Pengaruh Inokulum Bacillus thuringiensis terhadap Perubahan Struktur Usus Tengah Ulat Grayak (Spodoptera litura F.)

Abstract

Bacillus thuringiensis was known as biocontrol agent of cotton leafworm growth. B. thuringiensis isolate produced protein crystal as Cry protein which on alkaline condition caused epitel cell in the midgut of cotton leafworm swelled. The aim of this research was to know the effect of B. thuringiensis inoculum from different subspesies to cotton leafworm and the histopatology change in its midgut. Bacillus thuringiensis subsp. aizawai (Bta), B. thuringiensis subsp. pakistani (Btp), B. thuringiensis 47 (Bt47), and B. thuringiensis Lot 2 (BtL2) were tested to 3rd instar larvae. The structures of its midgut were observed at 0, 24th, 48th, 72nd, 96th and 120th hours. They were preparated by Paraffin method and Hematoxylin-Eosin staining. Generally, all 0 hour treatments showed the similar condition with control which the peritrophic membrane and epithelial cells below were still normal. The peritrophic membrane was dissapear at 24th hours, followed by the swelling of epithelial cells and its cores at 48th till 72nd hours. At 96th and 120th hours, the epithelial cells were lysis and disintegrated. The BtL2 isolate had the highest and fastest damages, followed simultantly by Bta, Bt47, and Btp.