Importance of sepals in fruit and seed development in linseed (Linum usitatissimum L.)

Summary The green sepals in linseed (Linum usitatissimum L.) persist till almost the time of fruit ripening. Since the plant retains very few leaves and the fruits are better exposed to receive sunlight, the green sepals may be important in fruit and seed development. Influence of the removal of 0, 1, 3 and 5 sepals on the day of anthesis, 7, 15 and 25 days after anthesis on fruit and seed development was examined. Excision of all the fine sepals on the day of anthesis stopped fruit and seed development in the varieties M 10 and NP (RR) 45 but in Mukta the reduction was about 55%. Removal of three sepals also decreased fruit growth in Mukta and NP (RR) 45. The effect of removal of sepals was more pronounced on the number of seeds per fruit than on seed weight. Sepals fixed ¹⁴CO₂ and translocated ¹⁴C to seeds. However, the ¹⁴CO₂ fixation was maximum at early stages of fruit development, whereas a higher percentage of the fixed ¹⁴C was translocated at later stages of growth. It is suggested that the sepal size in linseed could be a useful selection criterion.     

The application of chemical mutagenesis and biotechnology to the modification of linseed (Linum usitatissimum L.)

Summary In the early 1980s the phenomenon of somaclonal variation induced by cell culture was exploited to produce genetic variation in linseed. The linseed variety Andro, derived from the widely grown Canadian variety McGregor, was selected in saline culture and was released for production in Canada. Andro possesses traits very different from its parent, such as increased seedling vigour and tolerance to heat stress. Additional stable somaclonal variation in characters such as yield, days to maturity, seed weight and oil content were subsequently induced in McGregor. However, despite extensive screening of the somaclonal variants, no significant variation in the fatty acid profile was found.Chemical mutagenesis using ethyl methanesulphonate was, however, succesful in modifying the fatty acid profile of McGregor. Initial screening of M₂ seed by the thiobarbituric acid colourimetric procedure was followed by gas chromatography to select half-seeds with atypical fatty acid profiles. Two independent, partially dominant genes were identified that were responsible for reducing the linolenic acid (18 : 3) from 50% to 2% while increasing linoleic acid (18 : 2) to 70%. A single, partially dominant gene, inherited independently of the linolenic acid genes, increased palmitic acid (16 : 0) from 7% to 30% and palmitoleic acid (16 : 1) from trace amounts to 4%. Agrobacterium-mediated transformation of linseed has also been successful. Herbicide tolerance genes for glyphosate, sulfonylurea and phosphinothricin have been incorporated into Canadian varieties. Commercially useful levels of tolerance to sulfonylurea herbicides have been achieved with no adverse agronomic affect. It is expected that a transgenic variety containing this resistance will be registered for commercial production in Canada in 1994.Standard breeding techniques, the application of antisense technology and the overexpression of fatty acid synthesis genes are being used to further modify the fatty acid profile of linseed, as well as for the transfer of abiotic stress-related genes identified in bromegrass.     

Inheritance of resistance to Oidium liniSkoric in linseed (Linum usitatissimum L.)

Summary Resistance to powdery mildew (Oidium lini) in each of the four linseed cultivars, viz., LC 216, LC 255, LC 256 and LC 269 was found to be conditioned by one dominant gene. Crosses between the resistant parents indicated that the same gene was present in all the cultivars and is designated as Ol.     

Parametric and nonparametric measures of phenotypic stability in linseed (Linum usitatissimum L.)

A combined analysis with three parametricand two nonparametric measures to assess G × E interactions and stability analyses toidentify stable genotypes of linseed across18 environments in Ethiopia wereundertaken. The combined analysis ofvariance for environments (E), genotypes(G) and G × E interaction was highlysignificant (p<0.01), suggestingdifferential responses of the genotypes andthe need for stability analysis. Theparametric stability measures ofcoefficient of variability and thestability variance showed that R12-N10D wasthe most stable genotype, whereascultivars' superiority measure indicatedChilalo to be the most stable cultivar.Like most of the parametric methods, thenon-parametric measures revealed thatR12-N10D had the smallest changes in ranksand thus was the most stable genotype incontrast to R12-D24C, which was unstableand the lowest yielder. A comparison of thefive stability measures showed that thecoefficient of variability, stabilityvariance and variance of ranks were similarin assessing the relative stability of thegenotypes, whereas cultivars' superioritymeasure deviated from the others. Thestability variance and variance of rankswere significantly rank correlated, andwere the best in determining thecomparative stability of linseed genotypes.The coefficient of variability was alsorelatively better than the cultivar'ssuperiority measure. Further studies ofrepeatability tests are, however, needed todetermine the best methods. The stabilitystatistics generally identified R12-N10D,followed by Chilalo, as the most stablevarieties, whereas R12-D24C and R11-M20Gwere the least stable varieties.     

