In this study, the effects of a silicon (Si) application on the biomass, chlorophyll level and silicon level of sugarcane moderate pest resistance (RB72454) and susceptible (SP801842) cultivars were tested. Investigat...In this study, the effects of a silicon (Si) application on the biomass, chlorophyll level and silicon level of sugarcane moderate pest resistance (RB72454) and susceptible (SP801842) cultivars were tested. Investigations were also carried out to assess the effect of silicon on Diatraea saccharalis infestation. The experiments were conducted in a greenhouse using the treatments consisting moderate pest resistant and susceptible culivar, with or without silicon application. The silicon was applied to the soil around the plants. The experiment was laid in complete randomized design with 4 treatments and 10 replicates. The data were subjected to an analysis of variance, and the averages were compared using the Tukey test (p ≤ 0.05). Significant changes were observed in the fresh and dry masses of the aerial portions and the root system, as well as in the plant chlorophyll and silicon levels. The silicon content increased in the susceptible variety which was significantly equal for moderate resistance variety. Chlorophyll content increased in silicon treated cultivars. Sixty days after the last application, 10 adult D. saccharalis moths were released onto each pot. However, due to the low infestation, the effects of silicon on the insect incidence could not be determined. One can conclude that silicon is beneficial for the growth of the aerial portions of sugarcane and causes a significant increase in chlorophyll levels.展开更多
The UV-A and UV-B wavelengths of solar radiation may seriously reduce viability of Metarhizium anisopliae conidia,a fungus used extensively in Brazil for insect pest control.The conidial tolerances to UV-A and UV-B ra...The UV-A and UV-B wavelengths of solar radiation may seriously reduce viability of Metarhizium anisopliae conidia,a fungus used extensively in Brazil for insect pest control.The conidial tolerances to UV-A and UV-B radiation were studied for one isolate(IBCB 425) commercially available product produced on rice grains.Aqueous or oil emulsion conidial suspensions were irradiated for 0(control),2,or 3 h using the solar simulator filtered with diacetate filter to remove UV-C radiation which afforded 652 mW·m-2 in the spectral range of 280～370 nm.The UV tolerance was based on conidial germination(viability) and virulence to Diatraea saccharalis larvae.Conidia formulated with oil emulsion had higher survival after 3 h of UV exposure,but the virulence of the conidia previously exposed to 2 h of UV radiation were similar when oil formulated or not.The mortality of D.saccharalis caterpillars exposed to non-UV-irradiated conidia was greater than that of larvae exposed to irradiated conidia,and the LT50 values were lower for the non-irradiated suspensions than for those irradiated.This apparent reduction in virulence was directly related reduction in viability or delay of germination of UV-irradiated conidia.展开更多
Southwestern corn borer （SWCB, Diatraea grandiosella） and fall armyworm （FAW, Spodopterafrugiperda） are major pests of sorghum in the southern United States. Host plant resistance is a desirable means for reducing...Southwestern corn borer （SWCB, Diatraea grandiosella） and fall armyworm （FAW, Spodopterafrugiperda） are major pests of sorghum in the southern United States. Host plant resistance is a desirable means for reducing plant damage and yield losses from both insects. In this study, we evaluated 12 sorghum lines for whorl-stage resistance to leaf-feeding SWCB and FAW in greenhouse and laboratory bioassays. Differential plant responses were detected against the two insects. Among 12 lines tested, CM1821, Della and PI196583 were resistant to both insects, while BTx2752 was largely susceptible. Line R.09110 was resistant to SWCB, but susceptible to FAW, whereas Redbine-60 was suscep- tible to SWCB, but not to FAW. In addition, we quantified various chemical components in the plants and determined their association with insect resistance. Tannin and chloro- phyll in leaves did not show any significant correlation with resistance to either insects, but contents of soluble protein in general were negatively correlated with resistance to both insects. Endogenous soluble sugar and dhurrin were only positively correlated with resistance to SWCB, but not with FAW resistance. To gain some molecular insight into resistance mechanism of sorghum to SWCB, we performed qPCR reactions for key genes encoding enzymes involved in dhurrin and jasmonic acid （JA） biosynthesis on selected resistant or susceptible lines. Although these genes were rapidly and strongly induced by insect feeding in all lines, the observed resistance is likely explained by higher constitutive dhurrin contents in some resistant lines and higher basal JA biosynthesis in others. Our results suggest that sorghum utilizes multiple strategies to defend itself against SWCB.展开更多
The sugarcane borer, Diatraea saccharalis （E）, is a major maize borer pest and a target of transgenic maize expressing Bacillus thuringiensis （Bt） proteins in South America and the mid-southern region of the Unite...The sugarcane borer, Diatraea saccharalis （E）, is a major maize borer pest and a target of transgenic maize expressing Bacillus thuringiensis （Bt） proteins in South America and the mid-southern region of the United States. Evolution of resistance in target pest populations is a great threat to the long-term efficacy of Bt crops. In this study, we compared the genetic basis of resistance to CrylAb protein in 3 resistant colonies of sugarcane borer established from field populations in Louisiana, USA. Responses of larvae to the CrylAb protein for the parental and 10 other cross colonies were assayed in a diet-incorporated bioassay. All 3 resistant colonies were highly resistant to the CrylAb protein with a resistance ratio of 〉 5 5 5.6 fold. No maternal effect or sex linkage was evident for the resistance in the 3 colonies; and the resistance was functionally nonrecessive at the CrylAb concentrations of 〈 3.16 μg/g, but it became recessive at 〉10μg/g. In an interstrain complementation test for allelism, the Fl progeny from crosses between any 2 of the 3 resistant colonies exhibited the similar resistance levels as their parental colonies, indicating that the 3 colonies most likely shared a locus of CrylAb resistance. Results generated from this study should provide useful information in developing effective strategies for managing Bt resistance in the insect.展开更多
基金the National Council for Scientific and Technological Development(Conselho Nacional de Desenvolvimento Cientifico e Tecnologico—CNPq)for providing a fellowship and other financial supportthe Minas Gerais Research Foundation(Fundacao de Pesquisa de Minas Gerais—FAPEMIG)for their financial support.
