冬季小麦叶片光合作用对温度响应方式的变化

冬季田间生长的小麦离体叶片净光合速率（Ｐｎ）对温度的响应有两种方式。在１２月上旬可以观测到第一种方式。在离体叶片周围空气温度从１０℃逐步升到３０℃后的１ｈ内Ｐｎ逐渐升高,在随后气温逐步降低到１０℃的过程中,Ｐｎ都比先前升温过程中同样温度下的数值高。３０℃下叶片胞间ＣＯ２浓度（Ｃｉ）降低和叶片无机磷含量增高表明,这种响应方式可能起因于一些光合碳同化酶活性的增高。在１２月中旬以后可以观测到第二种方式。Ｐｎ在３０℃下的１ｈ内逐步下降,在随后的降温过程中Ｐｎ都比升温过程中同样温度下的数值低。３０℃下叶片Ｃｉ和膜透性增高表明,这种响应方式可能是适应冬季低温的光合机构膜系统在高温下遭受破坏的结果。     

Virulence of Hessian fly (Diptera: Cecidomyiidae) in the Fertile Crescent

The Hessian fly, Mayetiola destructor (Say), is an important insect pest of wheat (Triticum spp.) in North Africa, North America, southern Europe and northern Kazakhstan. Both wheat and this pest are believed to have originated from West Asia in the Fertile Crescent. The virulence of a Hessian fly population from Syria against a set of cultivars carrying different resistance genes, in addition to other effective sources with unknown genes, was determined in the field and laboratory at the International Center for Agricultural Research in the Dry Areas (ICARDA) during the 2005/2006 cropping season. Only two resistance genes (H25 and H26) were effective against the Syrian Hessian fly population, making it the most virulent worldwide. This high virulence supports the hypothesis that Hessian fly coevolved with wheat in the Fertile Crescent of West Asia. The ICARDA screening programme is using this Hessian fly population to identify new resistance genes to this pest.     

Virulence Frequences of Puccinia triticina in Germany and the European Regions of the Russian Federation

From 2001 to 2003, leaf rust was collected in different regions of Germany and the Russian Federation to generate single spore isolates and to study the structure of the pathogen populations by analyses of virulence. The virulence of isolates was tested with 38 near‐isogenic lines each carrying a different resistance gene. The analyses of variance revealed significant effects for the frequency of virulent isolates, the regions and most interactions with years and regions, but no significance was found for the effects of years. In Germany, an increase of virulence frequencies was detected for Lr1 and Lr2a while a decrease was found for Lr3a, Lr3bg and Lr3ka. Such clear trends did not occur in Russia which may be due to the great agroclimatic differences between regions. The variance of the frequency of virulent isolates was used to estimate adequate sample sizes for the analysis of regional populations of leaf rust. This procedure resulted in more reliable information about the dynamic processes within the pathogen populations. In 2002 and 2003, all pathotypes in Germany had a combined virulence to Lr1, Lr2a, Lr2b, Lr15, Lr17 and Lr20 supplemented by a few other genes. The complexity of virulence was lower in the most frequent pathotypes. In Russia virulence to the alleles at locus Lr3 was very common. Using detached leaf segments in Germany and Russia it turned out that the most virulent pathotypes carry 34 and 32 virulence genes, respectively. Virulence to Lr9, Lr19, Lr24 and Lr38 was rare or even absent. The use of major genes, not overcome by corresponding virulent pathotypes, may contribute to more durable types of resistance in case they are combined with genes having different effects, e.g. adult plant resistance.     

萝卜品种指纹图谱SRAP与AFLP分析

应用SRAP与AFLP两种分子标记技术进行了萝卜品种鉴定分析。对萝卜基因组DNA的SRAP-PCR反应体系中引物、Mg2 、dNTPs浓度进行优化,确定最优体系为引物0.3μmol.L-1,dNTP 0.2 mmo.lL-1,Mg2 3.0 mmo.lL-1。对SRAP-PCR中的退火温度(50℃)设置了12个梯度处理,以em2-me2为引物时带型无明显差异。7个供试萝卜材料的SRAP和AFLP指纹图谱分析表明,供试材料均可被SRAP和14个AFLP引物准确鉴定,每对引物组合都产生独特的指纹图谱。11个SRAP引物组合共产生155条带,多态性条带84条。聚类分析与相对遗传距离(GD)表明,供试材料聚为4类,CB-03-2与SHCB-02-1亲缘关系最近(GD=0.054 9);齐虹大连和Heiseng的亲缘关系最远(GD=0.203 4)。基于16个AFLP标记引物组合分析结果表明,供试材料聚为3类,CB-03-2和SHCB-02-1的亲缘关系最近。SRAP与AFLP综合分析结果表明,供试材料可聚为3类,其中CB-03-2与SHCB-02-1亲缘关系最近(GD=0.047 6)。     

