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1.
Summary Lesion length, leaf length, and leaf width were measured on infected leaves two weeks after clip inoculation of 64 rice cultivars with two virulent isolates of Xanthomonas campestris pv. oryzae (X.c. pv. oryzae). No significant correlation was found between the lesion length and the leaf dimensions, indicating that physical leaf size does not affect the spread of the bacteria once these have entered the leaf. Lesion length is therefore an acceptable parameter for assessing resistance to (X.c. pv. oryzae), and is to be preferred above the parameter percentage diseased leaf area (% DLA), especially when small differences between genotypes are to be assessed. The confounding influence of differences in leaf length can cause large changes in the ranking order of cultivars when assessed by the % DLA. For this reason lesion length is a better assessor of the value of a quantitative resistance for breeding and research purposes than % DLA.  相似文献   

2.
Summary The effect of an inoculation with Pyricularia oryzae (isolate P06-6) on net leaf photosynthetic rate of rice (Oryza sativa) was studied with four cultivars. Measurements were taken on the sixth leaf of the main culm of plants in the early tillering stage. On cultivars CO39, IR50 and IR64 a susceptible infection type developed, but a clear difference in relative infection efficiency of the cultivars was observed. The highest number of lesions developed on leaves of CO39, whereas the lowest number was found on leaves of IR64. For all three cultivars the effect of a single lesion on the reduction in net leaf photosynthetic rate was found to be equal to a reduction in leaf area of three times the area occupied by the visible lesion. On IR68, a cultivar with complete resistance, brown specks of pinpoint size appeared without any effect on net leaf photosynthetic rate.  相似文献   

3.
E. C. Roumen 《Euphytica》1992,63(3):271-279
Summary Ten rice genotypes were inoculated with a virulent isolate of Magnaporthe grisea to study the effect of leaf age on components of partial resistance, and evaluate associations between these components. The number of sporulating lesions per cm2 leaf declined with increase of leaf age in all genotypes. The number of lesions per cm2 leaf area in one week old leaves was about 25% that of the number in very young leaves in the susceptible cultivar CO39, but less than 2% in the more resistant cultivars IR36, IR60 and IR62. Large differences between genotypes were found for the number of sporulating lesions that developed, and this factor was closely related to the period that leaves remained susceptible after appearance. The number of lesions in the most susceptible cultivar CO39 was about 7 times that in the cultivars IR60 and IR64. Differences between genotypes were also found for lesion size. The effect of aging on average lesion size was less pronounced than on lesion density. Lesion size and lesion density were positively correlated, but a rapid decline of density was not necessarily accompanied by a rapid decline of size. No apparent differences between genotypes were observed for latent period. Genotypes with leaves that became highly resistant soon after appearance expressed higher levels of partial resistance in the field.  相似文献   

4.
Summary Common blight disease in beans (Phaseolus vulgaris), caused by the bacterium Xanthomonas campestris pv. phaseoli, reduces crop yield and seed quality. Information is needed on the variation of leaves and pods disease reaction to strains of the bacterium after different inoculation methods. Phaseolus vulgaris cultivars Red Kidney Charlevoix, GN Harris, GN 1140, and GN Emerson were inoculated with three different strains of Xanthomonas campestris pv. phaseoli at two inoculum concentrations (108 and 106 bacterial cells/ml) using water soaking, multiple needle, and razor blade inoculation on leaves, and razor blade scratch, dissecting needle, and razor blade cut inoculation on pods. Differential cultivar disease reactions of leaves, pods, or both to the bacterial strains were observed in some cases. Significant interactions among cultivars, inoculation methods, strains, and inoculum concentrations (leaves) were found. A rapid leaf chlorosis developed 6 to 7 days after inoculation. Strains of bacteria did not show specificity in inducing this reaction, but rapid leaf chlorosis was associated with high inoculum concentration and with the water soaking and multiple needle methods. Another experiment was conducted to count the number of living bacterial cells deposited in the leaf tissue after inoculation by different methods. The number of bacteria deposited by water soaking or multiple needle was higher than that deposited by razor blade.Published as Paper No. 8584, Journal Series, Nebraska Agricultural Experiment Station. Research was conducted under Project No. 20–36.  相似文献   

