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.     

小麦纹枯病品种抗性鉴定技术及抗病资源的筛选与分析

分别用玉米粉－砂、麦粒和玉米秸秆作为小麦纹枯菌生长基质,培养获得小麦纹枯病菌接种物。土壤接种诱发试验表明,三种接种物在合适的接种强度下,均能有效诱发泪科纹枯病。据此建立的人工病围２对１５份小麦产多年连续鉴定结果表明,病圃具有较稳定的发病率,表现为典型的尖眼点或云纹病斑。对我国主要冬麦区的１３００份小麦品种资源、生产品种以及新育成品系进行了病圃鉴定,共筛选出抗纹枯病材料８５份,包括菜籽黄、紫秆子、白     

小麦纹枯病抗性及抗性遗传的初步研究

 从一个多亲本的复式杂交后代中,选育了4个高抗纹枯病的小麦新品系,编号为MN-3、7、18和19。抗病性鉴定证明,在对照品种绵阳19病株率100%,发病等级4~5级的情况下,这4个新品系的病株率和发病等级分别在3.65%~6.98%和0~1之间。这4个品系与高感纹枯病的小麦品种绵阳19杂交,在F2代群体中植株符合抗:感=3:1的分离比率,在隐性亲本的测交后代中符合1:1的分离比率;在这4个品系之间的杂交后代群体中未观察到抗性的分离。试验结果指出,4个品系均含有同一个抗小麦纹枯病的单显性抗病基因,该基因被命名为Ses 1。本研究指出了小麦抗纹枯病育种的可能性,并为进一步研究小麦宿主和纹枯病菌原的相互关系及其遗传学提供了材料。     

品种布局防治小麦条锈病的模拟研究

 用小麦条锈病大区流行模型PANCRIN进行的模拟试验结果指出:抗病品种的合理布局能有效地延缓和减轻抗病性丧失,但其效果易受品种面积、流行速率和越夏区面积浮动的影响。布局策略上首先要按照小麦条锈病菌越夏途径中不同成熟期的麦田进行细致的布局,也就是布局要和"打越夏"结合,效果才更显著。其次要控制每个抗病品种的面积而增多抗病品种的数目,在所用模型规定的条件下,每一抗病品种的种植面积百分比不可超过15%,抗病品种总数争取≥ 6个。此外,要尽量压缩感病品种面积,减少大区流行菌量,感病品种面积最好不超过10%。流行系统的定量控制是个极其复杂的问题,因此上述初步结果只能供作研究参考,还不能视为应用指标。合理布局的设计应以深入掌握越夏规律为基础,这需要进一步开展有关研究。目前情况下,生产上尽量增多抗病品种数目,只要上下游品种雷同的不多,也能多少延长抗病品种的使用年限。     

湖北省小麦品种(系)对赤霉病、条锈病、白粉病和纹枯病的抗性评价

为了解湖北省小麦品种(系)的抗病性水平,对2001年以来湖北省审定的46个小麦品种和在湖北省进行区域试验的447份小麦品系进行赤霉病、条锈病、白粉病和纹枯病等4种主要病害的抗病性评价。结果表明:1)参试品系中有1份材料对赤霉病表现高抗,未发现对纹枯病表现高抗或免疫的材料;对赤霉病和纹枯病的平均抗性评价分值分别为14.30和3.49,介于中感和高感之间;对条锈病和白粉病的平均抗性评价分值分别为13.43和8.34,介于中抗和中感之间。2)审定品种的综合抗性水平不高,对条锈病的抗性评价分值为12.47,介于中抗和中感之间,对其他3种病害的抗性介于中感和高感之间;审定品种的单产呈增加趋势,株高在不断降低,生育期相应延长,综合抗病性也在增强。3)审定品种的综合抗病性与对条锈病抗性的相关系数最高,为0.738;对纹枯病的抗性与株高呈显著正相关,与单产呈显著负相关;对赤霉病的抗性与株高无显著相关。鉴于此,湖北省需加强抗病育种力度,同时应充分做好小麦病害的防控。     

