Immigration of Bacillus thuringiensis to bean leaves from soil inoculum or distal plant parts (original) (raw)
Related papers
B. thuringiensis is a Poor Colonist of Leaf Surfaces
Microbial Ecology, 2008
The ability of several Bacillus thuringiensis strains to colonize plant surfaces was assessed and compared with that of more common epiphytic bacteria. While all B. thuringiensis strains multiplied to some extent after inoculation on bean plants, their maximum epiphytic population sizes of 10 6 cfu/g of leaf were always much less than that achieved by other resident epiphytic bacteria or an epiphytically fit Pseudomonas fluorescens strain, which attained population sizes of about 10 7 cfu/g of leaf. However B. thuringiensis strains exhibited much less decline in culturable populations upon imposition of desiccation stress than did other resident bacteria or an inoculated P. fluorescens strain, and most cells were in a spore form soon after inoculation onto plants. B. thuringiensis strains produced commercially for insect control were not less epiphytically fit than strains recently isolated from leaf surfaces. The growth of B. thuringiensis was not affected by the presence of Pseudomonas syringae when co-inoculated, and vice versa. B. thuringiensis strains harboring a green fluorescent protein marker gene did not form large cell aggregates, were not associated with other epiphytic bacteria, and were not found associated with leaf structures, such as stomata, trichomes, or veins when directly observed on bean leaves by epifluorescent microscopy. Thus, B. thuringiensis appears unable to grow extensively on leaves and its common isolation from plants may reflect immigration from more abundant reservoirs elsewhere.
Translocation and insecticidal activity of Bacillus thuringiensis living inside of plants
Microbial Biotechnology, 2009
The major biological pesticide for the control of insect infestations of crops, Bacillus thuringiensis was found to be present naturally within cotton plants from fields that had never been treated with commercial formulations of this bacterium. The ability of B. thuringiensis to colonize plants as an endophyte was further established by the introduction of a strain marked by production of green fluorescent protein (GFP). After inoculation of this preparation close to the roots of cotton and cabbage seedlings, GFP-marked bacteria could be re-isolated from all parts of the plant, having entered the roots and migrated through the xylem. Leaves taken from the treated plants were able to cause toxicity when fed to the Lepidoptera Spodoptera frugiperda (cotton) and Plutella xylostella (cabbage). These results open up new horizons for understanding the natural ecology and evolution of B. thuringiensis and use of B. thuringiensis in insect control.
Plant and Soil, 1994
The colonizing ability of a transcipient strain of Bacillus megaterium carrying a lepidopteran-specific crylA (a) gene of Bacillus thuringiensis in the phyllospheres of various economically important plants was studied. Similar experiments were also carried out using the parental B. thuringiensis var. kurstaki strain HD 1 for a comparison.While the transcipient remained on the leaves of cotton and okra for more than 28 days, its survival in phyllospheres of mulberry, peanut, chickpea, tomato and rice was rather limited to about 3 -5 days. The persistence of B. thuringiensis, on the other hand, was extremely short (i.e. less than 4 days) on all the crop plants tested.
Annals of Microbiology, 2007
The entomopathogenic bacteriumBacillus thuringiensis is widely used for the control of many agricultural insect pests and vectors of human diseases. Several studies reported also on its antibacterial and antifungal activities. However, to our knowledge there were no studies dealing with its capacity to act as a plant growth promoting bacterium. This review surveys the potential ofB. thuringiensis as a polyvalent biocontrol agent, a biostimulator and biofertiliser bacterium that could promote the plant growth. Also, discussed is the safety ofB. thuringiensis as a bacterium phylogenetically related toBacillus cereus the opportunistic human pathogen andBacillus anthracis, the etiological agent of anthrax.