Genetic analysis of the response of linseed (Linum usitatissimum L.) somatic tissue to in vitro cultivation

The response of linseed somatic tissue to in vitro cultivation can be improved if the gene action involved is known. Nine homozygous lines, seven F₁ and fifty F₂ plants were cultivated in MS basal medium with 0.1 mg/l BAP. Callogenesis and regeneration analyses were done using a random model in order to separate environmental and genotypic effects at 10, 20 and 30 days after culture initiation. Genetic variability for callogenesis and regeneration was observed, that could be used in a breeding program. The appropriate period for the evaluation of callogenesis was at 20 days after culture initiation. For regeneration, this moment would depend on the selection criterion adopted. To select genotypes on the basis of earliness in shooting at 10 days would be preferable, while for ability of producing shoots, 30days would be more suitable. For both characters the analyses of genetic action indicated that, non-additive effects were involved in the culture response, however the expression of callogenesis and regeneration ability had different genetic basis. This revised version was published online in August 2006 with corrections to the Cover Date.     

Genotypic and exogenous factors affecting shoot regeneration from anther callus of linseed (Linum usitatissimum L.)

Summary The objective of this study was to investigate factors affecting the regeneration capacity of linseed anther culture. Four different environmental conditions in a phytotron were tested with regard to their effects on anther donor plants of cv. Hella. Anther response and shoot regeneration from anther callus was maximal when donor plants were grown in a 16 hrs-day at 14°C day/8°C night temperature. Anthers of four linseed genotypes were cultured on different media. Maximum shoot regeneration was achieved when the induced calli were transferred onto a modified N6 medium containing zeatin (1 mg l^-1). Most of the calli regenerated shoots in the second subculture on regeneration media. Shoots were rooted on modified B5 or MS media containing NAA (0.1 mg l^-1). Cytological examinations of incubated anthers and root tips of regenerated plants indicated that the anther calli were derived from microspores.Abbreviations B5 Gamborg's (1975) medium - BAP 6-benzylaminopurine - 2,4D dichlorophenoxyacetic acid - N6 Chu's (1978) medium - NAA -naphthaleneacetic acid - MS Murashige & Skoog's (1962) medium - ZEA zeatin     

In vitro breeding of high-linolenic, doubled-haploid lines of linseed (Linum usitatissimum L.) via androgenesis

In the course of a breeding programme for high-linolenic-acid linseed (oilflax, Linum usitatissimum L.) doubled-haploid lines (DH-lines) of three F₁ hybrids were generated using an anther-culture technique. A total of 82 DH-lines were generated and multiplied in 1993, of which 39 were suitable for testing in a repeated field trial in 1994. Yield, fat content and fatty-acid composition were determined. The yield of the DH-lines was not significantly different from that of respective mid-parent values. Fatty-acid composition and fat content showed remarkable variation, and DH-lines exceeded cross parents in some cases for both fat content and linolenic-acid proportion. Superior DH-lines surpassed mid-parent linolenic-acid-content values by 4.5% and fat content by 1.9%. The results indicate that anther culture is a useful tool in linseed breeding.     

The effectiveness of early generation (F3) yield testing and the single seed descent procedures in two cowpea (Vigna unguiculata (L.) Walp.) crosses

Summary Two breeding procedures were compared in two cowpea crosses. Both procedures were started from the same selected F₂ plants in each cross. For the early generation yield testing, the F₃ lines were yield tested and a pedigree and bulk methods followed in F₄ and F₅. Each F₅ line was bulked to provide seed for a yield test in F₆. In the Single Seed Descent (SSD) procedure, a single seed was taken from each F₂ plant to produce the F₃ generation. The procedure was repeated for the F₄ and F₅. The F₆ SSD lines and the F₆ yield testing lines were compared in yield tests.The results showed that differences in yielding ability of F₃ lines persisted over generations indicating that selection was effective. This was confirmed by the high significant correlations between F₃ yields and those of later generations which ranged from r=0.51^* to 0.85^**.The grain yields of lines derived by the single seed descent procedure were as good as those derived from early generation yield testing.Significant linear correlation between visual rating of F₃ and F₆ yields with actual yields revealed that it is possible to identify promising lines of cowpea visually.     

