PhoR/PhoP双组分系统对枯草芽胞杆菌NCD-2菌落形态和芽胞形成的影响

 双组分PhoR/PhoP是枯草芽胞杆菌中普遍存在的以低磷为信号的调控系统。前期研究发现,PhoR/PhoP双组分系统正调控枯草芽胞杆菌NCD-2菌株脂肽类抗生素fengycin的合成,本研究分析了PhoR/PhoP双组分系统对NCD-2菌株菌落形态和芽胞形成的影响。在有机磷培养基上,NCD-2野生型菌株可以降解有机磷并且形成表面褶皱、立体结构较强的菌落形态,而phoR或phoP基因突变子丧失了降解有机磷的能力,菌落表面光滑、平坦。phoR和phoP基因突变子的互补菌株恢复到了与野生型相似的解磷能力和菌落形态。在低磷和高磷培养基中比较了NCD-2野生型及其衍生菌株的生长及芽胞形成情况,结果表明,在高磷培养基中,NCD-2野生型及其衍生菌株的生长速率没有差异,但在低磷培养基中,phoR和phoP基因突变子的菌体生长速率显著降低。芽胞形成能力测定结果表明,在低磷培养基中,NCD-2野生型菌株的芽胞形成率较高,而phoR和phoP基因突变子的芽胞形成率显著降低;在高磷培养基中,NCD-2野生型及其衍生菌株芽胞形成率普遍较低并且无显著差异。RT-PCR分析显示, phoR和phoP的突变均显著降低了芽胞形成相关基因spo II GA的表达,相比感应激酶PhoR,调控因子PhoP对spo II GA基因的影响更显著。     

球虫消毒剂的筛选及氨水对艾美耳球虫卵囊抑杀条件的优化

为了筛选有效的球虫消毒剂,本研究将柔嫩艾美耳球虫卵囊分别与16种常用消毒剂和1种高效抗球虫药物溶液（250 mg/L妥曲珠利溶液）混合作用2 h然后在2.5%重铬酸钾溶液中孢子化培养,或混合作用4 h后接种14日龄雏鸡,根据卵囊孢子化率、孢子化抑制率、每克粪便卵囊数量（oocysts per gram of feces,OPG）、病变计分和血便情况评价消毒剂和抗球虫药物抑杀球虫卵囊效果。结果显示,8%氨水对未孢子化卵囊和孢子化卵囊均表现为100%的抑杀效果;250 mg/L妥曲珠利、3%甲醛、4%苯酚、0.5%过氧乙酸、5% NaOH+10% NaCl和5% NaOH对球虫卵囊活性具有一定的抑制作用,孢子化抑制率超过10%,但是对孢子化卵囊抑杀作用不明显;而剩余10种常用消毒剂对球虫卵囊没有明显的抑杀作用。氨水抑杀球虫卵囊条件优化的试验结果显示,1%~8%氨水与未孢子化卵囊作用1 h以上,均可100%抑杀球虫卵囊活性。粪便干扰试验结果显示,粪便不影响2%和4%氨水对球虫卵囊的抑杀效果。本研究结果说明常用消毒剂和抗球虫药物不能有效杀灭球虫卵囊的活性,而氨水是一种高效球虫消毒剂。本研究结果可为开发新型高效球虫消毒剂和球虫病控制提供参考。     

特戊酸柠檬酯对植物病原真菌的抑菌活性

为了测定特戊酸柠檬酯的抑菌活性,采用生长速率和孢子萌发法测定了该物质对6种植物病原真菌的抑制作用,并分析了其对病原菌菌丝和孢子形态的影响。结果表明,该物质对所测6种病原真菌均具有一定的抑制作用,抑制菌丝生长的EC50在338.72～829.20 mg/L之间,其中对辣椒枯萎病菌的抑制作用最强,EC50为338.72 mg/L;抑制孢子萌发的EC50在59.63～131.69 mg/L之间,其中对番茄早疫病菌的抑制率最高,EC50为59.63 mg/L。比较了该物质与多菌灵、甲基托布津对番茄早疫病菌及梨黑斑病菌的抑制作用,结果表明,该化合物抑制2种病菌菌丝生长的EC50虽稍高于甲基托布津,但接近或低于多菌灵。同时经特戊酸柠檬酯处理后的病菌菌丝隔膜不明显,原生质浓缩,菌体扭曲变形、断裂;孢子不能正常萌发,部分畸形,出现疱疹样突起。     

温度对蜡蚧轮枝菌菌丝生长、产孢量及致病力的影响

室内测定表明,蜡蚧轮枝菌在10℃~33℃时均能生长,菌丝生长的适宜温度为15℃~28℃,最适温度为18℃~25℃。在10℃~30℃均可产生分生孢子,产孢适宜温度为15℃~30℃,25℃下产孢量最高,达1.25×108分生孢子/皿。在12℃和15℃较低温度下,产孢量分别为2.50×106和1.13×107分生孢子/皿。温度对蜡蚧轮枝菌对瓜蚜的致病力有显著的影响,25℃下致病力最强,其次为30℃,在低温下致病力较弱。     

剑麻斑马纹病菌生长和产孢方法的研究

对剑麻斑马纹病菌生长与产孢的最适培养基进行研究。结果表明:该病菌在燕麦培养基上生长速度最快,在蔗糖培养基上生长速度最慢,V8培养基最适生长;不同的培养基对产孢的作用有差异,所有培养基很少或没有产生孢子囊,而产生游动孢子的培养基,以PDA培养基最多;在培养基中加入不同的营养成分对产孢有较大影响,芝麻培养基+0.1%KNO3产生大量的孢子囊,其他很少或没有产生孢子囊,而PSA+0.1%KNO3产生游动孢子最多,10%剑麻汁培养基+0.1%KNO3产生的游动孢子最少。     

