Correct Option: A. Maize - smut Explanation of the Correct Answer 1. Understanding the Disease: Smut in Maize - Smut is a fungal disease caused primarily by the pathogen Ustilago maydis. It affects maize (corn) plants, leading to the formation of galls or tumors on the ears, stalks, and leaves of the plant. These galls are filled with black spores, which can spread the disease to other plants. - The disease can significantly reduce yield and quality of maize, making it a critical concern for farmers. 2. Why Option A is Correct - Maize is indeed affected by smut, making this pairing accurate. The relationship between maize and smut is well-documented in agricultural science, and it is a common issue faced by maize growers. Explanation of Why Other Options are Incorrect B. Sorghum - scab - Scab is primarily associated with wheat and barley, caused by the fungus Fusarium graminearum. While sorghum can be affected by various diseases, scab is not one of the primary diseases associated with it. Instead, sorghum is more commonly affected by diseases like anthracnose and downy mildew. Therefore, this option is incorrect. C. Rice - black arm - The term black arm is not typically associated with rice. Instead, it is a disease that affects cotton, caused by the bacterium Xanthomonas campestris. Rice is more commonly affected by diseases such as rice blast (caused by Magnaporthe oryzae) and bacterial blight. Thus, this option is also incorrect. D. Yam - blast - Blast is a disease that primarily affects rice, not yam. The disease is caused by the same pathogen that affects rice, Magnaporthe oryzae. Yam can be affected by diseases such as yam mosaic virus and tuber rot, but not blast. Therefore, this option is incorrect as well. Summary of Key Points

• Smut is a well-known disease affecting maize, making option A correct.
• Scab is primarily associated with wheat and barley, not sorghum.
• Black arm is a disease of cotton, not rice.
• Blast is a rice disease, not one that affects yam.

Revision Summary

• Maize is affected by smut (Ustilago maydis), leading to significant yield loss.
• Sorghum is not primarily affected by scab; it faces other diseases.
• Black arm is a cotton disease, not related to rice.
• Blast is specific to rice and does not affect yam.

Understanding these associations is crucial for effective crop management and disease control in agricultural practices.