Isolation of induced mutants in linseed (Linum usitatissimum) having reduced linolenic acid content

Summary Seeds of Linum usitatissimum cv. Glenelg were treated with either gamma-rays or EMS in an attempt to induce mutations with a lower level of linolenic acid in linseed oil. Two mutant lines were identified in which linolenic acid constituted approximately 29% of the total fatty acid content compared with 43% in seed oil from untreated Glenelg plants. The reduced level of linolenic acid in the mutants is accompanied by an increase in the level of linoleic acid to 30% compared with 18% in Glenelg, but there was no change in the proportions of other fatty acids. These proportions of linolenic acid and linolenic acid are respectively the highest and lowest yet reported in stable genotypes of L. usitatissimum. The strong inverse relationship between these two fatty acids in these genotypes suggests that linolenic acid is synthesised by desaturation of linolenic acid and indicates that it may be possible to breed an edible linseed oil having both low levels of linolenic acid and high levels of linolenic acid.     

Comparison of Mahalanobis's method and metroglyph technique in the study of genetic divergence in Linum usitatissimum L. germ plasm collection

Summary A group of fifty-seven varieties of Linum usitatissimum L. collected from different geographics sources was studied to understand the nature of genetic divergence using Mahalanobis's statistical distance (D²). Varieties having genetic similarity were grouped into fifteen clusters. Most of the clusters at individual level included varieties of different geographical regions. However, Argentine and Indian types formed separate and distinct constellations. The Indian group was situated at a maximum distance from Argentine and US groups, and was nearest to the Australian group. For improvement of Indian linseed, hybridization of indigenous types with Argentine and US types might result in superior recombinants.84.64% of the total divergence was attributable to plant height and seed size, which are based characteristics used in classifying the species into oil and flax types.Since it is difficult to compute D² values among large numbers of germplasm collections, another relatively simple and easy method, the metroglyph technique, was tried upon the same set of fifty-seven varieties. Comparisons between the results of the two analyses revealed the striking similarity as regards to group arrangement. It has been suggested that the metroglyph technique would be suitable for preliminary grouping prior to undertaking D² analysis.     

A comparison between single seed descent and early cross selection in wheat breeding

Summary Two selection procedures in wheat breeding were compared on the basis of their ability to supply high yielding inbred lines. The first procedure consists of an early selection between crosses in the F₃ generation, based on cross performance. In the second procedure selection is postponed until the F₆, which is derived by single seed descent. The two procedures are evaluated in a two year test, using pseudo-lines of spring wheat. These pseudo-lines consist of mixtures of varieties and enable an estimation of the true genetic parameters. In this way the accuracy of the predictions can be examined.The first year of this comparison comprised the actual selection process and in the second year an F₆ and F₇ generation were mimicked, based on the selected lines of the F₃ and F₆ respectively, and evaluated in a large yield test. This paper gives the final results after the second year. From the first year it was found that the F₃ cross predictions were very inaccurate, whereas selection in the SSD-F₆ appeared to perform well. This resulted in a higher yielding set of lines evolving from the SSD-F₆. Despite a pronounced genotype-year interaction this difference in yield level was also found between the F₇ and the F₆ lines, derived from the selected crosses in the F₃. We conclude that the early selection procedure is not advantageous compared to the fast SSD procedure.     

A comparison between single seed descent and early cross selection in wheat breeding

Summary Two selection procedures in wheat breeding were compared on the basis of their ability to supply high yielding inbred lines. The first procedure consists of an early selection between crosses in the F₃ generation, based on predictions of the cross mean and the between line variance. In the second procedure selection is postponed until the F₆, which is derived by single seed descent. The two procedures are evaluated in a two year test, using pseudo-lines of spring wheat. These pseudo-lines consist of mixtures of varieties and enable an estimation of the exact genetic parameters. In this way the accuracy of the predictions can be examined.In case of early selection, it appears that the predictions of the cross mean and especially the between line variance are very inaccurate. This is caused by the effects of plot size, intergenotypic competition and, to a lesser extent, dominance and/or epistasis. It results in an erroneous ranking of the crosses and the discarding of the potentially best cross. The F₆-SSD line estimates are much more accurate and thus the better lines are indeed selected. A first comparison between the two selection procedures therefore indicates a preference to the SSD method.     

