Evaluation of Chinese rice varieties resistant to the root-knot nematode Meloidogyne graminicola

The root-knot nematode Meloidogyne graminicola, which is distributed worldwide, is considered a major constraint on rice production in Asia. The present study used the root gall index and number of nematodes inside the roots to evaluate resistance/susceptibility to M. graminicola in different subpopulations of Oryza sativa(aus, hybrid aus, indica, hybrid indica, temperate japonica, tropical japonica). Nematode development in highly resistant varieties was also evaluated. Analyses of randomly selected 35 varieties showed the number of M. graminicola nematodes inside the roots correlated very strongly(r=0.87, P≤0.05) with the nematode gall index, and the results from pot and field experiments revealed similar rankings of the varieties for resistance/susceptibility. Among the 136 tested varieties, temperate japonica displayed the highest gall index, followed by tropical japonica, indica, hybrid indica, aus, and hybrid aus. Zhonghua 11(aus), Shenliangyou 1(hybrid aus) and Cliangyou 4418(hybrid indica) were highly resistant to M. graminicola under both pot and field conditions. Further examination of nematode development suggested that compared to susceptible rice, M. graminicola penetrated less often into highly resistant varieties and more frequently failed to develop into females. The promising varieties found in the present research might be useful for the breeding of hybrid rice in China and for the further development of practical nematode management measures.     

Inheritance Analysis and Identification of SSR Markers Linked to Late Blight Resistant Gene in Tomato

Late blight caused by Phytophthora infestans is the most serious disease of tomato production in China. Studies on the genetics of resistance and identification of molecular markers are very useful for breeding late blight resistant varieties. The objective of this paper was to study the inheritance of late blight resistance and identify simple sequence repeat （SSR） markers associated with resistance allele in tomato （Lycopersicon esculentum Mill）. The results came from an F2 progeny of 241 plants derived from a cross between 5~ inbred line that is susceptible to late blight and a resistant accession CLN2037E. The late blight responses of F2 plants were tested by artificially inoculation of detached-leaflets in plate and natural infection assayed under greenhouse conditions. Both methods showed that the resistance is dominant and inherited as monogenic trait. Genetic mapping and linkage analysis showed that the late blight resistance gene Ph-ROL was located on chromosome 9 with a genetic distance of 5.7 cM to the SSR marker TOM236.     

Evaluation of Soybean Germplasm from Provinces in Northeast China for Resistance to Phytophthora sojae

Soybean Phytophthora root rot (Phytophthora sojae) is a severe disease all over the world. Soybean germplasm from central and southern China for resistance has been evaluated by American researchers on a large scale. P. sojae has been found frequently in northeast of China in recent years, but not systematic evaluation of soybean germplasm for resistance has occurred there. By means of hypocotyl inoculation, 922 cultivars/lines from northeast of China were screened and evaluated for their response to race 1, and 25 of P.sojae. Generally resistance was less frequent in northeast of China than in central and southern China. Five cultivars/lines were identified that confer resistant responses to race 1,3,8,25 and four additional isolates of P.sojae. These cultivars/lines may provide valuable sources of resistance for future breeding programs.     

Identification and resistant characterization of legume sources against Meloidogyne incognita

Root-knot nematodes(RKNs; Meloidogyne spp.) are becoming a serious problem in legume production. This study identified Vigna genotypes exhibiting resistance to M. incognita(RKN) and characterized the modes of the resistance to M. incognita. In total, 279 accessions from 21 Vigna species were screened for resistance based on a galling index(GI) and an egg mass index(EI). Seven accessions were highly resistant to RKN with GI≤25, namely JP74716(V. mungo var. mungo; cultivated black gram), JP107881(V. nepalensis), JP229392(V. radiata var. sublobata; wild mungbean), Aus TRCF118141(V. unguiculata subsp. unguiculata; cultivated cowpea), Aus TRCF306385(V. unguiculata subsp. unguiculata), Aus TRCF322090(V. vexillata var. vexillata; wild zombi pea) and JP235929(V. vexillata var. vexillata). JP229392 and Aus TRCF322090 were the most resistant accessions having EI values of 18.74 and 1.88, respectively. Continuous culture of M. incognita on both JP229392 and Aus TRCF322090 resulted in a weakness in pathogenic ability for this RKN. The resistance in JP229392 and Aus TRCF322090 to RKN appeared to be antibiosis that was associated with reduced nematode penetration, retardation of nematode development and impeding giant cell formation. The Vigna germplasm resistance to RKN identified in this study could be utilized as gene sources for the development of RKN-resistant Vigna cultivars.     

