Pollination,fertilization and seed development in winter stocks of faba beans (Vicia faba L.)

Summary Incidences of pollination and fertilization were determined in five stocks of winter bean (two populations, two inbred lines, one cultivar) in two years. In the second year, irrigation was included as an experimental treatment and the development of seeds was monitored. Large differences between years were found in the measures of pollination and fertilization, and irrigation was associated with a small but significant increase in the proportion of ovules which were fertilized within fertilized flowers, particularly in the ovules furthest from the stigma. This increase was clearly reflected in the corresponding indices of seed maturation in the irrigated plants. Irrigation was not associated with any change in the proportion of ovules which aborted. Small but statistically significant differences in all of the measures of pollination and fertilization were found among the stocks. It is suggested that the variation in the incidences of pollination and fertilization was largely associated with variation in the synchrony of anthesis within racemes. The proportion of ovules within pods which matured as seeds and the proportion which aborted both varied significantly among the five stocks. Abortion appeared to act independently of fertilization in affecting the index of seed maturation, so both mechanisms should be considered when breeding for improved filling of pods.     

Rate and inheritance of cross-fertilization in faba bean (Vicia faba L.)

Summary To assess the feasibility for synthetic varieties of Vicia faba L., 108 faba bean genotypes were screened for cross-fertilization rate in five field experiments carried out in 1989 and 1990 at Wageningen.Significant genotypic differences were observed for outcrossing rate, which ranged from 1 to 55%. These percentages, however, are thought to be not high enough for a commercially feasible production of synthetic varieties.The inheritance of cross-fertilization rate, determined by testing the F₄ generation of a cross between two inbreds, both with high outcrossing rates, appeared to be of a polygenic nature, as was indicated by the wide variation in, and the continous distribution of, the cross-fertilization rates. Among the F₄ lines tested some had a significantly higher cross-fertilization rate than the parents. However, this difference was not found when these lines were retested, indicating that possibilities for successful selection for higher outcrossing rates might be limited.     

The identification of faba bean (Vicia faba L.) trisomics by translocation tester set

Summary Five subtelocentric primary trisomics of Vicia faba L. were isolated from crosses between asynaptic mutants and normal plants or translocation tester stocks. The extra chromosome of each trisomic was identified cytologically by critical multivalent association at metaphase I of meiosis.     

Mutagenesis of faba bean (Vicia faba L.) and the identification of five different genes controlling no nodulation,ineffective nodulation or supernodulation

Summary Mutagenesis ofVicia faba L. using ethyl methanesulfonate has yielded three mutants (f13, f73, f245) with ineffective nodulation (Nod⁺Fix^–), one mutant (f48) unable to nodulate (Nod^–) and one supernodulating mutant (f32) having 3 to 5 times more nodules than the control in the absence of combined nitrogen, and expressing nitrate tolerant nodulation (Nod⁺⁺, Nts). All of the mutant phenotypes were controlled by single and distinct recessive genes designatedsyml tosym5, respectively. Grafting experiments showed that the (Nod⁺Fix^–) and (Nod^–) phenotypes were both under root genotype control and that the (Nod⁺⁺, Nts) phenotype was under shoot genotype control.     

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

Summary Eight 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.     

Inheritance of seed coat colour in broad bean (Vicia faba L.)

Summary The inheritance of the seed coat colours violet, spotted, brown, green, red, black and beige was investigated in a 10×10 diallel cross between broad bean (Vicia faba L. major) lines. Spotted seed colour was dominant over any uniform seed coat colouring. Brown was dominant over black, green and normal (beige colour). Black and red seed parents behaved as recessive in all F₁ progenies. A 3 (coloured): 1 (normal) segregation ratio was observed in the F₂ of crosses of violet, brown, black, red and spotted seed coat parents to nornal seed coloured parents. Green x beige gave a segregation ratio of 9:7 in F₂. When two parents with different seed coat colour were involved in a cross, the F₂ showed a typical digenic segregation ratio thus demonstrating two unlinked and sometimes epistatic loci.Segregation of a multiallelic series at two loci explains all segregation ratios observed for seed coat colour in broad bean.     

