Efficacy of Selected Plant Extracts against <i>Pyricularia grisea</i>, Causal Agent of Rice Blast Disease

Rice blast disease, caused by a seed-borne fungus Pyricularia grisea, is an important and serious disease of rice (Oryza sativa L.) worldwide. The disease has been reported to cause yield losses of up to 40% in Tanzania. Studies were conducted to determine the effect of aqueous extracts of Aloe vera, Allium sativum, Annona muricata, Azadirachta indica, Bidens pilosa, Camellia sinensis, Chrysanthemum coccineum, processed Coffee arabica, Datura stramonium, Nicotiana tabacum and Zingiber officinalis for control of rice blast disease (Pyricularia grisea) in-vitro and in-vivo. The results indicate that processed C. arabica at 10% and 25% (v/v) had the highest (81.12%) and (89.40%) inhibitory effect, respectively, against P. grisea. Aqueous extract from N. tabacum at 10% concentration ranked third (80.35%) in inhibiting P. grisea. These were followed by extracts from 25% A. vera (79.45%) and 25% C. coccineum flower (78.83%). The results also indicate that, extracts from A. indica, A. vera, A. sativum, C. arabica, D. stramonium, C. sinensis, Z. officinalis and N. tabacum did not have any phytotoxic effect on seed germination, shoot height, root length, dry weight, seedling growth and seedling vigour index. These plant extracts can thus be used for rice seed treatment to manage rice blast disease.

Race Specificity of Major Rice Blast Resistance Genes to Magnaporthe grisea Isolates Collected from indica Rice in Guangdong, China

Race-specific resistance and field resistance of 30 rice blast resistance monogenic lines derived from different resources were evaluated. The spectra of resistance to 163 Magnaporthe grisea isolates collected from indica rice in Guangdong Province, China ranged from 0.6% to 89.6%. Most of the monogenic lines showed a narrow resistance spectrum and high susceptibility in rice blast area, whereas the lines with Pikh and Pi1(t) had the broad resistance spectra of 89.6% and 82.2% respectively, showing a high and stable blast resistance in fields. According to the cluster analysis of specific resistance to 163 blast isolates tested, the 30 monogenic lines were divided into 15 groups, and based on the principal factor analysis, nine kinds of race-specific resistance were identified. Pik, Piz5, Pi9 and Pish can be used as candidate resistance genes for rice breeding since their specific resistance differed from those of the backbone parents in Guangdong, China. Gene pyramiding of Pikh [or Pi1(t)], Pi9 (or Piz5) and Pish (or Pita2) will be effective to obtain broad-spectrum blast resistance in rice breeding program in Guangdong, China. The strategies for studying and application of rice blast resistance genes were discussed.

Resistance Evaluation of Some Chinese Leading Rice Maintainer, Restorer lines and Their Hybrids to Magnaporthe grisea

Six isolates of Magnaporthe grisea were selected to inoculate on 10 Chinese leading maintainer lines (B-lines), 14 restorer lines (R-lines) and their F1 hybrid plants. In the tested rice materials, R-lines were proved to be more resistant to blast than B-lines. The resistance frequency of about 25% F1 hybrid plants was less than their parents. In addition, 26 isolates of M. grisea collected from different rice growing areas of China were inoculated on 13 new improved hybrid rice combinations. The resistance frequencies of 5 improved hybrids were better than those of the controls and leading varieties in rice production of China.

Expression of a Magnaporthe grisea Elicitor and Its Biological Function in Activating Resistance in Rice

The expression of a protein elicitor from Magnaporthe griesea and its biological function in activating resistance in rice （Oryza safiva L） were reported. The gene of elicitor was expressed in Escherichia colicells and produced a His6-fusion protein with 42 kD apparent molecular weight on SDS-PAGE. The purified protein could induce the resistance to blast disease, with the control efficiency of 46.47% and 36.41% at the 14^th day and the 21^st day after blast inoculation, respectively. After treatment with the expressed protein, the phenylalanine ammonia-lyase （PAL） and peroxidase （POD） activities were promoted in rice plants, meanwhile, the transcription levels of STKM, FAD, PBZ1 and PR1 genes were increased in rice plants. Moreover, after comparing the profile of total rice leaf proteins on two-dimensional electrophoresis gel, about 14 proteins were found to be increased in expression level after the expressed protein treatment. All the results indicated that the expressed protein could act as an elicitor to trigger the resistance in rice.

