黑龙江省部分地区稻瘟病菌致病性分析及鉴别体系优化

为明确哈尔滨市及鸡西市稻瘟病菌致病性变化情况并优化鉴别体系,以24个水稻单基因系为鉴别体系,对2006—2008年采自2市的稻瘟病菌菌株进行致病型划分,并应用聚类分析方法完成鉴别体系优化。结果表明,应用水稻单基因系鉴别体系可将哈尔滨市2006—2008年采集的稻瘟病菌菌株划分为34、12和27个致病型,致病性相似系数分别为0.32~1.00、0~1.00和0.20~1.00;水稻单基因系对其抗性频率分别为2.86%~97.14%、8.33%~100.00%和10.00%~96.67%;鸡西市2006—2008年采集的菌株可划分为26、19和20个致病型,致病性相似系数分别为0.47~0.92、0.15~0.86和0.39~1.00;水稻单基因系对其抗性频率分别为3.85%~96.15%、5.26%~73.68%和4.76%~95.24%。适用于哈尔滨市的优化鉴别体系包括Pi-9、Pi-11、Pi-a、Pi-ks、Pi-5、Pi-i、Pi-sh、Pi-3、Pi-km和Pi-ta共10个基因,2006—2008年累计方差贡献率分别为86.15%、98.77%和87.39%;适用于鸡西市的优化鉴别体系包括Pi-9、Pi-11、Pi-a、Pi-ks、Pi-5、Pi-i、Pi-sh、Pi-1、Pi-7和Pi-t共10个基因,2006—2008年累计方差贡献率分别为82.58%、94.55%和90.37%。应用优化后的鉴别体系可将哈尔滨市2006—2008年采集的菌株划分为22、12和23个致病型,将鸡西市2006—2008年采集的菌株划分为22、14和18个致病型。     

华南籼稻稻瘟病菌致病型单基因鉴别寄主筛选

采用35个单基因鉴别寄主、12个日本清泽鉴别寄主共47个具有已知基因的鉴别寄主,对147个籼稻稻瘟病菌株进行致病型鉴别研究.147个菌株被划分为28个不同的致病类型.优势致病型为I-04、I-02和I-01,这3个致病型的菌株数占参试菌株的74.8%,而且与其他致病型比较,它们的致病谱较广.研究结果表明,F80-1(Pi-k)、IRBL7(Pi-kp)、IRBL16(Pi-sh(1))、IRBL21(Pi-7(t))、IRBL3(Pi-i)、IRBL9(Pi-z)、IRBL19(Pi-3)、IRBL10(Pi-z5)、IRBL11(Pi-zt)、IRBL18(Pi-1)、IRBL10(Pi-2)、F128-1(Pi-ta2)、F145-2(Pi-b)和IRBL22(Pi-9(t))等14个单基因鉴别寄主对以广东为主的华南籼稻区稻瘟病菌具有较好的鉴别能力,其中尤以F80-1(Pi-k)、IRBL7(Pi-kp)、IRBL16(Pi-sh(1))、IRBL21(Pi-7(t))、IRBL3(Pi-i)、IRBL9(Pi-z)、IRBL19(Pi-3)和IRBL10(Pi-z5)等8个单基因鉴别寄主的鉴别能力最强,IRBL11(Pi-zt)、IRBL18(Pi-1)、IRBL10(Pi-2)、F128-1(Pi-ta2)、F145-2(Pi-b)和IRBL22(Pi-9(t))等6个单基因鉴别寄主可鉴别抗性反应表现型较相似的致病型,并可用于细分致病型.3个优势致病型I-04、I-02和I-01对F80-1(Pi-k)等上述8个单基因鉴别寄主的抗性反应表现型依次为RRSRSSSMR、SSSSSSSS和SSRSSSSR.     

水稻品种抗稻瘟病分析及基因聚合抗性改良

为了解水稻品种抗瘟性及基因聚合改良的情况,通过喷雾和离体划伤接种法对黑龙江省20个水稻品种和16个外源抗瘟基因的抗性频率及6个主要水稻品种含有的抗瘟基因型进行了分析。结果表明,20个水稻品种抗性频率介于10.89%~68.32%之间,垦稻12抗性最低,龙粳40抗性最高;16个抗瘟基因抗性频率介于0~50.50%之间,Pi-sh、Pi-19和Pi-k~m基因抗性最低,Pi-z~t抗性最高;在联合抗病性方式下,龙粳40龙粳31和龙粳40龙稻14组合抗性改良效果略好;20个水稻品种的抗性相似系数介于0.24~0.75之间,在0.40水平上将其划分为5个类群;6个水稻品种共检测到抗瘟基因11个,Pi-1基因出现频率最高;在基因聚合方式下,龙粳39聚合后抗性最高,龙稻13聚合后抗性升幅最大。综合分析,供试水稻品种及单基因系品种抗性表现较差,基因聚合方式对水稻品种的抗性改良效果明显优于联合抗病性方式。     

