Effects of triazophos on biochemical substances of transgenic Bt rice and its nontarget pest Nilaparvata lugens Stål under elevated CO2

The brown planthopper (BPH), Nilaparvata lugens Stål, is a serious rice pest throughout Asia. Recent outbreaks of N. lugens populations were mainly associated with the overuse of pesticides and resistance to insecticides. Warmer global temperatures that are associated with anthropogenic climate change are likely to have marked ecological effects on terrestrial ecosystems. However, the effects of elevated CO₂ concentrations on the biochemical, physiological and nutrient quality of transgenic Bt rice that has been treated with pesticides and on the control efficacy of the pesticides are not understood. The present study investigated changes in soluble sugar content, free amino acid levels, oxalic acid levels, flavonoids levels, and triazophos residues in transgenic Bt rice (TT51) and the control efficacy of triazophos for N. lugens following triazophos foliar spray under conditions of elevated CO₂ (eCO₂). Our findings showed that the soluble sugar content of TT51 treated with triazophos under eCO₂ was significantly higher than that under ambient CO₂ (aCO₂) and also higher than that of the non-transgenic parent (MH63) under aCO₂. However, the results for free amino acid levels were the opposite of those for soluble sugar levels. The oxalic acid and flavonoid contents of rice plants significantly decreased with increases in triazophos concentration, CO₂ concentration, and days after treatment (DAT). The oxalic acid and flavonoid contents of TT51 treated with triazophos under eCO₂ were significantly lower than those under aCO₂ and also lower than those of MH63 under aCO₂. The residue concentration of triazophos varied with CO₂ concentration, rice variety, and DAT. The residues in TT51 treated with 80 ppm of trizaopos under eCO₂ were significantly lower than those under aCO₂ and those in MH63 under aCO₂. The survival rate of nymphs N. lugens in TT51 under eCO₂ was significantly higher than that under aCO₂ and that in MH63 under aCO₂ at 1 DAT or 15 DAT after the release of 2nd instars nymphs. These findings indicated that (1) for TT51, triazophos reduced the resistance of rice plants to N. lugens with an elevated CO₂ concentration, as N. lugens consumed more phloem sap on TT51 plants; (2) triazophos dissipation in TT51 under eCO₂ was significantly faster than that under aCO₂ and that in MH63 under aCO₂; (3) the control efficacy of triazophos for N. lugens significantly decreased under eCO₂. The present findings provide important information for integrated pest management among transgenic varieties.     

Characterization of sulfonylurea-resistant Schoenoplectus juncoides having a target-site Asp376Glu mutation in the acetolactate synthase

Schoenoplectus juncoides, a noxious weed for paddy rice, is known to become resistant to sulfonylurea (SU) herbicides by a target-site mutation in either of the two acetolactate synthase (ALS) genes (ALS1 and ALS2). SU-resistant S. juncoides plants having an Asp₃₇₆Glu mutation in ALS2 were found from a paddy rice field in Japan, but their resistance profile has not been quantitatively investigated. In this study, dose–response of the SU-resistant accession was compared with that of a SU-susceptible accession at in vivo whole-plant level as well as at in vitro enzymatic level.     

Biotransformation of clomazone in rice (Oryza sativa) and early watergrass (Echinochloa oryzoides)

Rice (Oryza sativa), a relatively tolerant species, and early watergrass (Echinochloa oryzoides; EWG), a relatively susceptible species, were exposed to ¹⁴C-labeled clomazone to determine accumulation, biotransformation, and mass balance. On a total mass basis, rice absorbed more clomazone than EWG (p < 0.05), but on a nmol/g basis, there was no significant difference between the two species (p > 0.05). Rice contained more extractable ¹⁴C residues (7.7 ± 0.5 vs. 4.8 ± 0.5 nmol in rice vs. EWG, respectively; p < 0.5), but the concentration in EWG was significantly higher (4.2 ± 0.5 vs. 1.8 ± 0.1 nmol/g in EWG vs. rice, respectively; p < 0.01). More metabolized residue was measured in EWG compared to rice (84.1% vs. 67.9%; p < 0.01). Both species produced hydroxylated forms, β-d-glucoside conjugates, and several other unidentified polar metabolites, but EWG generally produced higher metabolite concentrations. The concentration of the suspected active metabolite, 5-ketoclomazone, was significantly higher in EWG vs. rice (21 ± 2 vs. 5.7 ± 0.5 pmol/g, respectively; p < 0.01). Differences in sensitivity to clomazone between rice and EWG appear to be due to differential metabolism, but in this case the more susceptible EWG qualitatively and quantitatively metabolized more clomazone than the more tolerant rice. This is consistent with the action of a metabolically activated herbicide. This metabolic difference could be exploited to develop herbicide safeners for use with clomazone.     