A rapid approach for isolating a single fungal spore from rice blast diseased leaves

Single spore isolation is a fundamental approach in plant pathology and mycology to isolate and identify plant fungal pathogens from diseased samples.However,routine single spore isolation procedure is time-consuming and has a high risk of contamination by other microorganisms.In this study,we developed a rapid approach for isolating a single spore of the fungal pathogen,Pyricularia oryzae,from rice blast diseased leaves in the paddy field with low potential of contamination.First,rice blast leaves with single lesions were selected in the paddy field,and a single lesion was cut out and pressed and dragged gently across the surface of water agar.Next,a germinated single spore with a barely visible piece of agar was cut out of water agar with a dissecting needle under a stereomicroscope at approximately 120-fold magnification.Last,the germinated single spore with water agar was transferred onto oatmeal tomato agar for growth and preservation.Based on our experience,a skilled technician or student can successfully isolate single spore from over 150 independent diseased samples with nearly no contaminations in a single working day.This approach is also suitable for isolating single spore from other fungal disease samples that produce abundant aerial conidia.

Analysis of the Abnormal Segregation of Pathogenicity in Magnaporthe grisea by Using a Genetic Cross of Oryza and Eleusine Isolates

A genetic cross between Oryza isolate Y93-164a-1 and Eleusine isolate SA98-4 was established, and the pathogenicity of 151 F1 progeny isolates was investigated on both host plants rice and finger millet. Results showed that the segregation of pathogenicity in this genetic cross was abnormal, i.e., most of the progeny isolates were nonpathogenic on both host plants. However, no abnormal segregation was observed when middle repetitive sequence MGR586 and 31 single-copy RFLP markers from all of the chromosomes were genetically analyzed. At the same time, comparison of the chromosomal organization among two pairs of parental isolates did not find any genomic abnormity. These results suggested that the ＂abnormal＂ inheritance of pathogenicity in this cross was most likely due to the reassortment of numerous host species specificity genes but not the biased segregation of the host species specificity genes. The host species specificities in M. grisea were likely to be multigenically controlled, at least in the genetic cross involving rice pathogen and the grasses pathogen other than rice.

Pathotype Structure of Magnaporthe grisea in the Fields of Chongyang and Yuan'an in Hubei Province,China

[Objective] This study aimed to explore the pathotype structure of Magnaporthe grisea in Chongyang and Yuan'an in Hubei Province,China.[Method] From the rice-growing fields of Chongyang and Yuan'an in Hubei Province where rice blast occurs frequently,60 isolates which were pathotyped against two sets of host differentials:Chinese host differentials and CO39 NILs,were obtained.Then,20 pathotypes with the six indica host differentials(CO39 NILs) were observed,while 13 pathotypes in four race groups were observed out of the same single spore isolates with Chinese host differentials which consists of three indica cultivars and four japonica cultivars.The diversity of the pathotypes of M.grisea populations tested by CO39 NILs was 2.54 and the pathotype 137.1 occurred at predominantly high frequency(21.67%).The diversity of physiological races of M.grisea populations tested by Chinese host differentials was 1.22 and the race group ZA occurred at predominantly high frequency(73.33%).The diversity of physiological races of M.grisea in Chongyang and Yuan'an were also calculated.Overall,the diversity of pathotypes of M.grisea in Yuan'an was higher than that in Chongyang with the two sets of the host differentials.[Conclusion] This study provided current information on the pathotype spectrum of M.grisea populations in the rice fields of Hubei Province to allow the formulation of viable strategies for blast resistance breeding programs in Hubei Province.

