Molecular Confirmation on the Association of Crown Mealybug with Pokkah Boeng Disease in Sugarcane: A Prelude for Designing Management Strategy

Pokkah boeng (PB) caused by Fusarium sp. complex is a re-emerging disease that causes significant yield loss in sugarcane cultivation. Recently, the crown mealybug, Phenacoccus saccharifolii (Green), association aggravated the disease severity due to rapid spread which leads to an outbreak of the disease. The molecular association between crown mealybug and Fusarium sp. pathogens in the infected cane is not yet revealed. To understand the crown mealy bug association, the insects were collected from infected PB canes from different locations in Tamil Nadu. They were identified as P. saccharifolii based on morphological and molecular analysis of cytochrome oxidase subunit I (COI) and D2-D3 region of large ribosomal subunit gene (28S rRNA). Microflora were isolated from both the external and internal parts of P. saccharifolii. Fungal cultures were found to be present only in the external parts and they were confirmed as Fusarium sacchari based on morphological and molecular analysis using ITS and TEF-1α markers. Further, DNA was extracted from the mealy coating wax and confirmed the presence of F. sacchari using the TEF-1α gene. The scanning electron microscope (SEM) analysis confirms the presence of microconidia in the waxy threads of P. saccharifolii. The results of the pathogenicity assay using Fusarium isolates showed symptoms of chlorosis and necrosis. The pot culture experiment proved the association of crown mealybug with F. sacchari in aggravating the disease incidence. To our knowledge, this may be the first report on the molecular confirmation of crown mealybug in association with PB disease.