Systems analysis of wheat stripe rust epidemics in China

Stripe rust is the most destructive disease of wheat in China and shows long-distance spread with interregional epidemics. Systems analysis had been implemented by the epidemiology group at the China Agricultural University to study the epidemiology of this disease from field to regional levels. This paper reviews major achievements by this group from the 1970s to the present in this pathosystem in China. Field experiments were conducted to obtain necessary parameters for constructing various simulation models. Field-level models were generated to study the spatial and temporal disease developments, while region-level models were developed to study the disease long-distance spread, interregional epidemics and strategies for disease management. Interactions between host, pathogen and environment were also studied with modelling approaches to generate information on deployment of resistance for regional disease management.     

水稻条纹叶枯病产量损失与防治指标研究初报

通过对条纹叶枯病不同病情与产量损失关系的研究,初步探明了水稻条纹叶枯病对产量的影响,病株率(x)与产量损失率(y)之间的关系为正相关,回归方程为y=1.06 0.84x(R=0.9278)。据此提出水稻条纹叶枯病的防治指标为病株率3%。     

山西小麦品种和育种材料抗锈病、白粉病鉴定

2011—2015年,采用人工接菌方法,对25个育种单位的601份小麦品种和育种材料进行了小麦条锈病、叶锈病和白粉病的抗病性鉴定,筛选出对小麦条锈病抗性表现良好的品种材料36份,对小麦叶锈病抗性表现良好的品种材料16份,对小麦白粉病抗性表现良好的品种材料12份。     

2006年西北川西北小麦条锈病越夏概况和有关问题的探索

简述了2006年我国重要越夏区西北和川西北小麦条锈病菌越夏概况和特点,分析了条锈病越夏菌量低的原因,提出了进一步对小麦条锈病菌源区精准勘界、验证和评价定西和临夏等地菌源作用和地位,探求条锈病菌越夏菌源量引起全国大部地区流行的作用底限的建议。     

Proteome profiling of the compatible interaction between wheat and stripe rust

Over the last decade, comparative molecular profiling studies between compatible and incompatible plant-pathogen interactions have shown that susceptible response of the host to a pathogen requires factors that promote disease development. In this study, we examined proteome profiles during a compatible interaction between wheat and stripe rust. A 2D-LC system (ProteomeLab PF2D) was used for protein separation and to compare the proteome from infected and control samples. More than 700 protein peaks at each time point were compared between pathogen- and mock-inoculated samples. Selected proteins, with significant differences in abundance were identified by nanoLC-ESI- MS/MS and generated spectra were searched against the wheat protein databases from UniProt, and NCBI and the Puccinia database from The Broad Institute. In total, the identified proteins comprised of 62 % wheat and 38 % Pst proteins. All identified proteins were searched by bioinformatics-based algorithms to detect their subcellular localization and signal peptide motifs which have the potential to catch the candidate effector proteins. The wheat proteins were classified based on their function. Although a compatible interaction, many wheat proteins, such as antioxidants, PRs and cold-responsive proteins, are implicated in defense and stress tolerance. On the pathogen side, 64 proteins were identified, and included some important pathogenicity proteins that can play role in pathogen virulence and suppress the host defense. In addition, we discovered that nine proteins have a signal sequence and three of the hypothetical fungal proteins, PGTG_11681T0, PGTG_07231T0 and CBH50687.1, have been tentatively identified as candidate effectors.     

Virulence of Gaeumannomyces graminis var. tritici from fields under short-term and long-term wheat cultivation in the Pacific Northwest, U.S.A.

Gaeumannomyces graminis var. tritici was recovered from 63% of 731 winter wheat plants collected randomly from six sites where wheat had been grown in monoculture for the previous 7–22 years. Typical take-all was not evident at the time the plants were collected. The fungus was isolated by a baiting method without regard to the presence of take-all on the plants. Isolates from fields under short-term wheat cultivation (3 years or less after a break crop) were obtained by plating directly from infected roots of plants with typical take-all. Virulent isolates comprised 89 and 99% of those collected from long- and short-term wheat cultivation respectively. There was also only a slight difference in the proportions of virulent isolates among monoascosporic subcultures from the two groups of isolates. There was thus little evidence that, during prolonged wheat cultivation, declining virulence in the population of G. graminis var. tritici could account for the absence of take-all.     

