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  • 1
    Electronic Resource
    Electronic Resource
    Assessment of quantitative resistance of rice cultivars to Xanthomonas campestris pv. oryzae: A comparison of assessment methods (1990)
    Springer
    Euphytica 51 (1990), S. 185-189 
    Details
    ISSN: 1573-5060
    Keywords: Oryza sativa, rice ; Xanthomonas campestris pv. oryzae ; bacterial blight ; quantitative resistance ; lesion length ; percentage diseased leaf area ; leaf length ; leaf area
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00022450
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Residual effects of the Xa-4 resistance gene in three rice cultivars when exposed to a virulent isolate of Xanthomonas campestris pv. oryzae (1991)
    Springer
    Euphytica 55 (1991), S. 187-193 
    Details
    ISSN: 1573-5060
    Keywords: Oryza sativa ; rice ; Xanthomonas campestris pv. oryzae ; bacterial blight ; ghost gene ; quantitative resistance ; residual resistance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary F2 plants of five, and F3 plants of three, crosses between genotypes carrying the race-specific resistance gene Xa-4 and genotypes not carrying this gene were inoculated with two isolates of Xanthomonas campestris pv. oryzae. Half the tillers of each plant received isolate PX061, avirulent on the Xa-4 gene, the other half of the tillers received isolate PX099, virulent for the Xa-4 gene. The F2 and F3 populations segregated for a single dominant resistance gene, Xa-4. The parental, F2 and F3 genotypes not carrying Xa-4 had mean lesion lengths between 28 and 29 cm for both isolates. The Xa-4 carrying parents showed a mean lesion length of 2.7 cm with the avirulent isolate and of 12.4 cm with the virulent isolate. The Xa-4 carrying F2 and F3 genotypes had mean lesion lengths of 5.2 and 20.1 cm for the two isolates, respectively. These observations strongly indicate that the Xa-4 gene, carried by the rice genotypes studied (IR28, Cisadane and BR51-282-8), had a considerable residual effect when exposed to virulent isolate PXO99.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00025232
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Genetic analysis of, and selection for, factors affecting quantitative resistance to Xanthomonas campestris pv. oryzae in rice (1991)
    Springer
    Euphytica 53 (1991), S. 235-245 
    Details
    ISSN: 1573-5060
    Keywords: Oryza sativa ; rice ; Xanthomonas campestris pv. oryzae ; bacterial blight ; quantitative resistance ; polygenic resistance ; transgressive segregation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Four cultivars moderately resistant to Philippine isolates of Xanthomonas campestris pv. oryzae races 2, 3, 5 and 6 and highly resistant to race 1 were crossed with two susceptible cultivars and with each other. The F1 populations were as or more susceptible than the least resistant parent cultivar when assessed for lesion length (cm) by clip-inoculating booting plants with two race 2 and one race 6 isolates of X.c. oryzae. The F2 populations showed continuous distributions when assessed with the race 6 isolate PX099, although populations from crosses between moderately resistant cultivars were positively skewed. Mean broad-sense heritability in the F2 was 0.50. Selection for varying levels of resistance was carried out in the F2 and F3 generations. F3 lines selected from the F2 population modes had variances and ranges equal to those selected from the F2 population extremes and larger than the variances of the parent cultivars. Line selection in the F3 generation was more effective than plant selection in the F3 and in the F2. Realized h2 was 0.39 for line selection in the F3 but only 0.24 for plant selection. A number of lines more resistant than both parents were recovered in crosses between moderately resistant cultivars. Lines more susceptible than both parents were also recovered in crosses between moderately resistant cultivars, but few of these lines were as susceptible as the susceptible cultivars. This indicates that the moderately resistant cultivars had some resistance factor(s) in common. All test cultivars, including the susceptible cultivars, carry few to several factors for quantitative resistance. A model based on nine minor resistance factors is proposed to explain the pattern of transgression found in crosses between the six cultivars.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00023275
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Assessment of quantitative resistance of rice cultivars to Xanthomonas campestris pv. Oryzae: a comparison of inoculation methods (1991)
    Springer
    Euphytica 54 (1991), S. 169-175 
    Details
    ISSN: 1573-5060
    Keywords: Xanthomonas campestris pv. oryzae ; bacterial blight ; rice ; Oryza sativa ; clip inoculation ; spray inoculation ; quantitative resistance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Lesion size and lesion number were measured on cultivars of rice inoculated by clipping or spraying with virulent isolates of Xanthomonas campestris pv. oryzae. Mean percentage diseased leaf area (%DLA) gave a similar ranking for the two inoculation methods but differences in lesion size among cultivars were much more evident after clip than after spray inoculation. Correlation between the methods was high (r=0.82**), but some cultivars responded differently with the two techniques. Cultivars which had low scores following spray inoculation showed low disease progress during the first nine weeks after transplanting into a screen-house experiment. Assessment after clip inoculation measures resistance due to spread of bacteria within the leaf xylem system, an important component of quantitative resistance. Assessment after spray inoculation measures all resistance, including resistance to entrance of bacteria into the leaf. In order to select rice entries with improved quantitative resistance to X. c. oryzae based on both components, a screening based on lesion length after clip inoculation, followed by a test for lesion number after spray inoculation, is advised.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00039604
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    Paper (German National Licenses)
    Fulltext
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