Sensitivities of Phytophthora infestans to Metalaxyl, Cymoxanil, and Dimethomorph

The isolates of Phytophthora infestans on tomato in the Guangxi Zhuang Autonomous Region, China, were determined for the sensitivities to metalaxyl, cymoxanil and dimethomorph to give the basic information for integrating disease management. Sensitivities were tested by measuring the radial growth on agar medium amended with fungicide, compared with the floating-leaf-disk method. 239 isolates were collected from eight tomato growing areas during 2000-2006. The testing results indicated that the frequencies of sensitive, intermediate, and resistant isolates to metalaxyl were 42.26, 35.98, and 23.53%, respectively. Variations in sensitivities amongst isolates from different areas or different years were very high for metalaxyl. All isolates from Tianlin and Wuxuan were sensitive to metalaxyl, but the metalaxyl-resistant isolates predominated in Tianyang, with the frequency of 51.35%. The EC50 values of certain isolates from Tianyang were higher than 500 μg·mL^-1 and their resistance levels were over 100 000 folds. Cymoxanil has been used for nearly 10 years in Guangxi, and dimethomorph has been used for 5-6 years. However, there was no decrease in sensitivity of P. infestans populations and the sensitivities of the pathogen were nearly normally distributed. Hence, their mean ECs0 value [cymoxanil （0.1647 ±0.0255） μg·mL^-1, dimethomorph （0.0970 ± 0.0052） μg·mL^-1 could be used as the baseline sensitivities for monitoring the field resistance development. The comparison with the floating-leaf-disk method indicates that both the techniques provided equivalent results. These studies suggested that metalaxyl can be continuously applied in Tianlin, Wuxuan, and Nanning due to the resistant isolates that have not been found, while for those areas with resistant isolate, the use of metalaxyl should be reduced or alternated, and cymoxanil or dimethomorph was recommended for controlling late blight disease of tomato.     

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.     

Resistance identification of bivalent fungi-resistant genes transformed soybean to Phytophthora sojae

Soybean is one of the most important sources of edible oil and proteins in the world.However,it suffers from many kinds of fungal diseases which is a major limiting factor in soybean production.The fungal disease can be effectively controlled by breeding plant cultivars with genetic transformation.In this study,the resistance to Phytophthora sojae of five bivalent transgenic soybean lines was identified using the hypocotyls inoculation technique.The lines were the T,of the transgenic soybean which were transformed with kidney bean chitinase gene and barley ribosome inactivating protein gene,and were positive by Southern Blot analysis.The resistance difference was studied through comparing the death percentage of transgenic soybean with the control.The results showed that four lines were more resistant to P.sojae,whereas other one had no significant difference in comparison with the control.These transgenic soybean lines with enhanced resistance to P.sojae will be useful in soybean resistance breeding.     

Application of Synthetic Hexaploid Wheat Derived from T.Durum,Ae,Taushii in Common Wheat Breeding for FHB Resistance

The F1 and F4 plants of ‘synthetic hexaploid wheat/common wheat’ crosses and part of their parents were inoculated with Fusarium graminearum to evaluate FHB resistance.The results showed tht the scab resistance in the F1 varied with the synthetic wheat accessions used as crossing parents.In the F4,some resistant head lines were generated from the crosses,although their parents had different scab resistance levels.It indicated that synthetic hexaploid wheat are useful in wheat breeding for scab resistance.     

Pseudomonas oryzihabitans Suppresses Damage Caused by Root-knot Nematode Meloidogyne javanica on Tomato

Agricultural research made in recent years has found that many bacterial organisms act like biological control agents with minimal impact on the environment. These microorganisms and their toxic metabolites should be included in those which are acceptable to qualify a product as organic or integrated and enjoy all the benefits that entails. Hence, interest in the use of microorganisms as biological agents to protect crop plants against plant parasitic nematodes has been increasing. This study investigated the ability of.Pseudomonas oryzihabitans symbiotically associated with the entomopathogenic nematode Steinernema abbasi as a bioagent against plant parasitic nematodes which infected tomato crop. The bacterium is particularly effective against root-knot nematode in vitro affecting the behavior and mobility of root-knot nematode juveniles. Also, studies in planta demonstrated the efficacy of P. oryzihabitans by preventing tomato root system by invasion of juveniles of Meloidogynejavaniea when bacterial cells were applied to the root system before nematodes. This efficacy is dependent on bacterial cell concentration used and the time of the nematode exposure. However, a better nematode control might be achieved with multiple applications of the biocontrol agent. Furthermore, the results of this study provide evidence that the bacterium P. oryzihabitans produces metabolites, which have nematostatic effects.     