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.     

甘肃河东地区小麦条锈病(Wheat Stripe Rust)越夏指标的修订

小麦条锈病越夏气象指标,目前仍沿用二十世纪六十年代的研究结果,需要修订完善。文中利用甘肃河东地区2007-2014年50个不同海拔高度小麦条锈病单点病田率、病情指数调查资料、39个平均越夏病田率资料,采用统计学方法建立了小麦条锈病病情指数、平均病田率的气象统计模型,综合两种方法计算结果,确定了甘肃河东地区小麦条锈病越夏指标的上限为夏季最热时段8d滑动平均气温24~25℃,期间空气相对湿度越低对应的平均气温也越低。研究为当地准确发布中短期趋势预报,积极开展早期防治,控制病害越夏范围具有一定指导意义。     

Mapping of Aegilops umbellulata‐derived leaf rust and stripe rust resistance loci in wheat

Aegilops umbellulata, a non‐progenitor diploid species, is an excellent source of resistance to various wheat diseases. Leaf rust and stripe rust resistance genes from A. umbellulata were transferred to the susceptible wheat cultivar WL711 through induced homoeologous pairing. A doubly resistant introgression line IL 393‐4 was crossed with wheat cultivar PBW343 to develop a mapping population. Tests on BC₂F₇ RILs indicated monogenic inheritance of seedling leaf rust and stripe rust resistance in IL 393‐4 and the respective co‐segregating genes were tentatively named LrUmb and YrUmb. Bulked segregant analysis placed LrUmb and YrUmb in chromosome 5DS, 7.6 cM distal to gwm190. Aegilops geniculata‐derived and completely linked leaf rust and stripe rust resistance genes Lr57 and Yr40 were previously located in chromosome 5DS. STS marker Lr57/Yr40MAS‐CAPS16 (Lr57/Yr40‐CAPS16), linked with Lr57/Yr40 (T756) also co‐segregated with LrUmb/YrUmb. Seedling infection types differentiated LrUmb from Lr57. Absence of leaf rust‐susceptible segregants among F₃ families of the intercross (IL 393‐4/T756) indicated repulsion linkage between LrUmb and Lr57. YrUmb expressed a consistently low seedling response under greenhouse conditions, whereas Yr40 expressed a higher seedling response. Based on the origin of LrUmb/YrUmb from the U genome and Lr57/Yr40 from the M genome, as well as phenotypic differences, LrUmb and YrUmb were formally named Lr76 and Yr70, respectively. These genes have been transferred to Indian wheat cultivars PBW343 and PBW550, and advanced breeding lines are being tested in state and national trials.     

Histopathology provides a phenotype by which to characterize stripe rust resistance genes in wheat

The expression of the resistance phenotypes of QPst.jic‐2D and QPst.jic‐4B, two quantitative trait loci (QTL) for stripe rust resistance in wheat cv. Alcedo, were assessed relative to plant growth stage, while a histopathology analysis was undertaken to characterize the cellular interaction between Puccinia striiformis f. sp. tritici (the causal agent of stripe rust) and each QTL. QPst.jic‐2D expressed a partial resistant phenotype at seedling growth stages, with the level of resistance increasing as the wheat plant matured, conferring a disease‐free phenotype at heading. QPst.jic‐4B, however, did not express a resistant phenotype until booting (growth stage 41 on the Zadoks scale), displaying its full resistant phenotype at heading. Microscopic examination in flag leaves showed that infection sites formed in all genotypes tested, with full infection‐site establishment being observed by 36 h post‐inoculation (hpi). In lines carrying both QPst.jic‐2D and QPst.jic‐4B, as well as the parental cv. Alcedo, no microcolony formation, defined by the appearance of runner hyphae, was observed. Microcolony formation was observed in lines carrying only one, or neither QTL. Cell death associated with infection sites was observed for all genotypes, although the timing of first appearance and the extent of the cell death response varied considerably. In lines carrying both QPst.jic‐2D and QPst.jic‐4B cell death did not extend beyond one to three cells. In lines carrying only one QTL more extensive cell death was observed and cell death appeared later in lines with QPst.jic‐4B than QPst.jic‐2D. Cell death was also occasionally observed in lines without either QTL, although only at 264 hpi.     

