A new blast resistance gene identified in the Indian native rice cultivar Aus373 through allelism and linkage tests

Blast, caused by Pyricularia grisea , is a major constraint on rice production. To widen genetic diversity for disease resistance, the Indian native rice cultivar Aus373 was screened by F₂ segregation analyses to investigate the genetic basis of its high resistance. Aus373 was crossed with a series of Japanese differential cultivars (JDCs) and the Chinese susceptible cultivar Lijiangxintuanheigu (LTH). The resistance ratios of subsequent F₂ progenies were used to determine the number of blast-resistance loci present as well as allelic relationships with known loci. Resistance of Aus373 was governed by dominant alleles at two loci, one at the Pi-k locus and the second apparently at a new locus linked to an isozyme gene Amp-1 with a recombination fraction of 37.9 ± 3.0% on chromosome 2. This putative new locus and allele were designated Pi16 (t).     

Identification of a new resistance gene to a chinese blast fungus isolate in the Japanese rice cultivar aichi asahi

ABSTRACT Genetic analysis of the rice cultivar Aichi Asahi and some other Japanese cultivars for the high resistance to the blast fungus isolate CHNOS58-3-1 from China was performed. All the Japanese differential cultivars were resistant to the isolate except for 'Pi No. 4', which showed moderate resistance. Analysis of the F(2) population of a cross of the susceptible cultivar Reiho and the resistant cultivar Aichi Asahi indicated that the resistance of 'Aichi Asahi' to the isolate was conferred by one dominant gene. To identify the gene in other Japanese differential cultivars, AK lines, which were derived from a cross of 'Aichi Asahi' x 'K59' and assumed to harbor no known genes except for the new one, were used for the allelism tests. The new, completely dominant resistance gene was detected in 14 differential cultivars, but not in 'Pi No. 4', 'Yashiro-mochi', and 'K1', and was designated as Pi19(t). Pi19(t) was allelic or closely linked to Pita(2) on chromosome 12. Pi19(t) was extensively distributed among Japanese traditional local cultivars.     

Identification and mapping of a rice blast resistance gene Pi-g(t) in the cultivar Guangchangzhan

A single dominant blast resistance gene was identified in Chinese indica rice ( Oryza sativa ) cv. Guangchangzhan (GCZ), which shows complete resistance to Japanese isolate Ken53-33 of Magnaporthe grisea . Genetic analysis of the backcross (BC₁) and second-generation (F₂) populations from a cross between susceptible cv. Lijiangxintuanheigu (LTH) and GCZ indicated that the resistance was conferred by one dominant gene. This gene was mapped on the long arm of chromosome 2 and flanked by RM166 and RM208 at distances of 4·00 ± 4·90 and 6·30 ± 4·89 cM (centiMorgans), respectively. It was designated tentatively as Pi-g(t) .     

Identification of the rice blast resistance gene Pib in the National Small Grains Collection

The Pib gene in rice confers resistance to a wide range of races of the rice blast pathogen, Magnaporthe oryzae, including race IE1k that overcomes Pita, another broad-spectrum resistance gene. In this study, the presence of Pib was determined in 164 rice germplasm accessions from a core subset of the National Small Grains Collection utilizing DNA markers and pathogenicity assays. The presence of Pib was evaluated with two simple sequence repeat (SSR) markers and a dominant marker (Pib-dom) derived from the Pib gene sequence. Pathogenicity assays using two avirulent races (IE1k and IB1) and a virulent race (IB54) were performed to verify the resistance responses of accessions. Of the 164 accessions evaluated, 109 contained the Pib gene as determined using both SSR markers and pathogenicity assays, albeit different haplotypes were detected. The remaining 52 germplasm accessions were different in their responses to the blast races IB54, IE1k, and IB1, thus indicating the presence of R gene(s) other than Pib. The accessions characterized in this study could be used for marker-assisted breeding to improve blast resistance in indica and japonica cultivars worldwide.     

杂交稻对稻瘟病和稻白叶枯病的抗性鉴定

对广东省将推广的54份杂交稻组合对稻瘟病和白叶枯病的抗病性进行了鉴定。对稻瘟病的抗病性鉴定表明:抗病组合共49个,占90.7%;其中,高抗(抗性比≥91%)组合30个,占55.6%。对稻白叶枯病的抗病性鉴定表明:没有高抗(HR)和抗(R)的组合,仅有一个杂交稻组合(西胜2175)表现为中抗(mR),仅占1.9%,其余53个组合都表现感病,占98.1%。进一步分析表明:对稻瘟病表现高抗的30个杂交稻组合都不抗白叶枯病,而中抗白叶枯病的杂交稻组合西胜2175对稻瘟病表现为中抗,抗性比为74%。     

湘资3150 微效抗瘟性基因鉴定

 以湘资3150 和CO39 为亲本建立F10 重组自交系群体为材料, 在桃江病圃应用自然诱发接种法对群体的田间叶瘟抗性表现进行了分析。结果表明, 在LOD 2. 5 的域值上,共检测到14 个有效的微效基因QTL 位点(LOD 值均大于2. 5),分别位于水稻第3、8 和10 染色体上,其表型变异贡献值差异比较大,介于11. 78% ~ 40. 57% 之间;表明可能控制不同抗性表型的QTL 紧密连锁或者同一个QTL 对不同的抗性表型均具有抗性贡献。     