Virulence Structure of the Powdery Mildew (Blumeria graminis) Population Occurring on Triticale (x Triticosecale) in Poland

Powdery mildew, caused by Blumeria graminis is an important disease of cereals in many production regions. Until end of the last century triticale had been regarded as a species characterized by high level of resistance for this disease. However, after several years of intensive production on a big area in Poland, Germany and other European countries it start to be susceptible for many pathogens including B. graminis. Because of this, virulence structure of this pathogen population on triticale in Poland was evaluated across 2008–2010. Leaf samples with symptoms of the powdery mildew disease were collected randomly from nineteen localities. As a total, 1402 B. graminis isolates were collected: 23–25 isolates per locality in each year. Standard differential set of 28 genotypes was used: twenty‐one wheat with known resistance genes and seven triticale. Based on the obtained results it was possible to observe significant differences in virulence structure between years and localities. No virulence's against Pm21 (Yangmai5), and Pm3d + 4b (Kadett) were found in any year. All tested isolates were virulent on Moreno and Lamberto cultivars. In a total, 36% of tested isolates possessed 9, 11 or 12 virulence's per genotypes. Twenty five percent of tested isolates were virulent to 5 triticale cultivars. Correlation between pathotypes frequency and sampling region were not found what suggest that local epidemics play the most important role in triticale growing regions in Poland.     

Mycotoxin-producing Fusarium Species Occurring in Winter Wheat in Belgium (Flanders) During 2002–2005

Deoxynivalenol (DON) content and Fusarium spp. ( Fusarium graminearum , Fusarium culmorum , Fusarium avenaceum , Microdochium nivale and Fusarium poae ) of mycotoxin-producing Fusarium species in winter wheat in Belgium (Flanders) were determined. Field trials were set up in the varietal testing network of Flanders Agricultural Centre for Small Grains (Roeselare – Beitem, Belgium) and followed up during growing seasons 2001–2002, 2002–2003, 2003–2004 and 2004–2005. Fusarium infection and DON contamination were mainly influenced by location and environmental parameters. Mean DON levels ranged from 0 to 15 mg/kg. Over the period of four growing seasons cvs Deben, Ordeal and Napier had the highest DON contamination. Seasonal and local weather conditions before and during flowering together with local crop husbandry measures (crop rotation, soil preparation) seemed to be of great importance in explaining the variation in results obtained. At Bottelare a positive correlation between disease index and DON content was found for the growing seasons 2001–2002 and 2002–2003, but not the season 2003–2004. Fusarium graminearum and F. culmorum were in general the most frequently occurring Fusarium spp. in Flanders over the 4 years but the composition of the Fusarium population varied strongly from location to location and from year to year. Fusarium graminearum predominated in areas especially where maize was cultivated, whereas in areas with more small cereals in the crop rotation more F. culmorum was present. Also temperature played a role in the composition of Fusarium spp.     

萝卜品种指纹图谱SRAP与AFLP分析

应用SRAP与AFLP两种分子标记技术进行了萝卜品种鉴定分析。对萝卜基因组DNA的SRAP-PCR反应体系中引物、Mg²⁺、dNTPs浓度进行优化,确定最优体系为引物0.3 μmol·L^-1,dNTP 0.2 mmol·L^-1,Mg²⁺ 3.0 mmol·L^-1。对SRAP-PCR中的退火温度（50℃）设置了12个梯度处理,以em2-me2为引物时带型无明显差异。7个供试萝卜材料的SRAP和AFLP指纹图谱分析表明,供试材料均可被SRAP和14个AFLP引物准确鉴定,每对引物组合都产生独特的指纹图谱。11个SRAP引物组合共产生155条带,多态性条带84条。聚类分析与相对遗传距离（GD）表明,供试材料聚为4类,CB-03-2与SHCB-02-1亲缘关系最近(GD=0.054 9);齐虹大连和Heiseng的亲缘关系最远(GD=0.203 4)。基于16个AFLP标记引物组合分析结果表明,供试材料聚为3类, CB-03-2和SHCB-02-1的亲缘关系最近。SRAP与AFLP综合分析结果表明,供试材料可聚为3类,其中CB-03-2与SHCB-02-1亲缘关系最近(GD=0.047 6)。     

