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.
Plant development affects the cold-induced expression of plant defence-related transcripts in winter wheat
Abstract In winter cereals, low temperature hardening, plant age and genotype are known to influence the expression of resistance to snow mould diseases. A study was undertaken to determine the effects of genotype, plant age and duration of cold hardening on the temporal expression of the PR-protein and other defence-related protein transcripts under controlled environment conditions, and in the field during autumn, winter, and early spring. The plant defence-related proteins studied were classified into two groups based on their patterns of expression. The first group consisted of γ-thionin, chitinase, lipid transfer protein (LTP) and phenylalanine ammonia lyase (PAL) whereby transcript levels increased to maximum levels during November–December, but decreased gradually throughout the winter and early spring. Higher transcript levels were observed in late seeded treatments compared with early seeded treatments. Under controlled conditions, transcript levels accumulated rapidly in response to hardening, reaching maximum levels following 1-week and generally maintained levels throughout the hardening treatments. The second group consisted of β-1,3-glucanase, peroxidase and PR-1a whose transcripts increased to maximum levels in the field during November–December, then fluctuated throughout the winter and early spring. Higher transcript levels were observed in early seeded treatments compared to later seeded treatments. Under controlled environment conditions, these transcripts gradually accumulated in response to hardening at 2°C and reached maximum levels after 6 weeks. PR-1a, PAL, and LTP transcript levels were generally higher in the snow mould resistant cultivars PI181268 and D+ throughout the winter and early spring compared to the cold-hardy, snow mould susceptible cultivar, Norstar. Conversely the chitinase and γ-thionin transcripts were expressed at higher levels in the susceptible cultivar Norstar. These results demonstrate that the temporal expression of cold-induced, plant defence-related transcripts in winter wheat is differentially regulated among genotypes and during different plant development stages, and are the first to implicate LTPs in the expression of genotypic-based snow mould resistance in wheat. Potential plant defence signalling pathways involved in snow mould resistance induced at low temperatures during natural acclimation of winter wheat are discussed.
New molecular evidence on genome relationships and chromosome identification in fescue (Festuca) and ryegrass (Lolium)
The level of similarity between the DNA of Lolium multiflorum and three Festuca species, F. arundinacea, F. pratensis and F. glaucescens, was analysed on Southern blots, using DNA–DNA hybridization, and also on chromosomes using genomic in situ hybridization (GISH). It was demonstrated that the close relationship between L. multiflorum and the allohexaploid F. arundinacea arises principally from the affinity of L. multiflorum to one of the ancestral progenitors of F. arundinacea, namely F. pratensis. Using probes made from total genomic DNA of L. multiflorum, and also of L. perenne, particular regions of high homology, described here as ‘GISH bands’ were identified on F. pratensis chromosomes. These GISH bands, in combination with a specific probe for rDNA, provide us with new markers for the identification of chromosomes within the F. pratensis complement. Restriction analysis within the rDNA repeat unit revealed additional information on the close phylogeny of L. multiflorum and F. pratensis. The rDNA restriction patterns confirm that F. arundinacea originated as a hybrid between F. pratensis and F. glaucescens.