中国南方地区作物根结线虫种和小种的鉴定

对采自中国南方地区34种作物的根结线虫83个种群进行了单卵块纯化和培养，在形态学研究的基础上，结合利用全自动快速水平电泳系统测定了雌虫的酯酶和苹果酸脱氢酶，鉴定出南方根结线虫(Meloidogyne incognita)、爪哇根结线虫(M.javanica)、花生根结线虫(M.arenaria)和番禺根结线虫(M.panyuensis)。其中南方根结线虫是最主要的根结线虫。鉴别寄主试验表明，南方根结线虫的优势小种是1号小种。     

陕西省温室蔬菜根结线虫的种类鉴定

为了明确陕西省温室蔬菜根结线虫的种类,为有效防治奠定基础。采用传统的会阴花纹形态鉴定结合线粒体DNA分子标记技术,对采自陕西省7个市县的71份根结线虫样本进行了鉴定。结果表明,危害陕西省温室蔬菜的根结线虫种类为南方根结线虫M.incognita、爪哇根结线虫M.javanica、花生根结线虫M.arenaria,其中南方根结线虫是危害陕西大棚蔬菜的优势种群。同时,研究发现大多数地区为单一种群,但个别地区存在混合侵染现象。因此在防治时,应当以南文根线虫为对象,同时也应考虑到混合浸染的因素。     

丛枝菌根真菌对黄瓜南方根结线虫病的影响

采用盆栽试验的方法研究了丛枝菌根真菌对黄瓜根结线虫的防治作用.结果表明:在南方根结线虫危害条件下,接种摩西球囊霉(G.mosseae)、幼套球囊霉(G.etunicatum)、蜜色无梗囊霉(A.mellea)及其混合接种的黄瓜与对照相比,黄瓜植株的株高、及地上部干重无显著差异;接种AM真菌可显著降低黄瓜根系虫瘿数和根结指数,进而降低根结线虫病的发病指数,防治效果最好的是G.mosseae(编号:BGC JX 01)以及G.mosseae(2种)、G.etunicatum和A.mellea4种AM真菌等量混和接种,防治效果均超过了40%.     

新疆野生樱桃李抗根结线虫相关基因片段的克隆与表达分析

为选育抗根结线虫的李属砧木,以新疆野生樱桃李(Prunus sogdiana)扦插苗为试验材料,对其接种南方根结线虫(Meloidogyne incognita),从中筛选出12株抗病植株。根据已知的抗根结线虫基因的NBS-LRR保守结构域设计简并引物,并以抗病植株的DNA和cDNA为模板对抗根结线虫同源基因序列进行扩增。获得6个抗根结线虫同源基因片段,依次命名为psoRPM1、psoRPM2、psoRPM3、psoRPM4、psoRPM5和psoRPM6,GenBank登录号为:HM593974、HM593975、HM593970、HM593971、HM593972和HM593973。其中前4个基因片段与桃、甜樱桃、酸樱桃以及樱花中的抗病基因的同源性高达90%以上。基因序列分析表明,这6个基因片段均具有典型的NBS保守结构域。根据其氨基酸序列的特点,推断这6个基因片段均属于non TIR-NBS-LRR型抗病基因。RT-PCR表达分析结果显示,psoRPM1和psoRPM6在接种南方根结线虫12和24 h后表达量显著增加,预示着这2个基因片段可能参与了樱桃李对根结线虫的识别和防御过程。本研究在樱桃李中克隆出...     

PGPR接种时期和AM真菌对番茄根结线虫病的影响

作者于温室盆栽条件下研究了植物促生根围细菌(plant growth promoting rhizobacteria,PGPR)Bacillus sp.接种时期和丛枝菌根(arbuscular mycorrhiza AM)真菌摩西球囊霉(Glomus mosseae)接种对番茄(Lycopersicum esculentum Mill)生长发育及根结线虫(Meloidogyne incognitaMi)病的影响。结果表明于番茄播种时接种AM真菌摩西球囊霉+移栽时接种芽孢杆菌(Bacillus sp.)和南方根结线虫(M.incognita)的处理植株发病率和和病情指数最低、防效最高,分别为24.5%、12.5%和70.90%;并且显著增加番茄植株节点数、株高、茎粗、地上部干重及地下部干重。认为播种时接种AM真菌配合移栽时接种PGPR可以显著减轻南方根结线虫对番茄生长发育造成的危害程度,并且对南方根结线虫有较强的抑制效果。     

