The role of temperature and rainfall in the epidemiology of Puccinia striiformis f.sp. tritici in the summer rainfall area of eastern Australia

Infection of wheat seedlings by Puccinia striiformis f.sp. tritici was investigated under both laboratory (constant temperature) and field conditions using a 15-h period of 100% r.h. In laboratory studies, infection decreased from 100% at 15 4 C to 0.8% at 20.5 C, and it was estimated that no infection would occur at or above 20.8 + 0.2 C. In contrast, high levels of infection occurred under field conditions even when temperatures fluctuated within the range 19–30°C. Overnight infection experiments conducted at Toowoomba over an 18-month period demonstrated that periods of moisture and temperature favouring infection by P. striiformis f.sp. tritici occurred regularly, even during summer, and that high temperature was a limiting factor on only 3% of the nights tested. This indicates that stripe rust could oversummer readily in this region of the eastern Australian wheat belt, at least in sheltered areas, given a susceptible host. Regression equations relating mean temperature to infection and minimum temperature to infection identified mid to late autumn as an important period in the epidemic development of the disease in this region. The amount of rain recorded during this period was closely associated with subsequent levels of stripe rust observed in commercial crops over the years 1983–87.     

Microsatellite markers for genes lr34/yr18 and other quantitative trait Loci for leaf rust and stripe rust resistance in bread wheat

ABSTRACT Leaf rust and stripe rust, caused by Puccinia triticina and P. striiformis, respectively, are important diseases of wheat in many countries. In this study we sought to identify molecular markers for adult plant resistance genes that could aid in incorporating such durable resistance into wheat. We used a doubled haploid population from a Japanese cv. Fukuho-komugi x Israeli wheat Oligoculm cross that had segregated for resistance to leaf rust and stripe rust in field trials. Joint and/or single-year analyses by composite interval mapping identified two quantitative trait loci (QTL) that reduced leaf rust severity and up to 11 and 7 QTLs that might have influenced stripe rust severity and infection type, respectively. Four common QTLs reduced stripe rust severity and infection type. Except for a QTL on chromosome 7DS, no common QTL for leaf rust and stripe rust was detected. QTL-7DS derived from 'Fukuho-komugi' had the largest effect on both leaf rust and stripe rust severities, possibly due to linked resistance genes Lr34/Yr18. The microsatellite locus Xgwm295.1, located almost at the peak of the likelihood ratio contours for both leaf and stripe rust severity, was closest to Lr34/Yr18. QTLs located on 1BL for leaf rust severity and 3BS for stripe rust infection type were derived from 'Oligoculm' and considered to be due to genes Lr46 and Yr30, respectively. Most of the remaining QTLs for stripe rust severity or infection type had smaller effects. Our results indicate there is significant diversity for genes that have minor effects on stripe rust resistance, and that successful detection of these QTLs by molecular markers should be helpful both for characterizing wheat genotypes effectively and combining such resistance genes.     

Expression of adult plant resistance and its effect on the development of Puccinia striiformis f.sp. tritici in some Australian wheat cultivars

The onset of adult plant resistance (APR) to Puccinia striiformis was examined in seven Australian wheat cultivars under field conditions and in 14 cultivars under controlled environmental conditions. In most cultivars under field conditions the percentage leaf area affected by stripe rust at mid-tillering (GS 22–26; third leaf) was significantly less ( P < 0.05) than on the more susceptible cultivar Teal. The expression of APR was more conspicuous during tillering to node formation; at these growth stages chlorosis and/or necrosis developed in association with rust colonies on the most resistant cultivars. Under controlled conditions, the primary leaves of all cultivars except Olympic and Flinders displayed some resistance when compared with Teal (lower infection types, longer latent periods and/or less percentage leaf area affected). Studies on the spread of stripe rust from infection foci established in selected cultivars in the field indicated that the resistance detected at early growth stages in Suneca in controlled environmental studies also appeared to be effective in the field.     