Interspecific hybridization between Vicia faba (L.) and Vicia narbonensis (L.): Early pod growth and embryo-sac development

Summary Fertilized embryo-sac development and pod growth was studied in one Vicia faba cultivar, one Vicia narbonensis population and their reciprocal crosses. The initial development of endosperm and embryo was at least four days faster in V. narbonensis than in V. faba. Pods and ovules developed also faster in V. narbonensis than in V. faba. The growth rate of the hybrid pods followed the growth rate of the mother species, but was slower than that of the pods from selfed flowers. In the cross V. narbonensis × V. faba the ovules stopped growing 9 days after pollination, while in the reciprocal cross they stopped growing 15 days after pollination. Hybrid embryo-sacs from V. faba × V. narbonensis were aborted before they reached the stage of 256 endosperm nuclei or 200 embryo cells. Selfed V. faba embryo-sacs reached this stage in less than 9 days after pollination. In the reciprocal cross the embryo-sacs were aborted before they reached the stage of 128 endosperm nuclei or 80 embryo cells. Selfed V. narbonensis embryo-sacs reached this stage at the 4th day after pollination. Given that at these stages the embryo has less than 200 cells it was concluded that an in-ovule embryo culture technique should be developed to obtain hybrid plants.     

Pattern analysis and genotypic x environment interactions in faba bean (Vicia faba L.) populations

Summary Twenty-nine populations of faba bean (Vicia faba L. subsp. major, equina and minor) of mediterranean origin were evaluated for the genetic variability of 12 biomorphological characters at four locations in Apulia and Basîli cata regions (Italy) in 1983–84.A pattern analysis appoach, based on classification and ordination procedures is presented for to characterize differences among population in mean performance and response across environments. Informations about G × E interaction were obtained.Research work supported by CNR, Italy. Special grant I.P.R.A. Sub-project 1. Paper N. 1099.     

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

Summary Five 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.     

Inheritance of seedling colour in faba bean (Vicia faba L.)

Summary The inheritance of purple seedling colour was studied, in relation to the genetic control of flower colour. It was found that purple seedling colour is likely to be controlled by a single gene and that the trait is dominant over green seedling colour. White flowering prohibited the expression of the purple seedling colour, and is therefore thought to be epistatic.This character can be used to estimate rate of outcrossing in breeding programmes, as well as contribute to our knowledge of the biosynthesis of plant pigments and secondary metabolites such as tannins.     

Comparison of some selection procedures and objectives in faba beans (Vicia faba L.). II. Selection for crude protein content

Summary Starting with two heterogeneous F₂ populations, each based on 20 cross combinations, different types of selection were applied for four consecutive selection cycles. Three of the selection procedures involved crude protein content (CP) and are presented in this paper. They were selection for high CP (HP), selection for low CP (LP) and independent culling levels selection for high CP and an index for seed yield per plant (ICL). For ICL-selection the attention is focussed on CP in this paper.For all three selection procedures, predicted and realized responses were calculated and expressed as percentage of a corresponding random population. The selection intensities (i) differed over selection procedures and generations. Differences in i between HP and LP within generations were mostly of minor interest. The response to HP-selection was slightly higher than to ICL-selection, but this may be due to the higher selection intensity exerted with the former method.HP-and LP-selection showed some remarkable differences, which were interpreted as a tendency towards partial dominance of high over low protein content. The total response to HP-selection gradually increased, whereas LP-selection yielded the total response largely after only one cycle of selection. The predicted response showed a tendency towards overestimation in the case of HP-selection and to underestimation in the case of LP-selection.Selection for high protein yield through CP seems to be feasible, although improvement of yield stability may eventually be more necessary. As no consistent correlation, either positive or negative, between SYP and CP could be detected, selection for either of these characters may be considerd independently of selection for the other one.     

