Baobabopsis sp. 1

Description

Sporangiophores/Conidiophores not observed.

Conidia ellipsoidal-subglobose, (20-)20-24(-26) x (15-)16-19(-20) µm, hyaline, aseptate, without operculum or pore.

Oogonia formed in the leaf blades which split into a tangled mass of vascular fibres, subglobose-globose, (28-)30-36(-40) µm in diameter; wall (exosporium) 4-9 µm thick, golden brown, with warts on outer surface domed-subglobose, 2-6 x 3-5 µm, usually width > height.

Oospores one per oogonium, globose, (21-)22-25(-28) µm (n=15) in diameter, adnate with oogonium wall, with a single vacuole; wall (endosporium) 1-2 µm thick, hyaline, smooth.

Hosts
   
Host family: Poaceae
   
Host species:

Bothriochloa ewartiana - BRIP


Distribution

NT

Comments

his downy mildew fungus is known only from one collection in the Northern Territory, the specimen consisting of a single plant bearing both entire lower leaves and a few upper frayed leaves. The remnants of twisted and intermingled asexual reproductive structures and spores were found on the abaxial surfaces of some entire leaves on this specimen. Although the morphology of the conidiophores could not be determined with any certainty, that of the asexual spores were clear. There were no signs of an apical operculum or pore, so it is highly probable that the spores are conidia and germinate by the production of one or more germ tubes. 

Bonde and Peterson (1981) reported that several species of Bothriochloa (not including B. ewartiana) were susceptible to a Taiwanese isolate of what they believed to be Peronosclerospora sacchari under artificial inoculation conditions. However, there are no records of a downy mildew pathogen being found on Bothriochloa spp. growing under natural conditions in the World. In addition, the walls of oogonia of the Peronsclerospora species on the Australian specimen of B. ewartiana possess warts whilst those of P. sacchari do not.

Molecular studies show that it is a new species of Baobabopsis.

Highslide JS
Peronosclerospora sp. on Bothriochloa ewartiana - BRIP 49665.
Scale bar = 1 cm.
Highslide JS
Conidia of Peronosclerospora sp. on Bothriochloa ewartiana - BRIP 49665.
Scale bar = 10 µm.
Highslide JS
Oospores of Peronosclerospora sp. on Bothriochloa ewartiana - BRIP 49665.
Scale bar = 10 µm.