水稻主要抗瘟基因品系对江西省稻瘟病菌分离株系的抗性分析

为明确30个水稻抗瘟基因品系在江西水稻育种中的应用价值,利用2006—2012年分离自江西主要稻区的381个稻瘟病菌株,在抗瘟基因品系苗期喷雾接种,通过供试品系对稻瘟病菌的抗感反应来明确其抗病性。Pi-z^t、Pi-k、Pi-1（1）、Pi-z⁵、Pi-k（C）、Pi-k^p和Pi-9（t）7个水稻抗瘟基因对江西省稻瘟病菌群体表现出较高的抗性频率,其值分别为85.11%、82.95%、71.12%、68.69%、63.53%、62.61%和61.09%,且这7个抗瘟基因对ZG1、ZC15和ZB31小种的稻瘟病菌株的抗性频率均比其它小种菌株高。将抗瘟品系与稻瘟病菌接种反应结果转化为“0-1”模式进行聚类分析,7个抗性频率较高的抗瘟基因被划分为Pi-z^t、Pi-z⁵、Pi-9（t）和Pi-k、Pi-1（1）、Pi-k（C）、Pi-k^p两组不同的抗病类型品系。     

江西省稻瘟病菌毒性的群体结构分析

用江苏省的吴江、赣榆、通州、高邮和宜兴等5个代表地区的324个稻瘟病菌株接种13个日本已知抗病基因品种，结果表明，江苏省稻瘟病菌对携带有Pi-Ka,Pi-ta,Pi-ta2和Pi-sh抗病基因品种的可致病比例较高，毒力频率达64．2％－97．2％，对携带有Pi-iPi-z和Pi-b抗病基因的品种毒力频率较低，在0－11．9％之间；江苏省稻瘟病菌毒性的群体结构年度间有一定变化，表现为对某些抗病基因品种毒力频率的明显上升或下降。从江苏省10年主栽品种上分离的稻瘟病菌株对13个已知抗病基因品种的毒力频率测定结果表明，不同类型主栽品种上分离的菌株其毒性结构组成有一定差异,表明江苏省水稻主栽品种的抗性类型存在一定差异。     

水稻主要抗瘟基因对我国菌株的抗性分析和利用评价

为了明确主要抗瘟基因的抗性现状和利用价值,１９９５－１９９６年采用徕自浙江,四川,湖北,广东等７个省（市）的１５５个稻瘟病菌菌株,测定了日本１３个已知基因粳稻品种的抗性表现。结果表明,１３个抗瘟基因对我国菌株的抗性均不强,菌株毒力频率均在２０％以上。但对我国各稻区的菌株而言多数稻区仍有１－３个基因的抗性保持较高的水平,浙江稻区Ｐｉ－ｚ＾ｔ基因仍有很好的抗性,能抗９５．７％的浙江菌株,四川稻区Ｐｉ－     

Pi34-AVRPi34: a new gene-for-gene interaction for partial resistance in rice to blast caused by Magnaporthe grisea

The japonica rice (Oryza sativa) cultivar Chubu 32 has a high level of partial resistance to blast, which is mainly controlled by a dominant resistance gene located on chromosome 11. The partial resistance to the rice blast fungus (Magnaporthe grisea) in Chubu 32 has isolate specificity; isolate IBOS8-1-1 is more aggressive on Chubu 32 than are other isolates. We hypothesized that the gene-for-gene relationship fits this case of a partial resistance gene in Chubu 32 against the avirulence gene in the pathogen. The partial resistance gene in Chubu 32 was mapped between DNA markers C1172 (and three other co-segregated markers) and E2021 and was designated Pi34. In the 32 F₃ lines from the cross between a chromosome segment substitution line (Pi34⁻) from Koshihikari/Kasalath and Chubu 32, the lines with high levels of partial resistance to the M. grisea isolate Y93-245c-2 corresponded to the presence of Pi34 estimated by graphic genotyping. This indicated that Pi34 has partial resistance to isolate Y93-245c-2 in compatible interactions. The 69 blast isolates from the F₁ progeny produced by the cross between Y93-245c-2 and IBOS8-1-1 were tested for aggressiveness on Chubu 32 and rice cultivar Koshihikari (Pi34⁻). The progeny segregated at a 1 : 1 ratio for strong to weak aggressiveness on Chubu 32. The results suggested that Y93-245c-2 has one gene encoding avirulence to Pi34 (AVRPi34), and IBOS8-1-1 is extremely aggressive on Chubu 32 because of the absence of AVRPi34. This is the first report of a gene-for-gene relationship between a fungal disease resistance gene associated with severity of disease and pathogen aggressiveness.     

