Changes in Bacillus thuringiensis Tolerance Levels Due to Hybridization of Bt-Tolerant and Susceptible Silkworm Populations

• Published in: Pakistan journal of scientific and industrial research. Series B: biological sciences 2012-07, Vol.55 (2), p.101-107
• Main Authors: Begum, Hosne Ara, Hassan, Errol, Dingle, John, Alshehi, Aisha Alkhayat
• Format: Article
• Language: English
• Subjects: Bacillus thuringiensis; Health aspects; Physiological aspects; Population biology; Silkworms
• ISSN: 2221-6421; 2223-2567
• DOI: 10.52763/pjsir.biol.sci.55.2.2012.101.107

Males and females of a Bt-tolerant mulberry silkworm (Bombyx mori L.) population were crossed with females and males of a Bt-susceptible population, to produce Bt-tolerant silkworm hybrids, and to determine the expression of the Bt-tolerance pattern in the F1 hybrids. It was observed that when a Bt-tolerant (42% larval mortality) female (BtT ♀) silkworm was crossed with a Bt-susceptible (85% larval mortality) male (BtS ♂), the resultant F1 offspring showed lower levels of Bt-tolerance (87% larval mortality). On the other hand, when a Bt-tolerant male (BtT ♂) was crossed with a Bt-susceptible female (BtS ♀), the F1 hybrid showed higher levels of Bt-tolerance (35% larval mortality) characteristic. The probit statistics showed that both hybrids expressed Bt-tolerance or susceptible levels similar to their male parents. These different patterns of Bt-tolerance in F1 hybrids might be due to the transferring of a Bt-tolerant gene, from the parents to offspring, through the homozygotic male (ZZ) silkworm. Keywords: Bacillus thuringiensis, Bt-tolerance, Bombyx mori, insect hybridization, male homozygosity, hybrid performances