Aggressiveness of Phytophthora infestans on detached potato leaflets in four Nordic countries

Potato fields in Denmark, Finland, Norway and Sweden were sampled for single-lesion isolates of Phytophthora infestans . The aggressiveness of the isolates was determined on detached leaflets of potato cvs Bintje (susceptible) and Matilda (moderately resistant). The aggressiveness tests were carried out in the respective home countries of the isolates, with the exception of the Danish isolates. Fifteen Danish isolates were studied in each of the other three countries, including five isolates tested in all three laboratories. Results obtained from the Danish isolates revealed substantial differences between the test laboratories for infection efficiency, lesion growth rate and sporulation capacity on detached leaflets. When the laboratory effect was taken into account, the differences in aggressiveness between the countries were generally small or inconsistent between the test cultivars and epidemiologically insignificant. By contrast, variation among isolates within countries was substantial. The magnitude of the variation depended on country and cultivar. Maximal variation for the means of the isolates was between 89 and 185 h for latent period, between 100 and 1297 sporangia mm⁻² for sporulation capacity and between nearly zero and 6 mm day⁻¹ for lesion growth rate. Typically less than 1% of sporangia were able to cause infections, except in Norway. These extraordinarily low values may be an artefact of the testing method. High variation in results between the test laboratories emphasizes the need for caution when comparing results obtained by different research groups.     

避雨栽培对葡萄霜霉病发生的影响与葡萄冠层微气象因子的关系

系统比较了云南省石林县(‘红地球’)和弥勒县(‘水晶葡萄’)葡萄园采用避雨栽培和露天栽培对葡萄霜霉病Plasmoparaviticola(Berk.Curtis)Berl.de Toni.的防治效果,监测了田间葡萄园内避雨栽培和露天栽培处理中葡萄霜霉病的发生流行与植株冠层气象因子的变化情况,并结合适宜葡萄霜霉病病害循环的温度、相对湿度、叶面持露时间及田间葡萄植株冠层微气象因子的变化对避雨栽培有效防治葡萄霜霉病的气象原理进行了分析。结果表明,避雨处理可有效控制葡萄霜霉病的发生和危害,石林县和弥勒县两地葡萄园的防治效果分别达到97.84%和66.29%。弥勒县‘水晶葡萄’对霜霉病的抗性较强,霜霉病发生较轻,但在避雨栽培条件下霜霉病的病情指数也显著低于对照。植株冠层微气象因子变化分析表明,避雨栽培可以减少决定霜霉病菌能否成功侵染的叶面水膜持续时间,创造不适宜霜霉病菌萌发和侵入的条件,还可以显著减低棚内植株冠层适宜孢子囊产生的相对湿度的持续时间,减少霜霉病菌的侵染菌量,从而有效地控制了霜霉病的发生和危害。     

Life-table analysis of faba bean rust

In controlled near-optimum conditions (18 °C), monocyclic sporulation capacity and spore infection efficiency were assessed for faba bean rust on the first and second leaves of field bean. After a latency period of 8–10 days, lesions sporulated duringc. 50 days. Spore production on the second leaf,c. 9×10⁴ spores per lesion, was two times as high as spore production on the first leaf. Infection efficiency was similar for both leaf layers, with a mean value of 0.11 lesion per inoculated spore. Infection efficiency decreased strongly when spores originated from mother lesions older than 20 days. Three life-table statistics (the net reproduction numberR _o , the mean generation timeT _g , and the maximum relative growth rater _max ) were calculated.R _o was larger andT _g was longer for the second than for the first leaf, butr _max was nearly the same for both leaf layers (0.31–0.33 day^–1).r _max was compared with the exponential growth rater measured in a field experiment. From the difference between the two rates, the fraction of inoculum lost in field conditions was estimated at 0.54–0.94. The life-table statistics were also compared to those of other legume rusts, and implications of life-table analysis for comparative epidemiology were discussed.     

Components of resistance to Mycosphaerella graminicola and Phaeosphaeria nodorum in spring wheats

Summary Infection frequency (IF), latent period (LP) and sporulation rate (S) were assessed on 23 genotypes (cultivars, breeding lines and parents) in the field and 36 genotypes in the glasshouse (with 22 being in common) following inoculation with conidia of either Mycosphaerella graminicola or Phaeosphaeria nodorum. Significant variation was observed among genotypes for each resistance component. Genotypes resistant to Mycosphaerella graminicola had long LP and low S but variable IF. Genotypes resistant to Phaeosphaeria nodorum had low IF, long LP and low to moderate S. IF and S were independent while a negative correlation was observed between LP and S for Mycosphaerella graminicola only. LP was most consistently correlated with field response. Components measured in the field better discriminated resistant genotypes from others. Combinations of genotypes were sought for which one genotype may contribute to a reduced disease severity for S. nodorum and the other genotype may contribute to a reduced disease severity for S. tritici in mixtures. Such combinations of genotypes were rare.     

白僵菌在土壤中宿存的数量、毒力及产孢量变化研究

研究白僵菌在土壤中宿存情况,结果表明,球孢白僵菌在土壤中宿存两个月内,成菌落数呈波动状态,下降较慢,1g、5g、10g区分别下降50%,60%和64%。自第3个月起,成菌落数每月下降85%至95%,最终土壤中的成菌落数维持在10^3-10^4CFU/土样水平。不同处理浓度表明,处理浓度过大不利于白僵菌的长期缩存;而白僵菌在缩存过程中,其毒力和产孢能力的稳定性有利于害虫的持续控制。