Which is a similar term to $Hybrid$ $vigour$?

The entire collection having all the diverse alleles for all genes in a given crop is called

The plant, which is used for studying hybrid vigour or heterosis is

Mating between two individuals differing in genotype to produce genetic variation is called

Which crop developed by mutation breeding shows resistance to yellow mosaic virus?

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?