D. A. Lawes

Symbiotic variability in Vicia faba. 3. Genetic effects of host plant, rhizobium strain and of host × strain interaction

SummarySix Vicia faba populations were grown in all possible combinations with six Rhizobium leguminosarum strains in order to estimate the relative importance of the three genetic components of symbiotic variability. Additive genetic effects of host genotype and rhizobium genotype accounted for only 8.9% and 11.8% of the total phenotypic variation. Non-additive variation attriabutable to specific host genotype × rhizobium genotype interactions was by far the largest component of variation and accounted for 73.8% of phenotypic differences. Therefore the greatest improvement in symbiotic nitrogen fixation is likely to arise from simultaneous selection of both symbionts.

Genetic variation in stomatal characteristics and behaviour, water use and growth of five Vicia faba L. genotypes under contrasting soil moisture regimes

SummaryFive genotypes of Vicia faba L. with contrasting frequencies were grown in a controlled environment in soil moisture regimes of 100%, 78% and 61% of field capacity. Growth, water use and leaf conductance characteristics were measured. Stomata were more frequent on abaxial than adaxial surfaces, the abaxial/adaxial ratio ranging from 1.12 to 1.34. There were significant (P<0.001) correlations between calculated stomatal conductance, based on measurements of stomatal frequency and length, and leaf conductance measured with a diffusion porometer, in the two higher soil moisture treatments. In the 100% regime only, abaxial stomata opened wider than adaxial. Ranking of the genotypes for leaf conductance and plant transpiration was similar in all three regimes with large leaved types having the lowest conductance and greatest water use efficiency. Growing plants with reduced soil moisture availability improved water use efficiency, the ranking for which was also similar in all treatments. Relative growth rate and net assimilation rate were greatest with full watering, less in the 78% and least in the 61% regime. Leaf area ratio was less affected by available soil moisture and only in some genotypes.

Symbiotic variability in Vicia faba. 1. Genetic variation in the Rhizobium leguminosarum population

SummaryTwenty isolates taken at random from indigenous populations of Rhizobium leguminosarum sampled near Aberystwyth were each inoculated into plants of a standard Vicia faba variety grown aseptically under conditions free of combined nitrogen. Plants in association with the individual rhizobium isolates exhibited large differences in dry matter yield, nitrogen content, efficiency of nitrogen utilization and date of first flower. The implications of these differences to the productivity and reliability of varieties of field beans are discussed.

Variation in the crude protein content of field beans (Vicia faba L.) in relation to the possible improvement of the protein content of the crop

SummaryA survey of the protein content of various field bean varieties indicates a range of variation extending over sixteen units of crude protein from 22–38%. Analysis of single plants from within three WPBS varieties Dylan. Danas and Dacre indicates that a similar range exists within commercial varieties. Examination of the progenies of high and low protein single plant selections together with a preliminary estimation of heritability suggest that protein content is highly heritable. No significant correlations were found between protein content and seed yield.

Symbiotic variability in Vicia faba. 2. genetic variation in Vicia faba

SummaryEight varieties of Vicia faba were examined in association with a standard strain of Rhizobium leguminosarum and also with the application of mineral nitrogen. Large differences in dry matter yield, nitrogen percentage and total nitrogen uptake were apparent between varieties and between rhizobium and mineral nitrogen treatments; the interaction was also significant. Genotypic differences in both the effectiveness of the symbiosis with this strain of rhizobium and the efficiency of utilization of nitrogen were thus demonstrated. The implications of this variability on the assessment of varieties and the possiblity of exploiting it by plant breeding techniques are discussed.

Effect of temperature on the expression of the naked grain character in oats

SummaryThe effect of temperature on the expression of the naked grain character in oats was studied in a growth room experiment which compared eight naked oat genotypes grown at temperatures of 15, 20 and 25°C. Expression of grain nakedness and temperature level were positively associated and a genotype x temperature interaction was shown.

The inheritance of the naked grain character in oats studied in a cross between the naked variety caesar and the husked variety BO 1/11

SummaryThe inheritance of the naked grain character in oats was studied in a cross between BO 1/11 (husked) and Caesar (naked), by analysing plants of F1, F2, F3 and both (F1 × BO 1/11) and (F1 × Caesar) backcross generations. F1 and F2 plants were grown under both glasshouse and field conditions.Results suggest that the naked/husked character is basically governed by one major gene and modifying genes mask the effect of the main gene in the homozygous naked and heterozygous classes.Expression of the naked grain character was higher under glasshouse than under field conditions, indicating the large influence which environment can exert on the expression of this character.

Variation in photosynthetic activity in cereals and its implications in a plant breeding programme I. Variation in seedling leaves and flag leaves

SummaryThe extent of variation in photosynthetic activity in the seedling and flag leaves of fourteen oat varieties, and in the seedling leaves of three varieties each of wheat and barley has been investigated. The suitability of NaH14CO3 and Warburg manometric techniques for handling the attribute of photosynthetic efficiency in a plant breeding programme is assessed.Results obtained are considered in comparison with estimates of net assimilation rate (E), relative growth rate (R) and leaf area ratio (F) derived from growth analysis data. The relationships with yield and implications for a plant improvement programme are discussed.

Evaluation of the use of species hybrids and synthetic amphiploids in the improvement of the oat crop

SummaryCytogenetic studies on species hybrids and synthetic amphiploids in the Avenae are discussed in relation to their use in transferring variation from wild species of different ploidy into cultivated hexaploid oats. Procedures for the introduction of alien variation into the cultivated oat are proposed, based on our present knowledge of the genetic relationships between species in Avena.

Self-fertility and the distribution of seed yield in Vicia faba L.

SummaryFive lines of field beans (Vicia faba L.) bred and selected for a high level of self-fertility have demonstrated heritable differences in distribution of seed yield on the reproductive nodes when grown under conditions of selfpollination. Fully self-fertile genotypes produce a large proportion of the seed yield on the lower nodes. The breeding and selection for both self-fertility and the distribution of seed yield is discussed.