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. 2026 Jul 28;137:317–336. doi: 10.3897/mycokeys.137.192271

Morphology and multigene phylogeny reveal two new species of Micropsalliota (Agaricaceae, Basidiomycota) from Dhofar region, southern Oman

Hamed Al-Nadabi 1,✉, Shah Hussain 1,✉, Ahmed Al Sidairi 1, Khalifa Al-Zeidi 1, Ahmed Al-Raeesi 1, Rahil Al-Badi 1, Lujain Al-Rashdi 1, Jumana Al-Jashmi 1, Rethinasamy Velazhahan 2, Abdullah M Al-Sadi 2,3,4
PMCID: PMC13439166  PMID: 42559107

Abstract

Micropsalliota is a genus of small to relatively medium-sized saprotrophic mushrooms, with fibrillose-squamulose pileus surface, ellipsoid to amygdaliform or cymbiform basidiospores, usually with capitate cheilocystidia, and encrusted pileus hyphae. In this study, two new species, namely Micropsalliota latiumbonata and M. striata are described from Oman, based on morphology and multigene (ITS-28S-rpb2-tef1-α) phylogenetic analysis. Micropsalliota latiumbonata is characterized by a broadly umbonate pileus disc with fibrillose-squamulose surface, fibrils dark-brown and more or less recurved, cheilocystidia capitate with olivaceous capitulum, broadly fusiform to amygdaliform basidiospores measuring 6.0–7.0 × 4.0–4.5 µm, and occurring gregariously around termite mounds. Micropsalliota striata is another small-sized species with an acute papillate pileus disc with appressed fibrils, striate-appendiculate pileus margins, utriform cheilocystidia without a capitate apex, clavate to subglobose pileocystidia, and comparatively larger basidiospores (6.5–7.5 × 3.7–4.1 µm). Both the new species belong to Clade megaspora. A detailed description, photographs of basidiomata, illustrations of anatomical characteristics, a multigene phylogenetic tree, and morphological comparison with similar species are provided. With the description of these two species, the number of known species in Micropsalliota rises to 108.

Key words: Agarics, clade, megaspora, taxonomy, termite mounds

Introduction

The genus Micropsalliota Höhn. is a group of small, slender mushrooms, forming the basal lineage in the subfamily Leucocoprinoideae R.L. Zhao & J.X. Li within Agaricaceae Chevall. (Li et al. 2025). Morphologically, Micropsalliota has the following combination of characters, including agaricoid, small to relatively medium-sized basidiomata (except M. geesterani (Bas & Heinem.) R.L.Zhao & L.A.Parra with large basidiomata), fibrillose to squamulose pilei with fibrils/squamules often brownish, reddish or whitish in color, usually with umbonate pileus disc, annulus membranous (if present), brownish spore print, basidiospores ellipsoid to amygdaliform usually with apical thickening, cheilocystidia mostly capitate or subcapitate, and more or less with incrusted pileus hyphae (Al-Kharousi et al. 2022; Li et al. 2025).

In recent years, the taxonomic work on Micropsalliota has been accelerated with the introduction of many new species on the basis of morphology and DNA sequence data (Zhao et al. 2010; Wei et al. 2015; Chen et al. 2016; He et al. 2020; Li et al. 2021; Patil et al. 2022, 2025; Yan et al. 2022; Gao et al. 2024; Li et al. 2025; Wang et al. 2026). In a systematic study of Agaricaceae s.l. using genomic data, it was found that Micropsalliota forms a basal lineage with genera such as Leucocoprinus, Leucoagaricus, and Macrolepiota, collectively forming the subfamily Leucocoprinoideae (Li et al. 2025).

Currently, more than 100 Micropsalliota species have been described worldwide, distributed in tropical and subtropical regions of Africa (Heinemann 1983; Cao et al. 2025; Liu et al. 2025), Americas (Heinemann 1989; Guzmán-Dávalos and Heinemann 1994) and Asia (Zhao et al. 2010; Wei et al. 2015; Chen et al. 2016; He et al. 2020; Li et al. 2021; Patil et al. 2022, 2025; Yan et al. 2022; Gao et al. 2024; Li et al. 2025; Wang et al. 2026). Previously, only Micropsalliota ventricocystidiata Al-Sadi & S. Hussain has been reported from Oman (Al-Kharousi et al. 2022).

The southern part of Oman (Dhofar Governorate) experiences monsoon rains in July to September each year, which influence the growth and development of various kinds of mushrooms (Hussain et al. 2022, 2024a, 2024b, 2025a, 2025b). The area of Dhofar which is under the influence of monsoon rains, has a large population of a termite species (Macrotermes subhyalinus), making huge termite mounds (AlShamakhi et al. 2024). It was observed that these termite mounds provide a favorable habitat for the growth of various mushrooms (Hussain et al. 2024b, 2024c, 2026).

In this study, several mushroom specimens were collected during the 2025 monsoon season. Morphological characterization of basidiomata and multigene phylogenetic analyses showed that these collections represent two new species in the genus Micropsalliota, which are described here.

Materials and methods

Specimen collections and morphology

Basidiomata were collected during the rainy season, in August-September 2025, from Ain Athum, Ashwur and Qashrub areas, near Salalah, Dhofar Governorate, the southern region of the Sultanate of Oman. The basidiomata were photographed in their natural habitat, tagged with collection information (Rathnayaka et al. 2025), and macromorphological characters, including basidiomata size, shape, and color (according to Munsell Soil Color Charts; Munsell 1975) were recorded. The specimens were brought to the field station, where the fruiting bodies were dried at 45 °C in a fruit dehydrator (Semikorn Electronic Technology Co., Ltd., Guangdong, China). After drying, the samples were sealed in zipper bags and stored at −80 °C for two weeks to eliminate any insect eggs or larvae. The studied materials were deposited in the Fungal Collections at the Center for Environmental Studies and Research (CESAR), Sultan Qaboos University, Oman.

