微生物肥料新型功能作用机理与根际定殖增强策略

微生物肥料是支撑农业绿色发展的重要投入品,根际益生菌是微生物肥料菌种的主要来源。我国农业发展对促进作物根系发育、增强作物耐盐胁迫能力等新型功能的微生物肥料提出了需求,然而目前对根际益生菌促进作物根系发育和增强耐盐胁迫的分子机理研究仍然薄弱,成为制约优异菌种选育的瓶颈。另一方面,微生物肥料的根际定殖能力低也是导致其田间应用效果差的重要因素。本文综述了根际益生菌调控根系发育、增强植物耐盐的活性物质和作用机理,分析其根际定殖的过程和菌植互作机制,提出了增强根际定殖的策略,以期为微生物肥料研究提供参考。     

Recombination Facilitates Adaptive Evolution in Rhizobial Soil Bacteria

Homologous recombination is expected to increase natural selection efficacy by decoupling the fate of beneficial and deleterious mutations and by readily creating new combinations of beneficial alleles. Here, we investigate how the proportion of amino acid substitutions fixed by adaptive evolution (α) depends on the recombination rate in bacteria. We analyze 3,086 core protein-coding sequences from 196 genomes belonging to five closely related species of the genus Rhizobium. These genes are found in all species and do not display any signs of introgression between species. We estimate α using the site frequency spectrum (SFS) and divergence data for all pairs of species. We evaluate the impact of recombination within each species by dividing genes into three equally sized recombination classes based on their average level of intragenic linkage disequilibrium. We find that α varies from 0.07 to 0.39 across species and is positively correlated with the level of recombination. This is both due to a higher estimated rate of adaptive evolution and a lower estimated rate of nonadaptive evolution, suggesting that recombination both increases the fixation probability of advantageous variants and decreases the probability of fixation of deleterious variants. Our results demonstrate that homologous recombination facilitates adaptive evolution measured by α in the core genome of prokaryote species in agreement with studies in eukaryotes.     

Impact of Genetically Modified Potato Expressing Plant-Derived Insect Resistance Genes on the Predatory Bug Podisus maculiventris (Heteroptera: Pentatomidae)

The effects of the transgene proteins Galanthus nivalis agglutinin (GNA) and cowpea trypsin inhibitor (CpTI) on the predatory stinkbug Podisus maculiventris were studied under laboratory conditions. When the P. maculiventris were provided with tomato moth (L. oleracea) larvae injected with either GNA or CpTI at a dose of 10 μg day^-1, growth was significantly reduced and, as a consequence, female adult weight was also significantly reduced. For GNA-fed and CpTI-fed P. maculiventris, this weight reduction was 11.3 and 16.6%, respectively. Males, however, were not significantly affected. Female bugs that had not been exposed to the transgene proteins as nymphs, however, showed no reduction in fecundity when these adults were provided with prey injected with either GNA or CpTI at this same dose. When provided with hosts that had been reared on transgenic plants expressing either GNA or CpTI, no effects on the survival of nymphs were observed and only small, largely non-significant, reductions in weights were recorded throughout preadult development. Male nymphs fed on the GNA-fed prey did, however, exhibit a significant lengthening of preadult development of 0.8 days. The subsequent adults showed significantly reduced egg production for the GNA treatment. The results indicate that P. maculiventris may suffer some indirect adverse effects from foraging for prey in crops expressing either GNA or CpTI, due to prey being of inferior quality, rather than to direct toxicity of the transgene products themselves.     