冬小麦丙二烯氧化合酶基因(TaAOS)的克隆及其特性

丙二烯氧化合酶(allene oxide synthase,AOS)是茉莉酸脂加氧酶合成途径过程中的第一个酶.从冬小麦(Triticum aestivum L. cv.Jinghua No.3)克隆到了该酶的一个全长cDNA片段,其开放阅读框长约1 410 bp,编码一约含470个氨基酸残基的多肽,推测其分子量为51.9 kD.Southern分析显示其在基因组中以3个拷贝的形式存在.Northern杂交分析表明该基因表达可被外源的茉莉酸诱导,诱导10 h时达到高峰,进一步的RNA原位杂交表明该基因优先在幼叶中,尤其是在维管束附近的薄壁细胞中表达.同时,原位杂交还显示质膜钙通道的抑制剂La3 并不能抑制外源茉莉酸诱导该区域TaAOS的表达.     

粉质质量指数在冬小麦面团品质及烘烤品质中的应用价值研究

为了进一步了解粉质质量指数在小麦面团品质和烘烤品质评价中的作用,对90份冬小麦样品的粉质质量指数(FQN)与揉混仪参数、拉伸仪参数和面包品质参数之间的相关关系进行了研究。结果表明：FQN与揉混仪参数(峰值时间、峰值面积、8min尾高和斜率)有极显著的正相关关系,且以线性相关为主,可以用于评价小麦粉的耐揉性和筋力;FQN与拉伸曲线面积和最大拉伸阻力有较好的相关关系,但与延伸度相关性较小,且以非线性相关为主。因此,FQN不能很好地进行评价面团的拉伸特性;FQN与面包体积、面包评分和面包坚实度有一定的非线性相关关系,FQN可以用作评价面包烘烤品质的参数指标。     

昆虫病原线虫斯氏线虫和异小杆线虫对长角血蜱雌蜱的致病力

用昆虫病原线虫小卷蛾斯氏线虫（Sc BJ）、夜蛾斯氏线虫（Sf Otio）、拟双角斯氏线虫（Sc D43）、格氏斯氏线虫（Sg NC32）和嗜菌异小杆线虫（Hb E-6-7）对长角血蜱雌蜱进行感染试验,所用线虫剂量为4 000 Ijs/dish。结果表明,5种线虫均对长角血蜱雌蜱有致死效应。Hb E-6-7和Sc BJ两种线虫对雌蜱各发育期致病力最强,导致雌蜱的累积死亡率和半致死时间分别为饥饿雌蜱82.5%,9.0天和75.0%,8.8天;吸血雌蜱90.0%,8.0天和82.5%,8.0天;饱血雌蜱93.3%,7.3天和86.7%,7.3天。Sc D43对饱血雌蜱有较高的致死效应,为80.0%,但半致死时间较长,为11.7天。Sf Otio和Sg NC32对长角血蜱雌蜱的致死效应较低。饱血雌蜱较饥饿雌蜱和吸血雌蜱更易被线虫感染。     

冬小麦光合作用对开放式空气CO2 浓度增高(FACE)的非气孔适应

在同样CO2浓度下测定时,开放式空气CO2浓度增高(FACE,580 μmol CO2 /mol)条件下生长的冬小麦叶片的净光合速率、气孔导度和羧化效率都显著低于普通空气(380 μmol CO2 /mol)中生长的对照叶片.与此相一致,FACE叶片的可溶性蛋白、二磷酸核酮糖羧化酶/加氧酶(Rubisco)和Rubisco活化酶含量也都显著低于对照叶片.这些结果表明,在根系生长不受限制的田间条件下,冬小麦叶片的光合作用对高浓度CO2产生了适应现象,其主要原因可能是碳同化的关键酶Rubisco等含量的降低.     

