Seedling and adult plant resistance to leaf rust in 46 Chinese bread wheat landraces and 39 wheat lines with known Lr genes

Wheat leaf rust,caused by Puccinia triticina(Pt),is an important foliar disease that has an important influence on wheat yield.The most economic,safe and effective way to control the disease is growing resistant cultivars.In the present study,a total of 46 wheat landraces and 34 wheat lines with known Lr(leaf rust resistance)genes were inoculated with 16Pt pathotypes for postulating seedling resistance gene(s)in the greenhouse.These cultivars and five wheat differential lines with adult plant resistance(APR)genes(Lr12,Lr22b,Lr34,Lr35 and Lr37)were also evaluated for identification of slow rusting resistance in the field trials in Baoding,Hebei Province of China in the 2014–2015 and 2015–2016 cropping seasons.Furthermore,10 functional molecular markers closely linked to 10 known Lr genes were used to detect all the wheat genotypes.Results showed that most of the landraces were susceptible to most of the Pt pathotypes at seedling stage.Nonetheless,Lr1 was detected only in Hongtangliangmai.The field experimental test of the two environments showed that 38 landraces showed slow rusting resistance.Seven cultivars possessed Lr34 but none of the landraces contained Lr37 and Lr46.Lr genes namely,Lr9,Lr19,Lr24,Lr28,Lr29,Lr47,Lr51 and Lr53 were effective at the whole plant stage.Lr18,Lr36 and Lr45 had lost resistance to part of pathotypes at the seedling stage but showed high resistance at the adult plant stage.Lr34 as a slowing rusting gene showed good resistance in the field.Four race-specific APR genes Lr12,Lr13,Lr35 and Lr37 conferred good resistance in the field experiments.Seven race-specific genes,Lr2b,Lr2c,Lr11,Lr16,Lr26,Lr33 and LrB had lost resistance.The 38 landraces showed slow rusting resistance to wheat leaf rust can be used as resistance resources for wheat resistance breeding in China.

Identification and Molecular Tagging of Leaf Rust Resistance Gene (Lr24) in Wheat

This research was aimed to develop AFLP markers co-segregated with gene Lr24 and validate the using for marker assisted selection （MAS）. An F2 population developed from the cross between the resistant line TcLr24 and the susceptible line Thatcher was tested for resistance to the Puccinia triticina races BGQQ and SHRT using for genetic analysis and molecular marker. A total of 224 AFLP primer combinations were used to test the resistant and susceptible parents, as well as the resistant bulk and the susceptible bulk. Four AFLP markers, P-AGA/M-CTT289 bp, P-AGC/M-CAC1ss bp, P-AGC/M- CAC162 bp, and P-ACG/M-CGC239 bp, were co-segregated with Lr24. The AFLP fragment from the primer combination P- ACG/M-CGC was cloned, sequenced and converted into a STS marker named as ASTS212. Thatcher backgrounded NILs and 115 varieties were examined by using this STS marker and the marker SCS13026oz developed by Gupta. 5R615, 5R616, IR13, and 1R17 were identified and validated to contain gene Lr24. The marker is dominant and may be useful in identification the resistance gene Lr24 in wheat and wheat breeding programs.

Postulation of seedling leaf rust resistance genes in 84 Chinese winter wheat cultivars

Wheat leaf rust（caused by Puccinia triticina） is one of the most important fungal diseases in China. There are tens of winter wheat cultivars which are approved to be released by the government at a national level and more than 100 wheat cultivars at the provincial level. But there is no information about leaf rust（Lr） genes in these cultivars, which makes it difficult for farmers and breeders to select which cultivars they should plant in their fields and use in their breeding programs. The objective of this paper was to identify the leaf rust resistant genes at seedling stage present in the 84 commercial wheat cultivars from China that have been released in the past few years. A set of 20 near isogenic lines with Thatcher background and 6 lines with known Lr genes were used to test the virulence of 12 races of P. triticina（Pt）. By comparing the infection types（ITs） produced on the 84 cultivars by the 12 Pt races with the ITs on the differential sets, the Lr genes were postulated. In addition, 8 molecular markers of Lr genes such as Lr9, Lr10, Lr19, Lr20, Lr21, Lr24, Lr26 and Lr29, which are closely linked to or co-segregated with the Lr gene, were used for further validation of the genes in the 84 Chinese winter wheat cultivars. Twelve Lr genes, including Lr1, Lr3,（Lr3bg）,（Lr3ka）, Lr11, Lr13, Lr14 a, Lr16, Lr26, Lr27, Lr30 and Lr31 were postulated to be present either singly or in combinations in these Chinese wheat cultivars. Lr3 and Lr26 were detected most often in the tested cultivars, with frequencies of 51.2 and 38.1%, respectively. No wheat Lr genes were detected in 16 cultivars, and 4 cultivars may carry unknown Lr genes other than those used in this study. Lr9, Lr20, Lr21, Lr24, Lr25 and Lr29 were not present in any of the 84 tested accessions.

