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1.
The rice root-knot nematode (RKN), Meloidogyne graminicola, is an important pathogen affecting rice production in South and Southeast Asia. Efficacy of resistance and tolerance in selected M. graminicola-resistant African rice genotypes TOG5674, TOG5675 and CG14 and -susceptible Asian rice genotypes IR64 and UPLRi-5 were examined under a range of initial population densities (Pi) and water regimes. Resistance to M. graminicola in resistant rice genotypes was not broken with increasing pathogen pressure (Pi = 15,000 to 60,000 J2/plant). Resistant rice genotypes were even tolerant to the damage and yield loss caused by high pathogen pressure. On the other hand, increasing Pi levels caused more damage on susceptible rice genotypes. Final nematode population densities in the root systems of resistant and susceptible rice genotypes were significantly lower under flooded conditions than under upland and drought conditions. TOG5674, TOG5675 and CG14 were more tolerant to M. graminicola infection even when grown under upland and drought conditions while IR64 and UPLRi-5 were highly sensitive.  相似文献   

2.
近年水稻主要线虫病害的研究进展   总被引：3，自引：2，他引：1  
目前,以拟禾谷根结线虫Meloidogyne graminicola、水稻干尖线虫Aphelenchoide besseyi、水稻潜根线虫Hirschmanniella oryzae、水稻茎线虫Ditylenchus angustus和旱稻孢囊线虫Heterodera elachista为主的水稻寄生线虫侵染水稻以及其它禾本科作物引致的线虫病害,已造成了严重的经济损失。近年来,对拟禾谷根结线虫的致病机制和寄主的防御机制等方面的研究已取得了显著进展,但对其它水稻寄生线虫与寄主互作机制的研究还存在较大空白。水稻寄生线虫的防治多依赖化学农药,抗性品种和生物防治等措施的实施存在一定的局限性。本文对上述5种主要水稻寄生线虫病的发生为害、致病机制以及防治方法等进行了综述,并对水稻寄生线虫致病机理的研究以及抗性品种、生物防治和诱导化合物的应用进行了探讨。  相似文献   

3.
Recently a Meloidogyne species complex was detected parasitizing and causing damage to irrigated rice in southern Brazil, highlighting the need to study the genetic diversity of these species and their pathogenicity to Oryza spp. in order to select genotypes of rice with multiple resistance. This study compared the genetic diversity of Brazilian Meloidogyne spp. isolates from irrigated rice and evaluated the reaction of four wild accessions of Oryza species (O. glumaepatula, O. longistaminata, O. grandiglumis, and O. alta) and two cultivated species, O. glaberrima and O. sativa (control) to M. ottersoni, M. oryzae, and two variants of M. graminicola (Est G2 and Est G3). Genetic variability was assessed using RAPD and AFLP markers. M. graminicola and M. ottersoni showed high intraspecific variability: 83.76% and 41.14%, respectively. Cluster analysis showed a clear separation among rice root-knot nematodes (RKNs) into subclades according to their esterase phenotypes with 100% bootstrap. For rice resistance screening, plants were inoculated with 5,000 eggs, and the nematode reproduction factor evaluated 90–120 days postinoculation. O. glumaepatula, an American wild species, was highly resistant or resistant to all rice RKNs tested and is a valuable source of multiple resistance. Overall, the other rice species also showed different levels of resistance. Conversely, O. longistaminata exhibited low levels of resistance. M. graminicola Est G3 was the most aggressive isolate. Sources of resistance against RKN in wild Oryza genotypes, especially in an AA genome like O. glumaepatula, may be of great interest for future breeding programmes in cultivated rice.  相似文献   