A thin hand-cut section from pileus covering, lamellae, and stipe was prepared for microscopic observation, using 5% aqueous KOH (w/v) and stained in 1% Congo red (w/v) for better contrast. Microscopic features, including the size, shape, color, surface features of basidiospores, basidia, cheilo-, pleuro-, and caulocystidia, and pileipellis were observed under a light microscope (ECLIPSE Ni-U, Nikon Co., Ltd., Japan). Basidiospores’ notations are presented as: [n/o/p] where n is the number of basidiospores measured, from o number of basidiomata, and from p collections; the dimensions (a)b–c(d), where b–c includes at least 90% of measurements and ‘a’ and ‘d’ are extreme values. Q is the length/width ratio for individual spores; av. Q is the mean Q. For morphological description, Bas et al. (2011) was followed.

DNA extraction, amplification, and sequencing

DNA was extracted from dried specimens using Tissue DNA Preparation – Column Kit (Jena Bioscience GmbH, Jena, Germany). Three DNA regions were amplified, including internal transcribed spacer (ITS) and D1/D2 domains of the large subunit of nuclear ribosomal DNA (28S), and a segment of a protein-coding gene, the translation elongation factor 1 alpha (tef1-α). The primers were ITS5/ITS4 for ITS (Gardes and Bruns 1993; White et al. 1990), LR0R/LR5 for 28S (Vilgalys and Hester 1990), and EF1-983F/EF1-1567R for tef1-α (Rehner and Buckley 2005), respectively. Conditions for polymerase chain reactions (PCR) were set as: an initial denaturation at 94 °C for 3 min, followed by 35 cycles of denaturation at 94 °C for 30 s, annealing at the gene-specific temperature and duration (ITS: 56 °C for 40 s; 28S: 52 °C for 45 s; tef1-α: 60 °C for 46 s), extension at 72 °C for 50 s, and a final extension at 72 °C for 10 min, followed by a 4 °C soak. PCR reactions were performed with PuReTaq Ready-To-Go PCR beads (GE Healthcare UK Limited, Buckinghamshire, UK). These reagents were added to each PCR bead: 1.0 µL of each primer (10 µmol/L), 2 µL of DNA template, and 21 µL nuclease-free water. The amplified regions were purified and sequenced with same primers at Macrogen Inc. © (Seoul, Republic of Korea).

Sequence alignment and phylogenetic analyses

The newly generated sequences of both forward and reverse primers of ITS, 28S, and tef1-α were cleaned to consensus sequences using BioEdit v. 7.0.9 (Hall 1999). In BLAST searches, the ITS sequences of the proposed new species Micropsalliota latiumbonata showed the highest similarity of 96.56% with an undescribed species from Oman M. sp. DRB-23-013 (PV088726) and 95.01% with M. appendiculata LE F-315913 (OR161109, Vietnam), while 2nd new species M. striata has 97.50% similarity with the undescribed species M. sp. DRB-23-013 (PV088726, Oman). A combined dataset of ITS-28S-rpb2-tef1-α was constructed (Gao et al. 2024; Yan et al. 2025). The final dataset comprised 112 specimens, including 109 Micropsalliota specimens and three outgroup taxa (Agaricus arabiensis SQUH-SNT007, Coniolepiota spongodes PNG012/MFLU 09-0012, and Hymenagaricus wadijarzeezicus JHN-22-019). These taxa were used as outgroups because they belong to the subfamily Agaricoideae R.L. Zhao & J.X. Li (Agaricaceae), a lineage phylogenetically distinct from the ingroup taxa, making them suitable for rooting the phylogenetic tree (Li et al. 2025). The dataset was based on the sequences employed in the recent phylogenetic studies of Micropsalliota (Yan et al. 2022; Gao et al. 2024; Yan et al. 2025). The dataset was aligned using MAFFT v.7 (Katoh et al. 2019), and adjusted in BioEdit v.7.0.9.0 (Hall 1999) and finally in ClustlX v. 2.1 (Larkin et al. 2007). Details of the sequences used in this study are given in Table 1.

Table 1.

Sequence information used in the phylogenetic analyses of Micropsalliota, bold are the newly generated sequences, (–) means data unavailable.