A SSR Marker for Leaf Rust Resistance Gene Lr19 in Wheat

Microsatellite was carded out in Thatcher, six near-isogenic lines and F2 progeny of TcLr19xThatcher to develop molecular markers for leaf rust resistance gene Lr19. Thirteen primer pairs were screened, of which one primer pair Xgwm44 displayed polymorphsim in the population of TcLr 19, Thatcher, and their F2 generations. One marker closed linked to Lr19 resistance trait was obtained, and was named Xgwm44139bp with the genetic distance 0.9 cM. The research shows that Lr19 has more potential in marker-assisted breeding programs in wheat and provides a step stone for mapping genetic map, physical map and the eventual cloning.

Identification of AFLP Markers Linked to Leaf Rust Resistance Genes Using Near Isogenic Lines of Wheat

The present investigation was undertaken to find molecular markers linked to leaf rust resistance genes, Lr9 and Kharchia local mutant KLM4-3B. Preliminary AFLP analysis was carried out with different stocks, a survey of primer combinations with different selective nucleotide indicated that for each primer combination, the number of scorable loci ranged from 34 to 123. Only a limited primer combination used in the set of parental and near isogenic lines showed a high level of polymorphism for AFLP marker. Putative AFLP marker were found to be linked to Lr9, Lr19 and KLM4-3B. The alien genes were readily identified.

Molecular Genetic Diversity in Iranian Populations of <i>Puccinia triticina</i>, the Causal Agent of Wheat Leaf Rust

Wheat leaf rust caused by Puccinia triticina, is the most common and widely distributed wheat rust in the world. In order to study the genetic structure of leaf rust population 14 pairs of AFLP and 6 pairs of FAFLP primers evaluated on 86 isolates samples collected in Iran during spring of 2009. Results showed that almost all investigated isolates were genetically different and special pattern of AFLP allele’s that confirm high genetic diversity within leaf rust population was observed. Analyses showed, all provinces were classified into three major groups particularly similar clusters were found between then neighboring provinces. Rust spore can follow the migration pattern in short and long distances to neighbor in provinces. Results indicated that the greatest variability was revealed by 97% of genetic differentiation within leaf rust populations and the lesser variation of 3% was observed between the rust populations. These results suggested that each population was not completely identical and high gene flow has occurred among the leaf rust population of different provinces. The highest differentiation and genetic distance among the Iranian leaf rust populations was detected between leaf rust population in Sistan and Baluchistan and highest similarity was observed between in Ardabil provinces. The high pathogenic variability of leaf rust races in Ardabil and Northern Khorasan may be an indication that these two regions are the center of origin of pathogenic arability. Present study shows that leaf rust population in Iran is highly dynamic and variable.

PCR-based molecular markers linked to the leaf rust resistance gene Lr19 in different bread wheat cultivars

61 varieties of wheat collected in the gene fund of the Research Institute of Crop Husbandry were screened using SCAR-markers associated with the gene of resistance to brown leaf rust, Lr19. As a result of PCR analysis using SCS123 marker the 737 bp locus was detected in 48 genotypes. The expected fragment of the 688 bp was detected in 53 genotypes using the SCS253 marker. The results obtained using both markers indicate that the Lr19 gene is present on 7D chromosomes of 45 genotypes. The existence of the Lr19 gene has not been proven only for 5 from the 61 analyzed wheat genotypes.

Molecular mapping of leaf rust resistance genes in the wheat line Yu 356-9

The Chinese wheat line Yu 356-9 exhibits a high level of resistance to leaf rust. In order to decipher the genetic base of resistance in Yu 356-9, gene postulation, inheritance analyses, and chromosome linkage mapping were carried out. Gene postulation completed using 15 leaf rust pathotypes and 36 isogenic lines indicated that Yu 356-9 was resistant to all pathotypes tested. F1 and F2 plants from the cross Yu 356-9 （resistant）/Zhengzhou 5389 （susceptible） were tested with leaf rust pathotype ＂FHNQ＂ in the greenhouse. Results indicated a 3：1 segregation ratio, indicative of the presence of a single dominant leaf rust resistance gene in Yu 356-9 which was temporarily designated as LrYu. Bulk segregant analysis and molecular marker assays were used to map LrYu. Five simple sequence repeat （SSR） markers on chromosome 2BS were found closely linked to LrYu. Among these markers, Xwmc770 is the most closely linked, with a genetic distance of 5.7 cM.

