Two main studies were conducted in order to complement the investigation on variability in the Portuguese population of the fungus Magnaporthe grisea. Seven selected isolates with different combinations of virulence genes to the Japanese differential cultivars (JDCs) PR 14 (vir-a), PR 82 (vir-ks), PR 80 (vir-ks, vir-a, vir-i, vir-t), PR 72 (vir-ks, vir-a, vir-i, vir-ta, vir-t), PR 65 (vir-ks, vir-a, vir-i, vir-z, vir-ta), PR 166 (vir-ks, vir-a, vir-i, vir-km, vir ta2, vir-kp, vir-t), PR 177 (vir-ks, vir-a, vir-i, vir-k, vir-km, vir-kp, vir-t) were used to test the susceptibility of 65 rice cultivars with different origin. At present, several cultivar groups have been identified. Studies to determine the resistance genes on the two most resistant cultivars from the germ bank of Estação Agronómica Nacional, i.e., "Estrela A" and "Regina", were initiated by crossing them with the 12 JDCs cultivars and the cultivar "Sariceltik", supposed not having any resistance gene.
With the aim to fit the Portuguese isolates of M. grisea in the European lineage of this fungus, 30 isolates were studied using RAPD techniques with selected primers and inoculation on tester cultivars. For the five European lineage of the M. grisea previously determined by CIRAD-CA team, we have detected lineage 1, 2 and 5 in the Portuguese population.
In the previous years the classical characterisation of Seiridium spp. isolates showed no significant differences in what concerns morphological aspects and pathogenicity. The molecular characterisation of Seiridium isolates will be performed using the RAPD technique. Up to the moment the extraction phase is being optimised and the first results are very promising: the fungus is cultivated in a complete liquid medium and the extraction gives rise to a sufficient quantity of DNA of good quality.
In order to evaluate the extent of genetic variability among the lupin anthracnose agents and to clarify the taxonomy, a collection of 18 isolates, obtained from different parts of the world, was analysed at the levels of pathogenicity, growth in culture, spore shape and molecular diversity/markers. Differences were found among the isolates, which can be separated into three groups. According to primer-specific PCR analysis and ITS sequence analysis, all isolates showed close homology to C. acutatum and appeared to belong to this species. These studies are being continued relatively to other molecular markers and new isolates obtained as a result of disease survey in Continental Portugal and Azores Isles.
The survey for autochthonous baculovirus was continued during 1999. Some suspicious samples were kept for posterior entomopathogen identification. However, some of them can be the result of alien contamination and not caused by new Portuguese baculovirus strains
Protecção das Plantas
e dos Produtos Agrícolas Armazenados