Bipolaris heliconiae Alcorn, Aust. Syst. Bot. 9(5): 814 (1996).
Index Fungorum number: IF 436839; Mycobank number: MB 436839; Facesoffungi number: FoF 11035; Fig. 1
Holotype – AMH10416.
Colour code follows – Methuen Handbook of Colour (Kornerup and Wanscher 1978).
On leaf of Dypsis lutescens in terrestrial habitats. Infection spots amphiphilous, fructifications amphigenous, small, circular, dark brown, latter collapse to each other. Sexual morph: Undetermined. Asexual morph: stromatal cells 2–5 in groups, light to olivaceous brown (7D8). Setae and hyphopodia absent. Conidiophores superficial, straight to curved, solitary or in groups, unbranched to rarely dichotomously branched, basal cell of conidiophores slightly bulbous, geniculate in fertile region, scars slightly thickened, smooth walled, light brown (7D8), 2–12 septate, 103.30–335.50×7.0–16.5 μm. Conidia acropleurogenous, cylindrical, clavate to obclavate, smooth walled, light brown (7D8), transversely septate, 1–11 septate, hilum slightly thickened, non-protuberant, base truncate, tip obtuse, 43.0–192.0×7.5–17.0 μm.
In-vitro culture, vegetative hyphae, unbranched to branched, septate, thin and thick, pigmented, subhyaline to very light olivaceous brown(7D8), 3.0–9.0 μm wide. Chlamydospores absent. Setae and hyphopodia absent. Conidiophores arising from superficial hyphae, macronematous, mononematous, unbranched to dichotomously branched, straight to flexuous, multi-septate, smooth walled, scars slightly thickened, light olivaceous brown (7D8), up to 612.0 × 9.5 μm. Conidia acropleurogenous, straight to slightly curved, clavate to obclavate, non-protuberant, hilum slightly thickened, olivaceous to light olivaceous brown (7D8), transversely septate, smooth walled, base truncate, tip obtuse, pseudoseptate, 3–7 septate, inner cells discoid, 72.5–10.0×15.5–21.5 μm.
Culture characteristics – On semi-synthetic agar medium PDA (Potato Dextrose Agar) greyish white (5A1), greyish brown (5A2) reaching 3 cm diam in 8 days at 25 °C, with irregular margin, puffy, surface filamentous.
Material examined – India, Maharashtra, Pune District, on infected leaves of Dypsis lutescens (Arecaceae), 5 September 2021, P.N. Singh, AMH10416 (holotype); ex-type living culture, NFCCI5165 (National Fungal Culture Collection of India- WDCM 932, new record for India).
GenBank numbers – ITS=ON028647, LSU=ON032299, TEF1-α=ON148454.
Notes – The present taxon is distinct from type species Bipolaris heliconiae (BRIP 17186) (Alcorn 1996) in having smaller conidia (72.65–99.75 ×15.72–21.55 μm with 3–7 septa vs. 65–150 × 15–19 μm with 7–10 septa). In addition to this, the conidia of NFCCI 5165 are clavate to obclavate, whereas conidia of BRIP 17186 are fusoid to clavate fusoid. Bipolaris heliconiae (NFCCI 5165) clusters with Bipolaris heliconiae (BRIP 17189) and B. heliconiae (BRIP 17186) (Alcorn 1996) with 97% bootstrap support. On megablast analysis, our ITS sequence is showing 99% similarity (397/400) with 1 gap (0%) with both Bipolaris heliconiae (BRIP 17189) and Bipolaris heliconiae (BRIP 17186) (Fig. 2).
Figure 1 – Bipolaris heliconiae NFCCI 5165 (AMH10416, holotype). a Substratum (leaf of Dypsis lutescens). b Stereomicroscopic surface view of infected leaf. c Colony morphology on PDA (front view on 7th days). d Branched conidiophores. e An unbranched cylindrical conidiophore. f–m Different types of conidia. n–o SEM images of conidia. p SEM images of branched conidiophores with numerous conidia. Scale bars d–o=10 μm, p=20 μm
Figure 2 – Phylogenetic tree of Bipolaris heliconiae (NFCCI 5165) constructed based on combined sequence data of ITS, LSU and TEF by Maximum-Likelihood method. Curvularia tuberculata CBS 146.63 was used as out-group. The analysis involved 51 nucleotide sequences. Evolutionary analyses were conducted in IQ–TREE multicore version 1.6.11 (Nguyen et al. 2015) by the Maximum–Likelihood method using the best suitable model (TITNe+R2 model). Newly generated sequence is in blue. One–thousand bootstrap replicates were analyzed to get ultrafast bootstrap values, and the values above 50% were represented on nodes in the tree. Ex-type strains are in bold and new isolate is in blue