Molecular Markers for Leaf Rust Resistance Gene Lr45 in Wheat Based on AFLP Analysis

Amplified fragment length polymorphism （AFLP） analysis was carried out in Thatcher, near isogenic lines （NILs） canting different genes conferring resistance against wheat leaf rust, and TcLr45 × Thatcher F2 progenies were used to develop markers for Lr45 gene. Sixty AFLP primer combinations were screened and most of them provided clear amplification products, 31 primer combinations displayed polymorphism of TcLr45 in 23 NILs. Two AFLP markers closely linked to the gene Lr45 were acquired： P-AGG/M-GAG261bp, which was found closely linked to the Lr45 locus at a distance of 0.6 cM on one side, and P-ACA/M-GGT105bp, which was found at a distance of 1.3 cM on the other side. The specific hands were cloned and subsequently sequenced. The 261-bp fragment produced by P-AGG/M-GAG showed 86% similarity with the sequence of Vulgate Hort I gene; the 105-bp fragment produced by P-ACA/M-GGT showed 96% similarity with the phosphatidylserine decarboxylase gene of the Triticum monococcum. Both included an open reading frame （ORF）.

Advances in Localization and Molecular Markers of Wheat Leaf Rust Resistance Genes

Genetic resistance is the most economical method of reducing yield losses caused by wheat leaf rust. To identify the leaf rust resistance genes in commonly used parental germplasm and released cultivars become very important for utilizing the genetic resistance to wheat leaf rust fully. Up to date, about 90 leaf rust resistance genes have been found, of which 51 genes have been located and mapped to special chromosomes, and 56 genes have been designated officially according to the standards set forth in the Catalogue of Gene Symbols for wheat. Twenty-four wheat leaf rust resistance genes have been developed for their molecular markers. It is very important to isolate, characterize, and map leaf rust resistance genes due to the resistance losses of the genes caused by the pathogen continuously.

Phenotypic and Molecular Assessment of Wheat Genotypes Tolerant to Leaf Blight,Rust and Blast Diseases

Globally among biotic stresses,diseases like blight,rust and blast constitute prime constraints for reducing wheat productivity especially in Bangladesh.For sustainable productivity,the development of disease-resistant lines and high yielding varieties is vital and necessary.This study was conducted using 122 advanced breeding lines of wheat including 21 varieties developed by Bangladesh Wheat and Maize Research Institute with aims to identify genotypes having high yield potential and resistant to leaf blight,leaf rust and blast diseases.These genotypes were evaluated for resistance against leaf blight and leaf rust at Dinajpur and wheat blast at Jashore under field condition.Out of 122 genotypes tested,20 lines were selected as resistant to leaf blight based on the area under the diseases progress curve under both irrigated timely sown and irrigated late sown conditions.Forty-two genotypes were found completely free from leaf rust infection,59 genotypes were identified as resistant,and 13 genotypes were identified as moderately resistant to leaf rust.Eighteen genotypes were immune against wheat blast,42 genotypes were categorized as resistant,and 26 genotypes were identified as moderately resistant to wheat blast.Molecular data revealed that the 16 genotypes showed a positive 2NS segment among the 18 immune genotypes selected against wheat blast under field conditions.The genotypes BAW 1322,BAW 1295,and BAW 1203 can be used as earlier maturing genotypes and the genotypes BAW 1372,BAW 1373,BAW 1297 and BAW 1364 can be used for lodging tolerant due to short plant height.The genotypes WMRI Gom 1,BAW 1349 and BAW 1350 can be selected for bold grain and the genotypes WMRI Gom 1,BAW 1297,BAW 1377 can be used as high yielder for optimum seeding condition but genotypes BAW 1377 and BAW 1366 can be used for late sown condition.The selected resistant genotypes against specific diseases can be used in the further breeding program to develop wheat varieties having higher disease resistance and yield potential.

