Infection of wild-type plants with BSCTV C2− mutant strain (engineered by introducing a stop codon in the C2 ORF) or infection of SAMDC1 mutant plant with wild-type BSCTV strain resulted in enhanced DNA methylation, reduced viral titer and reduced susceptibility confirming the key role of C2 and SAMDC1 in regulating host DNA methylation. The gene discussed is SAMD5; the disease is infection.