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- Blandón-Díaz, Jorge Ulises
(författare)
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Insights into population structure and epidemiology of Phytophthora infestans from Nicaragua
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Late blight caused by Phytophthora infestans (Mont) de Bary is a constraint to both potato and tomato crops in the northern highlands of Nicaragua. This thesis describes studies on population structure and epidemiology of P. infestans from Nicaragua. The genotypic and phenotypic variation in isolates of P. infestans collected in potato and tomato growing areas of northern Nicaragua were analyzed using genotypic (SSR fingerprinting and mtDNA haplotyping) and phenotypic markers (mating type, virulence and fungicide sensitivity). Genotypic markers revealed no polymorphism among the P. infestans isolates tested. Phenotypic variation was observed. Nicaraguan population of P. infestans is dominated by a clonal lineage of the A2 mating type, Ia mtDNA haplotype and no evidence of genetic population differentiation among potato and tomato isolates was found. The aggressiveness of P. infestans isolates sampled from potato and tomato fields was determined through cross-inoculations experiments. Potato and tomato isolates both had a shorter LP, higher SP, and were more aggressive on tomato leaflets compared to potato ones. The adequacy of the late blight simulation model LATEBLIGHT (version LB2004) was evaluated under Nicaraguan conditions. During 2007-2008 field experiments were conducted in Nicaragua. The simulation model was considered adequate as it accurately predicted high disease severity in susceptible cultivars without fungicide sprays, and demonstrated a decrease in the disease progress curves with additional fungicide applications, similar to that observed in the field plots. The quantitative relationship between host resistance and the need for fungicide was also investigated using simulations performed with LATEBLIGHT, as well as field trials.
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| 3. |
- Blandón-Díaz, Jorge Ulises, et al.
(författare)
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Phenotypic Variation Within a Clonal Lineage of Phytophthora infestans Infecting both Tomato and Potato in Nicaragua
- 2012
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Ingår i: Phytopathology. - 0031-949X .- 1943-7684. ; 102, s. 323-330
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Tidskriftsartikel (refereegranskat)abstract
- Late blight caused by Phytophthora infestans (Mont.) de Bary is a constraint to both potato and tomato crops in Nicaragua. The hypothesis that the Nicaraguan population of P. infestans is genotypically and phenotypically diverse and potentially subdivided based on host association was tested. A collection of isolates was analyzed using genotypic markers (microsatellites and mitochondrial DNA haplotype) and phenotypic markers (mating type, virulence, and fungicide sensitivity). The genotypic analysis revealed no polymorphism in 121 of 132 isolates of P. infestans tested. Only the Ia haplotype and the A2 mating type were detected. Most of the tested isolates were resistant to metalaxyl. The virulence testing showed variation among isolates of P. infestans. No evidence was found of population differentiation among potato and tomato isolates of P. infestans based on the genotypic and phenotypic analysis. We conclude that the Nicaraguan population of P. infestans consists of a single clonal lineage (NI-1) which belongs to the A2 mating type and the Ia mitochondrial DNA haplotype. Moreover, based on the markers used, this population of P. infestans does not resemble the population in countries from which potato seed is imported to Nicaragua or the population in neighboring countries. The data presented here indicate that the NI-1 clonal lineage is the primary pathogen on both potato and tomato, and its success on both host species is unique in a South American context.
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| 4. |
- Yuen, Jonathan, et al.
(författare)
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Assessing the Adequacy of the Simulation Model LATEBLIGHT Under Nicaraguan Conditions
- 2011
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Ingår i: Plant Disease. - 0191-2917 .- 1943-7692. ; 95, s. 839-846
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Tidskriftsartikel (refereegranskat)abstract
- In this study, the adequacy of the late blight simulation model LATEBLIGHT (version LB2004) was evaluated under Nicaraguan conditions. During 2007 to 2008, five field experiments were conducted in three potato-production regions in northern Nicaragua. Two susceptible ('Cal White' and 'Granola') and one resistant ('Jacqueline Lee') potato cultivars were evaluated without use of fungicides and with three application intervals (4, 7, and 14 days) of the fungicide chlorothalonil. The simulation model was considered adequate because it accurately predicted high disease severity in susceptible cultivars without fungicide protection, and demonstrated a decrease in the disease progress curves with additional fungicide applications, similar to that observed in the plots. The model also generally predicted inadequate fungicide control, even with a 4-day spray interval, which also occurred in the field. Lack of adequate fungicide protection would indicate the need for cultivars with higher levels of durable resistance, and that farmers should consider more effective fungicides applications (higher dosages or different chemistries) if susceptible cultivars are used.
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