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At least 109 records · Page 6Linked to original sources

PubMed2004

The assessment of the rice cultivars/lines resistance to blast disease in Mazandaran province, Iran.

Blast, caused by Magnaporthe grisea, is one of the most important diseases in rice production regions of the world including Iran. To determine progress of rice blast disease on the selective cultivars and lines also to assay some components of partial resistance, a set of Iranian rice cultivars (Local and breeding) along with near-isogenic lines (NILs) and breeding lines from International Rice Research Institute (IRRI) were tested with some field races of the fungus in blast nursery and five of selective races in greenhouse. These experiments were conducted in a Randomized complete Block Design (RCBD) with three replications (except greenhouse experiment on the leaves). Traits in this study consisted of Infection Neck Number (INN), Neck Lesion Size (NLS), Infection Type (IT), percent Diseased Leaf Area (DLA) and Area Under Disease Progress Curve (AUDPC); also IT, Sporulation Lesion Number (SLN), Sporulating Region Diameter (SRD) and percent DLA were measured in leaf blast in greenhouse (one replication). The Iranian local cultivars and NILs i.e. Co-39 and C104-PKT located as susceptible group for AUDPC, IT, INN and NLS. Iranian breeding cultivars, breeding lines from IRRI and NILs (except Co-39 and C104-PKT) were resistant or indicated hypersensivity reaction (HR). Some cultivars (Fujiminori, Onda, and Hassan Saraii) were semi susceptible to leaf blast in nursery. The main point is correlation in 1% (a = 0.0001) between the traits in greenhouse and blast nursery. Neck node infection of Haraz cultivar in greenhouse experiment to IA-89 race is very important, because Haraz is a resistant cultivar to blast disease in Iran.

Immunity, Innate↗

PubMed2005

Genetic and physical mapping of Pi37(t), a new gene conferring resistance to rice blast in the famous cultivar St. No. 1.

The famous rice cultivar (cv.), St. No. 1, confers complete resistance to many isolates collected from the South China region. To effectively utilize the resistance, a linkage assay using microsatellite markers (SSR) was performed in the three F2 populations derived from crosses between the donor cv. St. No. 1 and each of the three susceptible cvs. C101PKT, CO39 and AS20-1, which segregated into 3R:1S (resistant/susceptible) ratio, respectively. A total of 180 SSR markers selected from each chromosome equally were screened. The result showed that the two markers RM128 and RM486 located on chromosome 1 were linked to the resistance gene in the respective populations above. This result is not consistent with those previously reported, in which a well-known resistance gene Pif in the St. No. 1 is located on chromosome 11. To confirm this result, additional four SSR markers, which located in the region lanked by RM128 and RM486, were tested. The results showed that markers RM543 and RM319 were closer to, and RM302 and RM212 completely co-segregated with the resistance locus detected in the present study. These results indicated that another resistance gene involved in the St. No. 1, which is located on chromosome 1, and therefore tentatively designated as Pi37(t). To narrow down genomic region of the Pi37(t) locus, eight markers were newly developed in the target region through bioinformatics analysis (BIA) using the publicly available sequences. The linkage analysis with these markers showed that the Pi37(t) locus was mapped to a approximately 0.8 centimorgans (cM) interval flanked by RM543 and FPSM1, where a total of seven markers co-segregated with it. To physically map the locus, the Pi37(t)-linked markers were landed on the reference sequence of cv. Nipponbare through BIA. A contig map corresponding to the locus was constructed based on the reference sequence aligned by the Pi37(t)-linked markers. Consequently, the Pi37(t) locus was defined to 374 kb interval flanking markers RM543 and FPSM1, where only four candidate genes with the resistance gene conserved structure (NBS-LRR) were further identified to a DNA fragment of 60 kb in length by BIA.

China↗

PubMed2006

A novel form of resistance in rice to the angiosperm parasite Striga hermonthica.

The root hemiparasitic weed Striga hermonthica is a serious constraint to grain production of economically important cereals in sub-Saharan Africa. Breeding for parasite resistance in cereals is widely recognized as the most sustainable form of long-term control; however, advances have been limited owing to a lack of cereal germplasm demonstrating postattachment resistance to Striga. Here, we identify a cultivar of rice (Nipponbare) that exhibits strong postattachment resistance to S. hermonthica; the parasite penetrates the host root cortex but does not form parasite-host xylem-xylem connections. In order to identify the genomic regions contributing to this resistance, a mapping population of backcross inbred lines between the resistant (Nipponbare) and susceptible (Kasalath) parents were evaluated for resistance to S. hermonthica. Composite interval mapping located seven putative quantitative trait loci (QTL) explaining 31% of the overall phenotypic variance; a second, independent, screen confirmed four of these QTL. Relative to the parental lines, allelic substitutions at these QTL altered the phenotype by at least 0.5 of a phenotypic standard deviation. Thus, they should be regarded as major genes and are likely to be useful in breeding programmes to enhance host resistance.