小麦苗期抗纹枯病鉴定方法的改良及抗病品种筛选

Wheat sharp eyespot, caused by Rhizoctonia cerealis and R. solani, is a soil-borne fungal disease, which poses a great threat to wheat yield. In order to increase the identification efficiency of wheat sharp eyespot resistance, an improved method of rapidly identifying wheat sharp eyespot resistance was established by inoculating wheat seedlings with diseased wheat grains in greenhouse. To verify its reliability, four standard materials and 96 wheat varieties from Huanghuai wheat region were used for resistance assessment to sharp eyespot. Meanwhile, the resistance to Rhizoctonia solani of aforementioned materials in the field was identified by traditional methods. The results showed that the correlation coefficient between the four repetitions of the improved method ranged from 0.735 to 0.825, and the correlation coefficient between the average number of repetitions and the traditional method was 0.630. The results of wheat sharp eyespot resistance identification in Huanghuai wheat area showed that 66 wheat varieties were susceptible, accounting for 68.8% of tested materials. This indicated that the resistance of wheat varieties in Huanghuai wheat area to sharp eyespot was poor on the whole and needed to be improved urgently. At the same time, eleven wheat varieties which showed resistance to sharp eyespot at seedling and adult stages were screened, which include Zhengzhou 8998, Beijing 841, Handan 94-5316, Jimai 32, Jinmai 50, Jinmai 54, Longmai 157, Lumai 23, Shanhe 6, Shi 02-1 and Xinmai 18. Therefore, this study provides a method for identification of wheat sharp eyespot resistance at seedling stage, by which the resistance of wheat varieties to sharp eyespot can be quickly and efficiently identified. Furthermore, selected resistant materials provide important material resources for wheat sharp eyespot resistance breeding in Huanghuai wheat region and even in China.     

小麦苗期抗纹枯病鉴定方法的改良及抗病品种筛选

<正>小麦纹枯病又称尖眼斑(点)病,是由禾谷丝核菌(Rhizoctonia cerealis)和立枯丝核菌(Rhizoctonia solani)引起的一种以土壤传播为主的小麦真菌病害~([1])。引起小麦纹枯病的病原菌主要是禾谷丝核菌的第一菌丝融合群(CAG-1)~([2～4])。在自然条件下,病原菌首先侵染寄主植株基部叶鞘,随着     

Improved control of septoria tritici blotch in durum wheat using cultivar mixtures

Mixtures of cultivars with contrasting levels of resistance can suppress infectious diseases in wheat, as demonstrated in numerous field experiments. Most studies focus on airborne pathogens in bread wheat, while splash-dispersed pathogens have received less attention, and no studies have been conducted in durum wheat. We conducted a 2-year field experiment in Tunisia to evaluate the performance of cultivar mixtures with varying proportions of resistance (0%–100%) in controlling the polycyclic, splash-dispersed disease septoria tritici blotch (STB) in durum wheat. To measure STB severity, we used a high-throughput method based on digital image analysis of 3,074 infected leaves collected from 42 and 40 experimental plots during the first and second years, respectively. This allowed us to quantify pathogen reproduction on wheat leaves and to acquire a large data set that exceeds previous studies with respect to accuracy and precision. Our analyses show that introducing only 25% of a disease-resistant cultivar into a pure stand of a susceptible cultivar provides a substantial reduction of almost 50% in disease severity compared to the susceptible pure stand. However, incorporating two resistant cultivars instead of one did not further improve disease control, contrary to predictions of epidemiological theory. Susceptible cultivars can be agronomically superior to resistant cultivars or be better accepted by growers for other reasons. Hence, if mixtures with only a moderate proportion of the resistant cultivar provide a similar degree of disease control as resistant pure stands, as our analysis indicates, such mixtures are more likely to be accepted by growers.     