辣椒抗南方根结线虫基因的定位及标记辅助选择

用对南方根结线虫具有稳定抗性的辣椒材料09C649与感病材料09C108杂交并构建F2分离群体,遗传分析表明,09C649中对南方根结线虫的抗性由一对显性基因控制,将其暂命名为Me8。用236对SSR标记、1对SCAR标记、1对SSCP标记、8对EST-SSR标记及2对COSII标记对Me8进行基因定位。该基因被定位在辣椒第9号染色体上,与其距离最近的4个标记SSCP_B322、COS710、SCAR₃15和COS970,分别与该基因相距0、0.1、1.3和3.3cM。抗南方根结线虫基因N、Me1、Me3及Me7也都位于这一染色体区域,因此这4个分子标记可运用于对目前已发现的所有抗南方根结线虫基因的辅助选择中。用标记SCAR₃15对37份辣椒材料进行辅助选择,结果表明标记鉴定结果与抗性鉴定结果具有高度的一致性。     

番茄抗根结线虫Mi基因研究进展

目前国际上从番茄中发现了8个抗根结线虫基因，其中3个抗性基因Mi-1、Mi-3和Mi-5分别定位在番茄第6染色体和12染色体上，已经克隆出的Mi-1基因与其他植物抗病基因具有相似性，Mi基因与抗蚜虫的基因（Meu-1）密切相关，抗线虫Mi基因介导了对马铃薯蚜虫的抗性。     

商丘地区保护地番茄根结线虫种类鉴定

[目的]为了明确商丘地区温室蔬菜根结线虫的种类。[方法]保护地中采集带有大量根结的番茄根,经室内解剖镜下解剖,发现根内有大量根结线虫和卵。对雌虫和2龄幼虫的形态进行观察和测量,并制作雌虫会阴花纹切片进行比较鉴定。[结果]2龄幼虫体长425.27±9.98μm,尾长55.67±3.02μm,透明尾长14.20±1.52μm;雌虫口针长14.40±1.11μm,背食道腺开口到口针基部球的距离2.53±0.27μm。会阴花纹有明显的高而方的背弓,花纹背面和侧面的线纹呈波浪形、平滑,侧线不明显。[结论]危害商丘市保护地番茄的病原线虫为南方根结线虫。     

番茄抗根结线虫接种鉴定技术及其应用

用3个番茄抗线虫品种和两个感线虫品种作为试验材料,对北京地区危害番茄的南方根结线虫进行 苗期人工接种鉴定,研究结果表明,采用灌根接种法,适宜的接种体浓度为2000卵／株,适宜的接种苗龄为10 ～20 d,供试3种栽培基质培育的幼苗对接种效果没有明显影响,接种后30 d进行调查即可明显区分出不同 番茄品种对根结线虫的抗、感差异。运用该方法对28份番茄育种材料进行抗线虫评价,筛选出对线虫免疫的 材料8份,高抗线虫的材料12份,抗线虫材料3份,感病材料5份,其中抗线虫材料占82．1％,说明番茄蕴藏着 丰富的对改良线虫抗性有利用价值的基因资源。     

酸黄瓜对南方根结线虫抗性的光合响应

 【目的】酸黄瓜对南方根结线虫具有高度抗性,明确其抗性的光合响应特性,为进一步抗性基因的分离及功能鉴定提供理论依据。【方法】采用温室盆栽苗期人工接种技术,研究线虫侵染对抗、感黄瓜叶片光合作用、叶绿素荧光参数及相关生理指标的影响。【结果】线虫侵染使抗病材料酸黄瓜叶绿素（Chl）含量降低幅度显著小于感病材料北京截头,酸黄瓜Chl随氮素含量降低较北京截头平缓;抗、感材料净光合速率（Pn）、气孔导度（Gs）下降,酸黄瓜胞间CO2浓度（Ci）下降,而北京截头Ci上升,酸黄瓜Gs对叶片相对含水量（RWC）持续下降的反应较北京截头敏感;实际光化学效率（ΦPSⅡ）、光化学猝灭系数（qP）降低幅度酸黄瓜小于北京截头,非光化学猝灭系数（qN）升高幅度酸黄瓜显著高于北京截头;酸黄瓜Pn/Ci初始斜率变化不大,而北京截头Pn/Ci急剧降低。【结论】酸黄瓜叶绿素含量下降较小,从而保持了较高的净光合速率,使线虫侵染对酸黄瓜植株生长造成的影响不大。