4.
Panicle blast, caused by the fungus Magnaporthe oryzae (syn. Pyricularia oryzae), directly contributes to yield loss in the field. The effects of panicle development stage and temperature on panicle blast were studied and the infection process of M. oryzae in panicles was visualized. Rice panicles at different development stages from three rice cultivars were inoculated with a conidial suspension in vitro. The rice cultivar Lijiangxintuanheigu was highly susceptible to panicle blast at 5 days postinoculation (dpi) when the pulvinus distance was 15–20 cm. Nanjing 9108 was moderately susceptible to panicle blast when the pulvinus distance was 8–10 cm, but Yliangyou 800 was resistant. The effect of temperature on panicle blast was determined under 22–35 °C temperature treatments. Inoculated panicles placed at temperatures of 28 and 30 °C showed the highest lesion grade based on lesion length at 5 dpi. The infection process of M. oryzae in rice panicles was observed by confocal laser scanning microscopy (CLSM) and transmission electron microscopy (TEM). M. oryzae initially formed the appressorium to invade through the epidermis of rice panicles at 24 hours postinoculation (hpi). As the disease progressed, the invasive hyphae formed dense mycelial networks in the inner parenchyma cells at 60 hpi. Our results will contribute to the understanding of panicle development stage and temperature effects on panicle blast and improve resistance evaluation methods. Additionally, visualization of the infection process by CLSM and TEM are valuable methods to observe M. oryzae invasive hyphae inside rice panicle cells.  相似文献   

5.
Abstract

Studies were conducted to determine the influence of plant growth stage, inoculum density, temperature, and relative humidity (RH) on development of rust (Puccinia pupurea) in sorghum (Sorghum bicolor). Rust development was maximum (>80% severity), when plants of a susceptible sorghum genotype (IS 18420) were inoculated at the four‐ to five‐leaf stage with an inoculum concentration of 4 × 106 urediniospores per ml and incubated at 20–25°C under high RH (>90%) for 24 h. Disease severity (percentage leaf area covered with rust pustules) scores were taken 2 weeks after inoculation. Using this technique, 29 sorghum genotypes were screened for rust resistance in a greenhouse. This technique proved effective In discerning resistant and susceptible genotypes, and IS 3979, ICSH 110, ICSH 86647 and ICSH 871035 were identified resistant (<20% rust severity) compared with a susceptible control IS 18420 (90% rust severity). This technique is simple and rapid, and can be used effectively and economically to screen, on a large scale, germplasm lines and breeding populations in the greenhouse.  相似文献   

6.
In this study, an isolate of Magnaporthe oryzae expressing the green fluorescent protein gene (gfp) was used to monitor early events in the interaction of M. oryzae with resistant rice cultivars harbouring a blast resistance (R) gene. In the resistant cultivars Saber and TeQing (Pib gene), M. oryzae spores germinated normally on the leaf surface but produced morphologically abnormal germ tubes. Germling growth and development were markedly and adversely affected in leaves of these resistant cultivars. Penetration of host cells was never seen, supporting the idea that disruption of germling development on the leaf surface might be one of the resistance mechanisms associated with Pib function. Thus, this particular R gene appeared to function in the absence of host penetration by the fungal pathogen. Confocal laser scanning microscopy of M. oryzae‐infected susceptible rice cultivars showed the dimorphic growth pattern that is typically observed during the biotrophic and necrotrophic stages of leaf colonization in susceptible cultivars. The suitability of the gfp‐expressing M. oryzae isolate for further research on R‐gene function and identification of resistant genotypes in rice germplasm collections is discussed.  相似文献   

7.
Evolution of flooding tolerance in weedy rice has occurred in several rice-growing regions, but the genes related to this process and the environmental effects are unknown. The objective of this study was to analyse the expression of genes related to flooding tolerance in response to temperature and flooding during the initial establishment of weedy rice. The experiments were carried out with rice cultivars IRGA 417 and Nipponbare, which are sensitive to flooding, and weedy rice ITJ03 and AV04 genotypes that have high and intermediate tolerance to flooding, respectively. The expression of genes related to reserve mobilisation, anaerobic respiration, escape and quiescence strategies was analysed at periods up to 24 days after sowing. The flooding tolerance of weedy rice genotype ITJ03 was associated with the expression of RAmy3D and OsTPP7 , which are involved in the mobilisation of carbohydrate reserves, ADH1 and ADH2, which participate in anaerobic respiration, and SNRKL1 that triggers rapid elongation of the coleoptile and emergence. Although the genes PDC1, SUS3 and SUB1 are important for flooding tolerance in cultivated rice, their expression was not directly related to flooding tolerance in weedy rice. A temperature of 20°C reduced levels of expression of the RAmy3D, ADH2 and SNRKL1 genes and low temperature had a negative effect on the establishment of weedy rice. Breeding of rice genotypes with tolerance of low temperatures and anaerobic conditions may be a viable strategy to improve the control of weedy rice in paddy fields.  相似文献   

