Consider the following four measures (a-d) that could be taken to successfully grow chick-pea in an area where bacterial blight disease is common                                       

a. Spray with Bordeaux mixture
b. Control of insect vector of the disease pathogen
c. Use of only disease-free seeds
d. Use of varieties resistant to the disease

Which two of the above measures can control the disease?
1. (a) and (d)
2. (b) and (c)
3. (a) and (b)
4. (c) and (d)

Crop plants grown in monoculture are 

1. Low in yield.
2. Free from intraspecific competition.
3. Characterized by poor root system.
4. Highly prone to pests.

Which one of the following is linked to the discovery of Bordeaux mixture as a popular fungicide?            
1. Black rust of wheat
2. Bacterial leaf blight of rice
3. Downy mildew of grapes
4. Loose smut of wheat 

In order to obtain virus-free plants through tissue culture the best method is                  
1. protoplast culture
2. embryo rescue
3. anther culture
4. meristem culture