稻虱缨小蜂对吡虫啉处理的水稻植株挥发物的行为反应

利用"Y"型嗅觉仪测定稻虱缨小蜂对吡虫啉处理的水稻植株挥发物的行为反应,并通过GC-MS对挥发物组分进行了定性和定量分析.行为测试结果表明:吡虫啉和施用了吡虫啉的不同水稻品种挥发物对稻虱缨小蜂的寄主选择行为无明显影响.稻虱缨小蜂在不同浓度吡虫啉处理的水稻植株之间表现出明显的嗅觉偏好.当褐飞虱密度为10头/苗时,与高浓度吡虫啉处理相比,低浓度吡虫啉处理植株释放的挥发物引诱到了更多的稻虱缨小蜂(施药5天除外).GC-MS分析发现:与对照植株释放的挥发物相比,吡虫啉处理的稻株挥发物组分种类不变;吡虫啉浓度不同导致水杨酸甲酯等8种组分的相对含量明显不同;同时一些组分的相对含量因吡虫啉浓度与水稻品种、褐飞虱密度及施药天数等因子的互作发生了明显改变.     

大豆对灰斑病菌15号小种的抗病基因定位及标记检测

为明确大豆对灰斑病菌15号小种的抗性位点,以大豆抗病品种垦丰16、感病品种绥农10及其杂交F₂、F₃代群体为试验材料,在接种鉴定的基础上,运用SSR标记技术及分离群体组群分析法(BSA法)对垦丰16抗病基因进行了定位,并应用108份大豆新品系对标记进行了符合性检测。结果表明,垦丰16对15号小种的抗性受1对显性基因控制,抗病基因位于大豆染色体组的J连锁群上,将该基因定名为Rcs15。用Mapmaker/Exp 3.0 b进行连锁分析,获得了5个与抗病基因紧密连锁的SSR标记:Satt 529、Satt 431、Sat_151、Satt 547和Sat_224,标记与抗病基因间的排列顺序和遗传距离为Sat_151-10.7 cM-Satt 529-18.5 cM- Rcs15-6.7 cM-Satt 547-7.8 cM-Sat_224-10.7 cM-Satt 431。标记符合性检测结果显示,Satt 547和Sat_224的检测准确率达到85%以上,可用于分子标记辅助选择育种和抗源筛选。     

Triazophos resistance mechanisms in the rice stem borer (Chilo suppressalis Walker)

A field population of the rice stem borer (Chilo suppressalis Walker) with 203.3-fold resistance to triazophos was collected. After 8-generation of continuous selection with triazophos in laboratory, resistance increased to 787.2-fold, and at the same time, the resistance to isocarbophos and methamidophos was also enhanced by 1.9- and 1.4-fold, respectively, implying some cross-resistance between triazophos and these two organophosphate insecticides. Resistance to abamectin was slightly enhanced by triazophos selection, and fipronil and methomyl decreased. Synergism experiments in vivo with TPP, PBO, and DEM were performed to gain a potential indication of roles of detoxicating enzymes in triazophos resistance. The synergism results revealed that TPP (SR, 1.92) and PBO (SR 1.63) had significant synergistic effects on triazophos in resistant rice borers. While DEM (SR 0.83) showed no effects. Assays of enzyme activity in vitro demonstrated that the resistant strain had higher activity of esterase and microsomal O-demethylase than the susceptible strain (1.20- and 1.30-fold, respectively). For glutathione S-transferase activity, no difference was found between the resistant and the susceptible strain when DCNB was used as substrate. However, 1.28-fold higher activity was observed in the resistant strain when CDNB was used. These results showed that esterase and microsomal-O-demethylase play some roles in the resistance. Some iso-enzyme of glutathione S-transferase may involve in the resistance to other insecticides, for this resistant strain was selected from a field population with multiple resistance background. Acetylcholinesterase as the triazophos target was also compared. The results revealed significant differences between the resistant and susceptible strain. The V_max and K_m of the enzyme in resistant strain was only 32 and 65% that in the susceptible strain, respectively. Inhibition tests in vitro showed that I₅₀ of triazophos on AChE of the resistant strain was 2.52-fold higher. Therefore, insensitive AChE may also involved in triazophos resistance mechanism of rice stem borer.     

