Effect of two-component cultivar mixtures and yellow rust on yield and yield components of wheat

Four winter wheat ( Triticum aestivum ) cultivars and three two-component cultivar mixtures were planted in a replacement series both inoculated with or protected from yellow rust ( Puccinia striiformis ) in three environments. Each cultivar was susceptible to one or two of the rust races used. Mixtures yielded, on average, 7 and 4% more than their component pure stand means under inoculated and rust-free conditions, respectively. Though all yield components were affected by yellow rust, seed weight was the component that was most consistently influenced. The component genotypes within mixtures varied considerably with respect to yield, and the yield of the same component cultivar included in different mixtures sometimes differed significantly. The correlation between yellow rust severity/tiller and grain yield/tiller in mixture differed among cultivars and depended on their companion cultivar. Variance component analysis indicated that yellow rust was the most important experimental variable influencing grain yield. There was no relationship between yield of the cultivars in pure stands and their yields or competitive abilities in mixture. Disease did not change the competitive ranking of cultivars in mixture. Mixtures with complementary, negative, and overcompensatory interactions were identified. On average, mixtures showed no greater yield stability than did pure stands.     

Effect of genotype unit number and spatial arrangement on severity of yellow rust in wheat cultivar mixtures

Pure stands of a yellow rust-susceptible wheat cultivar, pure stands of a resistant cultivar, and a 1 : 1 random mixture of resistant and susceptible cultivars were compared to populations in which strips or hills of the cultivars were alternated to attain genotype units (units of the same host genotype) that were larger in area than that of a single wheat plant. These four host populations were grown in plots of different sizes in order also to alter the number of units per host population. The goal was to determine if increasing the number of genotype units in mixed populations of large genotype units improved disease control relative to pure-line populations by increasing the amount of inoculum exchange among genotype units. Random mixtures of the two cultivars always provided better disease control than did alternating strips or hills. Evidence for an effect of genotype unit number on the efficacy of mixtures for rust control was found in only one of three experiments. Random mixtures of the two cultivars increased grain yield relative to the pure stand mean, but alternating strips did not.     

小麦品种混（间）种对小麦条锈病防治效果和产量影响研究

利用甘肃甘谷县和四川盐亭县当地各4个对条锈病具不同抗性的小麦品种,按照抗感品种不同比例混（间）种研究各种植方式对小麦条锈病的防治作用和对小麦的增产效果,并以REM比较各混（间）种种植方式的效果。结果表明,混（间）种对本地菌源引起的病害有明显效果,混种对病害的减轻程度为29.6％～81.9%,对外来菌源引起的病害效果较差;混（间）种对于小麦的增产作用也表现不一,28个混间种处理中,仅8个处理（占28.6%）有增产效果。     

Spatiotemporal effects of cultivar mixtures on wheat stripe rust epidemics

The use of cultivar mixtures is increasingly practical in wheat stripe rust management. Field experiments with wheat cultivar mixtures were conducted to determine their effects on temporal and spatial patterns of stripe rust epidemics in three regions. In the Beijing and Gangu fields, where the epidemics were caused by artificial inoculation, disease incidence and the area under the disease progress curve (AUDPC) of the cultivar mixtures were significantly lower (P < 0.05) than those of the susceptible pure stands. We defined the relative effectiveness of cultivar mixture on disease development related to that in pure stands (REM). The results demonstrated that in many treatments of mixtures of susceptible cultivar with resistant cultivars at various ratios in different locations, their effects on disease reduction were positive (REM < 1). The reduction of epidemic rate in cultivar mixtures expressed in either early season or late season depended on the initial pattern of disease and cultivar mixture treatments. Semivariograms were used to determine the spatiotemporal patterns of disease in the Gangu field. The spatial analysis showed clear spatial patterns of the disease in all four directions of the fields on susceptible pure stands but not on cultivar mixtures. The results implied that the mechanisms of cultivar mixture on disease management might include the interruption of disease spatial expansion and a physical barrier to pathogen inoculum by resistant cultivars.     

