Physiological Macro-lesions Enhanced Resistance to Blast (Magnaporthe grisea) in Rice Near-isogenic Lines

Roll-leaf-1 （rl-1） and spot-leaf-1 （spl-1） were two near-isogenic lines, which were obtained after 3 to 4 backcrosses with early season indica rice Zhefu 802 as recurrent parent. Henna macro-lesions, referred as physiological or morphological markers, began to appear on leaves at 4.5- to 6.0-leaf stage. The rice seedlings were inoculated at 3.5-, 5.0- and 7.0-leaf stages with high pathogenic races Zhong A1 and Zhong B1 of Magnaporthe grisea, respectively. The resistance of rl-1, spl-1 and Zhefu 802 against blast was significantly different. The seedlings of Zhefu 802 at 3.5- to 7.0-leaf stage were susceptible to races Zhong A1 and Zhong B1 of M. grisea, whereas those of rl-1 and spl-1 at 3.5-, 5.0- and 7.0-leaf stages were susceptible, moderately resistant and resistant, respectively. These results suggested that the enhanced resistance of rl-1 and spl-1 related to the appearance of their morphological marker lesions. The experiment provided a basis for studying lesion mimic and hypersensitive response in association with disease resistance.

Improving the resistance of the rice PTGMS line Feng39S by pyramiding blast,bacterial blight,and brown planthopper resistance genes

Knowledge of rice(Oryza sativa L.)genes and various DNA markers can be used in genomic breeding programs aimed at developing improved elite rice cultivars.We used an efficient genomic breeding approach to pyramid four resistance genes(Pi2,Xa23,Bph14,and Bph15)in the popular photoperiod-and thermosensitive genic male sterile(PTGMS)rice line Feng39S.We performed foreground selection for the target genes,followed by recombinant selection and background selection.This process reduced the sizes of the genomic segments harboring the target genes(566.8 kb for Pi2,1143.9 kb for Xa23,774.7 kb for Bph14,and 1574.9 kb for Bph15)and accelerated the recovery of the recurrent parent genome to proportions ranging from 98.77%to 99.16%,thus resulting in four near-isogenic lines.To assemble the four resistance genes in Feng39S,we performed a double-way cross combined with foreground and background selection to generate two improved lines of Feng39S(Pi2+Xa23+Bph14+Bph15)with a recurrent parent genome recovery of 98.98%.The two lines showed agronomic performance,grain quality,and fertility–sterility transition characteristics similar to those of the original Feng39S line.The newly developed PTGMS lines and corresponding hybrid combinations were resistant to various field blast isolates and seven representative isolates of bacterial blight.At the seedling stage,the lines also showed resistance against brown planthopper.This study provides an efficient and accurate genomic breeding approach for introducing desirable traits into PTGMS lines.

Improving Rice Blast Resistance by Mining Broad-Spectrum Resistance Genes at Pik Locus

Magnaporthe oryzae is known for its genetic diversity and pathogenic variability,leading to rapid breakdown of resistance in rice.Incorporating multiple broad-spectrum blast resistance genes into rice cultivars would extend disease resistance longevity.Effective resistance breeding in rice therefore requires continual enrichment of the reservoir of resistance genes and alleles.We conducted a large-scale screen of rice blast resistance in about 2000 rice accessions.Among them,247 accessions showed at least medium resistance to the natural infection of rice blast and 7 novel Pik alleles were identified from them.Variations in gene sequences were then correlated with the phenotypic trait to enable the identification of favorable alleles.Among the seven novel Pik alleles,the resistant rate of Pik-R0/ME/7017 donors was greater than 80%,and the disease score was less than 3.Through molecular marker-assisted backcross breeding,we successfully transferred the three Pik alleles,Pik-R0/ME/7017,into an elite cultivated line Kongyu 131 to obtain BC_(3)F_(2)lines,which showed enhanced resistance to rice blast compared with the recurrent parent.Assessment of these near-isogenic lines in the greenhouse using 31 isolates of M.oryzae from Heilongjiang Province of China revealed that the resistant levels of the BC_(3)F_(2)lines with Pik-R0/ME/7017 were significantly higher than those of the established cloned resistance genes Pik-m and Pi1.Exploring such alleles will enrich our gene library for resistance to rice blast.

