We identified 84 different encoding sequences of the MHC gene within 210 clones from 13 resistant and 30 susceptible individuals for the “whole white” color pattern of using the specific primer pair DABF and DABR. The sequences were classified into 13 alleles and represented novel genes for this species. We identified a total of 267 and 130 nucleotide and amino acid variable sites, respectively. They exhibited high variable percentages (42.79% and 62.50%).The 624 bp-long nucleotide fragment included a 24 bp exon1, 276 bp exon2, 282 bp exon3, and 42 bp exon4, which encoded partial signal peptide, β1 domain, β2 domain, and partial transmembrane, respectively. The β1 domain possessed a greater number of variable sites than the β2 domain. We identified 150 nucleotide (54.35%) and 72 amino acid (78.26%) variable sites in the 276 bp β1 domain. In contrast, we only found 105 (37.23%) nucleotide and 54 (54.75%) amino acid variable sites in the 282 bp β2 domain. We observed 22 variable sites within 24 peptide binding residues (PBR) of the β1 domain. The ) were 1.366 for PBR, 0.992 for non-PBR in the β1 domain, and 0.792 for the β2 domain, implying that positive selection pressure was exerted on the β1 domain of MHC class II B gene of the “Whole white” color pattern of Cyca-DAB3*09 in the resistant individuals (7.81%) than in the susceptible individuals (1.37%, was only found in the resistant individuals (3.13% of all individuals). Conversely, were only observed in susceptible individuals. Our results may be used to guide anti-resistant breeding selection for the “Whole white” color pattern of.