Uromyces decoratus Syd. & P.Syd.

Tabe, Affoussatou, Aime, M. Catherine, Yorou, Nourou Soulemane & Piepenbring, Meike, 2022, New records and data on rust fungi (Pucciniales, Basidiomycota) in Benin, Phytotaxa 548 (2), pp. 127-145 : 140-141

Uromyces decoratus Syd. & P.Syd. , in Sydow et al., Ann. Mycol. 5(6): 491 (1907)

Figure 12

Uredinia amphigenous, mostly hypophyllous, circular or elongated, brownish, erumpent, subepidermal or exposed when the epidermis ruptures. Urediniospores globose or ellipsoidal, sometimes cylindrical or pyriform, (20–)16– 23(–30) × (15–)18–21(–23) µm (n = 60), pale yellow to brown, wall 1.5–2 µm thick, echinulate to warty, germ pores not seen. Telia hypophyllous, circular, dark brown to black, subepidermal, erumpent. Teliospores uni-cellular, globose, ovoid, ellipsoidal to broadly ellipsoidal, rarely cylindrical or angular, (25–)26–32(–35) × (15–)18–20 µm (n = 20), yellowish brown to dark brown, wall 2 µm thick, with relatively broad, shallow warts which are scattered or in irregular lines, each teliospore with one germ pore at the apex covered by a hyaline cap that is mostly 2–5(–7.5) µm long, pedicels hyaline, up to 75 µm long.

For specimen TA431 from Benin two sequences were obtained. The 28S rDNA sequence (904 bp) shows a similarity of 98% with U. galegae on Galega officinalis L. ( Fabaceae ) ( DQ250133 , unpublished sequence deposited by C. Aime in 2006). The ITS rDNA sequence (542 bp) shows a similarity of 93% with U. striolatus which is a microcyclic rust on Euphorbia cyparissias L. ( Euphorbiaceae ) closely related to species heterocyclic on E. cyparissias and diverse species of Fabaceae ( AF180201 , Pfunder et al. 2001). According to these results, U. decoratus is closely related to rust fungi infecting beans, but there are no sequences available for this species until now.

Host and distribution in Benin: —Uredinia and telia on Crotalaria retusa L. ( Fabaceae ), Central and Northeastern Benin.

Specimens examined: — Uredinia and telia on Crotalaria retusa : BENIN. Borgou: Nikki, Sèrékali , elev. 423 m, 9°55’ N, 3°02’ E, 18 September 2019, A . Tabé , M . Piepenbring , Y . Meswaet , and M. U . Schmidt, TA431 ( UNIPAR), GenBank Acc. no. LSU: OL 437040 , ITS: OL 437019 ; Borgou: Parakou, Nima , elev. 364 m, 9°24’ N, 2°41’ E, 30 December 2020, A . Tabé , TA437 ( UNIPAR) .

Known host species:—Primary hosts species: Crotalaria retusa and numerous other species of Crotalaria (Farr & Rossman 2020) . Secondary host species: not known.

Distribution: —Africa [ Ghana ( Leather 1959), Guinea ( Kranz 1964a), Ivory Coast ( Yen 1976b), Nigeria ( Lenné 1990), Senegal ( Bouhot 1966), Benin (this study)], Asia, Central America, South America (Farr & Rossman 2020).

Comments: —In Africa, Crotalaria spp. have been reported as hosts of Uromyces crotalariae (Arthur) J.W.Baxter , U. decoratus , and U. occidentalis Dietel. U. crotalariae is characterized by teliospores that can be 20–27 µm long and 27–32 µm broad or 24–30 × 20–27 μm (versus 26–32 × 18–20 µm in the specimen from Benin) and have verrucose to echinulate ornamentation ( Hennen et al. 2005) in contrast to flat warts partly in striae in the present specimen. U. occidentalis was described from Lupinus spp. from the USA ( Dietel 1903) and was mentioned once on a species of Crotalaria in Nigeria ( Eboh 1978). According to Dietel (1903), U. occidentalis is characterized by densely (not striate) warty teliospores measuring 17–26 × 16–21 µm (versus 26–32 × 18–20 µm in the Benin specimen). We consider that the identification proposed by Eboh (1978) is erroneous and that the specimen collected in Nigeria corresponds to U. decoratus , because he described urediniospores similar to those presented here for Benin as well as teliospores with warts partly in striae.

The present specimen is identified as U. decoratus based on the presence of teliospores with flat warts partly in lines and sizes similar to those reported for the type (20–28 × 14–20 µm; Sydow et al. 1907) or approximately 19–31 × 14–20 µm as measured from diverse specimens by Bouhot (1966). This species is reported here for the first time for Benin.

Figures

FIGURE 12. Uromyces decoratus on Crotalaria retusa (TA431). A Uredinia and telia on leaves B–C Spores drawn in optical sections or in surface view B urediniospores C teliospores. Scale bars: 10 µm.