Improving Blast Resistance of a Thermo-Sensitive Genic Male Sterile Rice Line GD-8S by Molecular Marker-Assisted Selection

The broad-spectrum blast resistance gene Pi-1, from donor line BL122, was introduced into a thermo-sensitive genic male sterile rice line GD-8S, which possessed good grain quality but high susceptibility to rice blast, by using backcross breeding and molecular marker-assisted selection. Five elite improved male sterile lines, RGD8S-1, RGD8S-2, RGD8S-3, RGD8S-4 and RGD8S-5, were selected based on the results of molecular marker analysis, spikelet sterility, recovery rate of genetic background and agronomic traits. Thirty-three representative blast isolates collected from Guangdong Province, China were used to inoculate the improved lines and the original line GD-8S artificially. The resistance frequencies of the improved lines ranged from 76.47% to 100%, much higher than that of the original line GD-8S （9.09%）. On the agronomic characters, there were no significant differences between the improved lines and GD-8S except for flag leaf length and panicle number per plant. The improved lines could be used for breeding hybrid rice with high blast resistance.

Development of elite restoring lines by integrating blast resistance and low amylose content using MAS

Blast resistance and grain quality are major problems in hybrid rice production in China. In this study, two resistance （R） genes, Pi46 and Pita, along with the gene Wxb, which mainly affects rice endosperm amylose content （AC）, were introgressed into an elite indica restoring line, R8166, which has little blast resistance and poor grain quality through marker-assisted selection （MAS）. Eight improved lines were found to have recurrent genome recovery ratios ranging from 88.68 to 96.23%. Two improved lines, R163 and R167, were selected for subsequent studies. R167, which has the highest recovery ratio （96.23%）, showed no significant differences in multiple agronomic traits. In contrast, R163 with the lowest recovery ratio （88.68%） exhibited significant differences in heading date and yield per plant compared with the recurrent parent. At two developmental stages, R163 and R167 had greatly enhanced resistance to blast over the recurrent parent. Similar trends were also observed for agronomic traits and blast resistance in R163- and R167-derived hybrids when compared with the counterparts from R8166. In addition, R163, R167, and their derived hybrids significantly improved the grain quality traits, including amylose content （AC）, gel consistency （GC）, chalky grain rate （CGR）, and degree of endosperm chalkiness （DEC）. It confirmed the success of efficiently developing elite restoring lines using MAS in this study.

Development and Identification of Novel Rice Blast Resistant Sources and Their Characterization Using Molecular Markers

To develop and characterize introgression lines for leaf and neck blast resistance, 326 introgression lines were developed using various accessions of six different AA genome wild species in the genetic background of elite Indian varieties like PRl14 and Pusa 44 and were screened for blast resistance. Stringent phenotyping coupled with genotyping using gene based markers led to the identification of four resistant introgression lines, which showed promising resistance and do not possess any of the tested genes. Furthermore, multi-location screening confirmed the field resistance of the four introgression lines to both leaf and neck blast. Molecular characterization of these introgression lines using genome-wide simple sequence repeat markers revealed the presence of small percentage of wild Oryza genome introgrssion. So these lines can be used for mapping and identification of novel leaf and neck blast resistance genes. Thus, these four introgression lines can be considered as new genetic resources for blast resistance.

Preliminary evaluation of resistance genes in rice against bacterial leaf blight in Guilan Province—Iran