Improvement of seed yield in Vicia faba L. By using experimental mutagenesis. II. Comparison of gamma-radiation and ethyl-methane-sulphonate (EMS) in production of morphological mutants

Summary Gamma-rays and EMS have been used in two dosages to test their effectiveness in inducing mutations in one major (cv. Aguadulce) and one minor (cv. Manfredini) Vicia faba cultivar. The plants of the M₁ and M₂ generations showed reduced emergence, survival, and fertility. EMS was more effective than gammarays in inducing mutations giving a mutation frequency in M₁ and a frequency of M₂ mutants from two to four times higher. The two mutagenic agents do not seem to differ in mutation spectrum. The minor cv. Manfredini was more sensitive to the lower dosage of gamma-rays than the major cv. Aguadulce. Both mutagens proved to be effective in enlarging the morphological variation of both cultivars.Research work supported by C.N.R. special grant I.P.R.A.-Sub-project 1. Paper N. 515.     

Comparison of some selection procedures and objectives in faba beans (Vicia faba L.). I. direct and index selection for seed yield

Summary Starting with two heterogeneous F₂ populations, each based on 20 cross combinations, different selection procedures were applied for four consecutive selection cycles. Three of the selection procedures involved seed yield per plant (SYP): (i) direct selection for SYP (DSY); (ii) indexselection for SYP (ISY) with plant length, the ratio of the vegetative top to plant length, end of grain filling and duration of the generative stage as auxiliary characters and finally; (iii) independent culling levels selection (ICL) for the index described above and crude protein content. For ICL-selection the attention is focussed on SYP in this paper.For all three selection procedures, predicted and realized responses were calculated and expressed as percentage of a corresponding non-selected population. The intensities of selection differed over selection methods and generations, mostly due to practical constraints.As far as predicted responses are concerned, ISY-selection seemed to be slightly superior to DSY-selection and DSY-selection to ICL-selection. This order may partly be due to differences in selection intensity. However, none of the predictions was very accurate, but the predictions of ICL-selection seemed to be the most accurate. This has been ascribed also to the relative mild selection intensity applied in ICL-selection. It is concluded that a decision in favour of a complicated selection procedure like index selection based on predicted responses only cannot be defended. As far as realized responses are concerned, DSY-selection seems to be slightly superior to the other two selection procedures, as it is the only procedure that resulted in a more or less stable positive response to selection.The auxiliary characters, especially plant length, showed a marked correlated response to all three selection procedures. In case of direct selection for SYP this seemed paradoxical with the inefficiency of index selection, but, it may reflect the differences in the genuine genotypic correlations and the estimated genotypic correlations.     

Extent, variation and breeding impact of natural cross-fertilization in German winter faba beans using hilum colour as marker

Faba bean is a partially allogamous grain legume, mostly sown as spring crop in Central Europe, and in few mild coastal areas of UK and France as a winter crop. A population with a genetically wide base, conceived and selected for superior winter hardiness showing promise as winter crop in Germany was evaluated. The reproductive behaviour of this population was evaluated for its degree of cross-fertilization at five German environments (1999–2001), and inbred lines bred from it, plus one F1 bulk and further checks, were assessed for variation in cross-fertilization at three German environments (2001). Seed hilum colour, a dominant-recessive, biallelic locus, was used as a morphological marker. Cross-fertilization (population mean value of 60%) was shown to be higher than in spring faba beans and was environmentally influenced. Genetic variation was demonstrated, heritability was high (h²= 0.75), and heterosis was negative. Inbred lines with a cross-fertilization of 70% can be easily bred. Breeding synthetic cultivars is recommended, their optimum number of components is expected to be higher than the optimum recommended for spring faba beans. This revised version was published online in July 2006 with corrections to the Cover Date.     

A short review of research on male sterility and prospects for F1 hybrid varieties in field beans (Vicia faba L.)

Summary It has not yet been possible to utilise cytoplasmically inherited male sterility (CMS) in Vicia faba, in the commerical production of F₁ hybrids. The main problem has been a rapid increase in the proportion of fertile revertants during multiplication. Investigations, mainly in France, have clarified environmental causes of phenotypic instability, CMS and maintainer lines with improved stability have been selected, and two new cytoplasms have been produced by mutation of the first two. CMS is known to be associated with cytoplasmic spherical particles, and recognisable types of double stranded RNA, and there may also be an association with mitochondrial DNA, and polypeptides of mitochondrial origin.The better understanding of CMS may eventually lead to more easily managed forms, either through genetic manipulation or biochemical assays that breeders can use for screening for stability.     