Phenotypic and Molecular Characterization of Wheat Leaf Rust Resistance Gene <i>Lr34</i>in Iranian Wheat Cultivars and Advanced Lines

Lr34 is a vital gene in developing resistance to leaf rust, stripe rust, and powdery mildew of wheat. Providing simultaneous resistance to various pathogens has made this gene valuable in breeding for wheat resistance to many diseases. The present study investigates the csLV34 marker’s capability in diagnosing this locus in130 wheat commercial cultivars and advanced wheat lines from Iran, and assesses the impact of this gene on disease severity in field conditions. To assess the reactions of cultivars and lines which contained Lr34 under epidemic conditions of leaf rust, these cultivars were cultivated during the 2009 and 2010 cropping season. Of the 130 studied cultivars, 43 contained Lr34. Cultivars that were selected and studied in stress conditions had the most frequent presence of Lr34. It can be concluded that this gene plays a vital role in increasing the tolerance of cultivars under stress conditions. Lr34 seems to cause active transition of materials out of the cell. In addition to being resistant to several important diseases of wheat, Lr34 can increase tolerance to stresses such as salinity. Considering the calculated value for AUDPC (3%-440%/d) in cultivars containing Lr34, it seems that some cultivars contained additional resistance genes. The rate of infection in all cultivars, when presence of Lr34 was detected through the molecular marker, was lower than in other cultivars. Field results confirmed the results of the analysis using the csLV34b molecular marker.

50个小麦品种抗叶锈基因鉴定

选育抗性品种是小麦叶锈病防治举措中最经济、可行的方法。为进一步挖掘抗病基因,选取河南、河北、山东等8个省小麦产区50个小麦品种。首先在苗期将16个叶锈菌生理小种(THFS、TGTS、THJS、FHKT、FGJN、KHKS、FCJQ、RFKS、THFM、MHGT、KHGS、KBGT、FHGT、PHHT、FHJT、FCJT)接种在36份小麦抗叶锈病近等基因系材料以及50个供试小麦品种上。因各菌种带有不同毒力,可根据表现型的差异,再将已知抗病基因紧密连锁的特异性分子标记与之结合分析,进而推测50份小麦材料中可能含有的抗叶锈病基因。通过基因推导、分子标记以及系谱分析综合鉴定抗锈性基因,结果表明,在50个品种中共检测出9个(Lr1、Lr2c、Lr10、Lr16、Lr26、Lr34、Lr37、Lr45和Lr46)已知抗叶锈性基因和少量未知基因。含有Lr1基因的有淄麦12等22个品种;含有Lr2c基因的有鲁麦14等10个品种;含有Lr10基因的只有莱州9361一个品种;含有Lr16基因的有科农199等25个品种;含有Lr26基因的有徐州24等15个品种;含有Lr34基因的有宝麦3号和京冬8号;含有Lr37基因的有淄麦12、鹤0927和荷9946;含有Lr45基因的有连麦2号等11个品种;含有Lr46基因的有山农19等38个品种。

咖啡锈病发生规律调查及施药适期研究

为筛选出防治咖啡锈病的有效杀菌剂,明确其施药适期,以提高防治效果,笔者调查咖啡锈病发生规律,在温室采用先接种后施药和先施药后接种的方法测试4种杀菌剂的防治效果,并验证筛选药剂的田间防治效果。结果表明:咖啡锈病发生盛期为10月至翌年3月。叶片接种夏孢子后72 h喷施4种杀菌剂,一定浓度的4种杀菌剂均有较好的治疗和预防效果。接种病原菌后10 d施用75%戊唑·嘧菌酯水分散粒剂(WG)3000倍液和25%嘧菌酯悬浮剂(SC)1500倍液,治疗效果分别为94.19%和83.87%;75%戊唑·嘧菌酯WG 3000倍液和25%嘧菌酯SC 1500倍液具有较好的预防效果,预防持效期分别为15 d和10 d。间隔9 d施药3次后田间防治39 d和68 d,75%戊唑·嘧菌酯WG 3000倍液相对防效分别为92.00%和81.08%,25%嘧菌酯SC 1500倍液的相对防效分别为88.29%和69.05%。可依据咖啡锈病的发生规律适时选用75%戊唑·嘧菌酯WG和25%嘧菌酯SC。

小麦叶锈菌2个候选效应因子的克隆及其qRT-PCR分析

小麦叶锈病是由隐匿柄锈菌(Puccinia triticina,Pt)侵染的一种气传性真菌病害,对小麦造成严重的产量损失。Pt产生的吸器是产生效应因子的主要场所,而效应因子是Pt致病的关键。本研究基于早期构建的小麦叶锈菌单胞菌系13-5-28-1(JHKT)在休眠孢子、萌发夏孢子和侵染6 d的转录组文库,在系统筛选候选效应因子的基础上,选取两个候选效应因子Pt12448和Pt34354进行克隆,利用qRT-PCR分析候选效应因子的表达模式,结果发现其中Pt12448基因表现为后期诱导上调,Pt34354基因则为前期诱导上调。研究结果将推进对小麦叶锈菌致病机制的研究进程。