The reactions of rice bacterial leaf blight races were identified in Guilan province—Iran on 12 near-isogenic lines and 14 pyramiding lines from International Network for Genetic Evaluation of rice (INGER) and 8 local and improved Iranian varieties were evaluated under natural photoperiod condition in the field. Inoculation was done at panicle initiation by clipping the sterilized scissors in the bacterial suspension to booting stage. Scoring of inoculated plants was made 21 days after inoculation. Infection levels of pyramiding lines containing two to five resistance genes, expect, IRBB53 and IRBB61 with respectively resistance gene combination, Xa5 + Xa13 and Xa4 + Xa5 + Xa7, were not so clear. Among near-isogenic lines IRBB1, IRBB2, IRBB4 and IRBB10 carrying resistance gene Xa1, Xa2, Xa4 and Xa10 were susceptible;IRBB8, IRBB11, IRBB3, IRBB5 and IRBB13 were moderately susceptible;(having resistance gene Xa8, Xa11, Xa3, Xa5 and Xa13) IRBB14, IRBB21 and IRBB7 with respectively resistance gene Xa14, Xa21 and Xa7 were moderately resistance to bacterial blight. Furthermore, most of the time gene combinations support the strategy of pyramiding appropriate resistance gene. Local varieties were more susceptible than improved varieties to leaf blight disease. Among local varieties, Tarom was the most susceptible. And also, there were no significant differences among improved varieties and all of them were moderately resistance.

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.

Cultivar Mixture Cooperation(CMC)of rice varieties(lines) with different blast resistant gene

We studied Cultivar Mixture Cooperation(CMC)of rice varieties(lines)by screening mixture ofrice varieties which possess different genes,1983-1996.

Proteomic analysis of blast-resistant near-isogenic lines derived from japonica rice, var. Yunyin, infected with Magnaporthe oryzae

Rice blast is one of the most devastating diseases in the world and outbreaks occur frequently.The differences in protein expression between blast resistant and susceptible near-isogenic lines(NILs)of japonica rice var.Yunyin infected with Magnaporthe oryzae were analyzed using proteomics,indicated that 67 different proteins were identified from 75 obtained proteins using the matrixassisted laser desorption/ionization time-of-flight mass spectrometry technique.Seven specific expression proteins,43 up-regulated proteins and 17 down-regulated proteins were identified among the 67 proteins.The bioinformatical analysis demonstrated that these 67 different proteins were involved in many biological physiological processes including five proteins related to photosynthesis,25 proteins related to metabolism,six proteins related to antioxidants,10 proteins related to protein synthesis and modification,five proteins related to signal transduction,four proteins related to adversity stress and 12 non-functional proteins.These identified proteins were directly or indirectly related to stress.Five proteins related to different physiological processes were selected.Their cDNA sequences were predicted and their expression patterns were analyzed using real-time PCR,demonstrated that the genes would response to M.oryzae and the response blindingly different between blast resistant and blast susceptible NILs.

抗稻瘟病水稻恢复系的分子标记辅助选育及抗性鉴定

【目的】开展抗稻瘟病水稻恢复系的分子标记辅助选育及抗性鉴定,为育成持久、广谱抗病优质杂交水稻新品种提供优异的遗传资源和技术参考。【方法】利用分子标记辅助选择和回交育种技术,将持久、广谱的抗稻瘟病基因Pi1、Pi2和Pigm导入恢复系桂R1703,获得了单基因、双基因和三基因导入系,并对其进行稻瘟病鉴定和农艺性状调查,分析不同抗稻瘟病基因间的抗性效应及抗性基因导入对受体亲本农艺性状的影响。【结果】通过对杂交后代和回交群体的Pi1、Pi2和Pigm基因相关分子标记检测,发现抗稻瘟病基因Pi1、Pi2和Pigm已成功导入到桂R1703中,筛选获得7个携带有抗稻瘟病基因且抗性和农艺性状综合表现优良的导入株系,表现出较强的稻瘟病抗性。单基因导入系中,抗稻瘟病基因的抗性效应排序为为Pigm>Pi2>Pi1;双基因和三基因导入系的稻瘟病抗性均强于单基因导入系,尤其以三基因导入系抗性最强,不同基因聚合的抗性效应排序为Pi1+Pi2+Pigm>Pi2+Pigm>Pi1+Pigm>Pi1+Pi2。7个瘟病抗性基因导入株系与桂R1703在穗长和千粒重方面无显著差异(P>0.05,下同),有2个瘟病抗性基因导入系的株高显著高于桂R1703(P<0.05,下同);有1个瘟病抗性基因导入系的单株有效穗显著高于桂R1703;有3个瘟病抗性基因导入系的单穗总粒数显著高于桂R1703;有5个瘟病抗性基因导入系结实率显著低于桂R1703;有2个瘟病抗性基因导入系的单株产量显著低于桂R1703;有4个瘟病抗性基因导入系的单株产量显著高于桂R1703。【结论】通过分子标记辅助选育可有效聚合多基因(Pi1、Pi2和Pigm基因),使恢复系桂R1703的稻瘟病抗性得到明显提升,获得一系列抗稻瘟病且与亲本其他性状相近的遗传材料,可作为亲本材料用于选育抗病优质的杂交稻。

