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The following points highlight the five important genera of family pucciniaceae. The genera are: 1. Gymnosporangium 2. Hemileia 3. Phragmidium 4. Ravenalia 5. Uromyces.
Genera # 1. Gymnosporangium:
Represented by 57 species, the genus is restricted to temperate regions. Most of the species are heteroecious and demicyclic, the telial stage occurs on Gymnosperms while aecial cups are formed on dicotyledons.
G. juniperi-virginiane forms pycnial and aecial stages on apples and telial stage on Junipers. The teliospores (teleutospores) are bicelled and pedicellate.
Genera # 2. Hemileia:
The genus parasitises Angiosperms mostly the members of Family Rubiaceae. Of the 40 species known, H. vastatrix is parasitic on coffee plants causing coffee rust.
Pycnial and aecial stages are not known, the uredinia are formed in sub-stomatal chambers. The telia are formed along with uredinia. Teliospores (teleutospores) are one celled, reniform, thinwalled and pale.
Genera # 3. Phragmidium:
The genus known by 60 species is an autoecious macro—or demicyclic rust parasitising the members of the family Rosaceae. The teliospores (teleutospores) are stalked, transversely septate and many celled. P. mucronatum and P. tuberculatum are important parasites of ornamental Roses.
Genera # 4. Ravenalia:
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Represented by 150 species, this autoecious rust parasitises legumes in mostly tropical countries. The teliospores (teleutospores) fuse to form a teliospore head in which each teliospore has a separate stalk. Each teliospore head is subtended by a sterile cyst cell. R. emblicae parasitises Phyllanthus emblica.
Genera # 5. Uromyces:
Species of the genus cause important rust diseases on members of family Leguminosae. Rust of beans caused by V. phaseoli.
Rust of gram caused by U. ciceris-arietini, Rust of pea caused by U. pisi and U. fabae and carnation rust caused by U. dianthi are some of the examples of the genus which is macro or microcyclic and heteroecious or autoecious.
The tehospores (teleutospores) are one celled, binucleate and thickened at the apex. In the Gram rust caused by U. ciceris arietini, the aecial and pycnial stages are not known, only the telial and uredionial stages are known and produced on leaves. Trigonella polycerata acts as collateral host.