5.
Development of leaf spot resistant mustard cultivars is a relevant objective in view of heavy crop losses caused by this pathogen. Thirty-eight species belonging to 9 genera, including cultivated and wild allies, of the genus Brassica were evaluated under epiphytotic conditions for two years. Inoculations were done on whole plants (in vivo) and on detached leaves (in vitro). Data on incubation period, number of lesions per leaf, lesion size and leaf area covered by lesions were recorded. Species which never produced disease symptoms throughout the growing period in pots and until 72 hours after inoculation in detached leaf assays during both years were treated as resistant, while those that produced symptoms were classified as moderately resistant, susceptible or highly susceptible depending upon incubation period, size of lesions and leaf area covered by disease symptoms. Eight species (Brassica desnottesii, Camelina sativa, Coincya pseuderucastrum, Diplotaxis berthautii, D. catholica, D. cretacea, D. erucoides, and Erucastrum gallicum) were found completely resistant, whereas others were classified as moderately resistant (12), susceptible (11) or highly susceptible (9). Since resistance is unavailable within the cultivated species, these 8 resistant wild species could be used as donor parents for introgressing resistance to leaf spot disease in Indian mustard. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

6.
Rice blast (Magnaporthe oryzae) is the most destructive and epidemic disease of rice. Use of host resistance is the best alternative for disease management. The leaf and neck blast resistance of 182 rice breeding lines were assessed for leaf and neck blast and classified relative to a susceptible check-Masuli and resistant check-Laxmi, from greenhouse experiment in 2005 and 2006. The test plants were inoculated with 105 conidial suspension/ml of M. oryzae at 21 days old seedlings for the leaf blast, and at neck base for the neck blast. Among them, for leaf blast, 77 rice lines were resistant, 43 were moderately resistant, 39 were moderately susceptible and 23 were susceptible. While among the selected 31 rice lines evaluated for neck blast, 4 lines were resistant, 4 were moderately resistant, 16 were moderately susceptible and 7 were susceptible. Leaf and neck infection was significant and positively correlated (r = 0.30, P = 0.05). The rice lines, Barkhe 1032, Barkhe 1034, Barkhe 1035, Barkhe 1036, Barkhe 2014, Barkhe 2024, Barkhe 3019, Super 3004 were resistant to leaf blast and Barkhe 1006, Barkhe 1032, Barkhe 1035, Barkhe 3004 were resistant to neck blast. The rice lines with identification # 11, 69, 137, 168, 182 from Masuli × MT4 parentage, and Barkhe 3017 were susceptible to both leaf and neck blast. Progenies of Irradiated Pusa Basmati (IPB), Kalinga III/IR64 (KIII/IR64), and Masuli/IR64 were resistant to both leaf and neck blast. However, most progenies from Masuli/MT4 showed susceptible reaction to both leaf and neck blast. Thus, rice lines form the IPB, KIII/IR64 and Masuli/IR64 will be promising resistant sources for rice blast in breeding programme.  相似文献   

7.
C. C. Creen  J. C. Wynne 《Euphytica》1986,35(2):561-573
Summary Ten peanut (Arachis hypogaea L.) genotypes were evaluated fro components of partial resistance to Cercospora arachidicola Hori in the field and in two detached leaf tests in the greenhouse. The relationships among the resistance components in the two environments were examined by computing rank correlations among the components measured in the greenhouse and among those measured in the field. A comparison of field and greenhouse testing for partial resistance was made by determining the correlations between components measured in the two testing methods. The genotypes were significantly different for all the components of resistant measured in the field and for most of the components measured in the greenhouse. In the field study necrotic area/10 cm2 leaf area was moderately correlated (r=0.58) with lesion number/10 cm2 leaf area and highly correlated (r=0.71–0.76) with total lesion number, predicted number of days after planting (X) to reach a standard lesion count, and defoliation. In the greenhouse only the correlation between necrotic area (mm2)/10 cm2 leaf area and sporulation/leaf was highly significant (r=0.71–0.83) in both greenhouse tests. Necrotic area (mm2)/10 cm2 leaf area measured in the field was significantly correlated with that measured in the greenhouse (r=0.66). Sporulation/leaf measured in the greennhouse was significantly correlated (r=0.66) with lesion increase in the field (measured as predicted X). It should thus be possible to evaluate and select for components of partial resistance in the greenhouse to develop resistant lines for the field.  相似文献   