航天诱变水稻对叶瘟和穗瘟的抗性鉴定

采用蒙古稻旱晚播活体菌株接种法 ,对JB-1号返回式卫星搭载回的 12个稳定的水稻突变体作了稻瘟病抗性鉴定 ,结果明确 ,航天诱变水稻材料 971-5、974 -4、974-5均抗叶瘟和穗瘟。     

New gene for bacterial blight resistance in rice located on chromosome 12 identified from minghui 63, an elite restorer line

ABSTRACT Bacterial blight, caused by Xanthomonas oryzae pv. oryzae, is a serious disease of rice worldwide. A new dominant gene for bacterial blight resistance in rice, Xa25(t), was identified from Minghui 63, a restorer line for a number of rice hybrids that are widely cultivated in China. This gene conferred resistance to Philippine race 9 (PXO339) of X. oryzae pv. oryzae in both seedling and adult stages. It was mapped to the centromeric region of chromosome 12, 2.5 cM from a disease resistance gene-homologous sequence, NBS109, and 7.3 cM from a restriction fragment length polymorphism marker, G1314. The genomic location of this gene is similar to the previously identified blast resistance genes, Pi-ta and Pi-ta2.     

Mediation of partial resistance to rice blast through anaerobic induction of ethylene

ABSTRACT The correlation between anaerobic soil conditions and increased resistance to rice blast disease has long been observed without benefit of an adequate explanation. We researched flood depth, dissolved oxygen (DO), and ethylene relative to expression of partial blast resistance in cvs. M-201, Newbonnet, LaGrue, Mars, and Cypress. Cultivar blast index (BI) and flood DO decreased with increasing flood depth. BIs were positively correlated with DO. Total leaf blast lesions were 3.4 and 3.2 times greater in cvs. M-201 and LaGrue growing in a 5.0-mul liter(-1) DO nutrient solution than when growing in a 0.1-mul liter(-1) DO solution. Treatment with 0.25 mM ethephon, which releases ethylene, lowered BIs of Newbonnet, LaGrue, and Cypress growing upland when applied drench, foliar, or foliar-drench. If flooded, BIs of ethephon-treated cultivars were decreased by drench and foliar-drench applications only. BIs of upland plants were unchanged, whereas BIs of analogous flooded plants increased following treatment with 0.31 mM aminoethoxyvinylglycine (AVG), an ethylene biosynthesis inhibitor. We hypothesize that varying anaerobic conditions mediate production of phytohormones, particularly ethylene, which modify expression of inherent partial blast resistance in these rice cultivars.     

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) .     

A major quantitative trait locus for rice yellow mottle virus resistance maps to a cluster of blast resistance genes on chromosome 12

ABSTRACT Two doubled-haploid rice populations, IR64/Azucena and IRAT177/ Apura, were used to identify markers linked to rice yellow mottle virus (RYMV) resistance using core restriction fragment length polymorphism (RFLP) maps. Resistance was measured by mechanical inoculation of 19-day-old seedlings followed by assessment of virus content by enzyme-linked immunosorbent assay tests 15 days after inoculation. IR64/Azucena and IRAT177/Apura populations, 72 and 43 lines, respectively, were evaluated, and resistance was found to be polygenic. Resistance was expressed as a slower virus multiplication, low symptom expression, and limited yield loss when assessed at the field level. Bulked segregant analysis using the IR64/Azucena population identified a single random amplified polymorphic DNA marker that mapped on chromosome 12 and corresponded to a major quantitative trait locus (QTL) evidenced by interval mapping. When pooling RFLP data, integrated mapping of this chromosome revealed that the QTL was common to the two populations and corresponded to a small chromosomal segment known to contain a cluster of major blast resistance genes. This region of the genome also reflected the differentiation observed at the RFLP level between the subspecies indica and japonica of Oryza sativa. This is consistent with the observation that most sources of RYMV resistance used in rice breeding are found in upland rice varieties that typically belong to the japonica subspecies.     

东农415稻瘟病抗性遗传分析及基因定位

 粳稻品种东农415自育成以来一直以其早熟、抗病、高产特性而著称,在黑龙江省稻瘟病高发区种植20多年均表现高抗稻瘟病。本研究利用158个采集于黑龙江省不同稻区的稻瘟病菌株对东农415进行接种鉴定,结果表明东农415对黑龙江省稻瘟病菌株有很强的抗性,抗谱高达89.2%。以东农415与丽江新团黑谷(LTH)杂交衍生的F₁和F₂群体为遗传分析试验材料,通过接种鉴定,发现东农415对稻瘟病菌株F-10-11的抗性由一个显性基因控制。进一步采用分子标记结合隐性群体分离分析法,以对菌株F-10-11极端感病的99个F₂单株为作图群体,将东农415的抗病基因定位在第2染色体,距离基因两侧标记RM5300和RM213的遗传距离分别为7.6和3.0 cM,暂命名为Pi-dn(t)。将Pi-dn(t)位点映射到水稻参考基因组图谱上,在抗病位点基因组区段内发现3个编码基因Os02g56010、Os02g55540和Os02g56400具有抗病基因结构域,可作为Pi-dn(t)的候选基因。     