水稻抗稻瘟病基因Pi-d(t)~1、Pi-b、Pi-ta^2的聚合及分子标记选择

冈 4 6B(G4 6B)是水稻生产应用中的一个农艺性状十分优良的保持系 ,其主要的缺陷是稻瘟病抗性较弱 ,通过对地谷 ,BL 1,Pi 4号等三个分别含抗病基因Pi d(t) 1 、Pi b、Pi ta2 的稻瘟病抗性材料与G4 6B聚合杂交 ,并利用抗病基因连锁的分子标记对杂交后代进行辅助选择 ,在聚合杂交的F2代及B1C1代群体中共获得了 15株含Pi d(t) 1 、Pi b、Pi ta2 等三个抗稻瘟病基因的材料 ,其可能的基因型分别为 :三基因杂合体Pi d(t) 1 pi d(t) 1 Pi bpi b Pi ta2 pi ta2 4株 ,双基因杂合体 10株 ,其中Pi d(t) 1 Pi d(t) 1 Pi bpi b Pi ta2 pi ta2 6株 ,Pi d(t) 1 pi d(t) 1 Pi bpi b Pi ta2 Pi ta2 3株 ,Pi d(t) 1 pi d(t) 1 Pi bPi b Pi ta2 pi ta2 1株 ,双基因纯合体Pi d(t) 1 Pi d(t) 1 Pi bpi b Pi ta2 Pi ta2仅 1株 ,这一研究结果为进一步改良G4 6B的稻瘟病抗性奠定了基础 ,同时这一研究结果表明利用分子标记可快速、有效地实现多个抗病基因的聚合 。

水稻主要抗瘟基因对福建稻瘟菌群体的抗性分析

用1995-2003年间在福建省水稻产区采集的稻瘟菌代表菌系的108个分离菌,它们在CO39近等基因系上测定被 划分为30个毒性类型,用它们在30个水稻抗稻瘟病近等基因系或单基因系品种上进行抗病性测定。结果表明水稻抗稻 瘟病基因Pi-kh抗性最强,抗性频率高达98．15％,Pi-1和Pi-9(t)也具有较高的抗性频率,是较好的抗源;对2个和3个Pi 基因的联合抗性频率的分析,发现一些联合抗性频率极高,甚至有达到100％的组合,表明抗瘟育种采用多个Pi基因聚合, 易于获得抗性强的品种。根据抗病基因与供试菌株互作的亲和性,对供试30个Pi基因可能的系统关系分析得到的初步信 息可为抗病基因的聚合与布局策略提供参考。

云南稻瘟病菌系谱与致病型的关系

为探究稻瘟病菌无性世代DNA水平的变异 ,寻找云南稻瘟病菌谱系 (geneticlineage ,G)和致病型之间的对应关系 ,根据稻瘟病菌散布的重复序列Pot2 (Pyriculariaoryzaetransposon) ,对云南水稻主产区稻瘟病菌菌株DNA进行了rep PCR(repetitivepolymerasechainreaction)扩增 ,获得rep PCR指纹。聚类分析将 134个稻瘟病菌代表菌株划分为G1～G8等 8个谱系 ,揭示云南水稻主产区稻瘟病菌无性系丰富的遗传多样性。进一步接种分析了8个谱系的 2 9个稻瘟病菌菌株对 33个云南主产区水稻品种的亲和性 ,依其毒性谱 ,采用STATISTICAL 5 0软件的UPGMA程序进行聚类分析 ,将其划分为P1～P6等 6个致病型群 (pathotypegroup)。结果表明同一谱系的稻瘟病菌菌株多数对应 2～ 3个致病型群 ,少数 1个或 4个致病型群 ;但G1～G8等 8个谱系中的部分菌株都可对应致病型群P2。因此 ,云南水稻主产区稻瘟病菌谱系和致病型群之间属于复杂关系类型。此外 ,33个水稻品种中的合系 16和京国 92抗全部 2 9个稻瘟病菌株 ,云粳 2 0和合系 30对全部供试菌株表现感病 ,这对云南水稻主产区品种布局提供了稻瘟病抗性方面的依据。因此 ,从育种应用和生产实际需要出发 ,水稻品种抗瘟谱测定仍然必要。