平板式光生物反应器中紫球藻培养条件的优化

研究了平板式光生物反应器中紫球藻(Porphyridium cruentumNaegeli)的培养条件,运用均匀设计法对光照强度、通气速率、装液量、接种密度以及pH等影响紫球藻生长的因素进行优化,获得了在平板式光生物反应器中培养紫球藻的最佳条件:光照强度10 000 lx、通气速率350 L.h-1、装液量6 L、藻细胞接种密度1.1×106mL-1、pH9.0。在最佳条件下藻体的生物量产率和生物量产量分别达到0.431 g.L-1.d-1和3.240 g.L-1,最大生长速率达0.652 g.L-1.d-1,胞外多糖含量高达0.665 g.L-1。另外,在培养过程中隔天补充培养液有利于紫球藻生物量的增加和胞外多糖的产生。     

有益微生物缓解花生连作障碍机理研究进展

花生是我国重要的油料作物,种植过程中会遇到连作障碍问题.有益微生物可以有效缓解花生连作障碍,其机理包括有益微生物分解化感物质、改变花生根际微生物区系、增加花生抗病能力、促进花生结瘤固氮、促进花生养分吸收五个方面.阐明该机理,对花生连作障碍缓解有指导意义,对其他作物连作障碍的缓解也有参考价值.     

中微量元素和有益元素对水稻生长和吸收镉的影响

采用盆栽试验,研究了中微量元素和有益元素对水稻生长和吸收镉的影响。结果表明,在所有测试的元素和施用方法中,硅酸钠叶面喷施显著增加稻谷产量,而碳酸钙、硼酸、硅酸钠土施和亚硒酸钠显著降低了稻谷产量。镁、锌、铁的盐酸盐形态对水稻籽粒的增产效果优于硫酸盐形态,而钙、铜的硫酸盐形态增产效果略高于盐酸盐形态。在钙、镁、硫三种中量元素中,钙增加了水稻籽粒中的Cd浓度和吸收量,而镁和硫则降低了籽粒中的Cd浓度和吸收量,以硫磺粉处理为最低。稻草中的Cd浓度和总量均以氯化镁处理为最高,硫磺粉处理最低。镁能有效抑制Cd从秸秆向籽粒的转移,其盐酸盐优于硫酸盐。在微量元素中,锌对水稻Cd的吸收抑制作用最为显著,其次是铜,而有益元素肥料硅酸钠叶面喷施则显著增加了稻谷中的Cd浓度和吸收量。硫酸亚铁、氯化锰、氯化铜、硼酸和硼砂处理都能有效地抑制Cd从秸秆向籽粒的转移,而硅酸钠叶面喷施和锌处理则促进了Cd的转移,表明硅酸钠抑制水稻吸收Cd的机制很可能发生在土壤中,而非在植株体内或地上部分。在Cd污染土壤上选用适宜的中微量和有益元素肥料及其施用方法,能有效降低水稻对镉的吸收和稻米中的Cd含量。     

农田景观格局对害虫天敌生态控害功能的调控作用

如何提升农田景观的生态服务功能是当前景观生态学和害虫防治学的前沿研究热点.基于区域农田景观格局可显著调节植物-植食性昆虫-天敌之间相互关系的理论基础,本文系统概括总结了农田景观格局及其变化对农田重要天敌多样性与生态控害功能的影响.从不同天敌类群的角度,分析了农田景观格局对捕食性天敌、寄生性天敌、有益微生物及其生态控害功能的调控作用.同时,对优化农田景观作物布局、采取合理的植被生境管理策略进行了展望.本文可为应用植被生境管理提升农田景观中天敌的生态系统服务功能提供参考,进一步促进区域生态农业响应"化学农药减量施用"的战略目标提供理论支撑.     