模拟酸雨对小麦条锈病流行学组分的影响

为明确酸雨对小麦条锈病菌孢子萌发及病害流行学组分的影响,采用不同酸度的模拟酸雨(p H值分别为2.5、3.5、4.5和5.6)处理小麦条锈病菌Puccinia striiformis f.sp.tritici生理小种CYR32和CYR33的夏孢子,并将不同酸度模拟酸雨处理后的夏孢子接种小麦感病品种铭贤169,采用组分分析法研究酸雨对病害发展过程的影响。结果表明,随着模拟酸雨酸度的增强,生理小种CYR32和CYR33的夏孢子萌发率均显著降低,萌发24 h后对照组生理小种CYR32和CYR33的夏孢子萌发率分别为93.7%和79.8%,在p H 3.5模拟酸雨处理后萌发率仅为13.1%和8.6%。温室内接种试验结果显示,不同酸度模拟酸雨对生理小种CYR32和CYR33的侵染概率、潜育期和病情指数均有显著影响,对生理小种CYR32和CYR33病斑扩展率影响不显著;与对照相比,p H 3.5模拟酸雨处理后生理小种CYR32和CYR33的侵染概率分别下降79.9%和79.8%。结果表明强酸雨(p H 3.5)显著延长小麦条锈菌潜育期,减少病斑产孢量,降低病情指数和病害进展曲线下面积。     

小麦持久抗条锈病品种Champlein的抗性遗传分析

小麦条锈病是小麦生产中最重要的病害,培育抗病品种是防治条锈病最经济、有效、安全的措施。‘Cham-plein’引自法国,对条锈菌生理小种表现良好持久抗性。为了明确其抗性遗传特点,以感病品种‘铭贤169’与其杂交、自交和回交获得了F1、F2、F3和BC1代,人工接种小麦条锈菌生理小种CY32,在温室和田间对‘Champlein’进行遗传分析。结果表明:苗期‘Champlein’对CY32的抗病性由1对显性基因控制;成株期‘Champlein’对CY32的抗病性由2对显性和1对隐性抗条锈病基因以互补方式控制;系谱分析表明基因可能来源于‘Vilmorin27’。     

Focus expansion of bean rust in cultivar mixtures

Radial expansion of foci in mixtures of susceptible and resistant bean cultivars was studied at two sites in Ethiopia. The foci expanded in a wave-like fashion. At Ambo (1990), radial expansion velocity ranged from 6 cm per day in mixtures with 20% susceptible plants to 15 cm per day in plots with the susceptible plants only. At Debre Zeit, the velocity ranged from 3 cm per day in a mixture with 20% susceptible plants to 16 cm per day in plots with 100% susceptible plants. At both sites the radial expansion velocity of foci correlated linearly with the logarithm of the fraction of susceptible plants in the mixture. Velocities of focus expansion at Ambo and Debre Zeit were approximately equal in plots consisting of susceptible plants only. At lower proportions of susceptible plants the velocities at Debre Zeit were lower than at Ambo. Indications were given as to the environmental factors responsible for the observed difference between sites. At each site, the variation between plots showed a clear spatial pattern, probably due to environmental factors.     

Effect of plot geometry on epidemic velocity of wheat yellow rust

The size and shape of field plots can impact on both the cost and outcome of epidemiological experiments. In previous studies, epidemic velocity of yellow rust (caused by Puccinia striiformis f.sp. tritici ) on wheat ( Triticum aestivum ) has been examined in long, narrow plots (6·1 m by 73–171 m). The present study compares spread in square, 61 × 61 m plots versus narrow, 6·1 × 61 m plots at two locations. The objective was to test whether plot shape has a substantial impact on spatiotemporal spread of yellow rust. Velocity increased curvilinearly with time for both plot shapes and at both locations. Curves of epidemic velocity versus time were nearly identical in square versus narrow plots in both the upwind and downwind directions. Contrary to expectation based on simulations, the results did not indicate faster disease spread in square plots, though the plot sizes studied may be beyond that at which there is a rapid change of disease increase with increasing plot area. Velocity also increased curvilinearly in all eight compass directions of the square plots. Results indicate that narrow plots, which are substantially less costly than equidimensional plots, may be justified for studying the spatiotemporal spread of wheat yellow rust and other diseases with similar epidemiological characteristics.     