稻瘟病菌群体遗传结构的研究进展

稻梨孢引起的稻瘟病是世界水稻生产的最重要病害,严重影响水稻的产量和米质。文中综述了分子标记技术在稻瘟病菌群体遗传结构研究上的应用,分析了病原菌遗传宗谱的特点及其与致病谱的关系,探讨了导致稻瘟病菌群体遗传结构发生变化的相关因素。

我国稻瘟病菌毒力基因的组成及其地理分布

用我国育成的 6个近等基因系和IRRI 日本合作育成的 2 4个单基因系 ,对来自我国吉林、辽宁、河北、江苏、浙江、四川、湖南、福建、广东和云南 10个省的 32 2个稻瘟病单孢菌株的毒力基因组成及其地理分布进行了测定和分析。结果表明 ,我国稻瘟病菌株含有与所有测试抗病基因相应的毒力基因 ,其中Av kh+、Av z +、Av z5+和Av 9(t) +的出现频率低于 2 0 % ,Av a(1) +、Av a(2 ) +、Av i+、Av 7(t) +、Av 3+、Av b +、Av kp+、Av ks(1) +、Av ks(2 ) +、Av ta(1) +、Av ta(2 ) +、Av t+、Av sh(1) +、Av sh(2 ) +、Av 19(t) +及Av km +的出现频率高于 5 0 % ;吉林省、浙江省、四川省、广东省和云南省尚未发现含有Av 9(t) +的菌株 ,四川省、广东省和云南省尚未发现含有Av kh+的菌株 ,福建省尚未发现含有Av z+的菌株 ,浙江省尚未发现含有Av zt+和Av z5+的菌株 ,其余 2 5个毒力基因在各稻区均有分布 ;我国稻瘟病菌群体的毒力基因在南方籼稻区和北方粳稻区的出现频率 ,与相应抗病基因的籼。

云南地方稻种资源的抗瘟性研究

以 B40、Tetep为感、抗稻瘟病对照 ,在全国 4个病区病圃 (云南保山、湖南烟溪、辽宁丹东、广东从化 )采用自然诱发 ,鉴定了 74份云南地方稻种资源的抗瘟性。结果表明 ,感病对照 B40在苗期病斑孢子层级、严重度、病斑叶面积率、穗颈瘟发病率均表现高感 ;抗病对照 Tetep分别为 1级、4级、5 .5 %和 4.79% ;Moroberekan前 3个指标分别为 3级、3级和 1.2 % ,其穗颈瘟发病率较高 ,达到 12 .0 %。云南地方稻种中 ,毫弄早、毫玉浪、大白谷等 3个品种在这 4个指标上表现抗病 ;在这 4个病圃中 ,它们对稻瘟病的抗性比 Tetep和 Moroberekan更强、更稳定 ;毫马粉、孟先大白谷等 2个品种在前 3个指标上表现抗病 ,但感穗颈瘟。

水稻品种多样性混栽持续控制稻瘟病研究

在对 2个主栽品种 (生产上推广的当家杂交稻组合 )和 2个间栽品种 (优质感瘟 )进行抗性基因同源序列(resistancegeneanalogue ,RGA)遗传背景研究的基础上 ,配制 4个混合间栽组合。在烟溪 (山区 )进行小区试验和示范比较 ,发现不同品种混合间栽后 ,间栽区各品种的平均病叶面积率比净栽区降低 2 .7%～ 4 .1% ;穗瘟相对防治效果达 36 .88%～ 5 5 .10 % ;混合间栽的主栽品种与净栽的主栽品种相比 ,叶瘟和穗瘟的病情严重度差异不大。混合间栽品种的单位面积产量比净栽区有不同程度的提高 ,小区试验的增产幅度为 8.9%～ 14 .9%。结果表明 ,选择抗瘟性遗传背景差异大、株高差异突出的品种 ,以 1行优质稻∶5行主栽稻混合间栽 ,能起到控瘟增产的作用。