Chromosome Mapping↗

PubMed2000

Ribozyme-mediated resistance to rice dwarf virus and the transgene silencing in the progeny of transgenic rice plants.

A hammerhead ribozyme (Rz) with long hybridizing arms targeting the mRNA of rice dwarf virus (RDV) segment 5 and a mutated nonfunctional ribozyme (mRz) were constructed. As predicted, Rz transcribed in vitro cleaved the target mRNA of RDV segment 5 into two fragments of 138 and 238 nucleotides in length. The Rz and mRz genes were each placed under the control of the CaMV 35S promoter and used to transform Japonica rice variety 'Tongling No. 1' via Agrobacterium tumefaciens. A total of 32 independent lines containing Rz or mRz was obtained as demonstrated by Southern blot analysis. Challenge inoculation with RDV viruliferous leafhoppers (Nephotettix cincticeps) showed that T1 plants containing the Rz transgene displayed high resistance or delayed and attenuated viral symptoms. In contrast, transgenic lines expressing mRz showed severe symptoms similar to the control plants transformed with the vector alone. These results suggest that Rz confers RDV resistance in transgenic rice. Genomic DNA PCR analysis confirmed that all of the examined T6 progeny plants contained the Rz transgene. However, accumulation of the Rz transcripts was detectable by RT-PCR only in the plants that were resistant to RDV. This suggested that loss of RDV resistance in progeny plants containing the Rz transgene may result from silencing of the Rz transgene.

Base Sequence↗

PubMed1999

Resistance to rice yellow mottle virus (RYMV) in cultivated African rice varieties containing RYMV transgenes.

The disease caused by rice yellow mottle virus (RYMV) is a serious problem for African rice growers in large-scale irrigated programs. As there are very few suitable natural sources of RYMV resistance, we have investigated a transgenic approach using widely grown, RYMV-susceptible cultivars of rice and a transgene encoding the RNA-dependent RNA polymerase of RYMV. Transformed lines were resistant to RYMV strains from different African locations. In the most extreme examples there was complete suppression of virus multiplication. Resistance was stable over at least three generations. Subject to satisfactory field testing, these transgenic lines may be suitable for introduction into RYMV-affected rice-growing areas. In the most resistant line, transcription analysis indicated that the resistance derives from an RNA-based mechanism associated with posttranscriptional gene silencing.

Genome, Viral↗

PubMed2005

Avidin expressed in transgenic rice confers resistance to the stored-product insect pests Tribolium confusum and Sitotroga cerealella.

Rice (Oryza sativa var. Nipponbare) was transformed with an artificial avidin gene. The features of this construct are as follows: (1) a signal peptide sequence derived from barley alpha amylase was added at the N-terminal region, (2) codon usage of the gene was optimized for rice, and (3) the gene was driven by rice glutelin GluB-1, an endosperm-specific promoter. Avidin was produced in the grain of the transgenic rice but not in the leaves. The concentration of avidin in the kernels was about 1,800 ppm. All larvae of the confused flour beetle (Tribolium confusum) and Angoumois grain moth (Sitotroga cerealella) died when fed transgenic avidin rice powder or kernels, respectively, whereas most of the test insects developed into adults when they were fed a nontransgenic rice control diet. Avidin extracted from the transgenic rice kernel lost most biotin-binding activity after 5 min heating at 95 degrees C.

Amino Acid Sequence↗

PubMed2004

Relationship between the minute structure and the lodging resistance of rice stems.

The aim of this experiment is to measure the morphological and mechanical properties, and to analyze the relationship between the morphology and lodging resistance of several different kinds of rice stem. Choose the typical species of tall, mid and short stem and hybrid rice, ten individual plants each species (all should be caulis), and when paddies are full heading, intercept the third internode above the ground. The minute structure characteristics include the size of outer diameter, Culm wall thickness, and the number of big and small vascular bundles. Mechanical properties include the tensile breaking point and the tensile elastic modulus. Based on the above characteristics it is concluded that the middle stem has the highest lodging resistance. Thus when we select the high-yield and lodging resistance species, the middle and rigid stem should be considered.

