龟纹瓢虫对烟粉虱和棉蚜取食选择及适合度比较研究

基于近年来棉田烟粉虱数量上升并与棉蚜呈混合或交替发生的态势,比较研究了棉田优势捕食性天敌龟纹瓢虫对棉蚜和烟粉虱的取食偏好和食物适合度.结果显示,龟纹瓢虫不同虫态对烟粉虱若虫和棉蚜均具有较好的捕食作用;在棉蚜和烟粉虱若虫不同比例共存的情况下,龟纹瓢虫成虫均显著地偏好取食棉蚜;空间增大和蚜虫数量不足有助于增加龟纹瓢虫成虫对烟粉虱若虫的控制效应.取食烟粉虱若虫和棉蚜若虫的龟纹瓢虫幼虫均能完成生长发育,对后代成虫性比亦无影响;但取食烟粉虱若虫的龟纹瓢虫幼虫期延长3d,死亡率升高5.45倍,幼虫和成虫体重明显减轻;成虫取食烟粉虱若虫不能满足其产卵的营养需求.综合分析认为,棉田具有一定数量(经济域值以下)的棉蚜,有利于增加龟纹瓢虫对烟粉虱的控制效应.     

小麦条锈菌生理小种动态预测

为定量预测小麦条锈病菌小种变化,通过田间小种圃人工接种试验、品种抗病性鉴定历史数据分析和专家评估等三种方法,获得了在中国多年栽种的192个小麦品种与24个小麦条锈病菌生理小种或菌系的接近实际的相对寄生适合度数据。以其为主要参数,结合历年不同小麦品种种植面积构建了多品种-多小种互作模型Cultivar-Race Dynamics Mode(CRDM)。该模型用VB6.0语言可视化编程,输入某年小麦条锈病菌各小种频率就能输出未来若干年各小种的频率。初步检验结果表明,此模型结构虽简单,但可以大体预测小种变化趋势。同时就模型的改进和条锈菌小种预测问题也进行了讨论。     

Resistance in Rhizoctonia solani to tolclofos-methyl

Isolates ofRhizoctonia solani were adapted in vitro to grow on a medium amended with tolclofos-methyl at a concentration 500 times that which initially almost completely inhibited growth.Acquired resistance was retained after five transfers on a fungicide-free medium. Pathogenicity of resistant isolates was not reduced, but their growth rates on PDA were significantly lower than those of the original isolates. Recovery of the resistant isolates was not improved on a selective medium amended with tolclofos-methyl.Samenvatting Na overenting op een medium dat tolchlofos-methyl bevatte, raakten enkele isolaten vanRhizoctonia solani gewend aan 500 maal de dosis die oorspronkelijk bijna alle groei verhinderde.Resistente isolaten vanR. solani bleven minder gevoelig voor tolchlofos-methyl na vijf overentingen op een medium zonder het fungicide. De pathogeniteit van resistente isolaten was niet verminderd, maar hun groeisnelheid op PDA was significant vertraagd vergeleken bij die van de oorspronkelijke isolaten. Isolatie van de resistente stammen werd niet verbeterd op een selectief medium waaraan tolchlofos-methyl was toegevoegd.     

宁夏南部山区马铃薯晚疫病菌寄生适合度测定

为了解宁夏南部山区马铃薯主栽品种对马铃薯晚疫病菌的抗病性情况,明确不同菌株的寄生适合度,采用离体叶片接种法,用4个马铃薯品种对采自宁夏南部山区的5个马铃薯晚疫病菌分离株进行了侵染率、病斑面积、产孢能力的测定和寄生适合度的计算。结果表明,‘克新18号’对供试的晚疫病菌分离株具有较高的抗病性,其次为‘中薯3号’和‘克新1号’,‘费乌瑞它’的抗病性最差;来源于固原原州区的分离株(GL2和GL7)寄生适合度较高,来源于泾源县的分离株(JZ)寄生适合度较弱。采自宁夏不同地区的晚疫病菌分离株对同一马铃薯品种的寄生适合度有较大差异,同一晚疫病菌株在不同马铃薯品种上的寄生适合度也有一定的差异,表明宁夏南部山区马铃薯晚疫病菌分离株存在一定的致病性分化。     

