Phytophtora ramorum - naujas invazinis augalų patogenas Lenkijoje

Phytophthora ramorum is the new invasive Algae like Oomycetes known since the last 10 years in the USA and Europe. In California the pathogen is causal agent of sudden oak death whereas in Europe as twig bight of ericaceous plants, rotting of Vibumum species and at least 30 others species including beech and red oak. In Poland P. ramorum was detected from Rhododendron, Calluna, Pieris and Photinia. Additionally P. citricola was isolatedfrom diseased Rhododendron stem parts and leaves whereas P. cactorum was found on rotted leaf blades of Photinia. Botrytis cinerea, Pestalotia sydowiana and Mucor spp. were also often isolated from diseased plant parts. Isolates obtained from those plants caused necrosis of leaf blades and tip shoot parts. There were no significant differences between pathogenicity of tested isolates toward 4 plant species. It indicates on one source of the pathogen. On all tested cultivars of Calluna and Calluna vulgaris development of necrosis was observed on tip parts of shoots. Both plant species and crowberry could be the potential source of P. ramorum in forests

Study on usability of Fusarium oxysporum Schlecht.f.sp. tulipae Apt. metabolites for screening for basal rot resistance in tulip

The usefulness of fungus culture filtrates and fusaric acid as selecting agents for Fusarium resistance breeding in tulip was examined on in vitro cultures of shoots and embryonic calli of seven tulip genotypes differing in resistance to Fusarium oxysporum Schlecht. f. sp. tulipae Apt. (F.o.t.) and four virulent F.o.t. isolates. Fusaric acid influenced the shoot growth of all cultivars tested in a similar way, irrespectively of their greenhouse resistance to basal rot. Also, the sensitivity of calli of the cultivars studied to fusaric acid did not correspond with their resistance to F.o.t. evaluated in the greenhouse screening. The phytotoxity of F.o.t. culture filtrates did not depend on their fusaric acid contents. There was a negative correlation between cultivar's resistance to F.o.t in greenhouse tests and the sensitivity of their shoots to fungus culture filtrates in in vitro tests. This indicates that defence mechanism against F.o.t. in tulip tissue may have a nature of hypersensitive response. Considering the results of our study, it may be concluded that the use of fusaric acid or fungus culture filtrates for the in vitro selection of somaclones resistant to F.o.t. in tulip is not feasible