Inheritance and molecular mapping of barley genes conferring resistance to wheat stripe rust

ABSTRACT Most barley cultivars are resistant to stripe rust of wheat that is caused by Puccinia striiformis f. sp. tritici. The barley cv. Steptoe is susceptible to all identified races of P. striiformis f. sp. hordei (PSH), the barley stripe rust pathogen, but is resistant to most P. striiformis f. sp. tritici races. To determine inheritance of the Steptoe resistance to P. striiformis f. sp. tritici, a cross was made between Steptoe and Russell, a barley cultivar susceptible to some P. striiformis f. sp. tritici races and all tested P. striiformis f. sp. hordei races. Seedlings of parents and F(1), BC(1), F(2), and F(3) progeny from the barley cross were tested with P. striiformis f. sp. tritici races PST-41 and PST-45 under controlled greenhouse conditions. Genetic analyses of infection type data showed that Steptoe had one dominant gene and one recessive gene (provisionally designated as RpstS1 and rpstS2, respectively) for resistance to races PST-41 and PST-45. Genomic DNA was extracted from the parents and 150 F(2) plants that were tested for rust reaction and grown for seed of F(3) lines. The infection type data and polymorphic markers identified using the resistance gene analog polymorphism (RGAP) technique were analyzed with the Mapmaker computer program to map the resistance genes. The dominant resistance gene in Steptoe for resistance to P. striiformis f. sp. tritici races was mapped on barley chromosome 4H using a linked microsatellite marker, HVM68. A linkage group for the dominant gene was constructed with 12 RGAP markers and the microsatellite marker. The results show that resistance in barley to the wheat stripe rust pathogen is qualitatively inherited. These genes might provide useful resistance against wheat stripe rust when introgressed into wheat from barley.     

The sensitivity of the epidemic growth rate to weather variables, with an application to yellow rust on wheat

ABSTRACT We first show how to estimate the exponential epidemic growth rate, r, for different combinations of three weather variables. Then we derive a method to quantify the sensitivity of r to a weather variable as a function of the pathogen life cycle variables of latent period, basic reproductive number, and the mean and standard deviation of the sporulation curve. The method can be used to identify the most important weather variable and pathogen life cycle component in terms of epidemic progress. The method is applied to yellow rust, caused by Puccinia striiformis, on winter wheat. We conclude that the most important weather variable for the progress of yellow rust is temperature, followed by dew period and light quantity. By far, the most important pathogen life cycle component is the basic reproductive number, especially at low and high temperatures. This disagrees with the general view that latent period is the most important variable at low temperatures. We discuss explanations of this.     

The control of Asian rust by glyphosate in glyphosate-resistant soybeans

BACKGROUND: Glyphosate is a widely used broad-spectrum herbicide. Recent studies in glyphosate-resistant (GR) crops have shown that, in addition to its herbicidal activity, glyphosate exhibits activity against fungi, thereby providing disease control benefits. In GR wheat, glyphosate has shown both preventive and curative activities against Puccinia striiformis f. sp. tritici (Erikss) CO Johnston and Puccinia triticina Erikss, which cause stripe and leaf rusts respectively. RESULTS: Laboratory studies confirmed earlier observations that glyphosate has activity against Phakopsora pachyrhizi Syd & P Syd which causes Asian soybean rust (ASR) in GR soybeans. The results showed that glyphosate at rates between 0.84 and 1.68 kg ha(-1) delayed the onset of ASR in GR soybeans. However, field trials conducted in Argentina and Brazil under natural infestations showed variable ASR control from application of glyphosate in GR soybeans. Further field studies are ongoing to define the activity of glyphosate against ASR. CONCLUSIONS: These results demonstrate the disease control activities of glyphosate against rust diseases in GR wheat and GR soybeans.     

Molecular marker mapping of leaf rust resistance gene lr46 and its association with stripe rust resistance gene yr29 in wheat

ABSTRACT Leaf and stripe rusts, caused by Puccinia triticina and P. striiformis, respectively, are globally important fungal diseases of wheat that cause significant annual yield losses. A gene that confers slow rusting resistance to leaf rust, designated as Lr46, has recently been located on wheat chromosome 1B. The objectives of our study were to establish the precise genomic location of gene Lr46 using molecular approaches and to determine if there was an association of this locus with adult plant resistance to stripe rust. A population of 146 F(5) and F(6) lines produced from the cross of susceptible 'Avocet S' with resistant 'Pavon 76' was developed and classified for leaf rust and stripe rust severity for three seasons. Using patterns of segregation for the two diseases, we estimated that at least two genes with additive effects conferred resistance to leaf rust and three to four genes conferred resistance to stripe rust. Bulked segregant analysis and linkage mapping using amplified fragment length polymorphisms with the 'Avocet' x 'Pavon 76' population, F(3) progeny lines of a single chromosome recombinant line population from the cross 'Lalbahadur' x 'Lalbahadur (Pavon 1B)', and the International Triticeae Mapping Initiative population established the genomic location of Lr46 at the distal end of the long arm of wheat chromosome 1B. A gene that is closely linked to Lr46 and confers moderate levels of adult plant resistance to stripe rust is identified and designated as Yr29.     