Effect of yellow rust on yield components of winter wheat in China

Experiments were done in 1983,1984 and 1985 in Beijing and Zhengzhou, People's Republic of China, to determine the relationship of yield components of wheat to the severity of yellow rust ( Puccinia striiformis f.sp. tritici ). Epidemics were manipulated by timing inoculation and fungicide applications. Disease, plant yield, number of ears per plant, number of grains per ear and 1000-grain weight were measured. Analysis indicated that there were interactions among the yield components. However, path coefficient analysis did not detect any statistically significant compensation and showed that there was a positive correlation among yield components. The correlation coefficients between AUDPC (area under disease progress curve, accumulated to each growth stage) and each yield component increased gradually with growth stage, thus providing no evidence of a critical stage at which a yield component was most affected by disease.     

小麦品种天选43抗条锈性遗传分析及抗病基因的分子标记

 天选43是由8845-01-01-1-1和抗源材料贵农22杂交选育而成的普通小麦品种,对我国目前所有条锈菌生理小种均表现良好抗性。为明确其抗条锈性遗传基础,本研究选用当前条锈菌流行小种CYR32和CYR33,对天选43与感病品种铭贤169杂交F₁、F₂和F₃代群体进行遗传分析,同时应用460对SSR引物对接种CYR32的天选43/铭贤169 F₂代150个单株群体进行抗病基因定位。结果表明,天选43对CYR32抗性由1对显性基因控制,而对CYR33抗性由1对隐性基因控制。筛选到10个与抗CYR32基因连锁的SSR标记Xwmc134、Xgwm413、Xbarc187、Xwmc406、Xcfd65、Xgwm18、Xbarc181、Xbarc137、Xwmc419和Xgwm230,两侧距离目的基因最近的标记为Xgwm18和Xgwm413,遗传距离分别为0.8 cM和3.4 cM,并初步将其抗病基因定位于小麦染色体1BS上,暂命名为YrTx43。基因来源、抗病遗传分析、分子标记检测及染色体位点分析表明,YrTx43很可能是与Yr24、Yr26具有等位性的抗条锈基因。     

中国小麦条锈菌鉴别寄主维尔抗条锈性遗传分析

小麦品种维尔是中国小麦条锈菌重要鉴别寄主.将该品种分别与完全感病品种铭贤169和其它抗病品种杂交,获得各组合的F1、BC1和F2代群体及部分F3家系.在温室对各组合亲本及F1、BC1和F2代群体进行了苗期抗性鉴定.结果表明,维尔对CY17和CY23菌系的抗性由1对主效隐性基因控制.等位性分析表明,维尔中抗CY17和CY23菌系的基因与Triticum spelta album中的1对抗性基因等位或紧密连锁,将其命名为YrVirl.而维尔对Su-1的抗性则由1对显性基因控制,将其命名YrVir2.同时采用CY17和CY23菌系对铭贤169/维尔组合的48个F3家系进行了苗期抗性鉴定,根据平均抗性指数和样本方差将这些家系分为3组,卡方测验证明了维尔对上述两菌系的抗性由1对主效基因控制,同时还可能受微效基因的影响.     

Effect of wheat cultivar mixtures on populations of Puccinia striiformis races*

This study quantifies the frequency of simple and complex races (races that can infect two or more components) of Puccinia striiformis in mixtures of wheat cultivars possessing different race-specific resistance genes. Treatments were designed so that the complex race changed depending on the host mixture, thus enabling us to observe the influence of pathogen complexity in different genetic backgrounds. Six cultivar mixtures and one pure stand of winter wheat were inoculated with three races of P. striiformis at two locations for two seasons. Potted plants of three winter wheat cultivars, each susceptible to one of the three races of the pathogen, were used to sample the pathogen during the field epidemics. Disease incidence on the differential cultivars was used to calculate the proportion of the three races in each treatment. The specific cultivars included in the mixtures influenced the frequencies of the three races. Increasing the number of virulent races in a mixture reduced the frequency of the complex race relative to the other two races. The results suggest that genetic background of the pathogen race, host composition, and interaction among pathogen races may be as important as cost of virulence in determining race frequencies in mixtures.     

