Question

Arrange the stages in the life cycle of "Puccinia graminis" in correct order of their occurrence, starting from Triticum aestivum
A. Teliospores appear as black raised streaks along leaf sheaths and stems of infected plants.
B. Basidiospores are discharged by an explosive mechanism and disseminated by wind.
C. Uredinospores germinate on wheat and spread the disease rapidly, under favorable conditions.
D. Basidiospores germinate on the leaves of the alternate host.
Choose the correct answer from the options given below:

• A. B, A, C, D
• B. D, B, C, A
• C. C, A, B, D
• D. D, B, A, C

Hint:

Remember the host association for {Puccinia} spores: Urediniospores and Teliospores are on the primary host (wheat). Basidiospores infect the alternate host (barberry). Aeciospores (from barberry) infect the primary host (wheat). The red rust (Uredinia) always precedes the black rust (Telia) on wheat.

Answer 1

The Correct Option is C

Step 1: Concept Summary:
The question requires ordering the life cycle stages of {Puccinia graminis} (black stem rust) starting with wheat ({Triticum aestivum}) infection. This fungus has a complex cycle involving wheat and barberry, with five spore stages.
Step 2: Detailed Explanation:
Life cycle starting on wheat:

Wheat Stage (Summer): Reddish-brown pustules (urediniospores) appear on wheat. Urediniospores spread the infection rapidly between wheat plants. This corresponds to statement C.

Wheat Stage (Late Summer/Autumn): The fungus produces black teliospores in the same pustules. Teliospores are the overwintering stage. This corresponds to statement A.

Post-Overwintering (Spring): Diploid teliospores undergo meiosis and germinate, producing basidia with haploid basidiospores. Basidiospores are released. This corresponds to statement B.

Alternate Host Stage (Barberry): Basidiospores cannot infect wheat. They infect the alternate host, barberry ({Berberis} sp.). This corresponds to statement D. (On barberry, pycniospores and then aeciospores are produced, which infect wheat to restart the cycle.)
Step 3: Solution:
The correct sequence from the wheat disease stage is C (Urediniospores) \(\rightarrow\) A (Teliospores) \(\rightarrow\) B (Basidiospore discharge) \(\rightarrow\) D (Basidiospore germination on alternate host). This is option (C).