Simulation studies on epidemics of wheat stripe rust (Puccinia striiformis) on slow-rusting cultivars and analysis of effects of resistance components

Simulation studies were conducted to analyse the effects of components of slow-rusting resistance to stripe rust ( Puccinia striiformis ) on wheat varieties using the Slow-Rusting Epidemic Simulation Model (SRESM). Five components, infection efficiency (IE), sporulation capacity (SC), lesion expansion rate (LE), latent period (LP) and infectious period (IP) were studied for their importance in epidemics under various weather and pathogen inoculum conditions. Simulation outputs were analysed statistically. The LE, IE and SC were found to be the most important components. However, final disease was more strongly influenced by weather and initial disease. The Integrated Resistance Index (IRJ), which combines the effects of resistance components, was used to predict the effects of various combinations of components in different types of weather and at different levels of initial disease intensity. These predictions provide guidelines for plant breeders and are useful in selecting varieties for specific regions.     

小麦锈菌夏孢子经盐酸处理后的形态观察

为了快速区分小麦条锈菌、叶锈菌和秆锈菌,用不同浓度的盐酸处理3种小麦锈菌的新鲜夏孢子和在4 ℃冰箱内保存4个月以上的锈菌夏孢子,在显微镜下观察夏孢子形态以及原生质体变化。结果表明, 24.5%、28.5%、32.5%、36.5%4种浓度的盐酸处理条锈菌夏孢子后其原生质体均浓缩成多个分散的小团。而同样方法处理叶锈菌和秆锈菌新鲜菌种时其原生质体浓缩成一个大团或多个小团,浓缩成一个大团的比例随盐酸浓度的增大而提高;用不同浓度盐酸处理保存4个月以上的2种小麦锈菌时,95%以上的夏孢子原生质体浓缩成多个分散的小团,少数（不超过5%）的夏孢子原生质体浓缩成一个大团。研究还发现叶锈菌和秆锈菌夏孢子活力、盐酸浓度等对夏孢子原生质体浓缩状况有很大影响,且与病菌生理小种有一定的关系。因此,锈菌夏孢子经36.5%浓盐酸处理后的原生质体浓缩状况只能作为小麦锈病田间快速诊断检测的辅助手段,不能作为锈病种类鉴别的唯一标准,必须结合病害症状特征、孢子形态以及分子生物学方法等进行综合判别。     

中国小麦条锈菌鉴别寄主维尔对条锈病的温敏抗性研究

维尔是中国小麦条锈菌重要鉴别寄主,通过潜育期变温处理对其进行温敏抗性检测和基因推导分析。本研究发现,维尔对小麦条锈菌流行小种条中32号的抗性表现为侵染型由常温下的高侵染型向高温下的低侵染型转变,侵染指数降低,呈现高温诱导抗条锈性;通过与已知的微效基因品系比较及方差分析,推测维尔对条中32号的温敏抗性可能是由2对高温诱导表达的温敏微效基因控制。建议将维尔作为温敏微效基因资源在抗病育种中利用,作为鉴别寄主用于小种鉴定时,要严格控制鉴定温度,不要超过18 ℃。     

小麦条锈菌冬孢子生物学特性研究进展

由小麦条锈菌引起的小麦条锈病是我国广大麦区的严重病害,研究其冬孢子产生原因与作用对于解析该病菌的生活史及遗传变异机制至关重要.通过对国内外相关研究成果的整理,综述了小麦条锈菌冬孢子的形态特征、生物学特性、寄主范围及其作用与功能等方面的研究进展.     

