cry Genes profiling and the toxicity of isolates of Bacillus thuringiensis from soil samples against American bollworm, Helicoverpa armigera

Abstract

Aims: The aim of this study was to search for Bacillus thuringiensis (Bt) harbouring cry1A gene which could effectively control cotton pest, American bollworm, Helicoverpa armigera. Methods and Results: cry gene profiling of 50 Bt isolates showed the presence of cry1, cry2, cry3, cry4, cry7, cry8 and cry9 genes. None of the isolates harboured cry1 gene alone. It was always found in combination with cry3. There was no isolate positive for cry10 gene. Considering isolates with single cry genes, the frequency of cry4 was predominant (22%) followed cry2 (6%), cry3 (4%) and cry8 (2%). Isolates having two cry genes in combination had 14% incidence for cry2 + cry4, 12% for cry3 + cry4 and 10% for cry1 + cry3. The most dominant three gene linkage was cry1 + cry3 + cry4. Further profiling of cry1 gene showed that cry1K gene was abundantly present in all combinations such as cry1A, cry1D, cry1F and cry1I. However, cry1C existed independent of other subtypes. Finally, the Bt isolates with cry1A were analyzed for 16S rRNA gene, which showed two distinct groups of isolates on the basis of sequence homology. Bioassays of spore-crystal mixtures of 8, 17, 21 and 26 harbouring cry1 against neonate larvae of H. armigera showed LC 50 1288, 1202, 467AE7, 524AE8 and 108AE5 lg ml )1 . The SBS-Bt26 showed fourfold higher toxicity than the cry 1Ac harbouring positive control, HD-73. Conclusions: None of the isolates harboured single cry 1 gene. They were always in combination of two or three genes. A Bt isolate (Bt26) had fourfold higher toxicity against H. armigera larvae compared with the positive control HD 73 and hence can be commercially exploited to control insect pest. Significance and Impact of the Study: The inter relationship between the cry genes content and the toxicity may allow better understanding of Bt ecology.

Arsenic in groundwater and its health risk assessment in drinking water of Mailsi, Punjab, Pakistan

“…Arsenic (As) is one of the harmful metalloids present in the groundwater resulting from both anthropogenic and natural sources (Baig et al 2010).Natural and anthropogenic activities such as weathering, erosion, biological activities, petroleum refining, the use of wood preservatives, pesticides, semi-conductors, paints, dyes, metals, soaps, drugs and herbicides significantly contaminate the ground water (Gecol et al 2004). …”

Characterization of lepidopteran-specific cry1 and cry2 gene harbouring native Bacillus thuringiensis isolates toxic against Helicoverpa armigera

“…The estimation of the success of Bt isolation ( Bt index) varied among the soil samples and the average Bt index observed in the study was 0.51. The average Bt index varies between soil samples all over the world as reported previously [25,21,33,34]. The likely reason for difference in Bt index is hard to access, however, the difference in geomorphology and the interaction of the bacterium with their insect hosts could influence their numbers in different environments.…”

“…The predominance of cry1 gene compared to all other cry genes in the native B. thuringiensis has been reported extensively [37,38]. However, predominance of cry genes other than cry1 has also been reported [25,28,39,40]. Twenty six out of 44 B. thuringiensis isolates showed the presence of either cry1 or cry2 genes among which 12 isolates showed the presence of cry1 and cry2 in combination (Table 2).…”

“…The different stages of bacterial growth as well as the crystal production was analysed by Scanning Electron Microscopy (SEM) as described previously [21]. Bt index was calculated as described by Baig et al [25].…”

Co-occurrence of arsenic and fluoride in the groundwater of Punjab, Pakistan: source discrimination and health risk assessment

“…In Pakistan, As and F − affected areas include Jamshoro, Sindh (Baig et al 2009a), Manchar Lake, Sindh (Arain et al 2008(Arain et al , 2009, Lahore and Kasur, Punjab (Farooqi et al 2007a, b), Muzaffargarh, Punjab (Nickson et al 2005), Dera Ghazi Khan, Punjab (Malana and Khosa 2011) and Tharparkar, Sindh (Brahman et al 2013a, b). In 2004, more than 40 people died in Hyderabad City from ingesting water contaminated with high levels of As and other toxic metals (Arain et al 2008).…”