文摘In this study, the effects of a silicon (Si) application on the biomass, chlorophyll level and silicon level of sugarcane moderate pest resistance (RB72454) and susceptible (SP801842) cultivars were tested. Investigations were also carried out to assess the effect of silicon on Diatraea saccharalis infestation. The experiments were conducted in a greenhouse using the treatments consisting moderate pest resistant and susceptible culivar, with or without silicon application. The silicon was applied to the soil around the plants. The experiment was laid in complete randomized design with 4 treatments and 10 replicates. The data were subjected to an analysis of variance, and the averages were compared using the Tukey test (p ≤ 0.05). Significant changes were observed in the fresh and dry masses of the aerial portions and the root system, as well as in the plant chlorophyll and silicon levels. The silicon content increased in the susceptible variety which was significantly equal for moderate resistance variety. Chlorophyll content increased in silicon treated cultivars. Sixty days after the last application, 10 adult D. saccharalis moths were released onto each pot. However, due to the low infestation, the effects of silicon on the insect incidence could not be determined. One can conclude that silicon is beneficial for the growth of the aerial portions of sugarcane and causes a significant increase in chlorophyll levels.
文摘The UV-A and UV-B wavelengths of solar radiation may seriously reduce viability of Metarhizium anisopliae conidia,a fungus used extensively in Brazil for insect pest control.The conidial tolerances to UV-A and UV-B radiation were studied for one isolate(IBCB 425) commercially available product produced on rice grains.Aqueous or oil emulsion conidial suspensions were irradiated for 0(control),2,or 3 h using the solar simulator filtered with diacetate filter to remove UV-C radiation which afforded 652 mW·m-2 in the spectral range of 280～370 nm.The UV tolerance was based on conidial germination(viability) and virulence to Diatraea saccharalis larvae.Conidia formulated with oil emulsion had higher survival after 3 h of UV exposure,but the virulence of the conidia previously exposed to 2 h of UV radiation were similar when oil formulated or not.The mortality of D.saccharalis caterpillars exposed to non-UV-irradiated conidia was greater than that of larvae exposed to irradiated conidia,and the LT50 values were lower for the non-irradiated suspensions than for those irradiated.This apparent reduction in virulence was directly related reduction in viability or delay of germination of UV-irradiated conidia.
文摘Southwestern corn borer （SWCB, Diatraea grandiosella） and fall armyworm （FAW, Spodopterafrugiperda） are major pests of sorghum in the southern United States. Host plant resistance is a desirable means for reducing plant damage and yield losses from both insects. In this study, we evaluated 12 sorghum lines for whorl-stage resistance to leaf-feeding SWCB and FAW in greenhouse and laboratory bioassays. Differential plant responses were detected against the two insects. Among 12 lines tested, CM1821, Della and PI196583 were resistant to both insects, while BTx2752 was largely susceptible. Line R.09110 was resistant to SWCB, but susceptible to FAW, whereas Redbine-60 was suscep- tible to SWCB, but not to FAW. In addition, we quantified various chemical components in the plants and determined their association with insect resistance. Tannin and chloro- phyll in leaves did not show any significant correlation with resistance to either insects, but contents of soluble protein in general were negatively correlated with resistance to both insects. Endogenous soluble sugar and dhurrin were only positively correlated with resistance to SWCB, but not with FAW resistance. To gain some molecular insight into resistance mechanism of sorghum to SWCB, we performed qPCR reactions for key genes encoding enzymes involved in dhurrin and jasmonic acid （JA） biosynthesis on selected resistant or susceptible lines. Although these genes were rapidly and strongly induced by insect feeding in all lines, the observed resistance is likely explained by higher constitutive dhurrin contents in some resistant lines and higher basal JA biosynthesis in others. Our results suggest that sorghum utilizes multiple strategies to defend itself against SWCB.
文摘The sugarcane borer, Diatraea saccharalis （E）, is a major maize borer pest and a target of transgenic maize expressing Bacillus thuringiensis （Bt） proteins in South America and the mid-southern region of the United States. Evolution of resistance in target pest populations is a great threat to the long-term efficacy of Bt crops. In this study, we compared the genetic basis of resistance to CrylAb protein in 3 resistant colonies of sugarcane borer established from field populations in Louisiana, USA. Responses of larvae to the CrylAb protein for the parental and 10 other cross colonies were assayed in a diet-incorporated bioassay. All 3 resistant colonies were highly resistant to the CrylAb protein with a resistance ratio of 〉 5 5 5.6 fold. No maternal effect or sex linkage was evident for the resistance in the 3 colonies; and the resistance was functionally nonrecessive at the CrylAb concentrations of 〈 3.16 μg/g, but it became recessive at 〉10μg/g. In an interstrain complementation test for allelism, the Fl progeny from crosses between any 2 of the 3 resistant colonies exhibited the similar resistance levels as their parental colonies, indicating that the 3 colonies most likely shared a locus of CrylAb resistance. Results generated from this study should provide useful information in developing effective strategies for managing Bt resistance in the insect.