Taxa Vouchers Country ITS 28S rpb2 tef1-α Reference
Micropsalliota alba – India EF069420 – – – Gao et al. 2024.
M. albella LE2016123 Thailand MN294514 MN294516 – – He et al. 2020.
M. albofelina LE312536 Vietnam OK257212 OK257209 – – Crous et al. 2021.
M. albofelina HKAS70329 China OR799877 OR799922 OR962218 OR962180 Gao et al. 2024.
M. albosericea SFSU-zrl-3049 Thailand HM436644 – – – Zhao et al. 2010.
M. allantoidea SFSU-zrl-2038 Thailand HM436648 HM436597 – – Zhao et al. 2010.
M. appendiculata HKAS131127 China OR799912 OR799956 OR962247 OR962204 Gao et al. 2024.
M. appendiculata LE F-315913 Vietnam OR161109 OR161104 – – Ivanova et al. 2023.
M. arginophaea SFSU-zrl-3110 Thailand HM436617 HM436577 – – Zhao et al. 2010.
M. arginophaea HKAS60309 China OR799878 OR799923 OR962219 OR962208 Gao et al. 2024.
M. bifida SFSU-zrl-3067 Thailand HM436640 HM436591 – – Zhao et al. 2010.
M. bifida HFJAU2998 China OM650272 OM650252 OM669858 – Yan et al. 2022.
M. bispora HFJAU3833 China PQ345346 PQ345351 PQ358515 PQ358519 Yan et al. 2025
M. bispora HFJAU4253 China PQ345347 PQ345352 PQ358516 PQ358520 Yan et al. 2025
M. brunneosquamata LD201236 Thailand KP316210 – – – Chen et al. 2016.
M. cortinata SFSU-zrl-2129 Thailand HM436630 HM436593 – – Zhao et al. 2010.
M. cortinata HKAS92221 China OR799879 OR799924 OR962220 OR962183 Gao et al. 2024.
M. delicatula HKAS54332 China OR799880 OR799925 OR962221 OR962209 Gao et al. 2024.
M. delicatula ZRL2015234 China MT671229 – – – Li et al. 2021.
M. dentatomarginata GX20170202 China MT671228 MT671242 – – Li et al. 2021.
M. digitatocystis HKAS123832 China OR799883 OR799928 OR962224 OR962185 Gao et al. 2024.
M. digitatocystis ZRL20180564 China MT671239 MT671250 – – Li et al. 2021.
M. ferruginea HKAS131130 China OR799885 OR799930 OR962226 OR962182 Gao et al. 2024.
M. ferruginea HKAS70562 China OR799884 OR799929 OR962225 OR962181 Gao et al. 2024.
M. fimbriata HKAS60241 China OR799886 OR799931 OR962227 OR962198 Gao et al. 2024.
M. fimbriata HKAS60261 China OR799887 OR799932 – OR962199 Gao et al. 2024.
M. furfuracea SFSU-zrl-3006 Thailand HM436621 HM436603 – – Zhao et al. 2010.
M. furfuracea HKAS60229 China OR799889 OR799934 OR962229 OR962201 Gao et al. 2024.
M. geesterani LAPAG520 Thailand KM923965 KM923966 – – Parra et al. 2016.
M. geesterani E.C. Vellinga 2263(L) Netherlands AF482857 AF482888 – – Parra et al. 2016.
M. gigaspora HKAS131118 China OR799890 OR799935 OR962230 – Gao et al. 2024.
M. gigaspora HKAS131119 China OR799891 OR799936 – – Gao et al. 2024.
M. globocystis HKAS131120 China OR799892 OR799937 – OR962186 Gao et al. 2024.
M. globocystis HFJAU1518 China OM650277 OM650255 OM669852 – Yan et al. 2022.
M. globocystis HKAS131133 China OR799895 OR799940 OR962234 OR962197 Gao et al. 2024.
M. globocystis HKAS92202 China OR799894 OR799939 OR962233 OR962196 Gao et al. 2024.
M. globocystis VDW1278 South Africa MT304640 – – – Yan et al. 2022.
M. globocystis SFSU-zrl-2049 Thailand HM436635 – – – Zhao et al. 2010.
M. globocystis HFJAU2709 China OM650278 OM650262 OM669856 – Yan et al. 2022.
M. globovelveta HFJAU3842 China PV277734 PV269809 PV289604 PV289605 Liu et al. 2025
M. gracilis SFSU-zrl-2041 Thailand HM436647 HM436583 – – Zhao et al. 2010.
M. gracilis HNL503432 Laos MW192914 – – – Yan et al. 2022.
M. inflata LE F-315912 Vietnam OR161110 OR161106 – – Ivanova et al. 2023.
M. jiangxiensis THJ20018 China ON117420 ON117438 – – Ji and He 2023.
M. jiangxiensis THJ20019A China ON117421 ON117439 – – Ji and He 2023.
M. latiumbonata QRB-14-25 Oman PZ127411 PZ127514 – PZ390627 This study
M. latiumbonata ASH-005-25 Oman PZ127410 PZ127513 – PZ390625 This study
M. latiumbonata ASH-006-25 Oman PZ127412 PZ127515 – PZ390626 This study
M. latiumbonata ASH-007-25 Oman PZ127413 PZ127516 – PZ386150 This study
M. latiumbonata ASH-009-25 Oman PZ127414 PZ127517 – PZ176529 This study
M. lateritia SFSU-zrl-2073 Thailand HM436631 – – – Zhao et al. 2010.
M. lateritia HKAS131124 China OR799896 OR799941 OR962235 OR962202 Gao et al. 2024.
M. longicystis HKAS131121 China OR799897 OR799942 OR962257 – Gao et al. 2024.
M. longicystis HKAS131126 China OR799898 OR799943 OR962258 – Gao et al. 2024.
M. megarubescens SFSU-zrl-2086 Thailand HM436620 – – – Zhao et al. 2010.
M. megarubescens HKAS60253 China OR799900 OR799945 OR962237 OR962189 Gao et al. 2024.
M. megaspora SFSU-zrl-3068 Thailand HM436624 – – – Zhao et al. 2010.
M. megaspora HFJAU1255 China OM650282 OM650258 OM669876 – Yan et al. 2022.
M. minor HFJAU2796 China OM650294 OM650266 OM669865 – Yan et al. 2022.
M. nana HKAS114619 China OR799901 OR799946 OR962238 OR962216 Gao et al. 2024.
M. nana HKAS115226 China OR799902 OR799947 – OR962217 Gao et al. 2024.
M. ovalispora HFJAU2010 China OM650295 OM650269 OM669866 – Yan et al. 2022.
M. ovalispora HFJAU3179 China OM650296 – OM669867 – Yan et al. 2022.