临夏州2005年小麦条锈病越夏调查

临夏回族自治州地处甘肃西南部,境内海拔1600～4300m,属高寒阴湿地区。独特的地理环境、适宜的气候及丰富的寄主条件,非常适宜小麦条锈病的发生流行和越夏。2005年小麦条锈病在本州大流行,全州4郾01万hm2小麦全部发病。为了进一步明确本州小麦条锈病越夏状况,我们根据越夏区不同海拔高度和不同生态环境,在全州设15个固定调查点,从5月中旬开始,每旬进行1次调查记载,并适时开展了全州病情普查。1越夏病情1郾1冬、春小麦发病情况2004～2005年度全州种植小麦4郾01万hm2,其中冬小麦1郾47万hm2。2005年5月24日在康乐县虎关、临夏市枹罕等地发现病…     

The relationship between wheat yield and stripe rust as affected by length of epidemic and temperature at the grain development stage of crop growth

Stripe (yellow) rust, caused by Puccinia striiformis f. sp. tritici. was associated with mean losses of up to 84% in the yield of wheat in southern New South Wales, Australia, between 1984 and 1987. Yield loss became smaller in cultivars with increasing levels of resistance in adult plant reaction and did not appear in cultivars with seedling susceptibility and moderate or better adult plant reaction levels in the 3 years when epidemics began after emergence of the flag leaf. However, in 1984 the stripe rust epidemic began during stem elongation, and yield losses of up to 21% occurred in cultivars with seedling susceptibility and a moderate or better adult plant reaction.
Yield was significantly negatively correlated with the proportion of leaf area affected by stripe rust at stages of crop development from the end of heading to late milk. The correlation was greatest at the early milk stage of growth where the relationship was logarithmic. Two factors significantly influenced this relationship. Yield loss increased as the length of the epidemic increased, and decreased as temperature increased during grain development. The relationship that was developed for predicting yield loss accounted for 80-5% of the variance across all experiments, and was:
y = 100(1- e ^10-4×(393+165 L -141 T ))
where y = yield loss (%); X = stripe rust (leaf area affected, range 0-99%) at early milk; L = time from 1% disease to early milk (range 0-70 days); and T = mean daily maximum temperature from 7 days before to 14 days after early milk (range 198-27.5°C).     

六盘山晚熟冬麦条锈病发生特点及发病规律研究

庄浪县地处六盘山晚熟冬麦区,小麦是全县主要粮食作物之一。2005年全县冬小麦播种面积2.27万hm2,平均产量只有2586kg,究其原因是以小麦条锈病(Puccinia striifomis West.)为主的病虫为害所致。依据《甘肃省植保专业统计工作暂行规定》抽样调查,条锈病属大发生年份,全县化学防治面积1.8万hm2,挽回产量损失10011t,但由于综合防治措施落实不到位,仍造成全县小麦减产22.3%,实际产量损失2375t。因此,深入研究条锈病发生发展规律,对控制其为害,提高小麦产量和品质,增加农民收入有着重要的作用。1小麦条锈病发生情况从20世纪80年代初至今26年中,根…     

平凉市小麦条锈病发生流行趋势预测模型研究

通过对平凉市25年(1984～2008年)的小麦条锈病病情和气象资料综合分析,筛选出影响本市小麦条锈病越夏菌量、秋苗发病、翌年春季流行趋势的主要因子,并应用逐步回归方法建立了本市小麦条锈病越夏菌量、秋苗发病、翌年春季流行趋势预测模型.回测结果表明,模型预测准确率达73.9%～82.6%.对准确预测小麦条锈病短、中、长期发生流行趋势,指导当地乃至全国冬麦区适期开展综合治理、及时控制其为害,有着重要的作用.     

南充市2009年小麦条锈病大发生的特点及成功防控措施

南充市2009年小麦条锈病大发生.调查分析了该病大发生的特点、原因和防控的成效,总结了防控的成功经验.     