浙江省水稻新品种(系)对稻瘟病的抗性研究

用4个稻瘟病菌小种对浙江省280份水稻新品种(系)进行稻瘟病抗性分析,结果表明:浙江省水稻新品种(系)对稻瘟病菌具有较好的抗性,籼稻和粳稻对参试菌株的全抗率分别为21.62%和39.05%,说明粳稻具有较籼稻更广的抗谱;浙江省新品种(系)对ZB13小种具有较高的感病率,籼稻和粳稻的感病率分别为69.37%和52.07%。     

Ultrastructural and cytochemical aspects of silicon-mediated rice blast resistance

ABSTRACT Although exogenous application of silicon (Si) confers efficient control of rice blast, the probable hypothesis underlying this phenomenon has been confined to that of a mechanical barrier resulting from Si polymerization in planta. However, in this study, we provide the first cytological evidence that Si-mediated resistance to Magnaporthe grisea in rice correlates with specific leaf cell reaction that interfered with the development of the fungus. Accumulation of an amorphous material that stained densely with toluidine blue and reacted positively to osmium tetroxide was a typical feature of cell reaction to infection by M. grisea in samples from Si+ plants. As a result, the extent of fungal colonization was markedly reduced in samples from Si+ plants. In samples from Si- plants, M. grisea grew actively and colonized all leaf tissues. Cytochemi-cal labeling of chitin revealed no difference in the pattern of chitin localization over fungal cell walls of either Si+ or Si- plants at 96 h after inoculation, indicating limited production of chitinases by the rice plant as a mechanism of defense response. On the other hand, the occurrence of empty fungal hyphae, surrounded or trapped in amorphous material, in samples from Si+ plants suggests that phenolic-like compounds or phytoalexins played a primary role in rice defense response against infection by M. grisea. This finding brings new insights into the complex role played by Si in the nature of rice blast resistance.     

黑龙江省水稻新品种（系）抗稻瘟病性鉴定及利用

1998-2009年采用稻瘟病人工接种和自然感病鉴定2种方法,共鉴定黑龙江省水稻新品种（系）485份（次）,鉴定出抗稻瘟病新品种（系）109份,12年间先后推广了‘空育131’、‘绥粳3号’、‘龙粳12’、‘龙粳14’、‘垦稻12’等49个新品种,推广了3个超级稻品种‘龙粳14’、‘龙粳18’、‘龙粳21’,18个新品种年种植面积超过6.67万hm2,获得了较高的经济效益和社会效益。     

OsDCL1基因沉默突变体诱导稻瘟病抗性的转录组分析

稻瘟病是严重危害水稻生长的真菌病害,每年给水稻生产带来重大经济损失。与野生型日本晴NPB相比,OsDCL1基因沉默突变体增强了水稻对稻瘟菌的广谱抗病性。为了解水稻OsDCL1-RNAi突变体的抗病机制,我们分析和比较了它和野生型日本晴NPB在稻瘟菌侵染前后转录组水平的变化。响应稻瘟菌侵染的7 129个差异表达基因(DEGs)中,NPB和OsDCL1-RNAi突变体分别有5 382和5 180个基因表达发生了变化,参与生物胁迫反应、信号通路、蛋白代谢和RNA调控4个通路的基因明显被富集。以野生型未受稻瘟菌侵染的基因表达为对照,在OsDCL1-RNAi突变体中共发现1 318个DEGs,且超过70%是上调的,其中很多基因参与了生物胁迫反应(26.9%)和信号通路(11%),上调表达基因中与生物胁迫反应相关的主要为PR基因和细胞壁相关基因。另外,还发现10个茉莉酸相关基因和11个水杨酸相关基因分别在OsDCL1-RNAi突变体中显著下调和上调表达。在OsDCL1-RNAi突变体中还发现WRKY和MYB等一些转录因子家族以及部分受体类激酶被诱导表达。用qRT-PCR方法验证部分差异表达的基因,其结果与DEGs基本一致。OsDCL1-RNAi突变体中转录组变化的分析,为深入了解该突变体抗瘟性增强的机制奠定了基础。     

施稻灵防治水稻稻瘟病效果试验

稻瘟病（PiriculariaoryzaeCavara）是水稻重要病害之一,笔者用贵州省道元精化有限公司生产的6％施稻灵是浮剂进行了田间药效试验,获得较好的防治效果,现报告如下：1材料与方法1．1试验设计本试验在岑巩县注溪乡稻瘟病重发区进行,试验田水稻品种为汕优63。供试药剂为6％施稻灵悬浮剂（贵州省道元精化有限公司产,贵州省植保植检站提供）,对照药剂为20％三环峻可湿性粉剂（上海东风农药厂产）。设5个处理：6％施稻灵悬浮剂25ml、35ml和50ml／667m2,20％三环隆可湿性粉剂100g／667m2和清水对照,每处理重复3次,计15个小区,小区面积为…