M. pakistanica LAH38139 Pakistan PP357040 PP383879 – – Maula et al. 2025
M. pakistanica LAH38140 Pakistan PP357041 PP383880 – – Maula et al. 2025
M. pileocystidiata AMH9975 India MG917970 – – – Patil et al. 2022.
M. pileocystidiata MMH1114 India MZ598496 – – – Patil et al. 2022.
M. pleurocystidiata SFSU-zrl-2023 Thailand HM436636 – – – Zhao et al. 2010.
M. pseudoarginea HKAS131125 China OR799903 OR799948 OR962239 OR962212 Gao et al. 2024.
M. pseudoarginea HFJAU2122 China OM650284 OM650260 OM669861 – Yan et al. 2022.
M. pseudodelicatula HKAS131129 China OR799905 OR799950 OR962241 OR962213 Gao et al. 2024.
M. pseudodelicatula HFJAU2228 China OM650288 OM650264 OM669863 – Yan et al. 2022.
M. pseudoglobocystis HKAS87127 China OR799908 OR799953 OR962244 OR962190 Gao et al. 2024.
M. pseudoglobocystis ZRL2013321 China KM889913 – – – Wei et al. 2015.
M. purpureobrunneola LE2016124 Thailand MN294513 MN294517 – – He et al. 2020.
M. pusillissima SFSU-zrl-3047 Thailand HM436645 HM436594 – – Zhao et al. 2010.
M. repanda LAPAF8 Togo KP739805 KP739804 – – Parra et al. 2016.
M. rosea LAH38149 Pakistan PP377825 PP378506 – – Maula et al. 2025
M. rosea LAH38186 Pakistan PQ623104 PQ623106 – – Maula et al. 2025
M. roseipes HFJAU2494 China OM650297 OM650270 OM669870 – Yan et al. 2022.
M. rubrobrunnescens SFSU-zrl-2120 Thailand HM436628 HM436588 – – Zhao et al. 2010.
M. rubrobrunnescens HKAS96929 China OR799914 OR799958 OR962249 OR962206 Gao et al. 2024.
M. rubrobrunnescens SFSU-zrl-2121 Thailand HM436629 HM436589 – – Zhao et al. 2010.
M. rufosquarrosa HFJAU1208 China OM650291 OM650267 OM669868 – Yan et al. 2022.
M. rufosquarrosa HFJAU1236 China OM650292 OM650268 OM669869 – Yan et al. 2022.
M. squarrosa HKA128713 China OR799916 OR799960 OR962251 – Gao et al. 2024.
M. squarrosa HKAS128633 China OR799915 OR799959 OR962250 – Gao et al. 2024.
M. sp. DRB-23-013 Oman PV088726 PV093920 – – Unpublished
M. striata ATM-009-25 Oman PZ127415 PZ127518 – – This study
M. subalba SFSU-zrl-2080 Thailand HM436646 HM436596 – – Zhao et al. 2010.
M. subalba HKAS105828 China OR799917 OR799961 – OR962211 Gao et al. 2024.
M. subarginea SFSU-zrl-2052 Thailand HM436612 HM436573 – – Zhao et al. 2010.
M. subarginea SFSU-zrl-2092 Thailand HM436611 HM436574 – – Zhao et al. 2010.
M. subumbonata AMH 10512 India PP837559 PQ576415 – – Patil et al. 2025.
M. subumbonata MMH 2312 India PQ577838 PQ580740 – – Patil et al. 2025.
M. suricatoides LE F-348071 Vietnam OR161111 OR161105 – – Ivanova et al. 2023.
M. suricatoides LE F-348072 Vietnam OR161112 – – – Ivanova et al. 2023.
M. tenuipes HFJAU1536 China OM650289 – – – Yan et al. 2022.
M. tenuipes HFJAU3180 China OM650290 OM650265 – – Yan et al. 2022.
M. umbonata HKAS131131 China OR799920 OR799964 OR962254 OR962194 Gao et al. 2024.
M. umbonata HKAS131132 China OR799921 OR799965 OR962255 OR962195 Gao et al. 2024.
M. ventricocystidiata SQUH-ATR004 Oman OM397373 OM630413 – – Al-Kharousi et al. 2022.
M. ventricocystidiata SQUH-GOB002 Oman OM397374 OM630414 – – Al-Kharousi et al. 2022.
M. ventricocystidiata JEB-001-25 Oman PZ127409 PZ127512 – PZ176528 This study
M. vulgaris HFJAU3350 China PQ345344 PQ345349 PQ358513 PQ358517 Yan et al. 2025.
M. vulgaris HFJAU5707 China PQ345345 PQ345350 PQ358514 PQ358518 Yan et al. 2025.
M. wuyishanensis HFJAU3048 China OM650298 – OM669878 – Yan et al. 2022.
M. xanthorubescens SFSU-zrl-3083 Thailand HM436638 HM436598 – Zhao et al. 2010.
M. xanthorubescens SFSU-zrl-3096 Thailand HM436637 HM436599 – Yan et al. 2022.
Agaricus arabiensis SQUH-SNT007 Oman OM971855 OM971859 ON568585 Hussain et al. 2022.
Hymenagaricus wadijarzeezicus JHN-22-019 Oman OR612998 OR613021 OR729600 Hussain et al. 2024b.
Coniolepiota spongodes PNG012/MFLU 09-0012 Thailand HM488756 HM488774 HM488796 HM488883 Vellinga et al. 2011.
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Maximum likelihood (ML) and Bayesian Inference (BI) methods were used for phylogenetic analyses. The BI phylogeny was performed using MrBayes v. 3.2.6 (Ronquist et al. 2012), and the best-fit model (GTR+F+I+G4) was selected following ModelFinder (Kalyaanamoorthy et al. 2017). Four Markov chains were run each for one million generations and sampled every 100th generations. Burn-in was determined by checking the likelihood trace plots in Tracer v. 1.7 (Rambaut et al. 2018) and subsequently discarded. Maximum likelihood (ML) analyses were tested with RAxML v. 8 (Stamatakis 2014) with 1000 bootstrap replicates. The best model (GTR+I+G) was chosen according to the corrected Akaike information criteria (AICc) (Lanfear et al. 2017). The BI posterior probabilities (PPs) and ML bootstrap percentages (BT) of ≥ 0.95 and ≥ 70%, respectively were considered significant and shown on phylogenetic tree (Fig. 1) in order of (BT/PPs). Tree files were visualized with FigTree v.1.4.2 (Rambaut 2012) followed by annotation in Adobe Illustrator CC2019.

