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| Author(s): |
Jorge Omar Gieco
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | Piracicaba. |
| Institution: | Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC) |
| Defense date: | 2002-08-30 |
| Advisor: | Luis Eduardo Aranha Camargo |
| Abstract | |
Leaf blotch caused by Septoria tritici Rob. is one of the most important diseases of wheat in more than 50 countries, being responsible for significant yield losses. The objectives of the present work were: (i) To study the interaction between resistance x phenological stage in the pathosystem wheat - Septoria tritici in 77 F11 progenies of wheat derived from the three-way cross Tadinia x (Yecora rojo x UC554); (ii) To Determine the degree of physiologic specialization among Argentinean and USA isolates of Septoria tritici through inoculation on cultivars and lines of bread wheat (Triticum aestivum L.); (iii) To evaluate the resistance to Septoria tritici in F11 wheat progenies derived from the three-way cross Tadinia x (Yecora rojo x UC554) in different phenological stages seeking the subsequent analysis with molecular markers, and (iv) To detect resistance genes to Septoria tritici through microsatellites and AFLP markers. The mapping technique used was Bulked Segregant Analysis, or analysis of mixtures of DNA of segregant individuals. Bulk extremes were composed based on greenhouse and field disease assessments made in three phenological stages: seedling, tillering and flag leaf, and two years (1999-2000). Resistant and susceptible extremes were analyzed with microsatellites and AFLP markers. 307 microsatellite primers belonging to the series wms and wmc were used, from which 262 polymorphic ones were chosen for further analysis. In the analysis with AFLP markers, combinations of two Pstl with ten Msel selective primers were used. Highly significant differences for damaged leaf area were found (p ≤ 0.0001) among progenies in all phenological stages studied. Joint analyses of variance for DLA indicated a highly significant interaction between progenies and phenological stages (p ≤ 0.0001), indicating the need to evaluate resistance in more than one phenological stage to guarantee the correct selection of resistant genotypes. Variations in aggressiveness among strains of Septoria tritici were detected, indicating the need of pathogenicity tests as a priority in the selection of resistant wheat materials, since the aggressiveness of each isolate can vary significantly depending on the host genotype. It was not possible to detect resistance genes in the population Tadinia x (Yecora rojo x UC554). Three factors can be pointed as responsible for this failure 1) Employment of a three way cross mapping population; 2) Presence of out-of- type progenies, and 3) Unexpected behavior of UC554 when inoculated with Septoria tritici. (AU) | |