Class 10 Answered

Hi Jerry,

The bulk of seed-specific diseases are caused by bacteria or viruses. This is because bacteria and viruses are more adept at entering and then travelling through the veins of the plant, and from the vascular system into the developing embryos of seeds. 
Fungi are restricted to the outer layers of the plant, where they initiate infection by means of air-borne spores and then proceed to spread by attacking nearby cells of the outer layers. The fungal spores are on the outside of the seed, in the layers of the seed coat.

Some of the seed-borne diseases in plants are as follows:

• “Microdochium” seedling blight on wheat is caused by Microdochium nivale. Seedling blight is invariably caused by fungi carried on the seed and can affect seed vigour and performance. 
• Leaf stripe on barley is caused by the fungus Pyrenophora graminea. This is a highly infectious seed-borne pathogen, found in the seed coat of the seed. The disease symptoms are very characteristic: long stripes developing on the leaves, often running the entire length of the leaf, pale green at first then yellow, and finally brown in colour.