Figure 1.

Figure 1.

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Multigene phylogeny of Micropsalliota generated by ML analyses, based on combine sequence data of ITS-28S-rpb2-tef1-α, with Agaricus arabiensis, Coniolepiota spongodes, and Hymenagaricus wadijarzeezicus as outgroup taxa. Bayesian posterior probabilities (PPs) and ML bootstrap percentage (BT) ≥ 0.95 and ≥70%, respectively, are shown above the nodes. Eleven clades were recovered, each branch represents species name, followed by voucher number, and country of origin, specimens studied during this work are in bold fonts, and both the new species are grouped in Clade megarspora.

Results

Phylogenetic analyses

The final aligned multigene dataset consisted of 112 specimens with 3310 characters long, including 1875 constant sites, 980 informative sites, and 455 uninformative sites. These 112 specimens represent 55 named species, and one unnamed species of the genus Micropsalliota, along with the three outgroup taxa. Both ML and BI methods generated phylogenies with similar topologies. The ML tree is shown (Fig. 1) with values of both maximum likelihood BT percentage and Bayesian PPs. The presented tree is almost similar to previous phylogenies of Micropsalliota (Gao et al. 2024; Yan et al. 2025), where 109 specimens of the genus grouped in 11 clades, each with strong to excellent phylogenetic support. The representative new species, Micropsalliota latiumbonata and M. striata, are grouped in the Clade megaspora with strong phylogenetic support (98%/0.97).

Taxonomy

Micropsalliota latiumbonata

S. Hussain, Al-Nadabi & Al‐Sadi sp. nov.

63BE31AA-8667-513D-A072-E6C7143605B3

862914

Figs 2, 3

Figure 2.

Figure 2.

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Basidiomata of the new species of Micropsalliota. a–d. Micropsalliota latiumbonata. a, b. (CESAR-ASH-007-25, holotype); c. ASH-009-25; d. QRB-14-25; e, f. Micropsalliota striata (CESAR-ATM-009-25, holotype). Scale bars: 15 mm.

Figure 3.

Figure 3.

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Illustrations of microscopic features of Micropsalliota latiumbonata (CESAR-ASH-007-25, holotype). a. Basidiospores; b. Basidia; c. Cheilocystidia (black dots represent the olivaceous content); d. Caulocystidia; e. Pileus squamules. Scale bar: 5 µm (a); 15 µm (b–e).

Etymology.

The specific epithet ‘latiumbonata’ refers to the broadly umbonate pileus disc of the new species.

Diagnosis.

Micropsalliota latiumbonata is a very small-sized species, characterized by a broadly umbonate pileus center, occurring gregariously in a specific habitat of termite mounds, and microscopically with olivaceous capitulum at the apex of cheilocystidia.

Holotype. •

Sultanate Of Oman: Dhofar, Salalah, Ashwur, on soil with grasses on termite mounds, 28 August 2025, S. Hussain, Al-Nadabi, A. Al Sidairi, K. Al-Zeidi & A. Al-Raeesi, ASH-007-25 (CESAR-ASH-007-25, holotype), GenBank accession: ITS = PZ127413, 28S = PZ127516, tef1-α = PZ386150.

Description.

Basidiomata small-sized. Pileus 10–18 mm, at young stage campanulate to hemispherical, becoming convex to plano-convex at mature stage, finally becoming plano-concave to concave in old specimens, with broadly umbonate disc; surface fibrillose-squamulose, fibrils more or less recurved, reddish-brown (10R 5/4–2.5YR 6/4) to dark reddish-brown (10R 3/10–10R 3/14), concentrated at the center, sparser towards the margins; margin appendiculate, whitish; in old specimens the entire basidiomata becoming dark-brown (5YR 1/2–7.5YR 1/2). Context membranous, whitish. Lamellae free, pale pinkish (10R 9/2–7.5YR 9/2) to dark grayish-brown (2.5YR 1/4–7.5R 2/4), broad to ventricose, with fimbriate edge, close with 0–3 series of lamellulae. Stipe 15–30 × 2–3 mm, central, cylindrical, slender, white, surface pruinose to furfuraceous downwards. Context of stipe secreting brownish red (5R 3/10–7.5R 3/10) liquid in some specimens on cutting. Annulus cortinate, whitish.

Basidiospores [141/2/2] (4.5)6.0–7.0(7.8) × (3.5)4.0–4.5(4.7) µm, on average 6.5 × 4.2 µm, Q = 1.4–1.7, av. Q = 1.6, in face view broadly fusiform with a truncate apex, in side view oblong to amygdaliform with slightly flattened on one side, pale brownish, slightly thick-walled, with a prominent apiculus, without germ-pore. Basidia 18–23 × 7.0–8.0 µm, clavate, hyaline, 4-spored, rarely 2-spored. Pleurocystidia absent. Cheilocystidia 32–46 × 9.0–12 µm, hyaline, narrowly utriform to tibiiform capitate apex, capitulum 5–8 µm in diam, smooth, with olivaceous content. Pileus squamules is a cutis, consisting of hyphae 11–15 µm in diam, pale brownish, smooth, cylindrical to elongated, constricted at septa, rarely branched. Caulocystidia 46–88 × 8.0–12 µm, tibiiform to cylindrical, with capitate apex, hyaline. Clamp connection absent in all tissues.

Habit, habitat and distribution.

Gregarious or scattered in small groups, saprotrophic, on the soil of a termite mound. Currently only known from southern Oman.

Additional specimens examined.

• Sultanate Of Oman: Dhofar, Salalah, Qashrub, on soil under herbaceous plants, 27 August 2025, S. Hussain, Al-Nadabi, K. Al-Zeidi & A. Al-Raeesi, QRB-14-25 (paratype CESAR-QRB-14-25), GenBank accession: ITS = PZ127411, 28S = PZ127514, tef1-α = PZ390627; Salalah, Ashwur, on soil with grasses on termite mounds, 28 August 2025, S. Hussain, Al-Nadabi, A. Al Sidairi, K. Al-Zeidi & A. Al-Raeesi, ASH-005-25 (paratype CESAR-ASH-005-25), GenBank accession: ITS = PZ127410, 28S = PZ127513, tef1-α = PZ390625; same area and same date, S. Hussain, Al-Nadabi, A. Al Sidairi, K. Al-Zeidi & A. Al-Raeesi, ASH-006-25 (paratype CESAR-ASH-006-25), GenBank accession: ITS = PZ127412, 28S = PZ127515, tef1-α = PZ390626; same area and same date, S. Hussain, Al-Nadabi, A. Al Sidairi, K. Al-Zeidi & A. Al-Raeesi, ASH-009-25 (paratype CESAR-ASH-009-25), GenBank accession: ITS = PZ127414, 28S = PZ127517, tef1-α = PZ176529.