小麦条锈菌鉴别寄主尤皮Ⅱ号抗条锈性遗传分析

小麦品种尤皮Ⅱ号是重要的中国小麦条锈菌鉴别寄主.为研究尤皮Ⅱ号的抗条锈性遗传基础,将该品种分别与感病品种铭贤169及其它抗病品种杂交,获得各组合的F1、BC1和F2代群体.在温室对各组合亲本及F1、BC1和F2代群体进行了苗期抗性鉴定.结果表明,尤皮Ⅱ号对CY29菌系的抗性由两对隐性基因独立或重叠遗传控制;对CY23的抗性由两对显性基因互补遗传控制;对CY31的抗性亦由两对显性基因互补遗传控制,而对Su-1的抗性则由一对显性基因控制.抗CY29的两对基因不抗CY23、CY31和Su-1,因此将这两对基因暂定名为YrJu1和YrJu2.抗CY23的两对基因中,其中一对同时抗CY31和Su-1,该基因与Spaldings prolific中的一对基因等位或紧密连锁,将该基因暂定名为YrJu3;另一对则与抗引655中的一对抗性基因等位或紧密连锁,暂定名为YrJu4.YrJu1、YrJu2、YrJu3和YrJu4均与其它供试品种中的已知抗性基因不同.     

小麦条锈菌鉴别寄主抗引655抗条锈性遗传分析

小麦品种抗引655是中国小麦条锈菌重要鉴别寄主。将该品种分别与完全感病品种铭贤169及其它抗病品种杂交，获各组合的F1、BC1和F2代群体。在温室对各组舍亲本及F1、BC1和F2代群体进行了苗期抗性鉴定。结果表明，抗引655对CY29菌系的抗性由2对显性抗条锈基因互补控制，对CY31和Su-1的抗性由1对显性基因控制。等位性分析表明，抗引655中抗CY29、CY31和Su-1的基因与Triticum speha album中的1对基因等位或紧密连锁。故而判定抗引655中除含有YrI外，还含有2对抗条锈基因，暂定名为YrKy1和YrKy2；YrKy1只抗CY29，YrKy2同时抗CY31和Su-1。系谱分析表明，抗引655中的抗条锈基因极有可能来自前苏联地方品种选育而成的旱熟36。     

Primary disease gradients of wheat stripe rust in large field plots

ABSTRACT Field data on disease gradients are essential for understanding the spread of plant diseases. In particular, dispersal far from an inoculum source can drive the behavior of an expanding focal epidemic. In this study, primary disease gradients of wheat stripe rust, caused by the aerially dispersed fungal pathogen Puccinia striiformis, were measured in Madras and Hermiston, OR, in the spring of 2002 and 2003. Plots were 6.1 m wide by 128 to 171 m long, and inoculated with urediniospores in an area of 1.52 by 1.52 m. Gradients were measured as far as 79.2 m downwind and 12.2 m upwind of the focus. Four gradient models-the power law, the modified power law, the exponential model, and the Lambert's general model-were fit to the data. Five of eight gradients were better fit by the power law, modified power law, and Lambert model than by the exponential, revealing the non-exponentially bound nature of the gradient tails. The other three data sets, which comprised fewer data points, were fit equally well by all the models. By truncating the largest data sets (maximum distances 79.2, 48.8, and 30.5 m) to within 30.5, 18.3, and 6.1 m of the focus, it was shown how the relative suitability of dispersal models can be obscured when data are available only at a short distance from the focus. The truncated data sets were also used to examine the danger associated with extrapolating gradients to distances beyond available data. The power law and modified power law predicted dispersal at large distances well relative to the Lambert and exponential models, which consistently and sometimes severely underestimated dispersal at large distances.     

小麦品种多样性对白粉病及产量和蛋白质的影响

 对品种多样性控制小麦白粉病的效果以及对产量和蛋白质的影响进行了研究,为利用品种多样性控制白粉病提供理论依据和技术支持。采用SSR技术分析5个小麦品种的亲缘关系;2008年和2009年按组合所含品种数为2、3、4和5个进行组合,在田间种植混种组合和单播小区,人工接种白粉菌,比较各小区中小麦白粉病的AUDPC值、产量和蛋白质变化。结果表明,5个品种亲缘关系相对较近;2个品种混合时以抗感搭配较好,随着抗病品种比例增加控病效果增强;2008年混合种植中有防治效果的组合占54.55%,相对防效为10.02%~47.58%,2009年有防治效果的组合占23.08%,相对防效在1.85% 到18.96 % 之间;在适当的组合中,如京冬8号/轮选987、京双16/京411/京冬8号对小麦白粉病有控制效果,混种不会影响产量和蛋白质含量;当有大量能克服本地品种抗性的外来菌源时混合种植的控病效果降低。品种多样性可以用做防治小麦白粉病的一项措施。     