福建省稻瘟病菌致病性及其无毒基因分析

利用41个已知抗性基因水稻品种测定2003—2006年从福建省闽东、闽南、闽西、闽北和闽中5个主要稻区采集分离的87个稻瘟病单孢菌株的致病性。结果表明,福建省稻瘟病菌群体含有与所有测试抗病基因相应的无毒基因,其中66.67%的稻瘟病菌株表现较强致病力。病菌群体对水稻抗病基因Pi-d2、Pi-k(1)、Pi-km、Pi-kh、Pi-1(1)、Pi-z5(1)、Pi-z5(2)和Pi-1(2)的毒力频率均低于10%,提示这些抗病基因在福建省可作抗源使用。2003—2006年福建省稻瘟病菌群体中分别出现了40、37、36和38个无毒基因,其中有34个无毒基因在各年份均有分布,有30个无毒基因在5个主要稻区均有分布,Avr-a(2)、Avr-3(2)、Avr-ks、Avr-4b、Avr-b、Avr-kp(C)、Avr-km(C)、Avr-ta(C)、Avr-11(C)、Avr-19(t)、Avr-t和Avr-a(1)无毒基因的出现频率均低于30%,提示与之相对应的抗病基因在福建省水稻品种抗稻瘟病育种中应慎用。含有17、14、23、18和16个无毒基因组合的病菌较多,其组合频率分别为13.79%、10.34%、9.20%、8.05%和8.05%。     

水直播条件下黑龙江省不同稻区稻瘟病菌致病性分析

为明确水直播条件下黑龙江省不同稻区稻瘟病菌Magnaporthe oryzae的致病性分化情况，以24个抗瘟单基因系品种为寄主，来源于2017—2018年黑龙江省水直播稻田的242株稻瘟病菌菌株为接种体，采用离体划伤方法接种，记录病斑反应型，计算有效致病菌株率和抗性频率，并进行聚类分析。结果显示，在水直播条件下，2017年，黑龙江省南部和中东部稻区稻瘟病菌菌株对抗瘟单基因系品种的有效致病菌株率介于8.33%~95.83%和20.83%~95.83%之间，无毒基因出现频率分别为575次和622次；2018年，南部和中东部稻区稻瘟病菌菌株对鉴别体系的有效致病菌株率介于29.17%~95.83%和20.83%~91.67%之间，无毒基因出现频率分别为536次和571次。2017年，黑龙江省南部和中东部稻区稻瘟病菌菌株的致病性相似系数介于0.15~1.00和0.14~1.00之间，以致病性相似系数0.40为阈值，可将菌株分别划分为5个类群和6个类群；2018年，南部和中东部稻区菌株的致病性相似系数介于0.15~0.93和0.26~1.00之间，以致病性相似系数0.40为阈值，可将菌株分别划分为5个类群和4个类群。2017年，抗瘟单基因系品种对黑龙江省南部和中东部稻区稻瘟病菌菌株的抗性频率介于11.29%~88.71%和10.77%~86.15%之间，其中抗瘟单基因系品种IRBL9-W（Pi-9）和IRBLz5-CA（Pi-z5）抗性表现最好；2018年，抗瘟单基因系品种对南部和中东部稻区菌株的抗性频率介于10.34%~82.67%和15.79%~85.96%之间，其中抗瘟单基因系品种IRBL9-W（Pi-9）和IRBLz5-CA（Pi-z5）抗性表现最好。表明水直播条件下黑龙江省稻瘟病菌致病性分化剧烈，稻瘟病菌整体致病力较强，但仍有部分水稻种质抗性较好且相对稳定，基因聚合后抗性会得到进一步提升。     