8.
BACKGROUND: Knockdown resistance (kdr) mutation (L1014F) is a well‐defined mechanism of resistance to pyrethroids and DDT in many insect species. Sensitive detection of the mutations associated with resistance is a prerequisite for resistance management strategies. The authors have developed a new real‐time molecular diagnostic assay based on SimpleProbe®/melting curve analysis for large‐scale kdr genotyping in the wild population of Culex quinquefasciatus Say, the principal vector of bancroftian filariasis. Melting curve analysis is based on the thermal stability difference between matched and mismatched DNA duplexes. The application of SimpleProbe® chemistry in insects described here is novel in entomology research. RESULTS: The mosquitoes homozygous for knockdown‐resistant and knockdown‐susceptible allele showed melting peaks at 60.45 °C ( ± 0.25) and 64.09 °C ( ± 0.24) respectively. The heterozygous mosquitoes yielded both peaks at approximately 60.5 °C ( ± 0.2) and 64.20 °C ( ± 0.23). Among the 92 samples genotyped, 16 were found to be homozygous resistant, 44 homozygous susceptible and 32 heterozygous. Comparative assessments were made of all the reported methods for kdr genotyping. CONCLUSION: The present method is cheaper, faster, more reliable and versatile than other alternatives proposed in detecting correct kdr genotypes in mosquitoes. This is the first report using a single‐labelled hybridisation probe to detect point mutations in insect populations. Copyright © 2010 Society of Chemical Industry  相似文献   

9.
The virulence structure of theMagnaporthe grisea rice population from the northwestern Himalayan region of India was deciphered on 24 rice genotypes harboring different blast resistance genes. Matching virulences appropriate to all the rice genotypes, except Fukunishiki (Pi-z, Pi-sh) and Zenith (Pi-z, Pi-a, Pi-i), were present in the pathogen population. Moreover, a very low percentage of isolates were virulent on Tetep (Pi-ta, Pi-k h, Pi-4b) and Tadukan (Pi-ta/Pi-ta 2). Although virulence was recorded on most of the lines tested, none was susceptible to all of the isolates. Three pairs of genotypes, namely, C101LAC:C101A51; K-1: Dular; and Dular: HPU-741, exhibited complementary resistance spectra as no isolate combined virulence to both the members of each of the three pairs of genotypes despite the fact that individual members were susceptible to a major portion of the pathogen population. The blast resistance genesPi-z, Pi-k h, Pi-l andPi-2 and their various combinations were construed to provide broad spectrum and durable blast resistance in Himachal Pradesh. Pathotype analysis revealed the existence of extremely high pathotypic diversity in the pathogen population. Based on the observed population structure forM. grisea, it was not possible to designate a minimum set of pathogen isolates that could be used in blast resistance screens to identify effective sources of blast resistance. The overall results suggested that the pathotype analysis alone is insufficient to describe the existing pathogenic variability, especially when this information has to be used for guiding the breeding programs aimed at developing durable blast resistance. However, population genetics approach of studying pathogenic specialization by monitoring the frequency of individual virulence genes and analyzing virulence gene combinations for their association or dissociation might generate useful information for developing durable blast resistance. http://www.phytoparasitica.org posting May 14, 2006.  相似文献   

10.
The life cycle of a Portuguese Meloidogyne hispanica isolate on susceptible cv. Easypeel and resistant (Mi‐1.2 gene) cv. Rossol tomato plants was studied in growth chambers at constant temperatures (10–35°C). The development within the egg and hatching were compared to those of a Portuguese M. arenaria isolate. The base temperature was 10·11 and 8·31°C with 179·5 and 235·3 thermal units for M. hispanica and M. arenaria, respectively, suggesting better potential adaptation to low temperatures by M. arenaria than M. hispanica. No egg development occurred at 10 or 35°C. An increase in invasion of tomato roots by M. hispanica second‐stage juveniles (J2s) was correlated with an increase in temperature on both tomato cultivars. Tomato cv. Rossol limited M. hispanica development at 20, 25 and 30°C, but not at 35°C, indicating that these high temperatures blocked the resistance mechanism provided by the Mi‐1.2 gene. At 15°C, J2s penetrated tomato cv. Rossol roots, but failed to develop and establish feeding sites. On tomato cv. Easypeel, nematode development and reproduction occurred at 20, 25 and 30°C, but at 20°C the life cycle was 1·5 and 2·0 times longer than at 25 and 30°C, respectively. No egg production was observed at 15°C. The results of this study showed that M. hispanica is most suited to soil temperatures around 25°C. Predicted climate change might favour the spread of this nematode species into southern Europe and northwards. The thermal requirements for M. hispanica development are analysed and compared with those of M. arenaria, M. hapla, M. incognita and M. javanica.  相似文献   

