Resistance mechanism to carboxylic acid amide fungicides in the cucurbit downy mildew pathogen Pseudoperonospora cubensis

BACKGROUND: Pseudoperonospora cubensis, the causal oomycete agent of cucurbit downy mildew, is responsible for enormous crop losses in many species of Cucurbitaceae, particularly in cucumber and melon. Disease control is mainly achieved by combinations of host resistance and fungicide applications. However, since 2004, resistance to downy mildew in cucumber has been overcome by the pathogen, thus driving farmers to rely only on fungicide spray applications, including carboxylic acid amide (CAA) fungicides. Recently, CAA‐resistant isolates of P. cubensis were recovered, but the underlying mechanism of resistance was not revealed. The purpose of the present study was to identify the molecular mechanism controlling resistance to CAAs in P. cubensis. RESULTS: The four CesA (cellulose synthase) genes responsible for cellulose biosynthesis in P. cubensis were characterised. Resistant strains showed a mutation in the CesA3 gene, at position 1105, leading to an amino acid exchange from glycine to valine or tryptophan. Cross‐resistance tests with different CAAs indicated that these mutations lead to resistance against all tested CAAs. CONCLUSION: Point mutations in the CesA3 gene of P. cubensis lead to CAA resistance. Accurate monitoring of these mutations among P. cubensis populations may improve/facilitate adequate recommendation/deployment of fungicides in the field. Copyright © 2011 Society of Chemical Industry     

Pharmacological analyses of two naturally occurring porcine melanocortin-4 receptor mutations in domestic pigs

The melanocortin-4 receptor (MC4R) is critical in regulating mammalian food intake and energy expenditure. Numerous mutations in the MC4R gene have been identified from obese humans. So far two naturally occurring porcine MC4R (pMC4R) mutations, D298N and R236H, have been identified from various strains of pigs and D298N is being utilized as a genetic marker to screen performance traits of pigs. In this study, we performed functional analyses of pMC4R D298N and R236H, including their ligand binding and signaling properties in transiently transfected HEK293T cells. Ligand binding assays showed that both D298N and R236H pMC4Rs had similar binding capacities and affinities for the natural agonist -MSH and the natural antagonist Agouti-related protein as wild-type pMC4R. In signaling assays, both mutants had normal EC₅₀ and maximal signaling to -MSH. In summary, pMC4R mutants D298N and R236H do not have any overt functional defects; therefore we suggest caution using these mutations as selection markers in breeding programs.     

甘蓝型油菜种子胎萌发生的影响因子研究

以黄籽油菜‘410’‘456’‘552’和黑籽油菜‘492’为试验材料,采用花期标记、定期采样、形态和生理分析等方法,研究了种子胎萌发生时期、环境对胎萌的影响以及胎萌与种子的形态和相关生理指标的关系。结果表明：4个甘蓝型油菜品种种子胎萌发生在种胚充实阶段(花后27～36 d左右),初始胎萌率为2.44%～3.90%,胎萌发生时期越早的品种的胎萌率越高;种子千粒质量与胎萌率呈显著或极显著正相关(r为0.84～0.97),含水量与胎萌率呈极显著负相关(r为–0.93～–0.98);种胚充实初期高温高湿的外部环境、较薄的种皮及相对较高的脂肪酶活性、可溶性糖含量、呼吸强度均易导致种子胎萌的发生,而种子电导率、总糖含量与胎萌率的相关性不显著。     

黑光灯对蔬菜地中黑盲蝽和绿盲蝽种群动态的监测

盲蝽是棉花的主要害虫,对蔬菜也有较大的危害。本研究利用黑光灯对蔬菜地刺吸式害虫进行调查,共发现刺吸式害虫6个科17种,其中以中黑盲蝽(Apolygus suturalis Jakovlev)和绿盲蝽(Apolygus lucorum Meyer-Dür)为主要害虫。同时研究了蔬菜地中黑盲蝽和绿盲蝽的数量和种群动态变化。结果表明,中黑盲蝽和绿盲蝽在孝感市云梦县1年发生4~5代,中黑盲蝽发生高峰期为6~8月,绿盲蝽发生高峰期为9月。     

墨玉县果树介壳虫发生规律研究及防治对策

介壳虫是近年来在和田地区严重危害果树的主要害虫之一.常见的种类主要有糖槭蚧、枣大球蚧、圆梨蚧.糖槭蚧、枣大球蚧在墨玉县一年发生1代,以2～3龄若虫在枝条上或隐蔽的树皮裂缝处越冬.梨圆蚧一年发生2～3代,以1～2龄若虫在枝干上越冬.介壳虫的危害盛期,第一次为越冬若虫自树液流动至成虫产卵期(或产仔),此时为化学防治关键适期,最佳适期为3月下旬～4月初.第二次危害盛期为小若虫孵化(或产仔)到若虫进入越冬,此时最佳化防适期为6月5～25日.该虫防治应采用综合防治措施,尽量减少药剂防治次数.     