Defence responses in flag leaves and spikes of common wheat Triticum aestivum cultivars with contrasting levels of basal resistance to blast caused by Pyricularia oryzae

Wheat blast, caused by Pyricularia oryzae, can cause large yield losses in crops. This study aimed to investigate defence responses in flag leaves and spikes of wheat cultivars BR-18 (moderately resistant) and BRS-Guamirim (susceptible), which differ in their levels of basal resistance. In contrast to cultivar BRS-Guamirim, infected plants of cultivar BR-18 showed more pronounced increases in activities of β-1,3-glucanase and chitinase as well as higher concentrations of lignin-thioglycolic acid derivatives in the flag leaves and total soluble phenolics in the spikes. Polyphenoloxidase activity increased in both flag leaves and spikes in response to fungal infection, regardless of cultivar. Phenylalanine ammonia-lyase (PAL) activity increased in infected flag leaves of both cultivars, especially in BR-18. PAL activity was lower in spikes of infected compared to noninfected plants of both cultivars, although to a lesser extent in BR-18. Compared to BRS-Guamirim, the antioxidative system in both flag leaves and spikes of BR-18 was more efficient in removing reactive oxygen species, reducing cellular damage caused by fungal infection. The lower catalase and peroxidase activities, associated with high superoxide dismutase activity, in flag leaves and spikes of infected BR-18 culminated in a high hydrogen peroxide concentration. The increase in ascorbate peroxidase activity was higher in both flag leaves and spikes of infected plants of BR-18 than in infected BRS-Guamirim. It was concluded that wheat resistance to blast depended on the basal level of resistance of the cultivar, which was mainly associated with the activities of defence enzymes and a more effective antioxidative system.     

Aggressiveness of Mycosphaerella graminicola Isolates from Susceptible and Partially Resistant Wheat Cultivars

ABSTRACT The selective effect of quantitative host resistance on pathogen aggressiveness is poorly understood. Because two previous experiments with a small number of bread wheat cultivars and isolates of Mycosphaerella graminicola had indicated that more susceptible hosts selected for more aggressive isolates, we conducted a larger experiment to test that hypothesis. In each of 2 years, six cultivars differing in their levels of partial resistance were planted in field plots, and isolates were collected from each cultivar early and late in the growing season. The isolates were inoculated as populations bulked by cultivar of origin, field replicate, and collection date on seedlings of the same six cultivars in the greenhouse. The selective impact of a cultivar on aggressiveness was measured as the difference in aggressiveness between early and late isolates from that cultivar. Regression of those differences on disease severity in the field yielded significance values of 0.0531 and 0.0037 for the 2 years, with moderately resistant cultivars selecting for more aggressive isolates. In a related experiment, the protectant fungicide chlorothalonil was applied to plots of two susceptible cultivars to retard epidemic development. When tested in the greenhouse, isolates of M. graminicola from those plots were significantly more aggressive than isolates from the same cultivars unprotected by fungicide.     

Leaf scald (Xanthomonas albilineans) incidence and its effect on yield in seven sugarcane cultivars in Guadeloupe

Seven 5—month-old sugarcane cultivars difTering in resistance to leaf scald disease were inoculated by the decapitation technique with Xanthomonas albilineans. The effects of disease progress and incidence on yields were studied for the plant (first harvest) and two ratoon crops (second and third harvest). The percentage of diseased stalks and disease severity at first harvest 5 months after inoculation were 0·7 and 0·4, respectively, for the most resistant cultivar and 71·0% and 63·3, respectively, for the most susceptible cultivar. They decreased in all cultivars in both ratoon crops, but were still important in one cultivar (B69379). Significant ( P = 0·05) yield reductions of 12% and 21% occurred in two of the seven cultivars (B69566 and B69379, respectively). The number of symptomatic sugarcane stalks in the first ratoon crop (second harvest) was lower than the number of stalks colonized by the pathogen. Symptoms and yield losses of cultivars R570 and B69566 varied with the crop. Yield losses occurred in cultivar R570 only in the plant crop when this cultivar displayed numerous symptoms. Cultivar B69566 appeared to recover from the disease to a certain extent from the plant to the second ratoon crop (third harvest), as did the resistant cultivars in the first ratoon crop. In contrast, severe leaf scald symptoms were observed in the case of cultivar B69379 regardless of the crop, and significant yield losses occurred in the two ratoon crops. These results support the recommendation that cultivar B69379 should not be replanted in Guadeloupe.     