Status and strategies in breeding for rust resistance in wheat

Wheat along with rice and maize is fulfilling half of the calories demands of the world. Global Wheat production has increased tremendously since green revolution in 1960’s and helped in minimizing hunger and malnutrition. Developing countries, which consume 60% of the global wheat production, have shown a higher yield increase than the developed countries in the past [1]. It was driven by the hunger prevalence in these countries and was attributable to the introduction of high yielding and rusted resistant semi dwarf varieties developed under the collaborative efforts of International and National research systems during the last 50 years. Whereas, climate change and the emergence of new pests and diseases are threatening the food sustainability. The evolution of new races of disease pathogens like stem rust (Ug 99) is of serious concern. In order to feed the ever increasing population we have to increase wheat production at the rate 1.6% which can be achieved by developing high yielding varieties having a good tolerance level for biotic and abiotic stresses.

Coffee Leaf Rust(Hemileia vastatrix)Disease in Coffee Plants and Perspectives by the Disease Control

Coffee Leaf Rust(CLR)is caused by Hemileia vastatrix in Coffea spp.It is one of the most dangerous phytopathogens for coffee plantations in terms of coffee productivity and coffee cup quality.In this review,we resume the problem of CLR in Mexico and the pathogenesis of H.vastatrix.The review abord plant-pathogen interactions which lead a compatible or incompatible interactions and result in CLR disease or resistance,respectively.The review abord Coffea spp.defense response pathways involved in H.vastatrix pathogenicity.Additionally,current measures to control H.vastatrix proliferation and germination were aborded focused on phytosanitary actions,and biological and chemical control.Finally,new trendlines to reduce the impact of CLR as nanoparticles and nanotechnology were analyzed.

吡唑醚菌酯与氟环唑复配对小麦叶锈病的防治效果及对小麦的安全性

为筛选适用于小麦叶锈病防治的化学药剂,本研究选取吡唑醚菌酯和氟环唑及二者不同比例复配组合,采用喷雾接种法,测定了吡唑醚菌酯和氟环唑单剂及其不同复配比例在作为保护剂使用时对小麦叶锈病的室内防治效果,并测定了室内筛选确定的最佳比例复配药剂对小麦的安全性及对小麦叶锈病的田间防治效果。室内防效试验显示:吡唑醚菌酯、氟环唑及二者不同比例复配对小麦叶锈病病斑扩展有强烈的抑制作用,其中吡唑醚菌酯的抑制作用更强,其EC_(50)值为0.01μg/mL。联合毒力评价表明:所有复配组合均表现出协同相加作用,吡唑醚菌酯·氟环唑质量比50∶133复配时增效系数(SR)最大,为1.50。室内及田间防治试验表明:在所设浓度梯度范围内,防效与浓度呈正相关;在有效成分120 g/hm^(2)剂量下,26%吡唑醚菌酯·氟环唑悬浮剂(SC)的田间防效为85.12%,优于各自单剂处理。安全性评价结果显示:所有处理均能保证不同品种小麦正常生长,未发生药害现象。研究表明,吡唑醚菌酯·氟环唑复配对小麦叶锈病有很好的防治效果,可为生产上防治小麦叶锈病和科学用药提供理论依据。

39份外引小麦种质的抗叶锈病基因检测及其抗性鉴定

为明确39份外引小麦种质的抗叶锈病基因组成,利用与抗病基因紧密连锁或共分离的分子标记对抗叶锈病基因进行检测,并结合田间接种鉴定对种质材料的叶锈病抗性进行评价。结果表明,抗叶锈病基因Lr1、Lr10、Lr20、Lr24、Lr26、Lr34、Lr37和Lr38在39份种质中均有分布,频率分别为30.77%、17.95%、2.56%、5.13%、12.82%、30.77%、23.08%和5.13%,其中携带Lr24和Lr38的种质抗性良好。Lr34和Lr37单独存在时,种质对叶锈病的抗性分别表现为中感和高感,两者聚合时能够提高载体种质的抗性水平,表现为中抗。此外,4份种质材料(KPL-1、OK.95571、莫斯科39和非黑土地24)对叶锈病的抗性表现突出,均达到0;级,是抗叶锈病育种的重要抗源,其中KPL-1和OK.95571分别携带3个和5个抗叶锈病基因;莫斯科39和非黑土地24仅携带Lr1,推测这两份材料含有其他未检测的抗叶锈病基因。综上,较多的抗叶锈病基因聚合有利于提高种质的叶锈病抗性。