ZLV Online

Rust frequently cause foliar diseases of poplars and can thus decrease poplar growth significantly, particularly in intensive plantations. Both in September 2005 and 2006 evaluation of rust intensity was made on 402 clones (in each year) of cotonwoods and black poplars (Aigeiros) and Balsam poplars (Tacamahaca) in a clonal archive growing at the FGMRI Research Station Kunovice. Rust intensity was evaluated according to a six-point scale (0 – without rust, 5 – defoliation caused by rust). We did not diferentiate between Melampsora larici-populina or M. allii-populina, the two species of rust occurring in the Czech Republic. Rather, the results were interpreted generally on the basis of host species: Populus nigra, P. deltoides, P. x euroamericana, P. trichocarpa, P. maximowiczii, and sometimes where subgroups exist within species (e.g. improved cultivars, group cultivated as reserve in situ, and host variety). The most affected clones were those of P. nigra (rating mean in 2005 – 3.05, rating mean in 2006 – 3.19). The least affected clones were those of P. maximowiczii (rating mean in 2005 – 0.76. rating average in 2006 – 0.48), followed by clones of P. deltoides (rating average in 2005 – 1.29, rating average in 2006 – 1.39). Of significant biological, and perhaps economic, interest was the fact that in the P. x euroamericana clones group of Czech crossbreedings = ´CZ´(crossed in 1961) no evidence of rust appeared in majority of the clones in 2005 as well as in 2006 (24 of 25 evalueted clones had an average rust rating of 0.04). Cultivars considered to be rust resistant were: ´Belloto´, ´Blanc du Poitou´, ´Cima´, ´Eckhof´, ´Ellert´, ´Flachslanden´, ´Hees´, ´Neupotz´, and ´Virginiana de Frignicourt´.