冬小麦春化作用相关cDNA克隆Vrc79的分子克隆

在低温需求型植物的发育过程中,春化作用是诱导植物成花的必要因子。在冬小麦春化进程中存在着一个核酸代谢的关键期,为了探讨春化作用的分子机理,以不春化及脱春化的冬小麦京冬1号（Ｔｒｉｔｉｃｕｍ　ａｅｓｔｉｖｕｍＬ．ｃｖ．Ｊｉｎｄｏｎｇ　Ｎｏ．１）胚芽的ｍＲＮＡ为对照,通过减法杂交构建了富集冬小麦春化相关基因的ｃＤＮＡ文库,经过差异筛选分离到了一个仅在春化２１ｄ这一关键期表达,而在不春化、春化４ｄ、脱春化不表达的春化相关。ｃＤＮＡ克隆Ｖｒｃ７９。Ｎｏｒｔｈｅｍ杂交及同源性分析表明它是一个在植物中新发现的不同于低温胁迫诱导基因的春化特异克隆,其对春化需求型植物的成花诱导可能起重要的调控作用。     

低温处理对冬、春小麦细胞Ca^2＋时空变化的影响

用Fluo-3/AM染色,通过激光扫描共聚焦显微镜（LSCM）方法,对静息态及连续降温条件下不同抗寒性小麦（Triticum aestivum L.）叶肉细胞原生质体[Ca^2 ]cyt（the free Ca^2 concentration in the cytoplasm）的时空变化进行了比较。结果表明,静息态下小麦原生质体整体荧光强度基本不变,暗示[Ca^2 ]cyt能维持在一稳定水平;同时,不同品种小麦间也显示了[Ca^2 ]cyt水平荧光强度的不同。温度由15℃连续降至约2℃时,抗寒冬小麦[Ca^2 ]cyt出现升高后的回复,2℃之后逐渐升高;冷敏感春小麦则无此回复过程,而是一直升高到最大值。推测这一不同的动态变化最终决定了植物在低温下产生冷适应的不同能力。这进一步为“Ca^2 是低温下生理信号的传导”这一假说提供了新的证据。     

Temperature Response Pattern during Afterripening of Achenes of the Winter Annual Krigia oppositifolia (Asteraceae)

Abstract Freshly-matured achenes of Krigia oppositifolia Raf. were buried in soil at near-natural temperatures for 0–35 months and then exhumed and tested in light and darkness at (12/12 hr) daily thermoperiods of 15/6, 20/10, 25/15, 30/15 and 35/20°C. Achenes required light for germination and exhibited an annual dormancy/nondormancy cycle, being dormant in spring and nondormant in autumn. High summer temperatures (30/15, 35/20°C) fully promoted afterripening, whereas low temperatures (5, 15/6°C) prevented it. As buried seeds came out of dormancy in summer, they first germinated at medium temperatures (20/10, 25/15°C), but with additional afterripening the maximum and minimum temperatures for germination increased and decreased, respectively. Thus, during afterripening, achenes exhibit type 3 temperature responses, which otherwise are known only in two perennial Asteraceae and one perennial Liliaceae. The physiological responses of achenes of K. oppositifolia are unlike those of most winter annuals, which have type 1 responses—i.e., the maximum temperature for germination increases during afterripening. Also, they are unlike the majority of Asteraceae, which have type 2 responses—i.e., the minimum temperature for germination decreases during afterripening. Type 1 responses, typical of most winter annuals, have yet to be reported in the Asteraceae.     

Virulence evolution and the trade‐off hypothesis: history,current state of affairs and the future

It has been more than two decades since the formulation of the so‐called ‘trade‐off’ hypothesis as an alternative to the then commonly accepted idea that parasites should always evolve towards avirulence (the ‘avirulence hypothesis’). The trade‐off hypothesis states that virulence is an unavoidable consequence of parasite transmission; however, since the 1990s, this hypothesis has been increasingly challenged. We discuss the history of the study of virulence evolution and the development of theories towards the trade‐off hypothesis in order to illustrate the context of the debate. We investigate the arguments raised against the trade‐off hypothesis and argue that trade‐offs exist, but may not be of the simple form that is usually assumed, involving other mechanisms (and life‐history traits) than those originally considered. Many processes such as pathogen adaptation to within‐host competition, interactions with the immune system and shifting transmission routes, will all be interrelated making sweeping evolutionary predictions harder to obtain. We argue that this is the heart of the current debate in the field and while species‐specific models may be better predictive tools, the trade‐off hypothesis and its basic extensions are necessary to assess the qualitative impacts of virulence management strategies.     