Genetics of resistance to 3 isolates of Ascochyta fabae on Faba bean (Vicia faba L.) in controlled conditions

Summary Genetics of resistance to Ascochyta fabae Speg. in Vicia faba L. was studied with a final objective to develop resistant faba bean varieties to Ascochyta blight. The study was conducted separately on 3 single spore isolates (AF10-2 and AF13-2 from Tunisia and AF4-3 from France) and belonging to different groups of virulence (GV1 and GV2). Important general combining ability (GCA) effects were found especially with isolates AF10-2 and AF4-3. Specific combining ability (SCA), although significant for the 3 isolates, was important only with AF13 -2, but less important than GCA. Additive gene effects were predominant to non-additive effects. Lines 29H and A8817 transmitted to their progenies resistance to the 3 isolates, whereas 14–12 and 19TB conferred resistance to their progenies only with isolates AF13-2 and AF4-3, respectively. In the material studied, resistance was generally controlled by dominant genes but also could be attributed to recessive genes although less frequent. Analysis of segregation in the F2 of 2 crosses between the resistant lines (A8817 and 29H) and the susceptible line (14–12) with isolate AF4-3 revealed dominant monogenic control at the level of leaves in the 2 resistant lines and, in addition, a recessive gene controlling resistance of stems. Non-allelic interactions were occasionally manifested and their origin appeared to be due to line 19TB. A recurrent selection scheme was proposed with the objective to develop improved open-pollination populations and synthetic varieties responding to the objective of the national Tunisian research programme on faba bean.     

Factors determining the performance of synthetics in Vicia faba L. 1. Heterogeneity,heterozygosity, and degree of cross-fertilization

Summary The relative performance of synthetic varieties in faba beans (Vicia faba L.) as compared with line varieties is the result of the joint effect of several factors. Factors investigated in the present study were (1) effects of heterogeneity and (2) heterozygosity on agronomic performance, (3) genetic variance for the degree of cross-fertilization among inbred lines and (4) genetic variance among homozygous and heterozygous genotypes for yield. The evaluation was based on multilocational trials in Germany with 36 inbred lines and derived entries with contrasting population structure (levels of heterozygosity and heterogeneity). When inbred lines and F₁-hybrids are included in the same mixture of genotypes, the resulting heterogeneity had a positive effect on yield. Relative mid-parent heterosis for yield was between 33% and 51%. The average degree of cross-fertilization was 53.5%, and its genetic standard deviation was 8.3%. The estimates for genetic standard deviation for yield among inbred lines were between 3.4 q/ha and 5.3 q/ha. The highest yielding synthetic variety is expected to outyield markedly the highest yielding line.     

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

Summary Twenty 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.     

Heterosis and hybrid performance in topless faba beans (Vicia faba L.)

Parental lines, F₁ and F₂ hybrids from a 7×7-diallel of topless faba beans and eight standard cultivars were grown in single-rows for two years at four sowing dates on a highly fertile loam soil near Göttingen. In grain yield, F₁ hybrids showed 21 to 54% advantage over the higher yielding parent. Compared with the midparental value an average heterosis of 50% was observed for grain yield. Corresponding heterosis mean values ranged from 3 to 37% for yield components and up to 11% for phenological traits. The grain yield of the highest yielding topless F₁ hybrid was equal to that of Alfred, the highest yielding indeterminate standard cultivar. High grain yield in the topless hybrids was closely correlated with high biomass yield, late ripening and tall plants generally having a high number of podded nodes and pods on the main stem. Due to their agronomic advantages, i.e., lower plant length, reduced lodging sensitivity and earlier ripening, efforts at breeding topless hybrids seemed to be worth-while in faba beans. However, their yielding ability must be improved further before they can compete with normal, semi-dwarf and stiff-strawed cultivars.     

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

Summary Six 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.