Variation for winter hardiness generated by androgenesis from
Festuca pratensis × Lolium multiflorum amphidiploid cultivars with different winter susceptibility
Androgenic populations produced from three Festuca pratensis × Lolium multiflorum amphidiploid (2n = 4x = 28) cultivars show wide within population variation for winter hardiness. Populations comprising a total of 423 androgenic plants derived from 23 donor plants from 3 Polish F. pratensis × L. multiflorum cultivars Felopa, Sulino, and Rakopan were studied over 3 years (1999–2002) in a field experiment at Lopuszna, Poland (20∘08′E, 49∘28′N, altitude 568 m). The results indicate that despite differences in winter hardiness between the three amphidiploid cultivars, the mean winter hardiness of androgenic progeny from each cultivar was the same. Thus an androgenesis component in a plant breeding programme may provide an opportunity to recover winter hardy genotypes from high yielding cultivars that are themselves adapted poorly to stress conditions. Androgenesis also evoked variation in snow mould resistance. In this case, androgenic plants with the greatest snow mould resistance were recovered from the least winter hardy donor cultivars and plants. The results indicated the low importance of snow mould resistance as a component of winter hardiness under the field conditions used for these experiments.
Impact of cold-induced antioxidant activity on frost resistance in androgenic Festulolium genotypes
The aim of the study was: (i) to state if selected in the field conditions androgenic Festulolium genotypes are diverse in frost tolerance, and (ii) to investigate if changes in anitoxidant activity could be recognized as a physiological marker of this type tolerance. Antioxidative system induced by prehardening (12°C) and hardening (2°C) temperatures was investigated in 6 androgenic genotypes generated from a Festuca pratensis × Lolium multiflorum (2n = 4x = 28) amphidiploid hybrid (four genotypes derived from the F 1 hybrids, and two genotypes derived from the Festulolium cultivar ‘Rakopan’). The electrolyte leakage, frost resistance expressed as the values of temperature causes 50% damages (LT 50 ), the activities of superoxide dismutase (SOD), catalase (CAT), non-specific peroxidase (PX) and ascorbate peroxidase (APX) were measured. The results obtained indicated weak diversity of frost tolerance among studied androgenic genotypes. Only the one genotype was chosen as the most resistant to frost, while the other genotypes demonstrated no significant differences in values of LT 50 coefficient recorded after hardening. Prehardening temperature of 12°C caused an increase in cell membrane permeability in all genotypes studied. After hardening ion leakage from cells declined up to the control level. Generally, cold activated SOD, PX and APX in leaves of the genotypes studied, and inhibited strongly CAT activity. The most frost tolerant genotype was characterized by high PX activity after hardening process. Abbreviations: APX – ascorbate peroxidase, CAT – catalase, EDTA – ethylenediaminetatraacetic acid, LT 50 – letal temperature causing 50% membrane cell damages, NBT – nitroblue tetrazolium, PPFD – photosynthetic photon flux density [μmol m -2 s -1 ], PX – non-specific peroxidase, RH – relative humidity, ROS – reactive oxygen species, SE – standard error, SOD – superoxide dismutase
Investigations on the rôle of organic matter in plant nutrition
1. As the result of decomposition of green manure in a swamp soil, the coarse fractions (including coarse and fine sand) of the surface layer (first 3 inches) decreased by 11·2 per cent. while the fine ones (silt+clay) increased by 9·8 per cent. in the course of 43 days. The effect was less pronounced in the manured soil maintained at 60 per cent. saturation, while no alteration was to be noticed in the case of the unmanured specimens. 2. Treatment with dilute hydrochloric acid prior to dispersion had no appreciable effect on the estimates of mechanical composition obtained in the different cases. Loss in solution was also comparatively small. 3. The silica-sesquioxide ratio increased slightly as the result of decomposition of green manure in swamp soil. The composition of the fine fractions was also altered, the total percentages of the oxides of iron, aluminium and silicon increasing from 90·5 to 99·3 in the course of 71 days. 4. The practical significance of the above and related observations has been discussed.