The genetic mechanisms of warfarin resistance in Rattus rattus found in the wild in Japan

Warfarin is commonly used worldwide as a rodenticide. It inhibits blood coagulation by inhibiting vitamin K 2,3-epoxide reductase (VKOR) activity leading to hemorrhage. However, it has been reported that repeated or long-term treatment with warfarin results in resistance emerging in wild rodents. Such resistance may explain why it is difficult to control rodents in many regions in Japan. In this report, we studied mutations in the VKOR gene (including the VKOR complex subunit 1 (VKORC1)), while also analyzing VKOR and clotting factor activity in black rats (Rattus rattus) in order to understand better the mechanism of warfarin resistance in this species.We sequenced the VKORC1 gene from 275 rats living in the wild in Japan. We found several types of novel base substitutions, some of which conferred warfarin resistance.There was no difference in coagulation times between warfarin-sensitive and resistant rats measured under physiological conditions. However, after warfarin administration, no effect was noted in warfarin-resistant rats, although a prolonged coagulation time was noted in warfarin-sensitive rats.We also determined the kinetic differences in hepatic microsomal VKOR-dependent activity between warfarin-resistant and sensitive rats. Warfarin-resistant rats showed 2-3-fold lower V_max/K_m values than did sensitive rats. In addition, we report that resistant rats found in the Tokyo area had a VKOR activity which was poorly inhibited by warfarin.Finally, we conclude that reduced VKOR activity and warfarin resistance in the Japanese black rat might be due to mutations in the VKORC1 gene. However, further study is needed to clarify how such rats can maintain adequate vitamin K-dependent clotting factor levels, while simultaneously exhibiting low VKOR activity and warfarin resistance.     

Effects of different treatment methods of the fungicide jinggangmycin on reproduction and vitellogenin gene (Nlvg) expression in the brown planthopper Nilaparvata lugens Stål (Hemiptera:Delphacidae)

Jinggangmycin is an antibiotic fungicide against the rice sheath blight, Rhizoctonia solani, in China. Previous investigations have shown that jinggangmycin leaf spray stimulated the fecundity of Nilaparvata lugens Stål (Hemiptera:Delphacidae), but the effects of different application methods and concentrations of jinggangmycin on the reproduction of N. lugens have not been investigated. Here, we investigated three treatment methods (foliar and stem sprays and topical treatment) and four concentrations (100, 200, 400 and 800 ppm) of jinggangmycin on the reproduction of adult female N. lugens. The results showed that leaf spray significantly stimulated the fecundity of N. lugens and increased the vitellin content in female ovaries and the gene expression level of vitellogenin (Nlvg), but there was no significant effect on reproduction found for stem spray. In four concentrations of jinggangmycin, leaf sprays at concentrations of 100, 200 and 400 ppm and topical treatments of 100 and 200 ppm significantly increased the number of eggs laid, the vitellin content and the gene expression level of Nlvg compared to the control. Therefore, we suggest that stem spray at high concentration should be applied (if possible) when jinggangmycin is used against rice sheath blight to facilitate harmonious control of rice pests.     