基因聚合对水稻稻瘟病的抗性影响

水稻稻瘟病是世界上广泛发生的水稻真菌性病害之一。本研究利用 10 0个稻瘟病菌株对以CO39为背景且带有单个基因和多个基因聚合的近等基因系进行接种分析 ,结果表明 ,Pi1和Pi2属两个广谱高抗稻瘟病基因 ,两基因可在我国南方稻区加以合理利用。基因聚合后抗谱增宽、抗性加强 。

稻瘟病菌拮抗微生物的筛选及鉴定

将稻叶和种子浸在NB培养液中 ,并研碎成匀浆液 ,用接种环挑少量匀浆液在NB琼脂平板上划线分离 ,获得 35 6个菌株 ,分别将它们接种于NB培养液中 ,振荡培养 3d ,并利用它们的培养液对稻瘟菌分生孢子进行萌发抑制试验 ,最终获得具显著抑制作用 (分生孢子萌发抑制率分别为 82 .5 %和 10 0 % )的 2个拮抗菌株。按照伯杰手册进行严格的鉴定 ,初步确定为枯草芽孢杆菌 (Bacillussubtilis)和短小芽孢杆菌 (B .pumil lus)。

水稻稻瘟病抗性基因研究综述(英文)

In this paper, authors gave the review of research progress in rice blast resistance genes. Number of genes conferring rice blast, widely used resistant materials to blast and method of rice blast identification have been summaried in details. The strategies of rice blast resistance breeding are also discussed.

四川省利用水稻品种多样性间栽技术持续控制稻瘟病

2002—2005年利用水稻品种多样性间栽控制稻瘟病技术在四川省18个市（州）113个县累计推广145．9×10^4hm^2，选用杂交稻和播稻品种搭配组合517个。结果表明，间栽播稻的平均发病率比净栽播稻下降56．97％，病情指数下降66．38％，控制有效率在22％～97％之间。间载杂交稻的平均发病率比净栽杂交稻下降28．95％，病指下降37．09％，控制有效率在32％～57％之间。其中杂播品种最佳组合为黄壳摇×川香优2号。竹丫谷×宜香优1577。4年水稻的平均复合产量为9598kg／hm^2，比净栽杂交稻提高产量7281kg／hm^2，增长8．68％。

水稻品种对稻瘟病菌粗毒素的抗性

从黑龙江省代表性灰色梨孢菌株的代谢产物中提取稻瘟病菌粗毒素,以北方农业生产中大面积种植的10个水稻品种为材料,研究了粗毒素对种子萌发、胚芽生长、愈伤组织形成的影响。结果表明,稻瘟病菌粗毒素对水稻种子萌发、胚芽生长、愈伤组织形成的抑制作用呈规律性变化,随着粗毒素质量分数的提高,抑制程度也相应地增强。根据粗毒素对水稻种子萌发、胚芽生长、愈伤组织形成的平均抑制率,龙粳14号、东农418号对粗毒素的毒害作用均表现出较强的抗性,而松粳6号对粗毒素的抗性则相对较弱。

基于中国鉴别品种及单基因品系的湖北省稻瘟病菌的致病型分布

基于中国鉴别品种和单基因品系,采用离体点液接种方法对湖北省水稻主栽区稻瘟病菌的生理小种进行了鉴定。根据监测结果,发现2008～2009年这两年中生理小种ZA群出现频率略微下降,ZB、ZC群的出现频率则在缓慢上升,总体上ZA群、ZB群和ZC群的出现频率相差不大。2009年的100个菌株基于单基因品系出现毒性类型分散,毒性类型的丰富度为3.46。