Pustula junggarensis B. Xu & Z. D. Jiang, 2016

Xu, Biao, Song, Jiage, Xi, Pinggen & Jiang, Zide, 2016, Pustula junggarensis (Albuginales, Oomycota), a new species of white blister rust on Takhtajaniantha pusilla from Junggar Basin in China, Phytotaxa 289 (1), pp. 83-87 : 84-85

Pustula junggarensis B. Xu & Z. D. Jiang , sp. nov. Fig.1

MycoBank no.:—MB817737

Etymology:—the new species in named after the location Junggar Basin where the pathogen was collected.

Holotype:— CHINA, Xinjiang, South Mountain of Manas County (N 44 o 57’56”, E 86 o 05’17”), on Takhtajaniantha pusilla (Pall.) Nazarova , 18 April 2016, coll. B. Xu and J. G. Song, HMUT T-1601 . Sequences ex holotype: GenBank KX 589297 for cox2 mtDNA and KX589300 for ITS nrDNA.

Additional collections examined (paratypes):— CHINA, Xinjiang, Shihezi County (N 44 o 14’17”, E 86 o 02’46”), on Takhtajaniantha pusilla , 19 April 2016, coll. B. Xu and J. G. Song, HMUT 16022 ; Shawan County (N 44 o 29’53”, E 85 o 37’82”), on Takhtajaniantha pusilla , 21 April 2016, coll. B. Xu and J. G. Song, HMUT 16023 .

Description: Mycelium intercellular. Sori covered by the epidermis of leaves and stems, distinct, round or irregular, often confluent, 1–2 mm diam., white to yellowish, mature sporangia dispersed through ruptured epidermis of the host plant ( Figs 1A, 1B ). Sporangiophores hyaline, clavate or cylindrical, straight to slightly curved ( Fig. 1D ), 35.5–55.6 μm long 13.2–14.8 μm wide, bearing sporangia in chains. Sporangia hyaline, primary sporangia depressed, (15.7)17.6–24.3(29.6) μm (av. 22.6 μm) × (15.1)17.6–21.6(24.8) μm (av. 18.7 μm) with wall of 1.8–3 μm thickenss (n=150), secondary sporangia subglobose, (15.3)18.2–21.8(23.4) μm (av. 20.9 μm) × (14.9)16.2–20.3(21.2) μm (av. 18.5 μm) with annulus of 1.5–2.3 μm thickness (n=120) ( Fig. 1C ). Oogonia globose to subglobose, 66.5–87.2 μm in diameter ( Fig. 1G ). Antheridia single ( Fig. 1G ), elongated 20–31 μm long, 6–12 μm wide. Oospores yellowish to dark reddish-brown, globose to subglobose ( Fig. 1F ), (45.4)54.6–65.4(68.5) μm (av. 62.5μm) in diameter (n=102), inner walls on average 2.7 μm thick (n=70), outer wall on average 5.2 μm thick (protuberances included) (n=85), protuberances 2.1–3.0 μm high, pattern reticulate with areolae 2.1–4.8 μm wide (n=75) ( Fig. 1E ).

Phylogenetic analyses

The GenBank BLAST search of the pathogen sequences showed that the Pustula junggarensis on Takhtajaniantha pusilla belonged to Pustula . Based on the molecular phylogenetic trees generated from the ML, ME and BI analyses of the cox 2 mtDNA regions, sequences of the three P. junggarensis specimens formed an independent clade with supports of 99, 97 and 0.99, respectively ( Fig. 2 ). The clade of the new pathogen was separated but sister to Pustula obtusata with supports of 96, 56, and 0.83, respectively. The ITS sequence data of these specimens were deposited in GenBank, but not analysed by phylogenetic approaches.

Figures

FIGURE 1. Pustula junggarensis. A, B: Disease symptoms and signs of the pathogen in stems and leaves. C: Sporangia; D: Sporogenous hyphae; E: Surface ornamentation of oospores; F: Oospores; G: Oogonium and antheridium; Bar: C, D = 20μm; E, F, G = 50 μm.

FIGURE 2. Phylogenetic relationship between Pustula junggarensis specimens and some reference sequences retrieved from GenBank, inferred by Minimum Evolution, Maximum Liklihood and Bayesian analysis using the cox2 mtDNA. Sequences of Pustula junggarensis are shown in bold. Numbers above the branches represent bootstrap support values of over 50% obtained from 1,000 bootstrap replicates. Bar = Number of nucleotide substitutions per site.