Note.

The new species Micropsalliota latiumbonata can be recognized by its growing habit, which mainly fruits on a termite mound; pileus with a broadly umbonate center, covered with reddish-brown squamules; and capitate cheilocystidia, with the capitulum containing olivaceous material. There are several species in the genus with a similar combination of characteristics, such as M. albosericea Heinem. & Leelav., M. ferruginea T. Gao & Z.W. Ge, M. fimbriata T. Gao & Z.W. Ge, M. gracilis Heinem., M. longicystis T. Gao & Z.W. Ge, M. nana T. Gao, H. Qu & Z.W. Ge. Micropsalliota albosericea has a whitish fibrillose pileus, basidiospores ovoid or cymbiform with apical thickening and smaller (5–5 × 2.8–3.2 µm), utriform cheilocystidia with capitate apex and hyaline (Heinemann and Leelavathy 1991). Micropsalliota ferruginea was recently reported from China, with a larger pileus (35–50 mm diam), covered with recurved squamules, without a prominent umbo, and smaller cheilocystidia (15–33 × 3–10 µm) with hyaline capitulum (Gao et al. 2024). Similarly, M. gracilis with an umbonate pileus center, covered with brownish-red squamules, basidiospores amygdaliform to ellipsoid and smaller (5.5–6.5 × 3.0–4.0 µm), ventricose to irregularly tibiiform cheilocystidia with hyaline capitate apex (Zhao et al. 2010). Micropsalliota longicystis shares capitate caulo- and cheilocystidia with the new species; however, it is differentiated from M. latiumbonata by its smaller basidiospores (5.0–6.0 × 3.0–3.5 µm), hyaline capitulum of cheilocystidia, and the presence of pleurocystidia (Gao et al. 2024). Micropsalliota nana differentiated from the new species by its silky fibrillose pileus with obtuse umbo, persistent annulus, basidiospores smaller (4.5–6.0 × 3.0–4.0 µm) ellipsoid to amygdaliform, hyaline capitulum of cheilocystidia, with encrusted hyphae in pileus squamules (Gao et al. 2024).

Based on multigene phylogeny, the close relatives of Micropsalliota latiumbonata are M. appendiculata D.D. Ivanova & O.V. Morozova, M. megaspora R.L. Zhao, Desjardin, Soytong & K.D. Hyde, M. repanda Heinem., M. jiangxiensis X.H. Ji & G. He, M. ferruginea, and the proposed new species M. striata sp. nov. Micropsalliota appendiculata has been reported from China and Vietnam under broad-leaved trees, with pyriform to subglobose cheilocystidia, presence of pleurocystidia (broadly clavate to clavate-capitate), with encrusted hyphae of pileus squamules (Gao et al. 2024). Micropsalliota megaspora can be differentiated from the new species by its larger basidiospores (6–8 × 3.8–4.5 µm), ventricose cheilocystidia with hyaline, subcapitate apices, and incrusted hyphae in pileus squamules (Zhao et al. 2010). Basidiomata of Micropsalliota repanda are comparatively larger (pileus diam up to 45 mm), with purplish-red pileal squamules, capitate hyaline (Heinemann 1980). Micropsalliota jiangxiensis with pileus 25–32 mm diam, covered with wood-brown fibrils, basidiospores 5.3–6.7 × 2.9–3.4 µm, ellipsoid, cheilocystidia cylindrical to subclavate with capitate apex, hyaline (Ji and He 2023).

Nucleotide differences in the ITS region of both the new species (Micropsalliota latiumbonata, M. striata) with their close relative M. appendiculata is given in Table 2.

Table 2.

Nucleotide differences in the ITS sequences of the new species and with their closely similar species, - means deletion.

Species Collection Variable positions
73 103 189 193 208 220 229 268 281 445 478 502 590 605 612 622 628 629 639
M. latiumbonata ASH-005-25 C T A G G A T T A T T A G T A T T C G
M. latiumbonata ASH-006-25 C T A G G A T T A T T G G T A T T C G
M. latiumbonata ASH-007-25 C T A G G A T T A T T G G T A T T C G
M. latiumbonata ASH-009-25 C T A G G A T T A T T G G T A T T C G
M. latiumbonata QRB-14-25 C T A G G A T T A T T G G T T T T C G
M. striata ATM-009-25 T G G T A A C G T A G G A T A C T T -
M. appendiculata LE F-315913 T G G T A T C G T A G G A T A T A - T
M. appendiculata HKAS131127 T G G T A T C G T A G G A T A T A - T
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Micropsalliota striata

S. Hussain, Al-Nadabi & Al‐Sadi sp. nov.

3039901B-ED86-5E12-BF24-42CCFD9BD4C2

862916

Figs 2, 4

Figure 4.

Figure 4.

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Illustrations of microscopic features of Micropsalliota striata (CESAR-ATM-009-25, holotype). a. Basidiospores; b. Basidia; c. Cheilocystidia; d. Pleurocystidia; e. Caulocystidia; f. Pileus squamules (back dashes showing the encrusted walls); g. Pileocystidia. Scale bar: 5 µm (a); 15 µm (b–g).

Etymology.

The specific epithet ‘striata’ refers to the fine striate pileus margin of the new species.

Diagnosis.

Micropsalliota striata is a small-sized species characterized by a striate pileus margin, a papillate disc, microscopically with the presence of pileocystidia and caulocystidia.

Holotype.