8.
Banana hybrids with resistance to Yellow Sigatoka and Black Leaf Streak disease were evaluated for resistance to the burrowing nematode Radopholus similis and to the lesion nematode Pratylenchus coffeae in a growth chamber at 24–28°. Plants produced by tissue culture were acclimatised for 6 weeks prior to inoculation. Forty-five days after inoculation with nematodes, the root systems were processed and nematode numbers assessed. Two cultivars of Grande Naine (Musa AAA, Cavendish subgroup, ITC1256 and cv902) and one cultivar of Yangambi Km5 (Musa AAA, Ibota subgroup, ITC1123) were used respectively as susceptible and resistant controls. Results based on multiplication rates and root infestations showed that three of these hybrids (FB918, FB919 and FB924) were not significantly different from the resistant control Yangambi Km5 with a lower multiplication of R. similis. Similarly four of these hybrids (FB918, FB919, FB920, FB924) showed a lower multiplication of P. coffeae, not significantly different from the same resistant control. This is the first study that shows a partial resistance to both nematode species, R. similis and P. coffeae within synthetic hybrids of M. acuminata, adding an important extra value to these dessert banana hybrids formerly bred to resist to Mycosphaerella leaf spot diseases.  相似文献   

9.
Summary Breeding for disease resistance in peppers (Capsicum spp.) to the bacterial spot pathogen (Xanthomonas campestris pv. vesicatoria (Doidge) Dye) has been based on either qualitative or quantitative evaluation methods. Quantitative evaluation of components of resistance, lesion number and lesion diameter, has been useful for determining quantitative resistance, but few breeders have applied these methods in routine selection programs. This study was aimed at determining the heritability and gain from selection for resistance to the bacterial spot pathogen based on three components of resistance. Random selections from a diverse intermated population of Capsicum annuum L. were self-pollinated for two generations to create S1 and S2 families. Thirty S1 families, corresponding S2 families and four homozygous check lines were evaluated. At forty-two days after seeding, two different leaves of each plant were inoculated by leaf infiltration with low concentrations (5×103 colony forming units) of Group 2 (XCV PT, race 1) and 4 (XCV P, race 1) of the bacterium, respectively. After 15 days, lesion number cm-2 and lesion diameter were measured. Total lesion area was calculated. Narrow-sense heritabilities for lesion number, lesion diameter, and total lesion area were 0, 43, and 31%, respectively, with Group 2, and 26, 43, and 33%, respectively, with Group 4. Actual S2 gain from 20% selection pressure in the S1 was approximately 50%, when selection towards resistance was based on total lesion area.  相似文献   

10.
Summary Soybean germplasm was screened for resistance to bacterial pustule disease. The etiological agent, Xanthomonas campestris pv. glycines, was isolated from the leaves of field grown soybean in Maharashtra, India. The screening of soybean stocks was carried out by excised leaf inoculation method. A differential susceptibility to the pathogen was observed in the tested stocks. Two stocks P-4-2 and P-169-3 were found to be completely resistant to the pathogen and displayed an incompatible reaction. Four cultivars, EC-34160, Bragg, Kalitur and PK-472 displayed moderate resistance and the remaining stocks were susceptible to the attack of the pathogen. The stocks P-4-2 and P-169-3 remained resistant even to a high concentration of 109 colony forming units (cfu)/ml of the pathogen.  相似文献   

