Stem rust (Puccinia graminis ssp. graminicola Urban) its hosts and harmfulness in grasses grown for seed
Stem rust development on four species of grasses was studied in field experiments conducted at Radzików in 1997-2001. Population of <i>Puccinia graminis</i> ssp. <i>graminicola</i> from different hosts was characterised and their harmfulness for grass grown for seed was estimated. The materials for study were ecotypes and strains of <i>Lolium perenne</i>, <i>Festuca rubra, Poa pratensis</i> and <i>Deschampsia caespitosa</i> collected in breeding nursery and cultivars and strains of <i>L.perenne, F.rubra, P.pratensis</i> cultivated for seed. It was found that the changes in environmental conditions during last years influenced earlier occurrence of stem rust on grasses in Poland. All examined species were the host of <i>P.graminis</i> ssp. <i>graminicola</i>, however the period of infection of particular hosts were different. <i>L.perenne</i> and <i>D.caespitosa</i> were infected in early summer but <i>F.rubra</i> and <i>P.pratensis</i> in late summer or in the autumn. Morphological analysis of spores of <i>P.graminis</i> ssp. <i>graminicola</i> have shoved significant differences between populations obtained from <i>L.perenne</i> and <i>D.caespitosa</i>. Some differences were found between populations from <i>F.rubra</i> and <i>P.pratensis</i> also, but they need more study. Every year occurrence of stem rust on <i>L.perenne</i> and <i>D.caespitosa</i> and its relation with spring temperature in Radzików indicated that populations of patogen could overwinter in local turf. Incidental appearance of stem rust on <i>F.rubra</i> and <i>P.pratensis</i> in centre of Poland allowed to suppose that spores of these forms might be transfer by wind from other regions. The investigation revealed that stem rust can be dangerous for <i>L.perenne</i> grown for seed when infection occurs at flowering time. It has been established that infection of <i>F.rubra</i> and <i>P.pratensis</i> in autumn should not be disregarded. Damages of leaves by <i>P.graminis</i> ssp. <i>graminicola</i> substantially limited plant heading in the next year.