European Journal of Soil Biology, 2013
ABSTRACT Out of twenty seven Gram positive and spore forming Bacilli, four Bacillus thuringiensis (Bt) were obtained from root nodules of six legumes. Three bipyramidal and one spherical crystal producing B. thuringiensis were isolated from root nodules of ricebean, lentil, gahat (Horsegram) and soybean plant. Double Intrinsic Antibiotic Resistance (IAR) markers were developed to detect/monitor the presence of B. thuringiensis in the natural environment. B. thuringiensis isolates were examined for their ability to enhance plant growth and ascending migration (from roots to aerial plant part) in four legumes in plant growth chamber at 28 C. Seed bacterization with B. thuringiensis isolates positively influenced the percent germination and enhanced the plant growth of ricebean, soybean, gahat, and lentil seedlings. All B. thuringiensis isolates were recovered from rhizosphere, root endophytic region, stem lower, upper part and leaf after 45 days after sowing (DAS). Isolate VRB1 was able to colonized rhizosphere and endophytic regions (root, stem and leaf) of gahat, soybean and ricebean after 45DAS. Similarly, isolate VL4C and VLS72.1 were able to colonize rhizosphere and endophytic regions (root, stem and leaf) of lentil and soybean. While, isolate VLG15 was able to colonized rhizosphere and endophytic regions (root, stem and leaf) of lentil, soybean and gahat. Therefore, this study suggests that this approach may be utilized for the development of insect resistant crop strategy in sustainable agriculture.
Survival and conjugation of Bacillus thuringiensis in a soil microcosm
Fems Microbiology Ecology, 2000
The survival and conjugation ability of sporogenic and asporogenic Bacillus thuringiensis strains were investigated in broth, in nonamended sterile clay soil monoculture and in mixed soil culture. The 75 kb pHT73 plasmid carrying an erythromycin resistance determinant and a cry1Ac gene was transferred in mating broth and soil microcosm. Survival of strains was assessed in soil monoculture and in mixed soil culture for up to 20 days. Sporogenic strains rapidly formed viable spores which were maintained until the end of the experiment. The asporogenic strains were no longer recovered after 8 days of incubation. This study shows that the environmental impact of asporogenic B. thuringiensis strains is lower than that of sporogenic B. thuringiensis strains. Thus, the use of asporogenic strains may significantly reduce any potential risk (gene transfer, soil and plant contamination) due to the dissemination of B. thuringiensis-based biopesticides in the environment. ß
South African Journal of Plant and Soil, 2007
Environmental effects of genetically modified plants are not yet fully understood. Experiments were conducted to determine relative amounts of the bioactive Bt protein in roots, leaves and stems of Bt maize and persistence of the protein in two soil forms (Shortlands and Oakleaf). The Bt protein activity was bioassayed using 2 nd to 3 rd instar larvae of diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae). Bioassay results showed that the extracts from different parts of Bt maize plants were equally toxic and caused overall larval motility of over 70%. It was also found that two years' storage of dried Bt maize material at room temperature, did not reduce the pesticidal activity of the protein toxin. When Bt maize plant materials were incubated in soils for two weeks under glasshouse conditions, the extracted toxin caused 20% larval mortality and within 7 weeks of incubation in both soils, the extracts obtained caused <10% larval mortality. However, extracts obtained from Bt maize plant materials incubated in the field showed decreased larval mortality, from 60% to 30% in two weeks and remained >25% after 12 weeks of incubation in the Shortlands soil and from 55% to 15% within four weeks and eventually down to 10% in 23 weeks of incubation in the Oakleaf soil. The findings suggest that Bt maize plant parts contribute comparable amounts of Bt protein toxin to the soil, and toxin persistence in the soil appears to depend on soil type, and temperature and moisture conditions.
2017
The purpose of this research are: 1) To test the effect of the application of Bacillus thuringiensis reproduced using the artificial medium against mustard leaf damage caused by leaf-eating pests; 2) Comparing the stability of the mustard plant agroecosystem after applicated by various concentrations of B. thuringiensis. Tests using a randomized block design with 5 treatments and 4 replications. The treatments were a) Control (application by water); b) Application B. thuringiensis using a concentration of 2 cc/l of water; c) Application B. thuringiensis using a concentration of 4 cc/l of water; d) Application B. thuringiensis using a concentration of 6 cc/l of water; e) Application B. thuringiensis using a concentration of 8 cc/l of water. Observed variables consist of any number of arthropod species found and the intensity of leaf damage. Data were analyzed by analysis of variance using a randomized block design, while the difference between the effect of treatment is determined by...