籼稻恢复系桂R106对稻瘟病的抗性评价及遗传分析

通过与‘丽江新团黑谷’及13个已知抗性基因品种杂交和接种广西稻瘟病菌系鉴定,研究了籼稻恢复系‘桂R106’对稻瘟病的抗性及遗传。结果表明,‘桂R106’对广西565个稻瘟病菌系的抗谱达98.11%,对广西6个主要优势菌系表现全抗,对菌系03E-11和03E-23的抗性均受一对显性基因控制。等位性分析确认,‘桂R106’中抗菌系03E-11的抗病基因与Pi-ta、Pi-12(t)、Pi-3、Pi-5、Pi-7、Pi-a、Pi-at、Pi-sh、Pi-i、Pi-km、Pi-19(t)、Pi-ks、Pi-b这13个已知基因不等位,认为它可能是一个未知的新基因。     

抗稻瘟病单基因系对籼稻稻瘟病菌小种鉴别力分析

 利用30个抗稻瘟病单基因系对146个来自广东的稻瘟病菌单孢分离菌株进行了致病性测定,其中17个单基因系对测试菌株的致病性有较好的鉴别力。基于主成分因子分析法,对17个单基因系和146个菌株组成的互作变量矩阵进行了因子提取,结果表明其中9个单基因系为代表的抽提因子可以解释变量总方差的80.437%,初步组建了这9个单基因系构成的稻瘟病菌生理小种单基因系鉴别寄主。按其对变量方差贡献大小排序,它们分别是:IRBLkp-K 60(Pi-k^p)、IRBLi-F5(Pi-i)、F128-1(Pi-ta²)、IRBL9-W (Pi-9(t))、IRBLsh-S (Pi-sh(1))、IRBLz-Fu (Pi-z)、IRBLkh-K3(Pi-k^h)、IRBL1-CL (Pi-1)、IRBLz5-CA (Pi-z⁵)。用这9个单基因系可将146个菌株划分为83个小种,将来自广西、福建、湖南、湖北、浙江、四川等籼稻区的54个菌株划分为26个小种。筛选的9个单基因系对我国籼稻区稻瘟病菌致病性有较强的鉴别力。在抗病性鉴定中,基于单基因系的代表菌株选择,可考虑应用聚类和变量分析法进行。     

Site‐directed mutagenesis of the cytochrome b gene and development of diagnostic methods for identifying QoI resistance of rice blast fungus

BACKGROUND: It is possible that a single nucleotide polymorphism (SNP) (G143A mutation) in the cytochrome b gene could confer resistance to quinone outside inhibiting (QoI) fungicides (strobilurins) in rice blast fungus because this mutation caused a high level of resistance to fungicides such as azoxystrobin in Pyricularia grisea Sacc. and other fungal plant pathogens. The aim of this study was to survey Magnaporthe oryzae B Couch sp. nov. isolates in Japan for resistance to QoIs, and to try to develop molecular detection methods for QoI resistance. RESULTS: A survey on the QoI resistance among M. oryzae isolates from rice was conducted in Japan. A total of 813 single‐spore isolates of M. oryzae were tested for their sensitivity to azoxystrobin using a mycelial growth test on PDA. QoI fungicide resistance was not found among these isolates. The introduction of G143A mutation into a plasmid containing the cytochrome b gene sequence of rice blast fungus was achieved by site‐directed mutagenesis. Molecular diagnostic methods were developed for identifying QoI resistance in rice blast fungus using the plasmid construct. CONCLUSION: As the management of rice blast disease is often dependent on chemicals, the rational design of control programmes requires a proper understanding of the fungicide resistance phenomenon in field populations of the pathogen. Mutation of the cytochrome b gene of rice blast fungus would be specifically detected from diseased leaves and seeds using the molecular methods developed in this study. Copyright © 2009 Society of Chemical Industry     

