Which of the following is commonly used to induce mutations in cereals?

What is the use of plants with desired characters?

Which one of the following is an improved variety of maize?

Fill in the blanks in the following statements ($A$ to $C$):
$(A)$ The capacity to generate a whole plant from any cell/explant is called ......$(i)$ .......
$(B)$ The transfer of resistance genes occurs through ........$(ii)$ ........ . Subsequently,......$(iii)$ ....... occurs between the target and the source plant.
$(C)$ The rice variety $IR8$ was developed in the country ........$(iv)$ .

The germplasm collections are usually maintained at a $A$ temperature in the form of $B$. Here $A$ and $B$ refer to:

Explain variants or mutation as a method of disease resistance.