温度对中华倒刺鲃不同生理生态性能的影响:驯化有益假说的验证

驯化有益假说(Beneficial acclimation hypothesis)认为生物表型的适应性变化会增强其在诱导这些变化产生的环境中的生理机能或适合度。然而,由于动物不同生理生态性能对环境驯化的响应可能不一致,那么,测试表型性状的选择对驯化有益假说的验证就尤为关键。为此,整合表征动物生存适合度的不同生理生态性能并探究其对环境驯化的响应模式就十分必要。以我国长江中上游广泛分布的中华倒刺鲃(Spinibarbus sinensis)为对象,考察了驯化温度(18℃、28℃)和测试温度(18℃、28℃)及其交互作用对该物种有氧运动能力和无氧运动能力的影响,为驯化有益假说等相关假说的验证提供参考。研究发现,中华倒刺鲃不同生理生态性能对温度驯化的响应存在差异:(1)驯化温度对表征中华倒刺鲃无氧运动能力的快速启动游泳无显著影响(除最大加速度外)(P>0.05),研究数据倾向于支持无益假说(No-advantage hypothesis);(2)驯化温度对表征中华倒刺鲃有氧运动能力的临界游泳速度(Critical swimming speed,Ucrit)和最大代谢率(Maximum metabolic rate, MMR)影响显著(P<0.05),18℃驯化-18℃测试下的Ucrit和MMR均优于28℃驯化-18℃测试下的Ucrit和MMR,结果部分支持驯化有益假说和冷有益假说(Cooler is better hypothesis);(3)驯化温度、测试温度、游泳速度对中华倒刺鲃的运动代谢率(Active metabolic rate,MO2)和单位距离能量消耗(The energetic cost of transport, COT)影响显著(P<0.05)。值得关注的是,当游泳速度小于30 cm/s时,驯化温度对MO2和COT无影响,结果支持无益假说;而当游泳速度大于30 cm/s时,在特定的流速下经过28℃驯化的中华倒刺鲃无论在28℃还是18℃的测试环境下MO2和COT均较低,结果倾向于支持热有益假说(Warmer is better hypothesis)。研究结果提示:驯化有益假说并不具有普遍性,热驯化相关假说的验证不仅受表型性状选择的影响,而且还与测试的环境选择压力有关。     

Dispersal ofAleochara bilineata [Col.: Staphylinidae] following inundative releases in urban gardens

Aleochara bilineata (Gyllenhal) [Coleoptera: Staphylinidae] is a common predator and endoparasite of root maggot [Diptera: Anthomyiidae] in both commercial crops and home gardens. To test dispersal activity ofA. bilineata in home gardens, marked beetles were released at rates of 0 and 1,000 in 1987 and 0, 250, 500, and 1,000/gardens/wk in 1988. Three percent of marked beetles were recaptured in release gardens. NaturalA. bilineata populations were very small in all gardens, and there was no detectable increase from 1987 to 1988. Recaptures were proportional to release rates. There was no significant difference in recapture rates between sexes. Recaptures and non-uniform distributions of markedA. bilineata in control gardens revealed that they were capable of flying at least 5 km under urban conditions, and of selecting particular gardens as suitable mating, foraging, and oviposition sites.      

Effect of exposure time on mass‐rearing production of the olive fruit fly parasitoid,Psyttalia lounsburyi (Hymenoptera: Braconidae)

Classical biological control programmes rely on mass production of high‐quality beneficial insects for subsequent releases into the field. Psyttalia lounsburyi (Silvestri) (Hymenoptera: Braconidae) is a koinobiont larval–pupal endoparasitoid of tephritid flies that is being reared to support a classical biological control programme for olive fruit fly in California. The mass‐rearing system for a P. lounsburyi colony, initiated with insects originally collected in Kenya, was evaluated with the goal of increasing production, while at the same time reducing time requirements for rearing in a quarantine facility. We tested the effect of exposure time of a factitious host Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), on parasitization, adult production, superparasitism, and sex ratio of P. lounsburyi and survival of the host. Parasitization rates were highest (31%) at 3‐ and 4‐hr exposure times, while adult production (i.e., emergence of wasp progeny) was highest (16%) at the 2‐hr exposure time. Superparasitism over the course of the study was 1.5% and did not appear to be a factor affecting parasitoid production. The sex ratio of wasp progeny was male‐biased and did not vary significantly over different exposure times. The rate of stings on host larvae increased with exposure time and was consistent with decreases in pupal eclosion from larvae and emergence rate of adult flies. When compared to current rearing procedures, the 2‐hr exposure time resulted in an overall 2.8‐fold increase in P. lounsburyi production when standardized for time.