小麦白粉病菌对温度不同敏感性菌株的寄生适合度研究

 利用离体叶片接种法,将12个对温度不同敏感性的小麦白粉病菌株分别在18℃和22℃条件下的流行组分（潜育期、侵染几率、单病斑累积产孢量和病斑日扩展面积）和寄生适合度进行了测定。结果表明,对温度不同敏感性菌株的流行组分在18℃和22℃条件下均存在显著性差异,且单病斑累积产孢量与病斑日扩展面积的相关性最高。各供试菌株在22℃条件下的寄生适合度均低于18℃条件下的寄生适合度。在两温度条件下,对温度低敏感性菌株平均寄生适合度高于对温度高敏感性菌株,特别是在较高温度下这种趋势更为明显。     

Strong resistance to the fungicide fenhexamid entails a fitness cost in Botrytis cinerea, as shown by comparisons of isogenic strains

BACKGROUND: Fenhexamid, a sterol biosynthesis inhibitor effective against Botrytis, inhibits the 3‐ketoreductase (Erg27) involved in C‐4 demethylation. Several fenhexamid‐resistant phenotypes have been detected in Botrytis cinerea populations from French vineyards. The field isolates with the highest resistance levels display amino acid changes in Erg27 (F412S, F412I or F412V). RESULTS: Fenhexamid‐resistant mutants were generated by site‐directed mutagenesis of the erg27 gene in a sensitive recipient strain to overcome the impact of different genetic backgrounds. The wild‐type erg27 allele was replaced by the three mutated alleles (erg27^F412S/I/V) by homologous recombination. These isogenic strains were shown to be fenhexamid‐resistant and were used to quantify the impact of F412 mutations on fungal fitness. Several parameters, including radial growth, the production of sclerotia and conidia, freezing resistance and aggressiveness, were quantified in laboratory conditions. Analysis of variance demonstrated significant differences between the mutant and parental strains for some characters. In particular, the mutants grew more slowly than the wild‐type strain and displayed variations in the production of sclerotia and conidia with temperature and susceptibility to freezing. CONCLUSIONS: The results highlight a moderate but significant impact of F412 mutations on the survival capacity of B. cinerea strains displaying high levels of resistance to fenhexamid in laboratory conditions, potentially limiting their dispersal and persistence, particularly in terms of overwintering, in field conditions. Copyright © 2011 Society of Chemical Industry     

棉铃虫对Cry1Ac抗性的稳定性及其对适合度的影响

为明确棉铃虫Helicoverpa armigera（Hübner）对苏云金芽胞杆菌Bacillus thuringiensis（Bt）Cry1Ac毒蛋白抗性的稳定性及其适合度变化,利用生物测定的方法研究了Cry1Ac抗性品系棉铃虫转到正常饲料饲养后的抗性衰退及再次筛选后抗性的恢复情况,并比较了敏感、抗性和抗性衰退后各品系间的适合度差异。在失去选择压的情况下,高抗品系棉铃虫对Cry1Ac的抗性迅速衰退,经过4代后抗性水平由最初的3626.67倍下降到1436.67倍;到第12代时抗性水平已低于10倍,随后品系保持较稳定的低抗水平;当重新进行抗性再筛选时,其抗性水平可快速恢复,抗性倍数快速回升,5代后恢复到1123.33倍。与敏感品系相比,高抗棉铃虫品系的适合度明显降低,相对适合度仅为0.33,但转到正常饲料连续饲养14代后,棉铃虫适合度明显上升,相对适合度为0.87,主要表现为卵孵化率和幼虫存活率等显著提高。