Suppression of rice blast by phylloplane fungi isolated from rice plants

Rice phylloplane fungi were evaluated for their potential as biocontrol agents for rice blast disease caused by Magnaporthe grisea. A total of 1923 fungal isolates were obtained from rice plants in fields at Ishigaki and Iwama and from potted plants placed in a cedar woods in Iwama as bait. Although 82.9% of isolated fungi could not be identified, species of Epicoccum were the most prevalent among identified isolates. Of the 1923 isolates, 967 were randomly selected for screening against rice leaf blast. Nine isolates (MKP5111B, MKP5112, J2JMR3-2, K2J131-2, I5R3-1, NOP541, K1KM134-1, NOP5112, MKP33222) suppressed the disease when a conidial or hyphal suspension of both the phylloplane fungus and pathogen were simultaneously used to inoculate rice plants cultured in pots in a growth chamber. Five of the isolates originated from potted plants in the woods and four from Ishigaki, a subtropical island. Five (MKP5111B, MKP5112, NOP541, NOP5112, MKP33222) of the nine isolates strongly suppressed conidial germination of M. grisea (0.7%) and formed inhibition zones (3–5mm width) in dual cultures with the pathogen. Methanol extracts from the isolates also inhibited mycelial growth of the pathogen. These results suggest that the five isolates produced antibiotic(s). These five isolates are likely identical or closely related fungal species because the sequence of their ITS regions were 100% similar. ITS sequence analysis also suggested that J2JMR3-2 was associated with a species of Fusarium. Under field conditions, J2JMR3-2 reduced both leaf and panicle blast severity, and three other isolates (MKP5111B, K1KM134-1, K2J131-2) suppressed leaf blast in one of the three experiments.     

Allelism of rice blast resistance genes in two Chinese rice cultivars, and identification of two new resistance genes

Blast, caused by Pyricularia grisea , is a major constraint on rice production. To broaden genetic diversity for resistance to this disease, two rice cultivars, GA20 and GA25 from Yunnan Province, China, were analysed for the genetic basis of their high resistance to blast. GA20 was crossed with 10 Japanese differential cultivars, and GA25 was crossed with nine of them and with the susceptible Chinese cultivar Lijiangxintuanheigu (LTH). The resistance of GA20 was governed by two dominant genes allelic to genes at the Pi-k and Pi-ta loci. The allele at the Pi-k locus was new, based on a reaction pattern different from known alleles at this locus. It could not be shown whether or not the allele at the Pi-ta locus is new, because races with virulence for Pi-ta were not tested. GA25 has one resistance gene, which is not allelic to genes at the loci Pi-a , Pi-k , Pi-z , Pi-ta , Pi-b , and Pi-t , but is linked to the Pi-i gene on chromosome 9 with a recombination frequency of 15.1 ± 2.8%.
The new allele at the Pi-k locus in GA20 is designated as Pi-k^g (t), and the new resistance gene in GA25 as Pi15(t) .     

湖南桃江病圃稻瘟病菌对24个水稻抗稻瘟基因的毒性分析

稻瘟病是水稻生产上的重要病害,了解稻瘟病菌群体毒性组成是水稻抗病品种合理布局的重要基础。2012-2015年从湖南桃江病圃中不含已知抗瘟基因的水稻品种‘丽江新团黑谷’上成功分离出351个稻瘟病菌单孢菌株,在温室于水稻5叶期采用离体接种法测定了其对24个水稻抗稻瘟病单基因系的毒性,结果表明,病圃中稻瘟病菌以广谱强致病性的菌株为主,病菌对不同抗瘟基因的毒力频率在50.56%~96.67%之间,而不同年度间对24个抗性基因均具毒性的菌株出现频率在0~15%之间。对2015年的每2个抗瘟基因的联合毒力分析表明,基因两两搭配后的联合抗病系数最高、联合致病系数最低的组合是Pi-3*Pi-k(RAC=0.19,PAC=0.43)。     

福建省稻瘟病菌对主要抗瘟基因及主栽品种的致病性分析

为明确福建省各稻区的主要抗瘟基因及主栽品种的利用价值,2012—2014年采用喷雾法测定了丽江新团黑谷上的193个菌株对30个水稻抗瘟基因及93个主栽水稻品种的致病性。结果表明,供试稻瘟病菌对30个抗瘟基因表现为强致病力和较强致病力的出现频率分别为13.47%和52.85%,对93个主栽品种表现为强致病力和较强致病力的出现频率分别为1.55%和11.40%;供试稻瘟病菌对抗瘟基因Pi-k~m、Pi-7(t)、Pi-k~p和Pi-9(t)的毒力频率均低于20%;供试稻瘟病菌对谷优2329、谷优5138、昌优964等37个品种的毒力频率均低于20%,对谷优系列、全优系列、深优系列、泰丰优系列及天优系列水稻品种的毒力频率均低于20%。研究表明,在福建地区抗瘟基因Pik~m、Pi-7(t)、Pi-k~p和Pi-9(t)可作为抗源使用,且谷丰A、全丰A、深97A、泰丰A和天丰A仍是抗瘟性较好的育种亲本材料。     