Elasticity↗

PubMed2004

Alpha-picolinic acid, a fungal toxin and mammal apoptosis-inducing agent, elicits hypersensitive-like response and enhances disease resistance in rice.

Alpha-picolinic acid (PA), a metabolite of tryptophan and an inducer of apoptosis in the animal cell, has been reported to be a toxin produced by some of plant fungal pathogens and used in screening for disease resistant mutants. Here, we report that PA is an efficient apoptosis agent triggering cell death of hypersensitive-like response in planta. Confirmed by Fluorescence Activated Cell Sorter (FACS), rice suspension cells and leaves exhibited programmed cell death induced by PA. The PA-induced cell death was associated with the accumulation of reactive oxygen species that could be blocked by diphenylene iodonium chloride, indicating that the generation of reactive oxygen species was NADPH-oxidase dependent. We also demonstrated the induction of rice defense-related genes and subsequent resistant enhancement by PA against the rice blast fungus Magnaporthe grisea. Hence, it was concluded that the PA-stimulated defense response likely involves the onset of the hypersensitive response in rice, which also provides a simple eliciting tool for studying apoptosis in the plant cell.

Apoptosis↗

PubMed2006

Testifying the rice bacterial blight resistance gene xa5 by genetic complementation and further analyzing xa5 (Xa5) in comparison with its homolog TFIIAgamma1.

The recessive gene xa5 for resistance to bacterial blight resistance of rice is located on chromosome 5, and evidence based on genetic recombination has been shown to encode a small subunit of the basal transcription factor IIA (Iyer and McCouch in MPMI 17(12):1348-1354, 2004). However, xa5 has not been demonstrated by a complementation test. In this study, we introduced the dominant allele Xa5 into a homozygous xa5-line, which was developed from a cross between IRBB5 (an indica variety with xa5) and Nipponbare (a japonica variety with Xa5). Transformation of Xa5 and subsequent segregation analysis confirmed that xa5 is a V39E substitution variant of the gene for TFIIAgamma on chromosome 5 (TFIIAgamma5 or Xa5). The rice has an addition gene for TFIIAgamma exists on chromosome 1 (TFIIAgamma1). Analysis of the expression patterns of Xa5 (TFIIAgamma5)/xa5 and TFIIAgamma1 revealed that both the genes are constitutively expressed in different rice organs. However, no expression of TFIIAgamma1 could be detected in the panicle by reverse transcriptase-polymerase chain reaction. To compare the structural difference between the Xa5/xa5 and TFIIAgamma1 proteins, 3-D structures were predicted using computer-aided modeling techniques. The modeled structures of Xa5 (xa5) and TFIIAgamma1 fit well with the structure of TFIIA small subunit from human, suggesting that they may all act as a small subunit of TFIIA. The E39V substitution in the xa5 protein occurs in the alpha-helix domain, a supposed conservative substitutable site, which should not affect the basal transcription function of TFIIAgamma. The structural analysis indicates that xa5 and Xa5 potentially retain their basic transcription factor function, which, in turn, may mediate the novel pathway for bacterial blight resistance and susceptibility, respectively.

Chromosome Mapping↗

PubMed1998

Identification and characterization of 14 transposon-like elements in the noncoding regions of members of the Xa21 family of disease resistance genes in rice.

The rice disease resistance gene Xa21, which encodes a receptor-like kinase, is a member of a multigene family. Based on comparisons of genomic sequences of seven family members, seventeen transposon-like elements were identified in the 5' and 3' flanking regions and introns of these genes. Sequence characterization revealed that these elements are diverse, showing similarity to maize Ds, CACTA and miniature inverted repeat-like elements, as well as novel elements. Only two elements were located in presumed coding regions, indicating that integration of transposable elements at the Xa21 disease resistance locus occurred preferentially in noncoding regions.

Amino Acid Sequence↗

PubMed2005

qUVR-10, a major quantitative trait locus for ultraviolet-B resistance in rice, encodes cyclobutane pyrimidine dimer photolyase.

