Cytogenetic study of F1 hybrids betweenCrepis dinarica andCrepis froelichiana (Asteraceae)

Crepis dinarica andC. froelichiana are two closely related species of theC. praemorsa complex. Even though they exhibit the same chromosome number (2n = 8) and similar idiogram shape, they differ widely in quantity and distribution of heterochromatin bands. The hybrids between these two species comprise three morphological types. Parental genomes were distinguished in hybrids by Giemsa differential staining (C-banding). Although meiosis presents only a few abnormalities (about 2.4%), the percentage of aborted pollen grains is very high (90%).     

The reaction to c-banding of c-banded constituents during mitotic cycle ofCrepis capillaris

The reaction to C-banding was investigated throughout the mitotic cycle ofCrepis capillaris (2n=6): (1) 18–22 C-bodies or C-bands were found during mid telophase and interphase to prophase and metaphase, and also 12–14 at late anaphase to early telophase in the mitotic cycle. Fewer C-bands in late anaphase to early telophase were due to the absence of minute bands; (2) large and medium sized C-bands were strongly stained by Giemsa, while small and minute bands stained palely. It is suggested that inCrepis capillaris the difference of color in C-banded segments following Giemsa staining is referable to the amount of constitutive heterochromatin rather than to the difference in the condensation and decondensation; (3) the size of C-bodies changed during telophase to interphase and prophase. It is inferred that the extent of C-bodies is regulated by both the length of DNA sequences of constitutive heterochromatin and the amount of proteins combined with C-banded DNA. It was shown that the reaction to C-banding is neither due to the differential condensation of chromatin nor to a higher concentration of DNA in the C-banded regions, in the C-banding mechanism as has been suggested so far at least.     

The relation between cell size,chromosome length and the orientation of chromosomes in dividing root cortex cells

Cells in the root meristem are organised in longitudinal files. Repeated transverse cell divisions in these files are the prime cause of root growth. Because of the orientation of the cell divisions, we expected to find mitoses with an spindle axis parallel to the file axis. However, we observed in the root cortex ofVicia faba large number of oblique chromosome orientations. From metaphase to telophase there was a dramatic increase of the rotation of the spindle axis. Measurements of both the size of the cortex cells and the chromosome configurations indicated that most cells were too small for an orientation of the spindle parallel to the file axis. Space limitation force the spindle into an oblique position. Despite this spindle axis rotation, most daughter cells remained within the original cell file. Only in extremely flat cells did the position of the daughter nuclei forced the cell to set a plane of division parallel to the file axis, which result in side-by-side orientation of the daughter cells. Telophase spindle axis rotations are also observed inCrepis capillaris andPetunia hybrida.. These species have respectively medium and small sized chromosomes compared toVicia. Since space limitation, which causes the rotation, depends both on cell and chromosome size, the frequency and extent of the phenomenon in former two species is comparatively low.     

Decreased preference and reproduction, and increased mortality of Frankliniella occidentalis on thrips-resistant pepper plants

The effect of thrips resistance in pepper (Capsicum annuum L.) – previously shown to result in impeded thrips population development (Maris PC, Joosten NN, Goldbach RW & Peters D (2003a) Restricted spread of Tomato spotted wilt virus in thrips‐resistant pepper. Phytopathology 93: 1223–1227. Maris PC, Joosten NN, Goldbach RW & Peters D (2003b) Spread of Tomato spotted wilt virus and population development of Frankliniella occidentalis in pepper resistant to thrips. Proceedings of the Section Experimental and Applied Entomology Netherlands Entomological Society (NEV) Amsterdam 14: 95–101.) – on thrips’[Frankliniella occidentalis Pergande (Thysanoptera: Thripidae)] reproduction, mortality, host preference, and behaviour was investigated. Reproduction, studied by oviposition and larval survival, was negatively affected by the thrips‐resistant (TR) phenotype, whereas the offspring's developmental rate did not differ on TR and the thrips‐susceptible (TS) phenotype. While thrips’ behaviour was hardly affected by thrips resistance, a significant preference for TS plants over the TR plants was found in different tests. When released on either a TR or a TS plant, thrips dispersed at significantly higher rates from the TR plants, demonstrating that not only an impeded reproduction, but also a reduced residence time adds to the reported lower thrips numbers on TR plants.     