11.
A refined inoculation method to evaluate false smut resistance in rice   总被引：1，自引：0，他引：1  
False smut, caused by Ustilaginoidea virens, is a serious disease of rice worldwide. To evaluate false smut resistance in rice, we developed a method combining the cultivation of the main culm of rice plants in the greenhouse and rapid preparation of a conidial suspension to inject into the leaf sheath. The method was used to evaluate false smut resistance in 18 varieties/lines of rice. For comparison, field trials were also carried out in 2007 and 2008. The results indicated that the greenhouse method was more reproducible than field trials: commercial varieties tested were resistant; almost all the forage varieties were highly susceptible; and blast-resistant varieties/lines were mostly resistant to false smut. Thus, this inoculation method will be useful for determining the level of false smut resistance in rice and for breeding resistant varieties.  相似文献   

12.
Large-scale cDNA-AFLP profiling identified numerous genes with increased expression during the resistance response of wheat to the Septoria tritici blotch fungus, Mycosphaerella graminicola. To test whether these genes were associated with resistance responses, primers were designed for the 14 that were most strongly up-regulated, and their levels of expression were measured at 12 time points from 0 to 27 days after inoculation (DAI) in two resistant and two susceptible cultivars of wheat by real-time quantitative polymerase chain reaction. None of these genes was expressed constitutively in the resistant wheat cultivars. Instead, infection of wheat by M. graminicola induced changes in expression of each gene in both resistant and susceptible cultivars over time. The four genes chitinase, phenylalanine ammonia lyase, pathogenesis-related protein PR-1, and peroxidase were induced from about 10- to 60-fold at early stages (3 h–1 DAI) during the incompatible interactions but were not expressed at later time points. Nine other genes (ATPase, brassinosteroid-6-oxidase, peptidylprolyl isomerase, peroxidase 2, 40S ribosomal protein, ADP-glucose pyrophosphorylase, putative protease inhibitor, methionine sulfoxide reductase, and an RNase S-like protein precursor) had bimodal patterns with both early (1–3 DAI) and late (12–24 DAI) peaks of expression in at least one of the resistant cultivars, but low if any induction in the two susceptible cultivars. The remaining gene (a serine carboxypeptidase) had a trimodal pattern of expression in the resistant cultivar Tadinia. These results indicate that the resistance response of wheat to M. graminicola is not completed during the first 24 h after contact with the pathogen, as thought previously, but instead can extend into the period from 18 to 24 DAI when fungal growth increases dramatically in compatible interactions. Many of these genes have a possible function in signal transduction or possibly as regulatory elements. Expression of the PR-1 gene at 12 h after inoculation was much higher in resistant compared to susceptible recombinant-inbred lines (RILs) segregating for the Stb4 and Stb8 genes for resistance. Therefore, analysis of gene expression could provide a faster method for separating resistant from susceptible lines in research programs. Significant differential expression patterns of the defense-related genes between the resistant and susceptible wheat cultivars and RILs after inoculation with M. graminicola suggest that these genes may play a major role in the resistance mechanisms of wheat.  相似文献   