Rice qUVR-10, a quantitative trait locus (QTL) for ultraviolet-B (UVB) resistance on chromosome 10, was cloned by map-based strategy. It was detected in backcross inbred lines (BILs) derived from a cross between the japonica variety Nipponbare (UV resistant) and the indica variety Kasalath (UV sensitive). Plants homozygous for the Nipponbare allele at the qUVR-10 locus were more resistant to UVB compared with the Kasalath allele. High-resolution mapping using 1850 F(2) plants enabled us to delimit qUVR-10 to a <27-kb genomic region. We identified a gene encoding the cyclobutane pyrimidine dimer (CPD) photolyase in this region. Activity of CPD photorepair in Nipponbare was higher than that of Kasalath and nearly isogenic with qUVR-10 [NIL(qUVR-10)], suggesting that the CPD photolyase of Kasalath was defective. We introduced a genomic fragment containing the CPD photolyase gene of Nipponbare to NIL(qUVR-10). Transgenic plants showed the same level of resistance as Nipponbare did, indicating that the qUVR-10 encoded the CPD photolyase. Comparison of the qUVR-10 sequence in the Nipponbare and Kasalath alleles revealed one probable candidate for the functional nucleotide polymorphism. It was indicated that single-base substitution in the CPD photolyase gene caused the alteration of activity of CPD photorepair and UVB resistance. Furthermore, we were able to develop a UV-hyperresistant plant by overexpression of the photolyase gene.

Base Sequence↗

PubMed2005

Loci controlling partial resistance to rice blast do not show marked QTL x environment interaction when plant nitrogen status alters disease severity.

Plant disease susceptibility is often increased by nitrogen (N) application. Therefore, it is important to know if resistance loci are effective in different plant N environments. One-hundred lines of the Bala x Azucena rice (Oryza sativa) mapping population were grown in two N treatments and tested for partial resistance to blast (Magnaporthe grisea) isolate CD100. Disease severity (DS), the number and size of lesions and plant N and C concentrations were measured and the results subject to quantitative trait loci (QTL) and QTL x environment analysis. There was a 66% higher plant N concentration in the high N treatment and DS increased significantly, mostly as a result of increased numbers of lesions. Nine regions contained QTL for disease traits but only one showed evidence of statistically significant QTL x treatment interaction. This was a large effect quantitative trait locus at marker R1933 on chromosome 12 which was less effective at high N. Apparently, blast disease is increased by higher plant N, but the efficacy of partial resistance genes is not greatly affected by N application.

Chromosome Mapping↗

PubMed1997

Evolution of the rice Xa21 disease resistance gene family.

The rice disease resistance gene Xa21, encoding a receptor-like kinase, is a member of a multigene family. Sequence analysis of seven family members revealed two distinct classes of genes. One member from each class encodes a receptor kinase-like open reading frame. The other five members encode truncated open reading frames of the predicted receptor kinase. A highly conserved 233-bp sequence (HC) was also identified among the seven family members. Recombination at the HC region between family members apparently resulted in the precise swapping of promoter regions. Large sequence duplications were generated by a presumed unequal crossover event in intergenic regions. Insertions of transposon-like sequences truncated two of the predicted open reading frames. A model for amplification and diversification of the Xa21 gene family is presented.

Amino Acid Sequence↗

PubMed2000

Complete nucleotide sequence of the rice tungro spherical virus genome of the highly virulent strain Vt6.

The complete nucleotide sequence of rice tungro spherical virus (RTSV) strain Vt6, originally from Mindanao, the Philippines, with higher virulence to resistant rice cultivars, was determined and compared with the published sequence for the Philippine-type strain A (RTSV-A-Shen). It was reported that RTSV-A was not able to infect a rice resistant cultivar TKM 6 (10). RTSV-Vt6 and RTSV-A-Shen share 90% and 95% homology at nucleotide and amino-acid levels, respectively. The N-terminal leader sequence of RTSV-Vt6 contained a 39-amino acids-region (positions 65 to 103) which was totally different from that of RTSV-A-Shen; the difference resulted from frame shifting by nucleotide insertions and deletions. To confirm the amino-acid sequence differences of the leader polypeptide, the same region was cloned and sequenced using a newly obtained variant of RTSV-type 6, which had been collected in the field of IRRI, and seven field isolates from Mindanao, the Philippines. Since all the sequences of the target region are identical to that of the Vt6 leader polypeptide, the sequence difference in the leader region seems not to correlate with the virulence of Vt6.

Amino Acid Sequence↗

PubMed2001

[A study on breeding of "Ganzaoxian 47" from dry seeds of rice carried by recoverable satellite].

OBJECTIVE: To observe and investigate the variation and heredity of the offspring of dry seeds of rice carried by satellite, hence to select early maturing mutants, and to cultivate directly "Ganzaoxian 47" new varieties for production application. Isozymes analyses and studies of the new varieties and its original CK varieties were made. METHOD: Dry seeds of rice restorer line were carried to the space on board a recoverable satellite for 7 d in 1992. After recovery the seeds were planted in the field to study the agricultural characters, yield, disease resistance, rice quality and peroxidase isozymes change. RESULT: Its agricultural characters, yield, disease resistance, rice quality and peroxidase isozymes all showed distinct changes, and new varieties were cultivate directively for production application. CONCLUSION: It could be considered that certain variations of the rice seeds induced by the space conditions were heritable to the offspring's, and directive cultivation of new varieties is possible for production application. It could be used as a new method for mutagenic seed breeding.