云南省水稻稻瘟病菌无毒基因AVR-Pia变异及水稻抗性基因Pia的有效性

为进一步了解田间稻瘟病菌Magnaporthe oryzae群体中AVR-Pia基因的分布及变异,利用水稻单基因系IRBLa-C水稻品种对自云南省13个市(州)采集分离得到的471株稻瘟病菌菌株进行抗性基因Pia有效性测定;利用无毒基因AVR-Pia特异性标记对471株稻瘟病菌菌株进行PCR检测和测序,并分析稻瘟病菌群体中无毒基因AVR-Pia的分布及DNA结构变异;利用有效性结果和PCR检测结果对471株菌株进行反应型划分,筛选鉴定菌株;利用鉴定菌株对云南省112份地方稻种进行Pia基因鉴定。结果表明,在471株稻瘟病菌菌株中,对含有Pia基因的水稻单基因系IRBLa-C表现为抗病和感病的菌株数分别为139株和332株,所占比例分别为29.5%和70.5%;在471株稻瘟病菌菌株中,分别有244株和227株菌株含有无毒基因AVR-Pia和不含有无毒基因AVR-Pia,所占比例分别为51.8%和48.2%,无毒基因AVR-Pia主要为完全缺失变异;在471株稻瘟病菌菌株中,A-和V+反应型菌株数分别为56株和161株,共217株,占总菌株数的46.1%,在13个市(州)稻瘟病菌群体中,A-和V+反应型菌株所占比例差异较大,其中在普洱市、红河哈尼族彝族自治州、昭通市、玉溪市4个市(州)的比例较大,分别为77.8%、57.1%、52.1%和50.0%;在112份云南省地方稻种质资源中,有20份地方稻品种含有抗性基因Pia,主要分布在9个市(州)中。表明云南省13个市(州)绝大部分水稻产区水稻Pia基因已丧抗性,含Pia基因的水稻种质在云南省分布较广。     

DNA fingerprinting of Pyricularia grisea by rep-PCR using a single primer based on the terminal inverted repeat from either of the transposable elements Pot2 and MGR586

We investigated the use of single primers complementary to sequences in the terminal inverted repeat (TIR) of either Pot2 or MGR586, transposable elements found in Pyricularia grisea, for DNA fingerprinting by repetitive-element-based polymerase chain reaction (rep-PCR). Under standard amplification conditions, rep-PCR with each single primer generated distinct fingerprint patterns among rice-infecting P. grisea isolates collected in Japan. With the Pot2-TIR primer, bands ranging in size from 0.2 to 8 kb and in number from 8 to 13 per isolate were amplified. Although fewer bands were amplified with the MGR586-TIR primer, this molecular technique should be more reliable to identify and classify P. grisea isolates by combining the data of fingerprint patterns from each TIR primer. In a cluster analysis based on DNA fingerprints from this rep-PCR with the Pot2-TIR primer, 10 reference isolates and 12 field isolates from Saga Prefecture in 2002 were separated into six clonal lineages. We also demonstrated that the 12 field isolates belonged to one clonal lineage. Thus, this rep-PCR method using the single primer Pot2-TIR will be useful for the analysis of the population structure of rice blast pathogens.     

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-k^h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。     

Molecular and Pathotype Analysis of the Rice Blast Fungus in North Vietnam

Rice blast caused by Pyricularia oryzae is a devastating disease worldwide. In Vietnam, rice blast is especially severe in the Red River Delta in the North. The genetic diversity of 114 P. oryzae isolates collected from rice in 2001 in the Red River Delta and nine additional Vietnamese P. oryzae isolates was analysed using Amplified Fragment Length Polymorphism (AFLP). DNA similarity and cluster analysis based on 160 polymorphic AFLP markers showed twelve different AFLP genetic groups among the 123 field isolates. Isolates collected from japonica hosts clustered separately from indica host isolates with at least 60% dissimilarity with little evidence for gene flow between the two populations. In the 2001 population originating from indica hosts, three genetic groups were predominant and represented 99% of the isolates sampled. One predominant clonal lineage represented 59% of the 2001 indica host population and was found in eleven provinces in the Red River Delta of North Vietnam. Significant genotype flow could be demonstrated between the indica population south of Red river and the indica population north of Red river. There was significant linkage disequilibrium between the AFLP loci within the indica population, indicating that this is not a random mating population. Pathogenicity tests of 25 isolates selected from the 12 AFLP groups on a set of 29 differential rice lines revealed two avirulent isolates and 23 pathotypes. Different combinations of known resistance genes were found to have potential for blast resistance breeding for North Vietnam. First two authors contributed equally