Transformation a mutant Monochoria vaginalis acetolactate synthase (ALS) gene renders Arabidopsis thaliana resistant to ALS inhibitors

Acetolactate synthase (ALS) genes from Monochoria vaginalis resistant (R) and susceptible (S) biotypes against ALS inhibitors found in Korea revealed a single amino acid substitution of Proline (CCT), at 169th position based on the M. vaginalis ALS sequence numbering, to serine (TCT) in conserved domain A of the gene (equal to the proline 197 in Arabidopsis thaliana ALS gene sequence). A. thaliana plants transformed with the single mutated (Pro₁₆₉ to Ser) M. vaginalis ALS gene (including transit signal peptide) showed cross-resistance patterns to ALS-inhibiting herbicides, like as sulfonylurea-herbicide bensulfuron methyl (R/S factor of 9.5), imidazolinone-herbicide imazapyr (R/S factor of 5.1), and triazolopyrimidine-herbicide flumetsulam (R/S factor of 17.6) when measuring hypocotyls’ length of A. thaliana. The ALS activity from the transgenic A. thaliana plants confirmed the cross-resistance pattern to these herbicides like as R/S factor of 8.3 to bensulfuron methyl, 2.3 to imazapyr, and 13.2 to flumetsulam.     

Modifying Myxococcus xanthus protoporphyrinogen oxidase to plant codon usage and high level of oxyfluorfen resistance in transgenic rice

Protoporphyrinogen oxidase (Protox) of Myxococcus xanthus (Mx Protox) is a 49-kDa membrane protein that catalyzes conversion of protoporphyrinogen IX (Protogen IX) into protoporphyrin IX (Proto IX). Upon heterologous expression in transgenic rice plants, Mx Protox is dually targeted into plastids and mitochondria, increasing resistance against the herbicidal Protox inhibitor oxyfluorfen. Here, we describe the chemical synthesis of the Mx Protox gene by assembling several small synthetic DNA fragments derived by ligation-PCR. Codon usage in the resulting 1416-bp gene was modified to correspond to that of the Arabidopsis Protox gene, a change that resulted in a decrease in G+C content from 71 to 49%. The modified Mx Protox gene was used to generate transgenic rice plants via Agrobacterium-mediated transformation. Integration, expression, and inheritance of the transgenes were demonstrated by Southern, Northern, and Western blot analyses. In plants transformed with the modified, low G+C-content Mx Protox gene, levels of Protox expression and enzyme activity were low compared to the levels observed for plants transformed with the native Mx Protox gene. Nonetheless, like the native gene, the modified gene conferred a high level of resistance to the herbicide oxyfluorfen in a seedling growth test.     

Biological and biochemical responses of Biomphalaria alexandrina to some extracts of the plants Solanum siniacum and Artemisia judaica L.

The molluscicidal activity of cold water, boiled water, methanol, ethanol, acetone and chloroform extracts of Solanum siniacum and Artemisia judaica L. plants against Biomphalaria alexandrina snails was carried out. The tests revealed plant’s ethanol extract was more toxic to the snails than the other tested extracts. Therefore, it was tested against snails’ fecundity (M_x), reproduction rate (R₀) and their infection with Schistosoma mansoni miracidia. In addition, biochemical parameters and the activities of some enzymes in tissues of snails treated with the two tested plants were determined. As well, glucose concentration in snails’ hemolymph was evaluated. Exposure of B. alexandrina snails to plant’s ethanol extract led to a significant reduction in their survival and snails’ fecundity, reproduction rate. In addition, it caused a considerable reduction in the infectivity of S. mansoni miracidia to the snails. Also, it caused a reduction in number of cercariae per snail during the patent period and in the period of cercarial shedding. The results revealed that the glucose concentration in hemolymph and Lactate level in soft tissues of treated snails were increased (P < 0.001) while glycogen, total protein, the lipid content and the pyruvate level in snail’s tissues decreased (P < 0.001). The activities of lactic dehydrogenase (LDH), pyruvatekinase (PK) and cytochrome oxidase (CY) enzymes in homogenate of snail’s tissues were reduced (P < 0.001) in response to treatment with the two tested plants while protease (PR) activity increased (P < 0.001). It is concluded that the application of LC₂₅ of ethanol extract of S. siniacum and A. judaica L. may be helpful in snail control as it interferes with the snails’ biology and physiology.     