• Sultanate Of Oman: Dhofar, Salalah, Ain Athum, on moist soil with mosses, 25 August 2025, S. Hussain, Al-Nadabi, A. Al Sidairi, K. Al-Zeidi & A. Al-Raeesi, ATM-009-25 (CESAR-ATM-009-25, holotype), GenBank accession: ITS = PZ127415, 28S = PZ127518.

Description.

Basidiomata small-sized. Pileus 15–20 mm, at young stage paraboloid to hemispherical, becoming convex to plano-convex and applanate at mature stage, with acute papillate disc; surface fibrillose, fibrils appressed, sparse towards the margin, light-pinkish (2.5R 9/4–10RP 9/4) to light yellowish-pink (7.5R 9/4–7.5R 9/6), concentrated at the disc, light-brown (5YR 4/4–7.5YR 4/4) to reddish-brown (10R 5/4–2.5YR 6/4); margins finely striate, exceeding the lamellae, appendiculate, whitish. Context membranous, whitish. Lamellae free, pale pinkish (10R 9/2–7.5YR 9/2) to light reddish-brown (2.5YR 5/4–2.5YR 6/4), ventricose, with fimbriate edge, close with 1–3 series of lamellulae. Stipe 25–40 × 2–3 mm, central, equal, slightly flexuous, slender, pale-pinkish (2.5YR 9/2–7.5R 9/2) to pale-brownish (10R 5/4–10R 6/4), surface pruinose to pulverulent downwards, glabrous upwards. Context of stipe unchanging on bruising or cutting. Annulus absent.

Basidiospores [104/2/1] (6.2)6.5–7.5(8.3) × (3.5)3.7–4.1(4.5) µm, on average 7.0 × 3.9 µm, Q = 1.6–1.8, av. Q = 1.7, in face view oblong to broadly fusiform with truncate apex, in side view amygdaliform to ellipsoid with slightly flattened on one side, pale brownish, slightly thick-walled, with prominent apiculus, without germ-pore. Basidia 14–17 × 5.5–7.0 µm, clavate to cylindrical, hyaline, regularly 4-spored. Pleurocystidia 28–36 × 9.5–11.5 µm, oblong to clavate or narrowly utriform to cylindrical, abundant, hyaline. Cheilocystidia 23–30 × 8.5–11.5 µm, narrowly utriform to utriform without a capitate apex, hyaline. Pileus squamules is a cutis, consisting of encrusted hyphae, 10–25 µm in diam, pale brownish, cylindrical to elongated, constricted at septa, rarely branched. Pileipellis is a hymeniderm to epithelium, consisting of subglobose to clavate pileocystidia, measuring 11.5–20.5 × 7.0–10.5 µm, hyaline, smooth. Caulocystidia 40–51 × 8.5–10 µm, clavate to cylindrical or cylindro-clavate, without a capitate apex, hyaline. Clamp connection absent in all tissues.

Habit, habitat and distribution.

Gregarious or scattered in small groups, saprotrophic, on moist soil with mosses. Currently only known from southern Oman.

Note.

The new species Micropsalliota striata is characterized by its acute papillate pileus disc, with striate pileus margins, having clavate to cylindrical caulocystidia, narrowly utriform to utriform pleuro- and cheilocystidia without a capitate apex, and comparatively larger basidiospores (6.5–7.5 × 3.7–4.1 µm) than M. latiumbonata. In the genus, there are several species with similar kind of characteristics, like: M. appendiculata, M. gigaspora T. Gao & Z.W. Ge, M. pileocystidiata P.B. Patil & S.A. Vaidya, M. pleurocystidiata Heinem. & Little Flower, M. pseudoarginea Heinem. and M. xanthorubescens Heinem. Micropsalliota appendiculata can be differentiated from the new species by its pyriform to subglobose cheilocystidia measuring (16–25 × 10–13 µm), pleurocystidia broadly clavate to clavate-capitate, pileipellis without pileocysidia (Gao et al. 2024). Micropsalliota gigaspora with a subumbonate to applanate pileus disc with crenate margins, stipe with a persistent annulus, lengthy basidiospores (7–9 × 4–5.5 µm), broadly-clavate to clavate cheilocystidia, and 2- and 4-spored basidia (Gao et al. 2024). Micropsalliota pileocystidiata, only known from the type location (Maharashtra, India), is a medium- to large-sized species with pyriform pileocystidia (Patil et al. 2022). Micropsalliota pleurocystidiata is a large-sized species, with a broadly umbonate pileus disc, basidiospores amygdaliform and smaller (5.0–6.0 × 3.0–4.0 µm), broadly ventricose to subcylindrical cheilocystidia (Zhao et al. 2010). Micropsalliota pseudoarginea with glabrous to finely pruinose cap surface, smaller basidiospores (4.0–5.0 × 2.5–3.2 µm), ellipsoid to subcymbiform shape, with clavate to ventricose cheilocystidia (Zhao et al. 2010). Micropsalliota xanthorubescens is a medium-sized species with a subumbonate pileus disc, clavate to ventricose cheilocystidia (Zhao et al. 2010).

Both the newly proposed species, Micropsalliota striata and M. latiumbonata, can be differentiated by several characteristics. Pileus disc in the former is acute papillate as compared to the broadly umbonate disc in the latter; the cap surface is sparsely covered with pinkish, appressed fibrils in M. striata, in contrast to much denser, recurved, and brownish fibrils in M. latiumbonata. Pleurocystidia and pileocystidia are completely absent in M. latiumbonata. Cheilocystidia in M. striata are without a prominent capitate apex; however, the cheilocystidia of M. latiumbonata have a characteristic capitulum with olivaceous content.

