermentation filtrate for 72 h was less than 20%.

The corrected mortality rate of D. destructor when treated with both undiluted and 20% fermentation filtrate, was 100% after only 12 h. When treated with When treated with 10% fermentation filtrate, the corrected mortality rate of D. destructor exceeded 50% within 48–72 h.