13.
In plant–pathogen interactions, strong structural and biochemical barriers may induce a cascade of reactions in planta, leading to host resistance. The kinetic speed and amplitudes of these defence mechanisms may discriminate resistance from susceptibility to necrotrophic fungi. The infection processes of two Ascochyta lentis isolates (FT13037 and F13082) on the recently identified ascochyta blight (AB)‐resistant Lens orientalis genotype ILWL180 and two cultivated genotypes, ILL7537 (resistant) and ILL6002 (susceptible), were assessed. Using histopathological methods, significant differences in early behaviour of the isolates and the subsequent differential defence responses of the hosts were revealed. Irrespective of virulence, both isolates had significantly lower germination, shorter germ tubes and delayed appressorium formation on the resistant genotypes (ILWL180 and ILL7537) compared to the susceptible genotype (ILL6002); furthermore, these were more pronounced on genotype ILWL180 than on genotype ILL7537. Subsequently, host perception of pathogen entry led to the faster accumulation and notably higher amounts of reactive oxygen species and phenolic compounds at the penetration sites of the resistance genotypes ILWL180 and ILL7537. In contrast, genotype ILL6002 responded slowly to the A. lentis infection and reaffirmed previous gross disease symptomology reports as highly susceptible. Interestingly, quantification of H2O2 was markedly higher in ILWL180 particularly at 12 h post‐inoculation compared to ILL7537, potentially indicative of its superior resistance capability. Faster recognition of A. lentis is likely to be a major contribution to the superior resistance observed in genotype ILWL180 to the highly aggressive isolates of A. lentis assessed.  相似文献   

14.
Experiments were conducted to (i) evaluate the efficacy of propanil formulations available in Sri Lanka in controlling Echinochloa crus‐galli; (ii) study the seedling growth of propanil‐resistant (R) and ‐susceptible (S) biotypes of the weed under different temperatures; (iii) quantify the level of resistance in R biotypes and; (iv) to suggest alternative control measures for R biotypes. Field studies showed that retail propanil formulations (36% a.i., EC) applied at 2.7 kg a.i. ha?1 gave less than 30% control of E. crus‐galli collected from several locations of the north dry zone of Sri Lanka. Chemical analysis revealed that there was no adulteration of propanil formulations at the retailer level. Growth studies conducted in controlled environments indicated that per cent germination and seedling growth of R and S biotypes were similar at the day/night temperature regimes imposed. However, per cent germination for plants grown under a 34/31°C (day/night) regime was 27–29% higher compared to those grown at 28/24°C. At the higher temperature regime, R and S biotypes reached the 2–3 leaf stage five days earlier, and the 4–5 leaf stage seven days earlier. The ED50 values from the dose–response experiments indicated that the R biotype was four times more resistant to propanil than susceptible ones. The resistance index (RI) did not vary significantly under different temperature regimes. Quinclorac (25% a.i., SC) applied at 200 g a.i. ha?1 and bispyribac‐sodium (10% a.i., SC) applied at 30 g a.i. ha?1 (recommended dosages) successfully controlled propanil‐resistant biotypes of E. crus‐galli. Conversely, oxadiazon and propanil (8% and 23% a.i., EC, respectively) applied at 280 + 805 g a.i. ha?1 did not result in satisfactory control.  相似文献   

15.
The study was carried out to assess the reaction of different rice genotypes in response to brown planthopper (BPH)Nilaparvata lugens (Stål.) attack and the possible use of these genotypes in BPH management. The resistant genotypes PTB 33, ADT 45 and ASD 7 and the moderately resistant genotypes CO 43 and KAU 1661 recorded the lowest nymphal preference, fecundity, feeding rate, survival, growth index, population buildup and plant dry weight loss per mg of insect dry weight produced, and more unhatched eggs, longer nymphal development period, days to wilt and higher Functional Plant Loss Index compared with the susceptible genotype TN1. In resistant and moderately resistant genotypes, a greater accumulation of defense enzymes such as peroxidase and polyphenol oxidase in response toN. lugens infestation was recorded one day after infestation, and more pathogenesis-related protein and chitinase activity was noted 3 days after infestation. The activity was sustained for more than a week after infestation compared with the susceptible genotype TN1.  相似文献   