11.
Summary The most economical means to control Verticillium wilt in lucerne, caused by Verticillium albo-atrum, is through resistant cultivars. Most Verticillium wilt resistance evaluations use some form of root-cut-soak inoculation procedure. In Trial 1, three lucerne cultivars were inoculated at eight plant ages and plant symptoms were scored at ten successive weekly intervals. Trial 2 consisted of two cultivars inoculated at ten plant ages and symptoms were evaluated at eight weekly intervals. In an experiment to study the genetics of resistance to this pathogen, four plants showing no visual symptoms were selected from each of four germplasms. The selected populations were crossed in diallel fashion. The population crosses plus the parents were evaluated for resistance to V. albo-atrum. Results from Trial 1 and Trial 2 showed disease severity increased with increasing inoculation age and with increasing scoring age. Cultivar symptom expression interacted with inoculation age, but not with scoring age. The diallel analysis supported resistance to Verticillium wilt being conferred by additive gene action, as heterosis was not detected and general combining ability mean square was 3.75 times larger than the specific combining ability mean square.  相似文献   

12.
Durable resistance to rice blast disease-environmental influences   总被引:5,自引:0,他引:5  
J. M. Bonman 《Euphytica》1992,63(1-2):115-123
Summary Blast is one of the most serious diseases of rice worldwide. The pathogen,Pyricularia grisea, can infect nearly all parts of the shoot and is commonly found on the leaf blade and the panicle neck node. Host resistance is the most desirable means of managing blast, especially in developing countries. Rice cultivars with durable blast resistance have been recognized in several production systems. The durable resistance of these cultivars is associated with polygenic partial resistance that shows no evidence of race specificity. This partial resistance is expressed as fewer and smaller lesions on the leaf blade but latent period does not appear to be an important component. Partial resistance to leaf blast is positively correlated with partial resistance to panicle blast, although some cultivars have been found showing leaf-blast susceptibility and panicle-blast resistance. A diverse set of environmental factors can influence the expression of partial resistance, including temperature, duration of leaf-wetness, nitrogen fertilization, soil type, and water deficit. Because of the great diversity of rice-growing environments, resistance that proves durable in one system may or may not prove useful in another. In highly blast-conducive environments, other means of disease management must be applied to assist host-plant resistance.  相似文献   

13.
Rice leaffolder (RLF) (Cnaphalocrocis medinalis (Guenée) is a destructive and widespread insect pest throughout the rice growing regions in Asia. The genetics of resistance to RLF in rice is very complex and not thoroughly explored. The present study was conducted to detect the quantitative trait loci (QTL) associated with RLF resistance involving 176 recombinant inbred lines (RILs) of F8 generation derived from a cross between IR36, a leaffolder susceptible variety and TNAULFR831311, a moderately resistant indica rice culture. Simple sequence repeat (SSR) markers were used to construct specific linkage groups of rice. All the RILs were screened to assess their level of resistance to RLF by measuring the leaf area damaged. Besides this, the length and width of the flag leaf of each RIL were measured since these two parameters were considered as correlated traits to the RLF resistance in rice. All the above parameters observed across the RILs showed quantitative variation. Correlation analysis revealed that damage score based on greenhouse screening was positively correlated with length and width of the flag leaf. Out of 364 SSR markers analysed, 90 were polymorphic between the parents. Multi-point analysis carried out on segregating 69 SSR marker loci linkage group wise resulted in construction of linkage map with eleven groups of 42 SSR markers. Through single marker analysis, 19 SSR markers were found to have putative association with the three phenotypic traits studied. Of these markers, RM472 was identified as a locus having major effect on RLF resistance trait based on length of the flag leaf. Interval mapping detected two QTLs on linkage group 1. Among these QTLs, the QTL flanked by RM576–RM3412 were found to be associated with width of the flag leaf and RLF resistance. The putative SSR markers associated with leaffolder resistance identified in the present study may be one of the loci contributing resistance to RLF in rice.  相似文献   