Models for predicting potential yield loss of wheat caused by stripe rust in the U.S. Pacific Northwest

Climatic variation in the U.S. Pacific Northwest (PNW) affects epidemics of wheat stripe rust caused by Puccinia striiformis f. sp. tritici. Previous models only estimated disease severity at the flowering stage, which may not predict the actual yield loss. To identify weather factors correlated to stripe rust epidemics and develop models for predicting potential yield loss, correlation and regression analyses were conducted using weather parameters and historical yield loss data from 1993 to 2007 for winter wheat and 1995 to 2007 for spring wheat. Among 1,376 weather variables, 54 were correlated to yield loss of winter wheat and 18 to yield loss of spring wheat. Among the seasons, winter temperature variables were more highly correlated to wheat yield loss than the other seasons. The sum of daily temperatures and accumulated negative degree days of February were more highly correlated to winter wheat yield loss than the other monthly winter variables. In addition, the number of winter rainfall days was found correlated with yield loss. Six yield loss models were selected for each of winter and spring wheats based on their better correlation coefficients, time of weather data availability during the crop season, and better performance in validation tests. Compared with previous models, the new system of using a series of the selected models has advantages that should make it more suitable for forecasting and managing stripe rust in the major wheat growing areas in the U.S. PNW, where the weather conditions have become more favorable to stripe rust.     

甘肃中部麦区小麦条锈病菌越夏调查及品种抗性变异监测结果初报*

2007-2009年,对甘肃省中部麦区小麦条锈病越夏情况进行调查,结果发现：条锈病菌在定西、临夏等中部麦区海拔1 718~2 350 m地带自生麦苗上可顺利越夏,病田率和病叶率分别为63.0%~80.0%和1.05%~5.80%,其越夏菌源量比陇南更大,是当地秋苗发病的初侵染源;秋苗病情调查结果表明,中部麦区秋苗病田率和病叶率均高于同期陇南麦区;品种抗性监测结果发现,34个供试品种（系）在中部麦区和陇南麦区的抗条锈性表现基本一致,部分品种发病程度重于陇南麦区。表明甘肃省定西、临夏等中部麦区已成为陇南小麦条锈病越夏区的重要组成部分。文中还对中部麦区越夏菌源的影响、作用及品种抗性变异因素等进行了讨论。     

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。     

GUS基因插入导致的小麦条锈菌突变体遗传稳定性和毒性变异研究

 对3个通过基因枪转化GUS基因获得的小麦条锈菌毒性突变体,进行GUS基因的表达活性检测、插入片段DNA的PCR电泳检测和Southern杂交验证;同时用17个国内鉴别寄主和37个黄淮麦区小麦主栽品种对这3个突变菌株进行了毒性谱的测定。结果表明突变菌株的外源GUS基因可稳定遗传;插入的外源基因片段引起了菌株毒性谱的改变。外源基因的插入位点与条锈菌的毒性基因相关。研究还表明插入突变体具有相对的遗传稳定性。研究结果可为克隆小麦条锈菌毒性基因和探明毒性基因的作用机理奠定理论基础。     

81份春小麦种质资源抗条锈病评价

本研究结合苗期分小种接种和大田成株期自然诱发条件下对供试的81份春小麦资源进行抗条锈病鉴定,分析其抗条锈病情况、抗病类型及抗病性关系,结果表明:具全生育期抗条锈病类型的资源有7份,具成株期抗条锈病类型的资源有39份,有30份资源为含有成株期和对部分小种失去抗性的全生育期抗病性的抗性类型;苗期分别接种7个小种后,表现抗病的资源数为9~25份不等,表现中抗的资源为2~6份不等,表现感病的有50~69份不等,成株期表现抗病的73份,表现中抗的3份,感病的5份,即供试种质资源大部分表现为苗期感病,而成株期具有抗病性。聚类分析结果表明,该81份种质资源抗性聚类相对分散,遗传多样性水平较高。研究结果为小麦育种提供优良的抗条锈性资源。     

应用real-time PCR 定量检测田间小麦条锈菌潜伏侵染的研究

 为快速、及时地定量检测处于潜育状态下的小麦条锈菌菌量,本研究于2009－2010年实施田间试验,在北京和甘肃各设3个试验小区,将小区分割成1 m×1 m或1.5 m×1.5 m的小格。初春刚返青叶片出现症状前,在每小格内采集30片叶,提取叶片基因组DNA,应用已建立的real-time PCR定量测定方法,计算每个样本的分子病情指数(molecular-detected disease index, MDI）。在本试验的天气条件和试验设计下,采样10 d后,调查田间标记采样点的发病情况,计算病情指数DI,比较MDI和DI的关系,建立回归模型。结果表明：甘肃甘谷3个试验小区的MDI和DI存在极显著的相关性（R₂¹=0.813 6,R₂²=0.884 5,R₂³=0.592 8）;北京上庄3个试验小区的MDI和DI也存在极显著的相关性（R₂¹=0.742 3,R₂²=0.578 4,R₂³=0.858 4）。本研究证明了应用分子生物学方法可估测小麦条锈病潜育侵染程度的可能性,为建立分子定量测定田间潜育侵染量系统提供了可靠依据。     

