The species structure of plant parasitic nematode populations from the rhizosphere of winter wheat grown with crop rotation or in 48-year-old monoculture was analyzed and compared. Dominating species: Bitylenchus dubius, Merlinius microdorus, Paratylenchus neglectus and Heterodera avenae, in monoculture plots, had higher populations than in crop rotation plots. Heterodera avenae eggs and larvae were infected by pathogenic fungi in 68% of the monoculture crops (vs. 65–66% of the cysts from crop rotation), 12–20% of Paratylenchus sp. specimens were colonized by bacteria, mainly by Bacillus penetrans. This study shows nematological changes occurring in long-term wheat breeding, thus providing additional information necessary to fight dangerous viral vectors of the examined cereal.
The effects of gamma irradiation on the vernalization requirements, growth and development of winter wheat grown in a rainout shelter were studied during two successive growing seasons. Dry grains of winter wheat cv. Kobra were irradiated with 300 Gy radiation from a cobalt 60 gamma irradiator. Treated and control grains were pregerminated and subjected to vernalization for 0, 42 or 54 days. Morphological parameters of the plants developing from irradiated seeds (M1 generation) and the plants grown from the seeds produced by the irradiated plants (M2 generation) were measured in order to track the studied effects over two generations. Irradiation of dry grains slowed the growth and development of the plants regardless of the temperature treatment. The measured yield structure elements appeared to be lower for irradiated plants, but no clear effect of radiation on vernalization requirements was noted