The effect of Trichoderma harzianum and T. koningii on the control of tan spot (Pyrenophora tritici-repentis) and leaf blotch (Mycosphaerella graminicola) of wheat under field conditions in Argentina

The effect of six isolates of Trichoderma harzianum and one isolate of T. koningii on the incidence and severity of tan spot (Pyrenophora tritici-repentis) and leaf blotch of wheat (Mycosphaerella graminicola) was evaluated under field conditions. Significant differences between wheat cultivars, inoculum types and growth stages were found. Three of the isolates tested (T2 for M. graminicola, T7 for P. tritici-repentis and T5 for both of them) showed the best performance in controlling leaf blotch and tan spot when coated onto seed or sprayed onto wheat leaves at different growth stages, with significant severity reduction up to 56%. At tillering, six of the isolates reduced the severity of P. tritici-repentis and M. graminicola compared to the control by up to 39% and 12-53%, respectively. In some experiments, the biocontrol preparation (T2 and T5) gave a level of disease control similar to that obtained with Tebuconazole (70 and 48%, respectively). The effect of Trichoderma against P. tritici-repentis was also observed at the heading stage, when six of the treatments reduced disease severity by 16-35%. This is the first report on the efficacy of Trichoderma spp. against wheat necrotrophic pathogens under field conditions in Argentina.     

臭氧对原位条件下冬小麦叶片光合色素、脂质过氧化的影响

运用开顶式气室(OTC-1)研究了O3胁迫对原位条件下冬小麦叶片的光合色素、脂质过氧化和抗氧化系统的影响.结果表明:随着O3浓度的升高,各个生育期小麦叶片中叶绿素含量下降,叶绿素组成发生改变,且在灌浆期变化明显;叶片相对电导率(REC)增大,丙二醛(M DA)含量增加;过氧化氢酶(CAT)、过氧化物酶(POD)活性和类胡萝卜素(C ar)含量降低,超氧化物歧化酶(SOD)活性在O3浓度低于1×10-7(φO3)时逐渐升高,而后急剧降低.可见O3促进了小麦叶片老化,加剧了膜脂过氧化,破坏了抗氧化系统功能,影响了叶片的正常生理代谢.     

Effect of strain and cultural conditions on the production of cytochalasin B by the potential mycoherbicide Pyrenophora semeniperda (Pleosporaceae,Pleosporales)

The seed pathogen Pyrenophora semeniperda has demonstrated potential as a mycoherbicidal biocontrol for eliminating persistent seed banks of annual bromes on western North American rangelands. This pathogen exhibits variation in virulence that is related to mycelial growth rate, but direct laboratory tests of virulence on seeds often have low repeatability. We developed a rapid and sensitive high pressure liquid chromatography method for quantification of the phytotoxin cytochalasin B in complex mixtures in order to evaluate its use in virulence screening. All 10 strains tested produced large quantities of this metabolite in solid wheat seed culture, with production varying over a fourfold range (535–2256 mg kg^?1). No cytochalasin B was produced in liquid potato dextrose broth culture, showing that its synthesis is strongly dependent on cultural conditions. In a Bromus tectorum coleoptile bioassay, solid culture extracts showed mild toxicity similar to the cytochalasin B standard at a concentration equivalent to 10^?4 M cytochalasin B (72–95% of control), whereas at 10^?3 M equivalent, the extracts exhibited significantly higher toxicity (8–18% of control) than the cytochalasin B standard (34% of control). This suggests the possible presence of other phytotoxic metabolites. Cytochalasin B production in solid wheat seed culture exhibited the predicted significant negative correlation with mycelial growth rate on potato dextrose agar, but the correlation was not very strong, possibly because cytochalasin B production and growth rate were measured under different cultural conditions.