Code: Bot_1049/2017_DSC7443

Habitat: (sub)mediterranean maquis scrubland; narrow, dirt road side, almost flat terrain, calcareous, skeletal ground, Karst region; warm, dry and quite sunny place; average precipitations ~ 900 mm/year, average temperature 12-14 deg C, elevation 125 m (410 feet), (sub)mediterranean phytogeographical region.

Substratum: small, living shrub of Rosa sp. (canina ?) leaves and buds.

Place: West part of Krk Island, between villages Brzec and Poljica, Adriatic Sea, Kvarner bay, Croatia EC.

Comments: Phragmidium mucronatum is a common rust fungus growing on roses (Rosa). It feeds off the plant’s own supplies thereby weakening it. This is the reason why gardeners hate it. Taxonomy of rust fungi is very ‘difficult’ (see number of synonym names for Phragmidium mucronatumit above!). Also its life cycle is very complex. Leaf rust of roses grows through several different stages. It produces four different forms of spores. The original pustules (aecia) produce aecidospores (each spore has two nuclei, they appear usually in chains), which infect other leaves or other parts of the plant and in turn produce the yellow-orange pustules and wounds. They form urediniospores (dikaryotic spores, which disperse widely, spreading infection), which germinate to form black pustules. They contain teliospores (thick-walled resting spores) which overwinter on fallen leaves, to germinate in the spring producing basidiospores (spores produced by specialized fungal cells called basidia), which are blown by wind. Pictures show the orange, spring time stage with urediospores.


Proposed Names

57% (1)
Recognized by sight: Vivide orange and on Rosa.
Based on microscopic features: Urediospores not smooth, minutely, (sharply ?) warted; spores of irregular shape. Dimensions: 20 [24.3 ; 26.2] 30.5 × 15.3 [19.9 ; 21.9] 26.5 microns; Q = 0.9 [1.2 ; 1.3] 1.5; N = 30; C = 95%; Me = 25.2 × 20.9 microns ; Qe = 1.2. Olympus CH20, NEA 40x/0.65, magnification 400x (spores), NEA 10x/0.25, magnification 100x (squash), dry material; in water. AmScope MA500 digital camera.

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Created: 2017-05-15 12:09:05 PDT (-0700)
Last modified: 2017-05-15 12:09:14 PDT (-0700)
Viewed: 31 times, last viewed: 2019-11-19 18:35:03 PST (-0800)
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