四川省小麦品种抗条锈现状及对策措施

近年来小麦条锈病在四川连年大发生。究其原因,最主要是大面积生产小麦品种抗锈性的丧失。分析本省小麦品种抗锈性现状,是新审定品种区试抗性水平有较大提高,但新品种一经大面积推广后抗锈性衰退现象十分严重。目前本省已采取多种有效措施,包括提高品种审定时的抗锈性指标,实行老品种"退役"制,加大品种更换的力度和合理品种布局,以及建立科学的抗锈性评价体系等。但要进一步提高本省小麦品种的整体抗锈性水平以控制小麦条锈病的发生和为害,还需要加强品种抗源及其抗性遗传背景的研究,加强学科间协作和对外交流,加大良种补贴面等。     

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。     

小麦品种对小麦白粉病菌侵染信号传递初探

 通过测定抗病性不同的小麦品种在接种小麦白粉病菌后钙调素含量的变化发现其存在差异。如抗病品种钙调素含量高峰出现在接种后4 h,即寄主与白粉病菌接触阶段。而感病品种接种后24 h出现钙调素含量高峰。比较测定了不同的钙调素抑制剂对小麦品种抗白粉性的影响,发现10mmol/L TFP和5 mmol/L CPZ处理使抗病品种变为高度感病,50 mmol/L CPZ处理使小麦感染白粉菌后反应型下降,表明钙调素与小麦抗白粉性有关。     

A New Source of Resistance to Tapesia yallundae Associated with a Homoeologous Group 4 Chromosome in Thinopyrum ponticum

ABSTRACT Wheat (Thinopyrum ponticum line SS767; PI 611939) with 42 chromosomes previously was identified as a new source of eyespot resistance. Individual plants of SS767 were tested for reaction to Tapesia yallundae, the major pathogen of eyespot in the Pacific Northwest region of the United States. Resistance of this line was similar to the resistant winter wheat cv. Madsen (carrying gene Pch1 for eyespot resistance). Polymerase chain reaction analysis with primers specific for the J or E genomes revealed that SS767 contains Thinopyrum chromatin. Cytological and Cbanding analyses demonstrated that SS767 is a chromosome substitution line in which wheat chromosome 4D is replaced by a homoeologous group 4 chromosome of Thinopyrum ponticum. Genomic in situ hybridization using St genomic DNA from Pseudoroegneria strigosa as a probe, which can differentiate chromosomes from different genomes of Thinopyrum, indicated that this chromosome belongs to the J genome. Molecular analysis of an F(2) population segregating for chromosome 4J and resistance to eyespot confirmed that eyespot resistance in line SS767 is associated with chromosome 4J of Thinopyrum ponticum. This is the first report of genetic control of resistance to eyespot derived from Thinopyrum ponticum. This source of resistance provides a new opportunity to improve wheat resistance to eyespot by adding to the diversity of resistance sources available.     

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.     

Jasmonic acid induces resistance to economically important insect pests in winter wheat

BACKGROUND: Insect damage induces chemical changes in plants, and frequently these changes are part of a defensive response to the insect injury. Induced resistance was activated in winter wheat using a foliar application of synthetic jasmonic acid. Field trials were conducted to observe effects of jasmonic acid application on some wheat insects. Two wheat cultivars (Cubus and Tommi) were sprayed twice at growth stages (GS) 41 and 59 with two concentrations of jasmonic acid, along with control plots that were sprayed with water. RESULTS: There was a significant difference in the number of thrips and wheat blossom midges (WBM) among treatments in both cultivars. Plants in control plots had higher numbers of thrips and midges than in treated plots. There were higher numbers of thrips in the Tommi cultivar than in the Cubus cultivar, while the latter had higher numbers of WBM larvae than the Tommi cultivar. There was a positive correlation between WBM numbers and infested kernels in both cultivars. This study also indicated that jasmonic acid enhances the wheat yield in sprayed plots compared with control plots. CONCLUSIONS: The results indicate that jasmonic acid induced pest resistance in wheat plants and may act as a resistance mechanism of wheat against insect herbivores. Copyright © 2010 Society of Chemical Industry     