芽胞杆菌CQBS03抑菌蛋白TasA基因的克隆及原核表达

为了探讨柑桔溃疡病生防菌芽胞杆菌Bacillus CQBS03菌株TasA基因的功能,采用PCR方法从CQBS03基因组DNA中扩增出编码TasA基因的全长DNA序列,并构建pEASY-E1/TasA原核表达载体,经大肠杆菌Escherichia coli表达获得TasA基因的融合表达蛋白,纸碟法检验融合蛋白对柑桔溃疡病菌Xanthomonas citri citri的抑制作用。结果显示,CQBS03菌株的TasA基因包含1个786 bp的完整开放阅读框（GenBank登录号为JQ309841）,编码261个氨基酸残基;该序列与来源于解淀粉芽胞杆菌B.amyloliquefaciens的1个已知同源TasA基因序列FJ713580的相似性达99.75%。原核表达产物经SDS-PAGE分析,检测到约31 kD的融合蛋白;纯化后的融合蛋白对柑桔溃疡病菌有明显的抑制作用,72 h后抑菌圈直径达11.5 mm。研究表明TasA基因是生防菌芽胞杆菌CQBS03抑制柑桔溃疡病菌的功能基因之一,并且该基因对原核表达宿主没有抑制作用,具有较好的开发利用前景。     

Resistance in the highly DDT-resistant 91-R strain of Drosophila melanogaster involves decreased penetration,increased metabolism,and direct excretion

Resistance to 4,4′-dichlorodiphenyltrichloroethane (DDT) in the 91-R strain of Drosophila melanogaster is extremely high compared to the susceptible Canton-S strain (>1500 times). In addition to enhanced oxidative detoxification, the 91-R strain also has a reduced rate of DDT penetration, increased levels of reductive and conjugative metabolism, and substantially more excretion than the Canton-S strain. Contact penetration of DDT was ∼30% less with 91-R flies, which also had significantly more cuticular hydrocarbons and a thicker, more laminated cuticle compared to Canton-S flies, possibly resulting in penetration differences. DDT was metabolized ∼1.6-fold more extensively by 91-R than Canton-S flies, resulting in dichlorodiphenyldichloroethane (DDD), two unidentified metabolites and polar conjugates being formed in significantly greater amounts. 91-R flies also excreted ∼4-fold more DDT and metabolites than Canton-S flies. Verapamil pretreatment reduced the LD₅₀ value for 91-R flies topically dosed with DDT by a factor of 10-fold, indicating that the increased excretion may involve, in part, ATP-binding cassette (ABC) transporters. In summary, DDT resistance in 91-R is polyfactorial and includes reduced penetration, increased detoxification and direct excretion.     

水稻纹枯病菌拮抗细菌的筛选及鉴定

为获得对水稻纹枯病有生防效果的拮抗细菌,从江苏南京、徐州和常州等地采集的土样中分离细菌分离物1914株,采用平板对峙法筛选获得70株对水稻纹枯病菌有较强抑菌活性的分离物,其中11株对5种水稻病害病原菌均有抑制作用;对11株拮抗菌进行田间防效和室内促生试验,测定菌株分泌的抑菌物质和促生物质,并进行种属鉴定.结果表明,拮抗菌对水稻纹枯病的盆栽和田间小区防效在48.41％和43.03％以上;均可产生蛋白酶与嗜铁素,而不产生几丁质酶,除XF-174外其余10个菌株均可产生纤维素酶;对水稻苗株高和鲜重具有促生作用,并均可产生赤霉素(GA3);除ZF-273和XF-174外的9个菌株可产生吲哚乙酸(IAA),且细菌发酵液中IAA和GA3含量与水稻株高和鲜重的增长率呈正相关.结合各菌株形态特征、生理生化特性和16S rDNA与gyr-B序列分析结果,鉴定SF-181为枯草芽胞杆菌Bacillus subtilis,XF-174为荧光假单胞菌Pseudomonas fluorescens,其余9个菌株为解淀粉芽胞杆菌B.amyloliquefaciens.     