Soybean production in eastern and southern Africa and threat of yield loss due to soybean rust caused by Phakopsora pachyrhizi

Soybean is a major source of oil and proteins worldwide. The demand for soybean has increased in Africa, driven by the growing feed industry for poultry, aquaculture and home consumption in the form of processed milk, baked beans and for blending with maize and wheat flour. Soybean, in addition to being a major source of cooking oil, is also used in other industrial processes such as in the production of paints and candle wax. The demand for soybean in Africa so far outweighs the supply, hence the deficit is mainly covered through imports of soybean products such as soybean meal. The area under soybean production has increased in response to the growing demand, a trend that is expected to continue in the coming years. As the production area increases, diseases and insect pests, declining soil fertility and other abiotic factors pose a major challenge. Soybean rust disease, caused by the fungus Phakopsora pachyrhizi, presents one of the major threats to soybean production in Africa due to its rapid spread as a result of the ease by which its spores are dispersed by the wind. Disease control by introducing resistant soybean varieties has been difficult due to the presence of different populations of the fungus that vary in pathogenicity, virulence and genetic composition. Improved understanding of the dynamics of rust ecology, epidemiology and population genetics will enhance the effectiveness of targeted interventions that, in turn, will safeguard soybean productivity.     

新疆小麦条锈病发生特点及流行规律初探

根据2006年以来新疆各地植保站对小麦条锈病的系统调查结果,结合调查统计资料,分析了1990年以来新疆小麦条锈病的年度发生变化趋势,明确了近年来的主要发生区域.初步阐述了该病在新疆越夏、秋苗感染、越冬和春季流行的独立周年循环规律,首次提出新疆小麦条锈病越夏区的5种类型及其分布区域.分析认为,主栽品种抗病性丧失和气候变化是导致该病近年来严重流行的主要因素.对进一步摸清该病在新疆的流行规律需要重点研究的问题进行了讨论.     

秋季麦田翻耕与自生麦苗条锈病发生程度关系研究

在小麦条锈病核心越夏区对比试验结果表明.小麦收获后翻耕,具有降低自生麦苗密度、推迟生育期、降低条锈病发生程度,从而减少条锈病越夏菌源,降低秋苗发病程度的作用.相比较而言,机械翻耕比畜力翻耕的作用更明显.延迟到麦收后30 d翻耕比传统的麦收后10 d翻耕的作用更明显,翻耕后镇压耙磨有时表现有降低发病的作用.根据临夏地区特点.小麦收获后30 d左右、冬小麦播种前应进行耕翻,在平川麦区应加大机耕推广力度.考虑到耙磨还有保墒作用,翻耕后均应镇压耙磨.     

Species and Mating-Type Distribution of Tapesia yallundae and T. acuformis and Occurrence of Apothecia in the U.S. Pacific Northwest

ABSTRACT Eyespot of wheat is caused by the discomycete fungi Tapesia yallundae and T. acuformis. T. yallundae is considered the most important causal agent of the disease in this region but no apothecia of either species have been found in the U.S. Pacific Northwest (PNW). Two compatible isolates of T. yallundae from the PNW were used to inoculate a field plot in the fall of 1998 and apothecia developed in the spring and fall of 2000 on standing wheat stubble. In the spring of 2000, wheat stubble from eight naturally infected fields was examined for the presence of apothecia of T. yallundae and T. acuformis. Apothecia of T. acuformis were found in two fields but no apothecia of T. yallundae were found. This is the first report of apothecia of the eyespot pathogens occurring in the PNW. Species and mating-type distribution of T. yallundae and T. acuformis in the PNW were determined from 817 isolates collected from diseased wheat over 3 years at spatial scales ranging from within fields to across states. In all, 460 isolates were identified as T. yallundae and 357 isolates were identified as T. acuformis with MAT1-1/MAT1-2 ratios not significantly different from 1:1 based on chi(2) tests at most scales tested. The apparent increase in frequency of T. acuformis from previous surveys may indicate a shift in the predominant species causing eyespot. The occurrence of apothecia under field conditions, along with the widespread distribution of mating types of both species, suggests that sexual reproduction may be occurring in both species.