Pathogenic variability, inheritance of virulence and host-pathogen interaction with temperature in <i>Ascochyta fabae</i> f. sp. lentis on lentil

The frequency and distribution of Mating types 1 and 2 of Ascochyta fabae f. sp. lentis were studied by controlled crosses of 223 isolates from western Canada and 14 other countries with tester isolates. Both mating types were recovered from local and foreign sources. Mating type 1 was the most freq...

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Main Author: Kemal, Seid Ahmed
Other Authors: Morrall, Robin
Format: Others
Language:en
Published: University of Saskatchewan 1996
Online Access:http://library.usask.ca/theses/available/etd-10212004-000142
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spelling ndltd-USASK-oai-usask.ca-etd-10212004-0001422013-01-08T16:31:39Z Pathogenic variability, inheritance of virulence and host-pathogen interaction with temperature in <i>Ascochyta fabae</i> f. sp. lentis on lentil Kemal, Seid Ahmed The frequency and distribution of Mating types 1 and 2 of Ascochyta fabae f. sp. lentis were studied by controlled crosses of 223 isolates from western Canada and 14 other countries with tester isolates. Both mating types were recovered from local and foreign sources. Mating type 1 was the most frequent and Mating type 2 was not recovered from a large collection of isolates from the 1991 Canadian crop. However, no pseudothecia were observed on overwintered infected lentil stems from a field where both mating types had been identified. Incompatibility was observed between some domestic isolates and known testers but no self fertility was observed. The pathogenic variability of 84 isolates (domestic and foreign) was determined by inoculating seedlings of 10 lentil differentials (Chilean '78, Eston, Brewer, ILL358, ILL5588, ILL5684, Indianhead, Laird, Spanish Brown and Precoz) at 20°C in growth chambers. Isolates collected in 1978 and 1985 from western Canada were weakly virulent compared to 1992 collections. Although the 1992 isolates caused higher disease severity on all differentials, the greatest increase was observed on the widely grown cv. Laird. The foreign isolates varied from weakly to highly virulent but no geographic relationship was detected. Both ANOVA and cluster analysis showed a general lack of specific differential X isolate interactions, suggesting specificity at the host rather than the cultivar level. In field experiments, the differentials maintained the relative reactions observed in the growth chamber, except for ILL358 which showed adult plant susceptibility but seedling resistance. Both isolate virulence and host susceptibility generally increased with declining temperatures. Significant interactions occurred between temperature and differential and temperature and isolates. However, the ranking of differentials did not change with temperatures. In vitro and growth chamber experiments showed that the optimum temperature for mycelial growth and host infection was between 15 and 20°C. However, no strong correlation was found between mycelial growth and virulence. In crosses of isolates, the F<sub>1</sub> progeny included transgressive segregants with respect to virulence. This suggested that virulence is controlled by many genes with additive effects. The segregation of disease reaction in F<sub>2</sub> progeny of crosses between lentil genotypes was generally similar when judged by seedling tests or seed infection. Morrall, Robin University of Saskatchewan 1996-01-01 text application/pdf http://library.usask.ca/theses/available/etd-10212004-000142 http://library.usask.ca/theses/available/etd-10212004-000142 en unrestricted I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University of Saskatchewan or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report.
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description The frequency and distribution of Mating types 1 and 2 of Ascochyta fabae f. sp. lentis were studied by controlled crosses of 223 isolates from western Canada and 14 other countries with tester isolates. Both mating types were recovered from local and foreign sources. Mating type 1 was the most frequent and Mating type 2 was not recovered from a large collection of isolates from the 1991 Canadian crop. However, no pseudothecia were observed on overwintered infected lentil stems from a field where both mating types had been identified. Incompatibility was observed between some domestic isolates and known testers but no self fertility was observed. The pathogenic variability of 84 isolates (domestic and foreign) was determined by inoculating seedlings of 10 lentil differentials (Chilean '78, Eston, Brewer, ILL358, ILL5588, ILL5684, Indianhead, Laird, Spanish Brown and Precoz) at 20°C in growth chambers. Isolates collected in 1978 and 1985 from western Canada were weakly virulent compared to 1992 collections. Although the 1992 isolates caused higher disease severity on all differentials, the greatest increase was observed on the widely grown cv. Laird. The foreign isolates varied from weakly to highly virulent but no geographic relationship was detected. Both ANOVA and cluster analysis showed a general lack of specific differential X isolate interactions, suggesting specificity at the host rather than the cultivar level. In field experiments, the differentials maintained the relative reactions observed in the growth chamber, except for ILL358 which showed adult plant susceptibility but seedling resistance. Both isolate virulence and host susceptibility generally increased with declining temperatures. Significant interactions occurred between temperature and differential and temperature and isolates. However, the ranking of differentials did not change with temperatures. In vitro and growth chamber experiments showed that the optimum temperature for mycelial growth and host infection was between 15 and 20°C. However, no strong correlation was found between mycelial growth and virulence. In crosses of isolates, the F<sub>1</sub> progeny included transgressive segregants with respect to virulence. This suggested that virulence is controlled by many genes with additive effects. The segregation of disease reaction in F<sub>2</sub> progeny of crosses between lentil genotypes was generally similar when judged by seedling tests or seed infection.
author2 Morrall, Robin
author_facet Morrall, Robin
Kemal, Seid Ahmed
author Kemal, Seid Ahmed
spellingShingle Kemal, Seid Ahmed
Pathogenic variability, inheritance of virulence and host-pathogen interaction with temperature in <i>Ascochyta fabae</i> f. sp. lentis on lentil
author_sort Kemal, Seid Ahmed
title Pathogenic variability, inheritance of virulence and host-pathogen interaction with temperature in <i>Ascochyta fabae</i> f. sp. lentis on lentil
title_short Pathogenic variability, inheritance of virulence and host-pathogen interaction with temperature in <i>Ascochyta fabae</i> f. sp. lentis on lentil
title_full Pathogenic variability, inheritance of virulence and host-pathogen interaction with temperature in <i>Ascochyta fabae</i> f. sp. lentis on lentil
title_fullStr Pathogenic variability, inheritance of virulence and host-pathogen interaction with temperature in <i>Ascochyta fabae</i> f. sp. lentis on lentil
title_full_unstemmed Pathogenic variability, inheritance of virulence and host-pathogen interaction with temperature in <i>Ascochyta fabae</i> f. sp. lentis on lentil
title_sort pathogenic variability, inheritance of virulence and host-pathogen interaction with temperature in <i>ascochyta fabae</i> f. sp. lentis on lentil
publisher University of Saskatchewan
publishDate 1996
url http://library.usask.ca/theses/available/etd-10212004-000142
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