携有抗白叶枯病新基因Xa23水稻近等基因系的构建及应用(英文)

1993～ 1998年 ,构建了携有抗稻白叶枯病新基因 Xa2 3的近等基因系 ,命名为 CBB2 3。以全生育期高度感病并具有改良株型的籼稻品种 JG30为轮回亲本 ,与携有 Xa2 3的抗性供体 H4杂交 ,JG30 / H4的 F1 通过回交、自交直至 B5F4,各世代均用与目标基因 Xa2 3相对应的专化小种菌系 P6人工接种鉴定 ,同步进行株型和农艺性状选择 ,直至抗性稳定和农艺性状类似其轮回亲本。比较了 CBB2 3(携 Xa2 3)和 IRBB2 1(携 Xa2 1)对 2 0个菌系包括 10个菲律宾小种、3个日本小种和7个中国病原型代表菌系的抗谱 ,Xa2 3抗所有 2 0个菌系 ;Xa2 1抗 19个菌系 ,对菲律宾 10号小种则高度感病。用近等基因系 CBB2 3构建了 JG30 / CBB2 3组合的 F2 分离群体 ,通过 SSR标记筛选 ,初步将 Xa2 3定位于水稻第 11染色体。进一步筛选出 3个与 Xa2 3更紧密连锁的 AFL P标记。其中的 APKj2 3与 Xa2 3之间的图距约为 1.0 c M。并报道了在抗病育种中已有效的应用了携有 Xa2 3的近等基因系 CBB2 3。

广谱稻瘟病抗性基因Pigm和Pi2的抗谱差异及与Pi1的互作效应

Pigm是Pi2基因簇的等位或紧密连锁基因。本研究构建了4个不同遗传背景下Pigm和Pi2的系列近等基因系，204个菌株苗期接种结果显示其抗性频率均超过70％，但Pigm和Pi2的抗谱重叠度仅为54．4％~65．7％，聚合Pi1／Pigm和Pi1/Pi2以杂种的抗性频率均超过90％。穗瘟人工接种及病圃自然诱发鉴定表现与苗期接种一致的发病趋势。农艺性状调查结果显示获得的近等基因系与其轮回亲本基本相似，存在较少的累赘连锁。表明Pigm是一个与Pi2抗谱差异明显的广谱抗性基因，对稻瘟病抗性育种具有重要应用价值。

应用近等基因系研究Bt基因对水稻性状表现的影响

以密阳46(MY46)为轮回亲本,采取连续回交,结合GUS标记基因辅助选择技术,育成了Bt基因近等基因系抗螟虫密阳46(RIMY46).经考察,RIMY46及其所配杂种II32A/RIMY46的GUS反应和PCR检测均为阳性,且高抗螟虫.在早期营养生长阶段,RIMY46苗高比MY46低,分蘖数比MY46少,表明纯合态Bt基因对纯系植株的前期生长进程有一定延缓作用,这种影响随着植株长大而减小,最终除导致抽穗延迟和整精米率降低外,对其余8个农艺性状和9个稻米品质性状的影响则均不显著.比较Bt近等基因系所配杂种II32A/RIMY46和II32A/MY46有关性状的表现差异,结果则发现杂合态Bt基因对杂种F1性状表达均无明显的负作用.

