SUMMARYEight varieties of spring barley differing in their morphology and resistance to lodging were grown in a trial as main plots which were split for seven treatments: a natural control (C), a control with plots which were mechanically supported (S) and four artificially induced lodging treatments: permanent early lodging (PEL); temporary early lodging (TEL); permanent late lodging (PLL) and temporary late lodging (TLL). The seventh treatment (GR) was an application of the growth regulator BAS 09800W. In comparison with S, treatments PEL, TEL, PLL and TLL reduced grain yield by 38–1, 24–8, 22–0 and 13–9 % respectively. Natural lodging in C plots reduced the yield of the two weakest strawed varieties, Guilden and Jupiter, by 8 and 10% respectively in comparison with treatment S. Yields (C) of these two varieties were increased by GR which had no effect on the yield of other varieties, but reduced grain size in some cases. Treatment GR significantly reduced but did not eliminate natural lodging in weaker strawed varieties and reduced the length of the top four internodes. Lodging reduced grain size in terms of 1000–grain weight and sieving fractions and increased the content of husk and protein. Lodging susceptibility was positively correlated with plant height but showed no clear relationship with the number of vascular bundles, stem diameter, wall thickness, or with the content of lignin, cellulose and hemicellulose in the basal internodes. Lodging resistance appeared to be closely associated with short basal internodes.

The variety Chinese Spring of Triticum aestivum is susceptible to cold treatment applied at the juvenile plant stage, while the variety CappelleDesprez shows resistance to such treatment. By cytological and backcross procedures single homologous pairs of chromosomes from CappelleDesprez were substituted for their homologues in Chinese Spring. Assay experiments carried out on each of the 21 possible substitution lines indicated that three chromosomes, 4D, 5D and 7A of Cappelle-Desprez • were involved in the determination of cold resistance. The resistance expressed by the three substitution lines carrying these chromosomes was less than the reaction of Cappelle-Desprez to cold treatment. Also the magnitude of this resistance supported a hypothesis that the action of the three chromosomes was additive on the scale of measurement used. The possible relationships of the genes for cold resistance to the established genes controlling other developmental characters, also carried by these three chromosomes, are discussed.

The inheritance of the character complex of naked grain and multiflorous spikelets was studied in a diallel set of crosses comprising five varieties of naked oats (Avena nuda) As 78, Manu, Caesar, Nuprime and AJ86/2/1 -and one variety of husked oats (A. sativa), Marls Oberon. In the F1 generation the distribution of multiflorous spikelets was in all cases similar to that of the mid-parent. Crosses between the varieties of A. nuda produced only naked grain on plants in the Fa and F2 generations, indicating that 'nakedness' in the varieties studied was determined by the same loci.The three-gene model proposed by MOULE (1972) for the determination of A. nuda characters was inadequate to account for the observed F2 segregation in naked × husked crosses. An extension of this model is proposed to include a third modifying gene, N3, which in the homozygous dominant condition Produces the husked phenotype when the principal gene, N, is heterozygous. The model assumes complex epistatic relationships between the three modifying genes NI, N2 and N3. Published information and further experimental data suggest that the genotype NN --N3N3 is uncommon. The expression of the genes determining nakedness was greatly influenced by the environment.

SUMMARYResults of grain analyses for the content of nitrogen, oil and husk are presented from trials in the F1 and F2 generations of four subject varieties, Condor (Avena sativa), Sierra, Avon and Anita (A. byzantina), nine tester varieties, mainly of north-west European origin and the 36 crosses between them.Yield of grain crude protein per unit area was positively correlated with grain yield, but nitrogen content of the grain, expressed as a percentage of dry matter, was inversely related to grain yield in both trials. Although the highest values for grain nitrogen content were invariably associated with low grain yields, the highest yielders had average or slightly better than average values for nitrogen content.Analysis of straw samples from the F2 trial revealed considerable differences between varieties and crosses in the proportion of the total shoot nitrogen (grain + straw) ultimately found in the grain. The proportion of total shoot nitrogen translocated to the grain was positively correlated with the ratio of grain yield to straw yield. High grain yielders took up more nitrogen per unit area from the soil and translocated relatively more nitrogen to the grain from the vegetative tissues than did varieties with low grain yields.Yields of grain oil were highly positively correlated with yields of grain per unit area but there was no significant regression of oil content on grain yield in either trial. In the F2 trial, oil yield per unit area was positively correlated with oil content of the grain. The variety Avon and its crosses had consistently high oil content.There was no correlation between yielding ability and husk content of the grain, and some of the highest grain yields were associated with low mean husk contents. High husk content of the grain tended to be associated with stiffer straw.The results are discussed in relation to improving grain quality in the breeding of new varieties of oats.

A technique is described in which cereal seedlings after germination and hardening under controlled conditions in a growth chamber were subjected to freezing in tubes immersed in a solution of ethylene glycol. Susceptibility to freezing was estimated by measuring electrical conductance on the linear 0-100 scale of a standard 'Avometer' using platinum probes inserted near the base of the lamina of the first leaf. The use of the technique is illustrated by two experiments with winter barley cultivars chosen to represent a wide range of winter hardiness. Although significant cultivar differences in mean conductance existed prior to freezing, adequate differentiation was obtained by measurements after freezing only. The differentiation of these cultivars on mean conductance values after freezing was well correlated with their established winter hardiness.It is concluded that the technique is sufficiently sensitive for the preliminary screening of early generation material but that, because of significant cultivar x hardeningduration interactions, advanced breeding lines should be tested over a range of hardening and freezing regimes.