豫鲁皖三省重要小麦品种抗条锈基因推导

 根据对26个不同毒性谱的小麦条锈菌菌系的反应,并结合品种系谱分析,研究了河南、山东和安徽3省的50个重要小麦生产品种所具有的抗条锈基因。结果表明,没有1个品种可抵抗所有供试的26个条锈菌菌系,在已知的抗条锈基因中Yr 9所占比例最大,至少存在于17个品种中,Yr 2和Yr 1次之,分别存在于10个和8个品种中,个别品种则具有Yr A、Yr 3或Yr Sel,还有些品种可能具有未知的抗条锈基因或基因组合。由于上述已知基因对目前的条锈菌优势小种基本上均不抵抗,培育和推广具有效抗条锈基因的新品种迫在眉睫。     

我国小麦秋苗条锈病发生规律及其区间菌源传播关系

全国冬小麦秋苗均可遭受来自西北和西南越夏区条锈菌的侵染与危害, 条锈菌在寄主上进一步繁殖和发展, 引起本地或者外地小麦条锈病流行。不同麦区秋苗条锈病发生时间、发生程度及其菌源传播规律各不相同, 年度间亦存在差异。根据小麦条锈病发生流行频率、病菌越冬和越夏情况、秋季菌源和春季菌源的有无与多少、提供时间及其影响范围与作用, 结合地理生态条件、气候特点、小麦种植区划与栽培模式等, 将中国小麦条锈病发生流行区域划分为8个明显不同的生态区系, 即关中、华北春季流行区; 成都平原、江汉流域冬季繁殖区; 西北、川西北越夏易变区; 云贵高原越夏冬繁区; 新疆冬春麦常发区; 西藏高原青稞、小麦常发区; 南方晚播冬麦偶发区; 内蒙古、东北春麦偶发区。通过病害实地调查、病菌群体遗传多样性和高空气流轨迹分析, 进一步揭示了区间菌源传播关系。陇南、陇中、陇东、宁南、海东、陕西宝鸡以及川西北和云贵高原等地区离越夏区较近, 冬小麦播种较早, 秋苗条锈病发生早、发病重, 秋季随西北气流传播到平原冬麦区和海拔较低的冬麦区侵染危害秋播麦苗, 其菌源数量对全国小麦条锈病发生流行程度起着至关重要的作用, 是中国小麦条锈病的秋季菌源基地, 面积约67万hm2; 成都平原、江汉流域、陕南、豫南、云贵坝区等麦区, 离条锈菌越夏区相对较远, 小麦播种期也较晚, 秋苗发病较晚较轻, 但冬季气候温和, 雨露条件充沛, 条锈菌在冬季可以不断侵染和繁殖, 在早春可积累大量菌源, 然后向北部和西部广大麦区扩散传播, 引起小麦条锈菌春季侵染, 是中国小麦条锈病的春季菌源基地, 面积约200万hm2。云贵高原越夏冬繁区可为我国广大麦区特别是长江中下游麦区提供部分菌源, 荆州等鄂东南地区是云贵菌源向长江下游麦区传播的中转站。云南与甘肃之间存在大量的基因流, 推测云南可能是中国小麦条锈菌重要的起源中心。西南和西北秋季菌源对长江流域麦区的相对重要性有待进一步研究明确。     

86份贵协系小麦种质资源对条锈病的抗病性评价

小麦条锈病是发生于甘肃陇南麦区小麦生产上的最主要病害,利用和种植抗病品种(系)是防治该病害最经济有效且有利于保护环境的措施。2011-2013年度连续两年在甘肃省农业科学院植物保护研究所甘谷试验站田间对86份来自贵州大学的贵协系小麦种质资源材料进行了成株期抗条锈病鉴定,结果发现仅有‘贵协1’、‘贵协2’、‘贵协3’、‘贵协7’、‘贵协011-2-6’、‘贵协011-3-16’、‘贵协011-3-29’、‘贵协011-3-31’、‘贵协011-3-34’等9份材料表现抗病,且抗病性相对稳定,可作为一线抗源材料在陇南抗病育种中充分利用。