Effects of disease and plant competition on yield in monocultures and mixtures of two wheat cultivars

Disease seventy and crop yield were compared in monocultures and mixtures of two wheat cultivars. one susceptible and one resistant to Puccinia graminis f. sp. tritici. Part of each plot was inoculated and part treated with fungicide. Rust seventy was inversely related to the proportion of resistant plants present. Weight of grain in 100 heads of the susceptible cultivar increased as the amount of rust decreased. The susceptible cultivar yielded less than the resistant cultivar in monoculture, but was a stronger competitor in mixtures. Competitive abilities of the cultivars were independent of severity of rust in the mixtures studied.     

Evaluation and characterization of resistance to fusarium head blight caused by Fusarium culmorum in UK winter wheat cultivars

Fusarium head blight (FHB) resistance of 50 cultivars from the National List of winter wheat cultivars approved for sale (or were undergoing trails for approval in 2003) in the UK was compared with 21 reference cultivars from continental Europe which had previously been characterized for resistance. Only three UK National List cultivars (Soissons, Spark and Vector) had stable resistance over trial sites that was significantly greater than that of the FHB susceptible cultivar Wizard. In addition, under moderate disease pressure, 21 of the National List cultivars had levels of the trichothecene mycotoxin deoxynivalenol (DON) above the proposed European Union limit of 1·25 ppm in grain. Surveys show that levels of FHB and DON in the UK crop are currently very low, however, should disease pressure increase for any reason, then an improvement in the overall levels of FHB resistance of UK winter wheat germplasm will be required. In order to infer the origin of resistance and to identify potentially novel resistance, allele sizes of microsatellite (simple sequence repeat, SSR) markers linked to quantitative trait loci (QTL) for FHB resistance were compared between the test cultivars and known, characterized resistance sources. The major FHB resistance QTL from the Chinese cv. Sumai-3 (3BS, 5A and 6B), the Romanian cv. Fundulea F201R (1B and 5A) and the French cv. Renan (5AL) were screened with 17 SSRs. No National List cultivar had haplotypes similar to any of these QTL. However, the highly resistant German reference cultivar Petrus had an identical haplotype to cv. Fundulea F201R on 1B indicating that this cultivar has an allelic FHB resistance QTL at that location.     

Development of natural late blight epidemics in pure and mixed plots of potato cultivars with different levels of partial resistance

Late blight, caused by Phytophthora infestans , is the most severe disease of potato worldwide. Controlling late blight epidemics is difficult, and resistance of host cultivars is either not effective enough, or too easily overcome by the pathogen to be used alone. In field trials conducted for 3 years under natural epidemics, late blight severity was significantly lower in a susceptible cultivar growing in rows alternating with partially resistant cultivars (mixtures) than in unmixed plots of the susceptible cultivar alone. Partially resistant cultivars behaved similarly in unmixed and mixed plots. Mixtures of cultivars reduced disease progress rates and sometimes delayed disease onset over unmixed plots, but did so significantly only for the slowest epidemic. This suggests that reduction of area under the disease progress curve (AUDPC) in mixtures resulted from the cumulative action of minor effects. Disease distribution was focal in all plots at all dates, as shown by Morisita's index values significantly exceeding 1. Significant yield increases for the susceptible cultivar, and occasionally for the partially resistant ones, were observed in mixed-cultivar plots compared with single-cultivar plots. These results show that cultivar mixtures can significantly reduce natural, polycyclic epidemics in broadleaved plants attacked by pathogens causing rapidly expanding lesions.