Host Specific Phytohistological And Fitness Responses In Papaya Mealybug Paracoccus Marginatus Under Divergent Selection

Abstract

This study presents the phytohistological investigation of papaya mealybug PMB (Paracoccus marginatus Williams and Granara de Willink) across six host plants papaya, tapioca, cotton, mulberry, brinjal, and hibiscus highlighting their varied responses under divergent natural selection. Leaf samples from healthy and PMB-infested plants were examined for anatomical and biochemical changes. Significant structural alterations were observed in infested leaves, including distortion of abaxial and adaxial epidermal layers, disorganization of mesophyll tissues, enlargement of xylem and phloem cells, crystal body formation, and irregular cell arrangements, particularly in the midrib. Biochemical analysis revealed elevated tannin and phenol content, coupled with a decline in total carbohydrates, reducing sugars, and proteins in infested tissues. Susceptibility to PMB was pronounced in papaya and cotton, where severe histological damage and substantial reductions in primary metabolites were noted. On the other hand, tapioca showed resistance, as seen by higher secondary metabolite levels and less tissue damage. These results support the idea that diverse natural selection shapes resistance mechanisms by indicating that host plants respond to PMB infection with varying defense measures. This study can direct the creation of resistant crop types and offers insightful information on host-pest interactions.