16.
This study investigates the infection process of Phoma koolunga on field pea (Pisum sativum) stems and leaves using different susceptible and resistant pea genotypes for each tissue, viz. 05P778‐BSR‐701 (resistant) and 06P830‐(F5)‐BSR‐5 (susceptible) for stems and ATC 866 (resistant) and ATC 5347 (susceptible) for leaves. On both resistant and susceptible genotypes, light and scanning electron microscopy showed P. koolunga conidia infect stem and leaf tissues directly via appressoria or stomatal penetration, but with more infections involving formation of appressoria on stems than on leaves. On leaves of the resistant genotype, at 72 h post‐inoculation, P. koolunga penetrated more frequently via stomata (5.2 conidia per 36 893 μm2) than by formation of appressoria (1.8 conidia); yet no such difference was observed on stems of the resistant genotype. In contrast, at the same time point, the number of conidia infecting the susceptible genotype by formation of appressoria on either stems (135 conidia) or leaves (11.3 conidia) was significantly greater than via stomata (8 and 7.3 conidia, stems and leaves, respectively). Mean germ tube length of germinating P. koolunga conidia on both stems (29.8 μm) and leaves (32.9 μm) of the resistant genotype was less than on the susceptible genotype (40.5 and 63.7 μm, stem and leaves, respectively). In addition, there were differences in the number of germ tubes emerging from conidia on resistant and susceptible genotypes. These are the first insights into the nature of leaf and stem resistance mechanisms operating in field pea against P. koolunga.  相似文献   

17.
Differentin vivo resistance/susceptibility levels of 14 carnation cultivars toFusarium oxysporum f.sp.dianthi race 2, the causal agent of Fusarium wilt disease of carnation, were also expressed in anin vitro system and assayed as the degree of fungal colonization of callus cultures at 20° C. Temperature influenced thein vitro expression of carnation resistance. An incubation temperature of 27° C increased the colonization of calli derived from both the susceptible (‘Corrida’ and ‘Ambra’) and the resistant (‘Pulcino’ and ‘Pallas’) cultivars. At 15°C, the colonization of calli derived from Pulcino and Pallas diminished significantly more than for Ambra and Corrida. Inhibition of fungal growth on resistant calli was correlated to retardation in hyphal development. Both scanning electron microscopy and light microscopy observations showed that hyphae did not penetrate into carnation cells.  相似文献   

18.
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19.
Abstract

The effect of different rice-based crop rotation sequences on the population densities of Meloidogyne graminicola and on the yield of rice was evaluated in a microplot experiment under lowland rice field conditions. Ten treatments of cropping sequences were grown in four successive growing seasons: continuous growing of the susceptible rice cultivar Thihtatyin (rice-rice-rice-rice), four treatments of 1- season crop rotation sequences (rice-rice-chickpea-rice, rice-rice-black gram-rice, rice-rice-soybean-rice, rice-rice-cowpea-rice), and five treatments of 2-season crop rotation sequences (groundnut-rice-chickpea-rice, green gram-rice-black gram-rice, cowpea-rice-soybean-rice, sesame-rice-cowpea-rice, sunflower-rice-sesame-rice). Population densities of M. graminicola recovered from the rice plants and the nematode multiplication factors (Mf) in the soil in the continuous rice cropping sequence (rice-rice-rice-rice) was the highest among the ten cropping sequences. Lowest nematode Mf in the soil was observed in the 2-season crop rotation sequence sunflower-rice-sesame-rice and the highest was observed in the 1-season crop rotation sequence rice-rice-cowpea-rice among the nine crop rotation sequences. Highest rice yield was obtained in the 2-season crop rotation sequences green gram-rice-black gram-rice, sesame-rice-cowpea-rice and sunflower-rice-sesame-rice, which were about 2 times higher compared with the 1-season crop rotation sequences and about 3 times higher compared with the continuous rice cropping sequence.  相似文献   

20.
Chondrilla juncea is one of the most serious introduced weed species in Australia. Successful biological control has been achieved by the release of the rust fungus Puccinia chondrillina. Although P. chondrillina is thought to reduce the competitive ability of C. juncea by reducing plant size, the precise mechanism by which the pathogen controls its host is poorly understood. In this experiment, we examined the effect of P. chondrillina TU 788 infection on individual plant size, and size variability, in two genotypes (one resistant, one susceptible) of C. juncea. Exposure to P. chondrillina significantly reduced the average size of susceptible C. juncea plants, a reduction apparent in both roots and shoots. Plant size variability of the susceptible C. juncea genotype was also reduced by P. chondrillina. Plant size, and plant size variability of the resistant genotype were unaffected by exposure to rust, or association with rust‐affected plants. The effect of P. chondrillina on plant size in rust‐susceptible C. juncea plants shows how effective bio‐control of this weed may occur in field populations.  相似文献   

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