Comparison of selection procedures in breeding for seed yield in segregating sesame populations

Summary Four hundred sesame (Sesamum indicum L.) lines selected by five methods from five crosses were tested for yield and other agronomic characters in F₆ and F₇. More high yielding lines were isolated by the bulk method and in the cross involving two local cultivars when two seasons means and performance in each individual season were considered. The cross involving two exotic cultivars did not produce a single line superior to local recommended variety. The 80 highest yielding lines recorded a 10.8% increase in yield compared to the mean of 400 lines. Thirty five lines were among the top 20% both seasons with a 13.2% increase in yield. Highly significant seasonal and population effects were recorded. There were no significant differences among the methods of selection although the yield differences among lines were highly significant. Interactions of seasons × populations, seasons × methods, populations × methods and seasons × populations × methods were highly significant. The results indicate that simple and less expensive bulk method may be used with equal success as the pedigree, single seed descent or early generation testing methods when selecting for yield in segregating sesame populations. The importance of inclusion of a high yielding, locally adapted cultivar in the crossing programmes for yield breeding of sesame has also been revealed.Abbreviations BM Bulk method - EGT Early generation testing - G × E Genotype × environment - MSS Modified single seed descent - PM Pedigree method - SSD Single seed descent     

Seed colour, seed weight and seed oil content in Linum usitatissimum accessions held by Plant Gene Resources of Canada

The purpose of this study was to investigate variation of and relationships among seed colour, seed weight and seed oil content in cultivated flax (Linum usitatissimum L. ssp. usitatissimum). Seed from 2934 flax genebank accessions recently grown at Saskatoon, SK, Canada, originating from 72 countries was used to describe the variation of the seed characters. The dominant seed colour of the accessions was medium brown (2730 accessions, 93.0%), followed by yellow (126 accessions, 4.3%). Based on single observations for all accessions, the overall mean and standard deviation was 5.95 ± 1.22 mg/seed for seed weight and 38.3 ± 1.74% for oil concentration. Within three infraspecific groups of flax, seed weight, oil concentration and oil amount per seed increased in the following order: fibre flax (convar. elongatum), intermediate flax (convar. usitatissimum), large‐seeded flax (convar. mediterraneum). The world collection exceeded the range of variation of seed weight and oil concentration found in 52 North American cultivars. There was a weak, positive association of higher oil concentration with higher seed weight (r² = 0.32; P < 0.001). Yellow‐seeded flax had a higher seed weight (6.31 vs. 5.92 mg/seed) and oil concentration (39.4% vs. 38.3%) than brown‐seeded flax. There was a tendency for yellow seed colour to be associated with higher oil concentration in all seed weight classes. The results suggested that indirect selection for increased seed oil concentration in flax is possible by selection for higher seed weight and yellow seed colour.     

Comparative efficiency of honeycomb and conventional pedigree methods of selection for yield and fiber quality in cotton (Gossypium spp.)

The effectiveness of honeycomb pedigree selection (HPS) as compared to conventional pedigree selection (CPS) was studied in one intraspecific (G. hirsutum L. × G. hirsutum L.) cross population (population I) and one interspecific (G. hirsutum L. × G. barbadense L.) cross population (population II). Combined selection for yield and lint quality traits was applied for four cycles at two locations for population I and atone location for population II. Finally, the best F₆ lines derived by each method, together with the unselected population derived by single seed descent (SSD) and three check cultivars, were tested in comparative experiments, separately for each cross, at the same locations. In both populations the analysis of variance indicated significant differences among the groups of the material tested for seed cotton yield, mean boll weight, micronaire reading, staple length, and uniformity ratio. No significant differences were found with respect to plant height, lint percentage, and fiber strength in population I and with respect to lint percentage and fiber strength in population II. In population I, on the basis of mean seed cottonyield and number of superior lines derived by each method as compared to the check varieties and the unselected SSD population, HPS-lines were superior to CPS-lines for seedcotton yield, fiber length and boll weight. HPS-lines, however, did not differ significantly in seedcotton yield from the best check cultivar Eva. Finally, the material derived by CPS was earlier in maturity than the material derived by HPS and SSD. Also in population II, on the basis of mean seedcotton yield and number of superior lines derived by each method as compared to the unselected SSD population, HPS-lines were superior to CPS-lines. No significant differences, however, were identified between the material of the two methods for lint quality traits. It was concluded that in both populations HPS was more effective than CPS in identifying lines with high yielding ability and good lint quality. This superiority of HPS is attributed, at least partially, to its effectiveness in early generation selection. This revised version was published online in August 2006 with corrections to the Cover Date.     