Biomass↗

PubMed2006

Locus prl5 improves lodging resistance of rice by delaying senescence and increasing carbohydrate reaccumulation.

We investigated the reason for carbohydrate retention in the stem of rice (Oryza sativa L.) at full-ripe stage in a near-isogenic line (NIL63) carrying prl5, which confers lodging resistance without yield loss. NIL63 showed higher lodging resistance than Nipponbare (control) without reduced yield. At heading, the carbohydrate content in the NIL63 stem (culm and leaf sheathes) was the same as in Nipponbare. At 2 weeks after heading, the carbohydrate content in NIL63 was significantly higher than in Nipponbare. At 4 weeks after heading, the carbohydrate content in NIL63 had decreased to near the level in Nipponbare. At 6 weeks after heading, NIL63 showed higher carbohydrate reaccumulation. Chlorophyll degradation in the leaf blades of NIL63 was slower, and the chlorophyll content at 6 weeks after heading was higher than in Nipponbare. These results suggest that the delay in leaf senescence by prl5 results in carbohydrate reaccumulation in the stem after grain filling, increasing lodging resistance.

Carbohydrate Metabolism↗

PubMed2006

A novel approach for developing resistance in rice against phloem limited viruses by antagonizing the phloem feeding hemipteran vectors.

Rice production is known to be severely affected by virus transmitting rice pests, brown planthopper (BPH) and green leafhopper (GLH) of the order hemiptera, feeding by phloem abstraction. ASAL, a novel lectin from leaves of garlic (Allium sativum) was previously demonstrated to be toxic towards hemipteran pests when administered in artificial diet as well as in ASAL expressing transgenic plants. In this report ASAL was targeted under the control of phloem-specific Agrobacterium rolC and rice sucrose synthase-1 (RSs1) promoters at the insect feeding site into popular rice cultivar, susceptible to hemipteran pests. PCR, Southern blot and C-PRINS analyses of transgenic plants have confirmed stable T-DNA integration and the transgenes were co-segregated among self-fertilized progenies. The T(0) and T(1) plants, harbouring single copy of intact T-DNA expression cassette, exhibit stable expression of ASAL in northern and western blot analyses. ELISA showed that the level of expressed ASAL was as high as 1.01% of total soluble protein. Immunohistofluorescence localization of ASAL depicted the expected expression patterns regulated by each promoter type. In-planta bioassay studies revealed that transgenic ASAL adversely affect survival, growth and population of BPH and GLH. GLH resistant T(1) plants were further evaluated for the incidence of tungro disease, caused by co-infection of GLH vectored Rice tungro bacilliform virus (RTBV) and Rice tungro spherical virus (RTSV), which appeared to be dramatically reduced. The result presented here is the first report of such GLH mediated resistance to infection by RTBV/RTSV in ASAL expressing transgenic rice plant.

Animals↗

PubMed2002

[QTL analysis of sheath blight resistance in rice (Oryza sativa L.)].

In this study, an indica variety Zhai Ye Qing 8 (ZYQ8) and a japonica variety Jing Xi 17(JX17) and their double haploid (DH) population were used. Sheath blight resistance of the DH population and their parents was investigated using a syringe inoculation method. Quantitative trait loci (QTL) analysis was undertaken based on a constructed molecular linkage map of this population in Hangzhou and Hainandao respectively. A total of four sheath blight resistant QTLs (qSBR-2, qSBR-3, qSBR-7 and qSBR-11) were identified, and located on chromosome 2, 3, 7 and 11, respectively. Resistant alleles of qSBR-2, qSBR-3, and qSBR-7 were derived from the resistant parent ZYQ8, whereas resistant allele of qSBR-11 from susceptible parent JX17. qSBR-2, qSBR-3 and qSBR-7 were detected both in Hangzhou and Hainandao, whereas qSBR-11 was detected only in Hangzhou. Sheath blight response was significantly correlated with culm length and heading date in Hangzhou's test. Among the QTLs for culm length and heading date, only qCL-3 for culm length, was in the same chromosome region of qSBR-3, the other QTLs were not linked to the QTLs for sheath blight resistance.

Chromosome Mapping↗