Discussion

The present study contributes to the description of two new species of Micropsalliota from Oman, a region that remains underexplored for agaric diversity. In the phylogenetic analyses (Fig. 1), both the proposed new species were grouped in the Clade megaspora. Species in this clade have small pilei with fibrillose-squamulose surface, fibrils/squamules usually brownish, concentrated at the center, the center more or less umbonate, basidiospores ellipsoid to amygdaliform with apical thickening, cheilocystidia ventricose to clavate or subglobse with capitate or subcapitate apex. To the best of our knowledge, M. latiumbonata is the only species having capitate cheilocystidia with olivaceous content in the capitulum.

In this study, species of Micropsalliota were recovered in eleven major clades, similar to a previous phylogeny of the genus (Gao et al. 2024). A couple of species M. bispora J.Q. Yan, S.Nan Wang & H. Zeng and M. vulgaris J.Q. Yan, S.N. Wang & H. Zeng, were described after Gao et al. (2024), however, these species were not placed in any known clade of the genus (Yan et al. 2025). In the current phylogeny, M. bispora was grouped in Clade furfuraceae. Species in this clade have larger basidiospores size about 6.9 × 3.8 µm on average (Zhao et al. 2010; Gao et al. 2024). Similarly, M. vulgaris recovered in Clade cortinata. Species in this clade have a cortinate partial veil remnants at the pileus margin (Zhao et al. 2010; Gao et al. 2024). Clade bifida being the largest clade in Micropsalliota in terms of species, with the inclusion of M. pakistanica Maula, Saba, Asif & Akram (Maula et al. 2025), the number of species increased to 26. Most of the species in Clade bifida have small-sized basidiomata, except M. brunneosquamata Linda J. Chen, R.L. Zhao & K.D. Hyde and M. geesterani with large basidiomata and thickened fleshy pileus (Gao et al. 2024). One species was recently published with valid description; however, the name was invalid (as Micropsalliota rosea Akram, Maula, Saba & Asif (Maula et al. 2025). The species was redescribed with valid name Micropsalliota rosea Akram, Maula, Saba & Asif, but not assigned to any clade of the genus (Javeed et al. 2025). In the present study, M. rosea was grouped in Clade lateritia.

Species of Micropsalliota are saprotrophs in tropical habitats, usually fruiting on humus-rich degrading soil, under forest trees or roadsides (Zhao et al. 2010). In the present study, four collections of one of the new species Micropsalliota latiumbonata (ASH-005-25, ASH-006-25, ASH-007-25 and ASH-009-25) were found on termite mound, suggesting a possible ecological association between these mushrooms and termites. To the best of our knowledge, no species in Micropsalliota has been found on any termite mounds. However, four species of Hymenagaricus were recently reported from Dhofar region, Oman, occurring on termite mounds (Hussain et al. 2024b, 2026). Beside the termite-associated mushroom genus Termitomyces, a number of other mushroom genera, such as Agaricus, Lepiota, Leucocoprinus, Xanthagaricus, Conocybe, and Clitopilus were encountered fruiting on termite mounds in Dhofar region (person. Comm.). Termite mounds that contain abundant moisture and nutrients may provide a suitable habitat for mushroom growth and development. Consequently, further research is necessary to investigate the association between mushrooms and termite mounds in greater detail.

Supplementary Material

XML Treatment for Micropsalliota latiumbonata
XML Treatment for Micropsalliota striata

Acknowledgements

We would like to thank Said Al-Abri, Administrator, Research Centers, Sultan Qaboos University for facilitating the field visits. This research was funded by Sultan Qaboos University.

Citation

Al-Nadabi H, Hussain S, Al Sidairi A, Al-Zeidi K, Al-Raeesi A, Al-Badi R, Al-Rashdi L, Al-Jashmi J, Velazhahan R, Al-Sadi AM (2026) Morphology and multigene phylogeny reveal two new species of Micropsalliota (Agaricaceae, Basidiomycota) from Dhofar region, southern Oman. MycoKeys 137: 317–336. https://doi.org/10.3897/mycokeys.137.192271

Contributor Information

Hamed Al-Nadabi, Email: hamed@squ.edu.om.

Shah Hussain, Email: s.hussain2@squ.edu.om.

Additional information

Conflict of interest

The authors have declared that no competing interests exist.

Ethical statement

No ethical statement was reported.

Artificial Intelligence (AI) use

The authors accept full responsibility for the content of the manuscript, including the disclosure of any use of AI.

No AI tools were used in the preparation of this manuscript.

Funding

IG Grants, Sultan Qaboos University, Muscat, Oman, grant no. IG/-/DVC/CES/26/421.

Author contributions

Shah Hussain and Hamed Al-Nadabi: conceptualization, sampling, writing – original draft and review and editing, data curation, formal analysis, investigation, methodology, project administration, resources, supervision and visualization. Ahmed Al Sidairi, Khalifa Al-Zeidi, and Ahmed Al-Raeesi: sampling, review and editing. Rahil Al-Badi, Lujain Al-Rashdi, and Jumana Al-Jashmi: sample processing, molecular investigation. Rethinasamy Velazhahan and Abdullah M. Al-Sadi: review-editing, and supervision.

Author ORCIDs

S. Hussain https://orcid.org/0000-0002-5772-7206

A. Al Sidairi https://orcid.org/0009-0008-5476-2621

A.M. Al-Sadi https://orcid.org/0000-0002-3419-8268

Data availability

All sequence data generated in this study (Table 1) are available in NCBI GenBank (https://www.ncbi.nlm.nih.gov/genbank/). The multigene dataset used for phylogenetic analyses is available at Figshare (https://doi.org/10.6084/m9.figshare.32259831).

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Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

XML Treatment for Micropsalliota latiumbonata
mycokeys.137.192271-treatment1.xml (39.5KB, xml)
XML Treatment for Micropsalliota striata
mycokeys.137.192271-treatment2.xml (20.4KB, xml)

Data Availability Statement

All sequence data generated in this study (Table 1) are available in NCBI GenBank (https://www.ncbi.nlm.nih.gov/genbank/). The multigene dataset used for phylogenetic analyses is available at Figshare (https://doi.org/10.6084/m9.figshare.32259831).

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