福建省三明市主要森林病虫害的发生格局

利用1993-2007年的资料,分析了三明市主要森林病虫害发生的种类变化和时间与树种分布格局。结果表明,三明市主要森林病虫害包括21种虫(螨)害和11种病害,种类呈逐年增多趋势,其中板栗疫病、桉树焦枯病、毛竹枯梢病和萧氏松茎象等属危险性病虫害。1993-2003年森林病虫害发生面积呈波浪式缓慢上升,2004年后则急剧增大,呈现持续大面积发生格局;其成因主要有:(1)马尾松毛虫和刚竹毒蛾暴发周期缩短,发生强度增大;(2)竹蝗再度猖獗;(3)一些次要害虫如松墨天牛和竹舟蛾等上升为主要害虫;(4)萧氏松茎象和桉树焦枯病等新的危险性病虫害不断发生。松树和毛竹是主要受害对象,具有病虫害种类多和发生面积大的特点。笔者利用灰色理论,建立了有效的马尾松毛虫、刚竹毒蛾、竹蝗、毛竹害螨和松针褐斑病的灾变期预测模型。     

Resistance of Corynespora cassiicola from soybean to QoI and MBC fungicides in Brazil

Fungicide sprays on soybean in Brazil have contributed to the selection of less sensitive isolates of Corynespora cassiicola. We collected 59 isolates of C. cassiicola from three Brazilian states and two isolates from Paraguay. We investigated their EC₅₀ to quinone outside inhibitors (QoI) and methyl benzimidazole carbamate (MBC), any cross-resistance to compounds within QoI and MBC groups, and characterized the polymorphisms in their cytb and β-tubulin genes. Local associations of polymorphisms identified in each gene were statistically correlated with assays results. In total, 79% and 74% of the isolates were classified as resistant to QoI and MBC fungicides, respectively. There was positive cross-resistance to active ingredients within QoI and MBC groups. For QoI, all isolates presented heteroplasmy in G143A of cytb gene; the mutations F129L and G137R were not found. For MBC, 63% of isolates possessed E198A and 21% possessed F200Y mutations, associated with reduced control by MBC fungicides. Heteroplasmy was identified in two and one isolates from Brazil with E198A and F200Y mutations, respectively. The resistance factor for isolates with E198A (10.9) was statistically similar to the isolate with F200Y (8.8) mutation. Genic association analysis of the in vitro assays using discriminatory doses proved them to be accurate. Reduced sensitivity of C. cassiicola to QoI and MBC was also identified in isolates from Paraguay and resistance to QoI and MBC was widely present in C. cassiicola isolates from the main soybean-producing states in Brazil. Thus, integrated management measures should be adopted to manage soybean target spot in these countries.     

Genetic basis and origin of resistance to acetolactate synthase inhibitors in Amaranthus palmeri from Spain and Italy

BACKGROUND

Amaranthus palmeri is an aggressive annual weed native to the United States, which has become invasive in some European countries. Populations resistant to acetolactate synthase (ALS) inhibitors have been recorded in Spain and Italy, but the evolutionary origin of the resistance traits remains unknown. Bioassays were conducted to identify cross-resistance to ALS inhibitors and a haplotype-based genetic approach was used to elucidate the origin and distribution of resistance in both countries.

RESULTS

Amaranthus palmeri populations were resistant to thifensulfuron-methyl and imazamox, and the 574-Leu mutant ALS allele was found to be the main cause of resistance among them. In two Spanish populations, 376-Glu and 197-Thr mutant ALS alleles were also found. The haplotype analyses revealed the presence of two and four distinct 574-Leu mutant haplotypes in the Italian and Spanish populations, respectively. None was common to both countries, but some mutant haplotypes were shared between geographically close populations or between populations more than 100 km apart. Wide genetic diversity was found in two very close Spanish populations.

CONCLUSION

ALS-resistant A. palmeri populations were introduced to Italy and Spain from outside Europe. Populations from both countries have different evolutionary histories and originate from independent introduction events. ALS resistance then spread over short and long distances by seed dispersal. The higher number and genetic diversity among mutant haplotypes from the Spanish populations indicated recurrent invasions. The implementation of control tactics to limit seed dispersal and the establishment of A. palmeri is recommended in both countries. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.     

江西樟树害虫的发生、危害特点与IPM策略

樟树是江西省省树,在全省范围推广种植多年,樟树虫害发生呈逐年上升趋势。据前期调查数据及文献资料,汇总统计江西樟树害虫179种,其中,重要害虫26种,占14.5%,次重要害虫23种,占12.8%,非重要害虫130种,占72.6%,包括重要食叶害虫樟叶蜂、泡桐叶甲、黄刺蛾、丽绿刺蛾、褐边绿刺蛾、樗蚕、龙眼裳卷蛾、樟巢丛螟等;重要刺吸性害虫六点始叶螨、樟脊网蝽、黑刺粉虱、樟木虱、樟白轮盾蚧、思茅壶蚧等;重要钻蛀性害虫家白蚁、黄翅大白蚁、黑翅土白蚁、吉安樟筒天牛等;重要地下害虫粉白金龟、黑绒金龟等。据危害方式、发生特点将其归为强生态适应性害虫、r类害虫、隐蔽性害虫与嗜食性害虫,由此有针对性地提出其IPM策略。