14.
Summary In controlled inoculation studies with Septoria nodorum and Pyrenophora tritici-repentis, estimates of the relative proportion of each pathogen demonstrated differences in the responses of cultivars to pathogen mixtures that were not apparent from measurements of diseased leaf areas. Under field conditions estimates of the relative proportion of S. nodorum, P. tritici-repentis and S. tritici varied between field screening locations in Western Australian but also between lines within locations. Lines with known resistance to P. tritici-repentis and S. tritici, but susceptible to S. nodorum, could not be distinguished from susceptible lines on the basis of leaf area diseased or grain weight depression when S. nodorum was present in the disease complex. Such conditions, while suitable for the selection of combined resistance to these pathogens, were unsuitable for identifying resistance to individual pathogens. As symptoms were similar, the proportion of diseased leaf area sporulating with each pathogen provided a means of measuring the variation in disease development induced on lines varying in resistance. Knowledge of the components of disease and their relative importance were essential in understanding varietal response information under mixed infections of these leaf spot pathogens.  相似文献   

15.
Summary A comparative test of six inoculation methods was conducted using 2 halo blight race 2 virulent strains, Nebr. HB 16 and HB 21 (Pseudomonas syringae pv. phaseolicola), on five dry bean cultivars/lines (Phaseolus vulgaris L.) of known resistance and susceptibility. The water-soaking of leaves method caused the most severe reaction among the leaf inoculation methods, followed by the carborundum, spraying and multiple needle methods, respectively. The seed soaking method was considered too severe to be useful, since entries identified as resistant by the other methods, were susceptible with the former method. Great Northern Nebraska # 1 sel. 27 and PI 150414 had the highest level of leaf resistance, but the former developed systemic chlorosis with the stem stabbing method, but not the latter line. No systemic chlorosis was seen in either line with the other methods of inoculation. This suggests that there may be a different genetic mechanism conferring resistance/susceptibility to the toxin in these two lines when the stabbing method is used. No interaction occurred between method by genotype and isolate by method but significant interactions occurred between genotype by isolate and method by isolate by genotype. The leaf and pod reaction of forty cultivars/lines to the new halo blight Nebr. Charlevoix strain was also determined. Different combinations of degrees of resistance and susceptibility of leaves and pods were observed. GN Tara, GN Harris, and PI 150414 had the highest combination of leaf and pod resistance.Published as paper No. 7094, Journal Series, Nebraska Agricultural Experiment Station. Research was conducted under Project No. 20-036.  相似文献   

16.
Inheritance of resistance to rice stripe virus in rice line `BL 1'   总被引:9,自引:0,他引:9  
Rice stripe is the most serious virus disease in temperate rice-growing countries. The most economical and environmentally safe practice for controlling this disease is virus-resistant cultivars. ‘BL 1’ is an elite germplasm line with the blast resistance gene Pib, and has been used as a differential line for testing the pathogenicity of the blast fungus. We found that certain progenies from BL 1 showed resistance to both blast and rice stripe virus (RSV). The objectives of this study were to evaluate the RSV resistance in the field and under artificial conditions, to assess the reaction to the insect vector(small brown plant hopper, SBPH), and to examine its inheritance and its relationship to blast resistance in BL 1.BL 1 was susceptible to SBPH, but resistant to RSV in field and artificial inoculation tests. The inheritance of RSV resistance in F3 lines from the cross Nipponbare (NPB)/BL 1 was studied using artificial inoculation with a population of viruliferous SBPH. A serological assay for RSV infection using an enzyme-linked immunosorbent assay (ELISA) was used. RSV resistance in BL 1 was controlled by a single major gene with incomplete dominance. The locus responsible for RSV resistance was genetically independent of the blast resistance gene Pib. The resistance gene for RSV infection in BL 1 was also independent of Stvb-i, a gene widely distributed in resistant Japanese cultivars. Resistance to RSV must be diversified in rice cultivars considering the potential for future emergence of new RSV strains. The new resistance gene identified in BL 1, which has improved plant type and blast resistance, is considered useful for breeding RSV-resistant cultivars in japonica rice. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