Cell cycle analysis of tumour-derived cultures ofCrepis capillaris: A kinetic analogy with proliferation of animal tumour cells

Summary Analysis of the cell cycle by three methods has revealed unusual kinetics of proliferation in tumour derived suspensions ofCrepis capillaris. The different methods of analysis yield different estimates of cycle phase durations, and such discrepancies have been explained in terms of low growth fractions with rapid total cycle traverse. Specifically, confidence in the estimation of G₂ duration by the fraction of labelled mitosis analysis, and comparison with shorter G₂ estimates obtained by the two other methods, suggests that cells drop out in G₁. However, cells which do not drop out of the proliferative compartment traverse G₁ extremely rapidly. Extremely short cell cycle durations in which the G₁ phase is virtually non-existent are uncharacteristic of plant cell suspension cultures, in which the G₁ phase has previously been shown to be extended as compared with meristematic root tip cells. A model has been proposed in which a central core of rapidly dividing cells continuously loses cells into a subpopulation of resting or G₀ cells with the G₁ DNA content. Similarities between plant and animal tumours with respect to cell growth and division are discussed.     

光谱和光强度对西花蓟马雌虫趋光行为的影响

利用行为学方法研究了光谱、光强对西花蓟马Frankliniella occidentalis (Pergande)雌成虫的趋、避光行为的影响。结果显示：（1）在340~605nm波谱内14个波长其光谱趋光行为反应为多峰型,峰间主次较明显。趋光行为反应中,蓝绿区498~524nm有一较宽峰,趋光率20.31%;其它各峰依大小次序分别位于紫光380nm、蓝光440nm;（２）避光行为反应中,蓝光440nm处略高,避光率17.19%;紫外340nm处亦有一峰,避光率15.63%;（３）随光强增强其趋光反应率增大,白光、380nm和524nm刺激时其光强趋光行为反应呈一倒“L”型式样,498nm为峰型,440nm时为一较缓的平直线型;光强最弱时仍均有一定趋光率 ,最强时均未出现高端平台;（４）随光强增强其避光反应率增大,440nm为较平缓直线;340nm刺激时为较缓波动线。结果表明：光谱对其趋光行为有很大影响,光强度的影响较大且影响大小与波长因素有关。     

温度对西花蓟马(Frankliniella occidentalis)生长发育和存活率的影响

在15、20、25℃和30℃,RH75％的条件下,分析了温度与西花蓟马发育速率的关系,并测定了西花蓟马的发育起点温度、有效积温和存活率。结果表明：在15～30℃范围内,西花蓟马各虫期的发育速率随温度的升高而加快;用直接最优法对发育起点温度和有效积温进行估算,求得西花蓟马的卵、若虫、预蛹和伪蛹及世代发育起点温度分别为5．70、7．04、4．49、6．84℃和6．23℃;世代的有效积温为219．73d·℃。西花蓟马的世代存活率在25℃时最高,为40．12％;30℃时西花蓟马的存活率最低,为17．80％。     

