If a breeder wants to introduce a disease-resistant strain,what should be the first step?

Match the following columns:

Column-$I$	Column-$II$
$P$. Semi-dwarf varieties of wheat	$I$. Sonalika
$Q$. Semi-dwarf varieties of rice	$II$. $IR-8$
	$III$. Jaya
	$IV$. Kalyan Sona
	$V$. Taichung Native-$I$
	$VI$. Ratna

The dwarf varieties of wheat brought from Mexico into India were

Name the improved characteristics of wheat that helped India to achieve the Green Revolution.

Air layering is performed in case of:

Consider the following four statements $(a-d)$ regarding the successful cultivation of chickpea in an area where bacterial blight is common:
$(a)$ Spraying of Bordeaux mixture.
$(b)$ Control of the disease vector.
$(c)$ Use of disease-free seeds.
$(d)$ Use of disease-resistant varieties.
Which of the above are the most effective strategies for managing this disease?