Pesticides-induced depression of photosynthesis was alleviated by 24-epibrassinolide pretreatment in Cucumis sativus L

The phytotoxicities of nine pesticides (paraquat, fluazifop-p-butyl, haloxyfop, flusilazole, cuproxat, cyazofamid, imidacloprid, chlorpyrifos, and abamectin) at practical dosages on photosynthesis were investigated in cucumber (Cucumis sativus L. cv. Jinyan No. 4) by gas exchange and chlorophyll fluorescent measurements. Plants treated with paraquat showed the severest phytotoxic symptom with the highest reduction in net photosynthetic rate (Pn), while other pesticides except flusilazole inhibited Pn to various degrees. The inhibition of Pn by cuproxat was accompanied by declines both in stomatal conductance (Gs) and intercellular CO₂ concentration (Ci), whereas decreased Pn for the cyazofamid was associated with increased Ci. For other 6 pesticides, however, inhibition of Pn was accompanied by decrease in Gs, while Ci was increased or unaffected. Paraquat almost completely inhibited the maximal quantum efficiency of PSII (F_v/F_m), while other pesticides had no significant effect on F_v/F_m. Quantum efficiency of PSII (Φ_PSII) was significantly reduced by paraquat, fluazifop-p-butyl, and chlorpyrifos and the reduction was mostly attributed to decrease in photochemical quenching coefficient (qP). In comparison, Φ_PSII was not significantly affected by haloxyfop, flusilazole, cyazofamid, imidacloprid, and abamectin. Non-photochemical quenching (NPQ) was suppressed by paraquat and haloxyfop, while apparent upregulation was evident after exposure to other pesticides. Interestedly, inhibitions of Pn were alleviated by 24-epibrassinolide (EBR) pretreatment, as for the pesticides examined in this study except paraquat and flusilazole. EBR pretreatment also increased Φ_PSII and qP. It is likely that EBR enhanced the resistance of cucumber seedlings to pesticides by increasing CO₂ assimilation capacity and activities of antioxidant enzymes.     

Food consumption, utilization, and detoxification enzyme activity of the rice leaffolder larvae after treatment with Dysoxylum triterpenes

The toxicity and physiological (enzyme and nutritional indices) effect of Dysoxylum triterpenes 3β,24,25-trihydroxycycloartane and beddomei lactone were evaluated on the rice leaffolder Cnaphalocrocis medinalis (Guenée). The LC₅₀ [6.66 ppm (SD = 0.31), 5.79 ppm (SD = 0.33) for 3β,24,25-DHCL and BL, respectively] and LC ₉₀ [14.63 ppm (SD = 0.36), 13.49 ppm (SD = 0.27) for 3β,24,25-DHCL and BL, respectively] were identified by probit analysis. Fourth instars were exposed to various concentrations (1.5, 3, 6, and 12 ppm) of Dysoxylum triterpenes. Results showed that treated larvae exhibited reduced food consumption and enzyme activity. Food consumption, digestion, relative consumption rate, efficiency of conversion of ingested food, efficiency of conversion of digested food, and relative growth rate values declined significantly but the approximate digestibility of treated larvae was significantly higher as a result of treatment (in particular 6 and 12 ppm). Likewise, the gut enzymes acid phosphatases, alkaline phosphatases, and adenosine triphosphatases were significantly inhibited by the Dysoxylum triterpenes. The high biological activity of these triterpenes from Dysoxylum sp. could be used as an active principle during the preparation of botanical insecticides for insect pest like rice leaffolder.     

Resistance development in rice blast disease caused by Magnaporthe grisea to tricyclazole

Sensitivity to tricyclazole of 129 single-conidial isolates of rice blast fungus, Magnaporthe grisea, was determined. EC₅₀ values ranged from 0.06 to 1.12 mg/L with an average value of 0.46 ± 0.09 mg/L according to the detached leaf segment tests. No significant difference of sensitivity was observed between isolates from Guangdong and Jiangsu where decreased efficacy was reported, and from two other provinces where tricyclazole provided excellent disease control. In seedling tests, tricyclazole could control the most tolerant isolate GY-6 successfully with a efficacy of 81.5% at the concentration of 40 mg/L. Sensitivities of GY-6 and DY-2, the most sensitive isolate, to tricyclazole were both unstable in sub-cultured single-conidial offspring isolates, with respective mean EC₅₀ values of 5.40 ± 0.97 and 4.50 ± 0.88 mg/L calculated from seedling tests. There was no amino acid difference between them in the coding sequences of 1,3,6,8-tetrahydroxynaphthalene reductase and 1,3,8-trihydroxynaphthalene reductase. These results suggested that the decreased control reported in Guangdong and Jiangsu could not be attributed to the occurrence of resistance. When continuously “inoculated-reisolated-reinoculated” under the selection of tricyclazole in vivo, sensitivity of DY-2 decreased 10-fold after 20 generations, although the sensitivity of GY-6 did not shift significantly.     