Breeding for Modified Fatty Acid Composition by Induced Mutations in Linseed (Linum usitatissimum L.)

Seeds of linseed (Linum usitatissimum L.) cultivars ‘Raulinus’ and ‘Bionda’ were treated mutagenically with ethyl methanesulfonate (EMS) in order to broaden the variation of fatty acid composition in the seed oil and to select mutants with reduced linolenic acid (C18: 3) content. The M₂ generation was evaluated for fatty acid composition of the oil. Genetic variation for unsaturated fatty acids was demonstrated to be extended in the M₂ generation as compared to the controls. Finally in the M₅ generation of cv. ‘Raulinus’, lines with reduced C18:3 (< 40% vs. 55%) and correspondingly increased linoleic or oleic acid contents, respectively, could be selected. These mutants proved to be genetically stable as demonstrated by parent-offspring (M₄/M₅) regression.     

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.     

Intra-specific Variation for Salt Tolerance in Linseed (Linum usitatissimum L.)

Thirty-six accessions of linseed ( Linum usitatissimum L.) were screened for salt tolerance at the seedling stage after 2 weeks growth in solution culture salinized with 150mol m⁻³ NaCL Considerable variation in salt tolerance was observed in this set of germplasm. Two salt-tolerant accessions, T-5(69-S9)B and LS-2 and two salt-sensitive accessions P-70 and Aver-Rer-Seic, selected at the seedling stage, were grown to maturity in sand culture salinized with 0 (control), 70, 140, and 210 mol m⁻³ NaCl. Both the salt-tolerant accessions exceeded the two salt-sensitive accessions in biomass production, seed yield, and yield components, but the accessions did not differ significantly in seed oil content in the salt treatments. The tolerant accessions accumulated greater amounts of Na⁺ in the shoots and less in the roots compared with the salt-sensitive accessions. The shoot K⁺, K: Na ratios, and K⁺ versus Na⁺ selectivity were lower in the salt-tolerant accessions compared with the salt-sensitive accessions; the reverse was true for their roots. Contributions of Na⁺ and Ca²⁺ to osmotic adjustment were much higher in the two salt-tolerant accessions than in the salt-sensitive ones.
It has been established that there is a great deal of variation for salt tolerance in linseed. The degree of salt tolerance of this crop does not vary during ontogeny. The physiological basis of salt tolerance of this species appears to be associated with the inclusion of Na⁺ in the shoots.     

Use of immature seed germination and single seed descent for rapid genetic gains in pigeonpea

Long duration required for generation advancement in pigeonpea [Cajanus cajan (L.) Millsp] is one of the major bottlenecks in realizing rapid genetic gains. Therefore, a technology for rapid generation turnover is warranted to facilitate the development of new cultivars and recombinant inbred lines. Breeding of early‐maturing cultivars has now opened up the possibility of rapid generation advance (RGA) in this crop. This paper reports the development of an RGA technology that integrates the germination of immature seeds with single seed descent method of breeding. The results showed that immature 35‐day‐old seeds can be used successfully to turn over a generation of pigeonpea with 100% seed germination. These way 3/4 successive generations can be grown within a year. The methodology presented in this study will accelerate the breeding process for breeding cultivars and develop rapidly the materials required for genomics research in pigeonpea.     

Use of the Single Seed Descent Method in Breeding Safflower (Carthamus tinctorius L.)

The single seed descent (SSD) method of selection has been evaluated in safflower (Carthamus tinctorius L.). The initial population of this study was a BC₂F₁ from a cross between a well adapted and a high oil cultivar. Transgressive segregation for yield and oil content producing lines with considerably higher values than the better parent was observed in BC₂F₄ and BC₂F₅ generations. These results and the great saving of time and effort makes the SSD method a very desirable tool for safflower breeders.