西花蓟马诱导的番茄植株防御反应对B型烟粉虱行为的影响

【目的】明确外来入侵害虫西花蓟马Frankliniella occidentalis (Pergande)取食诱导的番茄植株防御反应对B型烟粉虱Bemisia tabaci (Gennadius) B-biotype行为的影响, 探讨西花蓟马与B型烟粉虱的种间竞争机制。【方法】利用“Y”型嗅觉仪行为分析法、 选择性试验法, 研究了不同处理组合（健康植株CK vs烟粉虱为害植株B、 健康植株CK vs西花蓟马为害植株F、 烟粉虱为害植株B vs烟粉虱和西花蓟马共同为害植株B+F）下, 烟粉虱对不同处理植株的取食行为反应及寄主偏好的差异性, 并利用GC-MS分析了不同处理植株挥发性物质的差异性。【结果】“Y”型嗅觉仪行为分析结果表明, 在CK vs B和CK vs F两个组合中, 烟粉虱雌成虫对健康植株和昆虫为害植株的偏好性差异不显著; 而在B vs B+F组合中, 烟粉虱为害株对烟粉虱雌成虫具有极显著的引诱作用（P<0.01）。选择性试验结果表明, 在CK vs B和CK vs F这两个组合中, 烟粉虱成虫均偏好健康株并喜好在其上产卵（P<0.01）, 在B vs B+F组合中, 烟粉虱成虫偏好烟粉虱单独为害株并喜好在其上产卵（P<0.01）。GC-MS分析结果显示, 本实验收集到9种挥发性物质, 其中有5种烯萜类物质, 其相对含量高达90%以上。与烟粉虱单独为害株相比, 烟粉虱和西花蓟马共同为害株所释放的挥发性物质中, 对烟粉虱具有排斥作用的β-水芹烯显著升高, 而对其具有吸引作用的β-月桂烯却显著减少。【结论】综合分析认为, 西花蓟马诱导的番茄植株防御反应可以显著影响B型烟粉虱的寄主选择行为及产卵选择性。     

CO2浓度升高对西花蓟马和花蓟马成虫体内解毒酶和保护酶活性的影响

【目的】阐明大气CO₂浓度升高对外来入侵昆虫西花蓟马Frankliniella occidentalis及其本地近缘种花蓟马F. intonsa的影响机制。【方法】测定和分析了CO₂人工气候箱内不同CO₂浓度（400 μL/L和800 μL/L）下饲养3代的这两种蓟马体内3种解毒酶［羧酸酯酶（CarE）、乙酰胆碱酯酶（AchE）和微粒体多功能氧化酶(MFO）］和3种保护酶［超氧化物歧化酶(SOD)、过氧化氢酶(CAT)和过氧化物酶(POD）］的活性。【结果】西花蓟马成虫体内的CarE, AchE, MFO, CAT和POD酶活性随着CO₂浓度的升高而显著上升（P＜0.05）,其中800 μL/L CO₂浓度下CarE和MFO酶活性分别比400 μL/L CO₂浓度下增加了24.78%和16.05%;800 μL/L CO2浓度下花蓟马成虫体内的CarE, MFO和CAT酶活性显著高于400 μL/L CO₂浓度下花蓟马成虫体内的相应酶活性,而AchE和POD酶活性在两种CO2浓度间差异不显著（P＞0.05）。800 μL/L CO₂浓度下西花蓟马和花蓟马成虫体内的SOD酶活性均显著低于400 μL/L CO₂浓度下的相应蓟马酶活性（P＜0.05）,分别下降了65.22%和42.20%。【结论】CO₂浓度升高是导致两种蓟马成虫体内CarE,MFO和SOD酶活性上升的主要原因,而AchE, CAT和POD酶活性的变化主要受蓟马种类的影响。两种蓟马可能通过改变体内解毒酶或保护酶的活性来适应高浓度CO₂的环境。     

西花蓟马取食不同豆科蔬菜的实验种群生命表

西花蓟马Frankliniella occidentalis(Pergande)是传入我国的重要入侵害虫,在贵阳地区对豆科蔬菜为害十分严重。在25℃条件下,组建了西花蓟马取食大豆叶片、豇豆叶片、四季豆叶片和四季豆豆荚时的实验种群生命表。结果表明:西花蓟马未成熟期取食四季豆豆荚时存活率最高,取食其它3种豆科蔬菜时存活率相差不大。西花蓟马取食四季豆豆荚时内禀增长力最高为0.1626,取食豇豆叶片时最低为0.0834,净增值率也是取食四季豆豆荚时最高,取食大豆叶片时最低,表明四季豆豆荚最有利于西花蓟马的生长发育和繁殖。在不同豆科蔬菜上的稳定年龄组配中未成熟期所占的比例很大,而成虫期所占的比例相对较小。