17.
Black spot disease, incited by the fungus Diplocarpon rosae Wolf, is the most important disease of roses (Rosa hybrida L.) in the outdoor landscape. Though partial resistance exists in cultivated germplasm, the genetic basis of this trait has not yet been elucidated. Six diploid and six tetraploid rose cultivars were crossed in two factorial combining ability arrays. Whole plant and detached leaf inoculation methods were used to assess partial resistance under two different disease pressures using a characterized single-spore isolate. Parents from both arrays had significant general combining ability effects across multiple inoculation methods and environments. Specific combining ability was not significant for either array. Parent per se performance was highly correlated with progeny performance on a family mean basis. High positive correlations among whole plant and detached leaf inoculation methods indicate that detached leaf assays can substitute for whole plant assays. Based on these results, a breeding strategy including parental selection and early, among-family selection is proposed. To our knowledge, this is the first investigation of combining ability for disease resistance in rose.  相似文献   

18.
Summary Four cultivars of Populus spp., compatible to varying degrees with four races of M. larici-populina Kleb., were raised in a controlled environment on a high (28°/20°C, day/night) and low (20°/10°C) temperature regime. Leaf discs cut from the plants were inoculated separately with four individual races of M. laricipopulina and subsequently incubated at either low (20°C) or high (25°C) temperature for 14 days when disease development on the discs was assessed using three parameters (Incubation period to flecking, uredia per leaf disc and uredospores per mm2). The degree of resistance in all cultivar/race combinations was high on cultivars cultured at a high temperature regime compared to those cultured on a low temperature regime. Analysis of variance demonstrated that the major components: pre-inoculation temperature regime, post-inoculation temperature regime, race and cultivar, and most second and third order interactions between these were highly significant (P<0.001) for most disease parameters. The variance of the temperature components and all interactions involving these were usually higher than those for the cultivar and race components and those interactions lacking temperature components.These results emphasize the importance of the temperature regime at which plants are raised and the temperature of incubation, following the inoculation in determining the relative degree of resistance of these cultivars of poplar to races of M. larici-populina. The implications of these results in the epidemiology of leaf rust and the stability of the host-parasite relationship are discussed.  相似文献   

19.
Summary Different inoculum densities had negligible effects on latent period, uredinium density and uredinium size measured on flag leaves of adult RL6058 (Thatcher*6/PI58548[Lr34]) plants kept at low (17.5°C) post-infection temperatures in a glasshouse. In a qualitative assessment of rust severity at higher (24.6°C) temperatures, all three components of resistance indicated a susceptible flag leaf response on RL6058. In the latter environment, precise estimations of receptivity to different inoculum densities showed that adult RL6058 plants supported significantly less pustules than the leaf rust-susceptible cultivar Thatcher. In tillering plants, statistically equal numbers of uredinia developed on RL6058 and Thatcher in all paired temperature-inoculum density combinations. Growth stage-related susceptibility, and higher temperatures conducive to a shorter latent period and larger uredinia, could result in high terminal severities of Puccinia recondita f. sp. tritici on wheat genotypes containing Lr34. The reduction in receptivity associated with this gene may contribute, however, to delayed disease increase on cultivars or lines with monogenic Lr34 resistance.  相似文献   

20.
Summary Rice cultivars (Oryza sativa L.) belonging to five ecotypes (aus, aman, boro, bulu and tjereh) and to two groups of Japanese rice (lowland and upland) are examined with respect to KClO3 resistance, phenol reaction and apiculus hair length. These characters have been used as available criteria to classify rice into two types indica and japonica, for the last thirty years.The findings of this study are that the aman, boro and tjereh ecotypes should be classified as typical indica; and that the Japanese lowland rice cultivars are mainly typical japonica. Some of the aus, bulu and Japanese upland rice cultivars differ from typical indica and typical japonica, so the respective terms aus type, bulu type and J.u.r. type, are proposed. Aman, boro tjereh and Japanese lowland rice are cultivated in lowland. Some of the aus, bulu and Japanese upland rice cultivars have the characteristics of upland rice. In general, lowland rice cultivars can be clearly classified into indica or japonica, while upland cultivars cannot.Abbreviations Aph dominant gene for apiculus hair length > 0.7 mm - aph recessive gene for apiculus hair length < 0.7 mm - J.u.r. type Japanese upland rice type  相似文献   

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