Correct option is A
Explanation-
Statement A: Frequency of genetic transformation is influenced only by the genes of Agrobacterium and not by those of the host plants. - INCORRECT
The transformation efficiency is influenced by both Agrobacterium and host plant factors like genotype, explant type, and tissue culture conditions. Saying it is "only" due to Agrobacterium is incorrect.
Statement B: Transgenic plants containing a single copy of the transgene are preferred over those that contain multiple transgene copies for subsequent genetic analysis. - CORRECT
Single-copy insertions reduce complications like gene silencing, and facilitate stable inheritance, making them preferable for genetic analysis.
Statement C: Supervirulent strains of Agrobacterium can be generated by increasing the copy number of virulence genes. - INCORRECT
Supervirulent strains are typically derived from specific modifications or sources (e.g., A281 strain), not just by increasing virulence gene copies. Overexpression alone does not guarantee supervirulence, and the relationship is not linear.
Statement D: A nonconditional negative selection marker has to be necessarily used with a strong constitutive promoter for the development of transgenic plants. - INCORRECT
Negative selection markers are not necessarily required, and their use with strong constitutive promoters is not mandatory. Conditional systems (e.g., inducible promoters) are also common, making this statement too absolute.
Final answer - Option a : A and D only