广西兴安地区褐飞虱发生动态及迁飞轨迹分析

为明确广西兴安地区单双季稻混作模式下褐飞虱发生规律,采用灯光诱捕和田间系统调查的方法研究了该地区早、中、晚稻田褐飞虱发生动态,并运用大气质点轨迹分析平台HYSPLIT 4.8对2011年褐飞虱迁飞高峰进行了迁飞轨迹分析。广西兴安地区褐飞虱种群数量随季节变化明显,年发生6代,迁飞活动主要集中在7月上旬至9月上旬。褐飞虱发生高峰期与单季中稻生长期吻合,在单季中稻田的发生量最大。2011年广西兴安褐飞虱5—6月迁入虫源主要来自海南稻区以及泰国、越南和老挝中部稻区;7—8月迁入虫源来自广西南部、东南部和广东西部稻区;回迁虫源来自湖南西南部和江西西部;10月从本地迁出的虫群主要迁向广西中部和贵州南部。研究表明,偏南方向的低空急流为褐飞虱的大规模迁入提供了运载气流,降雨是迫使稻飞虱降落的主要原因。     

Resistance to azoxystrobin in Alternaria isolates from pistachio in California

Failure to control Alternaria late blight in a few California pistachio orchards was observed after only 3-4 years of consecutive applications of azoxystrobin-based fungicide programs. A total of 72 isolates of Alternaria alternata, Alternaria tenuissima, and Alternaria arborescens, the causal organisms of Alternaria late blight, were collected from pistachio orchards with (58 isolates) and without (14 isolates) a prior history of azoxystrobin applications. The sensitivity to azoxystrobin was determined in conidial germination assays. Isolates from orchards with a history of azoxystrobin applications had EC₅₀ values greater than 100 μg/ml, whereas isolates from orchards without a prior history of azoxystrobin usage had EC₅₀ values ranging from 0.008 to 0.045 μg/ml. Azoxystrobin resistance correlated with a single mutation in the cytochrome b (cyt b) gene causing a change of glycine to alanine at amino acid position 143. A pair of PCR primers AF and AR was developed that amplified a 226-bp DNA fragment of the cyt b gene containing the mutation site from all three Alternaria species but not from 30 other fungal species frequently found on pistachio. PCR-restriction fragment length polymorphism (PCR-RFLP) analysis using the restriction enzyme Fnu4HI allowed differentiation of the PCR fragment of wild type cyt b gene from that of mutated gene. This method will aid in a fast detection of azoxystrobin resistance in these three Alternaria species.     

NbRbohB基因在本氏烟与疫霉菌互作中的功能分析

活性氧(active oxygen species, AOS)在植物抗病中发挥着重要作用,主要由NADPH氧化酶(nicotinamide adenine dinucleotide phosphate oxidase)系统产生.为明确NADPH氧化酶NbRbohB基因在本氏烟与疫霉菌亲和与非亲和性互作中的功能,采用荧光定量PCR技术以及病毒诱导的基因沉默方法探究了NbRbohB基因在本氏烟中对2种疫霉菌抗性中的作用,并利用NADPH氧化酶抑制剂对辣椒疫霉的抗性进行了检测.结果发现:2种疫霉菌均能诱导本氏烟发生氧迸发,且NbRbohB基因可能参与了疫霉菌诱导本氏烟发生的氧迸发过程.该基因沉默后降低了本氏烟对亲和互作辣椒疫霉菌的抗性,但对非亲和互作疫霉菌的抗性没有肉眼可见的影响;NADPH氧化酶抑制剂处理本氏烟后也能降低其对辣椒疫霉的抗性.表明该基因通过介导AOS产生,参与植物对亲和性与非亲和性互作疫霉的抗病反应,在亲和互作中尤为重要.