Question

Which of the following fungi is a parasite on mustard plant and causes the disease white rust of crucifers?
A. Albugo candida
B. Puccinia graminis tritici
C. Saccharomyces cerevisiae
D. Ustilago hordei

Answer 1

Hint: White rust of crucifers is a disease in which rusty white patches are formed on the lower surface of leaves and stem. These infected parts (leaves, stem and flower) become abnormal due to hypertrophy, fleshiness and distortion.

Complete answer:
The disease white rust of crucifers is caused by Albugo candida. It is an obligate parasite and causes white rust disease in the members of different families like Cruciferae (Brassicaceae), Compositae (Asteraceae).
Infected parts become abnormal due to hypertrophy (the enlargement of an organ or tissue in size) and distortion (the state of deformation).
The mycelium of the fungus is intercellular, branched, aseptate, multinucleate with knobs like haustoria which absorb food from host cells.
Puccinia graminis tritici is also a fungus which causes black rust in the cereal crops and causes reduction in the rate of photosynthesis.
Saccharomyces cerevisiae is a species of yeast (single celled fungus). This fungus is used in the wine making, baking and brewing. It is believed that it is isolated from the skin of grapes.
Ustilago hordei is also a fungus which causes covered smut in the barley.

So the correct answer is option A.

Note: Albugo reproduces both asexual and sexual methods. Asexual reproduction occurs by multinucleate conidia or sporangia and in sexual reproduction male and female sex organs are antheridium and oogonium respectively. Sexual reproduction occurs by gametangial contact.