丽江新团黑谷近等基因系抗稻瘟病分析

利用31个稻瘟病菌株对由国际水稻研究所育成以不具有主效抗性基因的丽江新团黑谷为轮回亲本的一套单基因近等基因系和8个抗性基因组合进行接种鉴定,结果表明,不同抗性基因的抗谱存在显著差异,其中IRBLZ-Fu(Pi-z)I、RBLZ5-CA(Pi-z-5)I、RBLZt-T(Pi-z-t)I、RBL9-W(Pi-9(t))的抗性频率分别为93%、97%、90%和96%,可初步认为Pi-z、Pi-z-5、Pi-z-t、Pi-9(t)为广谱抗性基因;不同抗性基因组合的抗谱均较其亲本宽,主要表现为抗性基因间的互补效应和积加效应,本研究为基因聚合培育广谱持久的抗性品种提供了理论依据。

高原粳稻子预44抗稻瘟病基因遗传分析和定位

以高感稻瘟病的低海拔粳稻江南香糯与高抗稻瘟病的高原粳稻子预44作亲本进行杂交,获得F1、F2、BC1F1和以F2单粒传构建的、由276个株系组成的F7重组自交系群体。分别用稻瘟病菌生理小种ZB13和ZE1对两亲本江南香糯和子预44及其杂交后代群体F1、F2和BC1F1进行抗性接种鉴定和遗传分析。结果表明,子预44对稻瘟病菌生理小种ZB13和ZE1的抗性都表现为单基因控制的显性遗传。进一步利用重组自交系F7群体的266个有效株系作为定位群体,将抗稻瘟病菌生理小种ZE1的基因定位在水稻第11染色体上与SSR标记RM206间遗传距离为0cM的位置,暂定名为Pi-zy(t)。这些结果为进一步将子预44中的抗性基因用于水稻抗病育种及该抗稻瘟病基因的克隆奠定了重要基础。

3个粳稻抗白叶枯病近等基因系的构建

自1989～1996年,选用分别具有抗水稻白叶枯病主效基因Xa 2、Xa 7和Xa 14的3个品种为供体亲本,以一个不携有抗病基因的改良型粳稻品种沈农1033为轮回亲本,通过6次回交、自交直至BC_6F_4代,经各世代抗性和农艺性状筛选,转育成3个粳型抗白叶枯病近等基因系(NIL),命名为CBB2、CBB7和CBB14。这些NIL除所带不同的抗病基因外,其生育期、株高、分蘖力、穗型大小等农艺性状与轮回亲本基本相似。经抗病反应型检测、遗传分析、育种及分子标记应用,初步证明这些NIL具有良好的实用价值。

基因聚合提高了水稻对白叶枯病的抗性

研究了含有单个抗性基因的水稻近等基因系和抗性基因聚合品系对浙江省白叶枯病菌４个主要小种的抗性，单个基因对这些小种的抗性均不高，对新近流行的小种大多感病；基因聚合品系对这些小种的抗性普遍提高，说明基因聚合是培育具有持久抗性品种的有效策略。

以丽江新团黑谷为遗传背景的抗稻瘟病基因累加系的选育及其抗性鉴定

以丽江新团黑谷(LTH)近等基因系为亲本,构建了3个F6重组自交系群体,以具鉴别能力的菌株进行抗稻瘟病筛选,共获得3组携带2个抗病基因的累加系5个,即:1)F-Kpib-3(Pi-kp/Pi-b),F-Kpib-6(Pi-kp/Pi-b);2)F-Kita2-7(Pi-k/Pi-ta2),F-Kita2-9(Pi-k/Pit-a2);3)F-Kmita(Pi-km/Pi-ta)。基因组成相同的累加系抗性相同,它们的抗病频率均高于相应的近等单基因系,3组抗病频率分别达100.0%、91.7%和50.0%。这些累加系可用于稻瘟病菌致病型鉴定、田间稻瘟病菌致病性变异监测和作为抗病亲本用于抗病育种。

携有不同主效白叶枯病抗性单基因的3个粳稻近等基因系的选育

自1986至1993年,我们选育了第一批携有抗水稻白叶枯病主效基因,Xa-3、Xa-4和Xa-12的3个粳稻近等基因系:CBB3、CBB4和CBB12（暂名）。以1个感病并具有改良株型的粳稻品种沈农1033为轮回亲本,通过回交、自交直至BC_5F_5代。各世代经抗性测定和株型选择,直至各系的抗性稳定和农艺性状趋于一致。进行了3个近等基因系与其供体基因的抗性反应型比较、农艺性状考查及抗性遗传分析。通过育种和电泳分析研究应用,证实了这批近等基因系有较好的利用价值。