Disease-weather relationships for powdery mildew and yellow rust on winter wheat

Key weather factors determining the occurrence and severity of powdery mildew and yellow rust epidemics on winter wheat were identified. Empirical models were formulated to qualitatively predict a damaging epidemic (>5% severity) and quantitatively predict the disease severity given a damaging epidemic occurred. The disease data used was from field experiments at 12 locations in the UK covering the period from 1994 to 2002 with matching data from weather stations within a 5 km range. Wind in December to February was the most influential factor for a damaging epidemic of powdery mildew. Disease severity was best identified by a model with temperature, humidity, and rain in April to June. For yellow rust, the temperature in February to June was the most influential factor for a damaging epidemic as well as for disease severity. The qualitative models identified favorable circumstances for damaging epidemics, but damaging epidemics did not always occur in such circumstances, probably due to other factors such as the availability of initial inoculum and cultivar resistance.     

Use of multispectral radiometry in wheat yellow rust experiments1

Winter-wheat field fungicide experiments were monitored by multispectral radiometry to determine yellow rust impact on crop growth and to predict yield loss caused by disease. Spectral reflectance data were highly correlated with yellow rust severity. Linear regression models with spectral ratios as independent variables explained 90–93% of the variation in yield between plots with different treatments of fungicide. The area under the NIR/Red curve, calculated from heading to soft-dough growth stages, was a good predictor of yield loss determined at harvest.     

A multiple disease test for field-based phenotyping of resistances to Fusarium head blight,yellow rust and stem rust in wheat

Wheat is affected by many diseases, in Germany eight fungal diseases are recorded during the cultivar registration process. For a commercially successful cultivar, therefore, at least moderate resistances to important diseases, like yellow rust (YR) and Fusarium head blight (FHB), are necessary. Additionally, in 2013 a regional stem rust (SR) epidemic occurred in Central Germany for the first time for decades. Our objective was to analyze the resistance of 36 commercially grown winter wheat cultivars to YR, FHB, and SR in three individual and one combined inoculation. Appreciable disease severities were achieved for YR and FHB at three to four locations in two years (= seven location × year combinations), for SR at one to two locations in two years (= three location × year combinations). Wheat cultivars showed a significant genotypic variation for all diseases with high heritabilities (0.90–0.95). Interaction between inoculation treatments (individual vs. combined) and wheat genotype was not significant for each of the three diseases. Accordingly, correlations between both inoculation treatments were very high (R²?=?0.95–0.99). Several cultivars showed multi-disease resistance (MDR) to YR, FHB, and SR. In conclusion, resistance ranking among genotypes was not changed when plants were challenged with all three pathogens together compared to factorial inoculations of only one of them. Substituting factorial inoculation trials by multi-pathogen inoculation makes it more efficient to select for MDR in practical breeding programs.     

Disease severity and yield of pure-line wheat cultivars and mixtures in the presence of eyespot, yellow rust, and their combination

Five winter wheat cultivars, six two-component cultivar mixtures, and one four-way mixture were grown in the presence of yellow rust, eyespot, both diseases, and neither disease for three seasons. On average, mixtures reduced the severity of yellow rust relative to their component pure stands by 53%. The four-component mixture provided better yellow rust control than did the two-way mixtures. Eyespot severity was reduced through mixing only in the absence of yellow rust and by only three of the seven mixtures (mean reduction = 13%). Yellow rust was 13% less severe in the presence of eyespot, and eyespot was 10% more severe in the presence of yellow rust. Averaged over all years, the mixtures increased yield relative to the pure stands by 6·2, 1·7, 7·1, and 1·3% in the presence of yellow rust, eyespot, both diseases, and neither disease, respectively. Two mixtures provided significant yield increases over the means of their component pure stands (7% and 9%) in the presence of eyespot even though one of them did not significantly reduce eyespot severity. Accounting for all disease treatments and years, four mixtures provided distinctly higher yield increases than the other three. In mixtures containing a resistant cultivar and a cultivar susceptible to eyespot, yield loss by the susceptible cultivar was not compensated for by increased yield of the resistant cultivar. The mixtures showed improved yield stability relative to the pure stands, with the four-component mixture being particularly stable.