Flax Accessions Research Articles

Geographic Patterns of RAPD Variation in Cultivated Flax

Geographic studies of plant molecular diversity can provide insights into plant domestication and enhance plant germplasm management and utilization, but such studies are lacking in cultivated flax (Linum usitatissimum L.). The objective of this study was to assess the geographic patterns of flax variability in a world collection of cultivated flax by random amplified polymorphic DNA (RAPD) markers. Sixteen RAPD primers were applied to screen 2727 flax accessions representing 63 countries and one group of unknown origin, and 149 RAPD bands were scored for each accession. Analyses of the RAPD data revealed a wide range of occurrence frequencies of polymorphic bands from 0.0004 to 0.9978 with an average of 0.537. The majority (84.2%) of the RAPD variation resided within accessions of each country and only 15.8% of the variation was present among accessions of different countries. Grouping the accessions into 12 major regions explained 8.2% of the RAPD variation. Accessions from the East Asia and European regions were most diverse, but accessions from the regions of Indian Subcontinent and Africa were most distinct. Accessions from the West Asia region were genetically more related to those from the Africa region and less to those from the Indian Subcontinent region. These findings are significant for understanding flax domestication and also are useful in classifying intraspecific diversity of cultivated flax, establishing a core subset of the flax collection, and exploring new sources of genes for flax improvement.

ISSR-based clustering of cultivated flax germplasm is statistically correlated to thousand seed mass.

Inter-simple sequence repeat (ISSR)-polymerase chain reaction (PCR) polymorphism was generated to provide useful markers for assessment of genetic diversity within flax germplasm collections. We used nine previously selected anchored ISSR primers for fingerprinting of 53 flax cultivars or genotypes and obtained 62 scorable bands, from which 45 bands (72.6%) were polymorphic. An efficient separation of 53 flax accessions into four groups and eight subgroups was achieved using unweighted pair group method with arithmetic means (UPGMA) clustering procedure based on genetic similarity expressed by the Jaccard similarity coefficient (JSC). Clustering procedure within both groups and subgroups successfully produced smaller homogenous clusters, whereas clustering between the main four groups of flax accessions displayed only a continuous decrease of similarity with a weak clustering effect. Statistical significance of grouping and subgrouping within a cluster dendrogram was estimated by calculation of the error flag and cophenetic correlation parameter for each branch. Principal coordinates (PCO) analysis mostly confirmed the separation by UPGMA clustering. We observed a statistically significant correlation between the number of total vs polymorphic bands in ISSR patterns. A one-way analysis of variance (ANOVA) test confirmed statistically significant differences in the average thousand seed mass (TSM) between eight subclusters of flax accessions from an ISSR-PCR-based UPGMA dendrogram, which indicate statistical correlation between flax ISSR polymorphism (the structure of ISSR-based clustering) TSM.

Improved method for fibre content and quality analysis and their application to flax genetic diversity investigations

Evaluation for fibre content and quality in a breeding selection program is time consuming and costly. Therefore, this study aims to develop a method for fast and reproducible fibre content analysis on small flax straw samples. A protocol has been developed and verified with fibre screening methods used commonly in flax breeding. A large number of different accessions of mostly fibre flax and some linseed, present in the core collection of CGN, were grown under comparable conditions and were analysed for their bast fibre contents by warm water retting and green decortication methods. From the core collection, a selection was made of a number of high, medium and low fibre yielding flax accessions with extremes in stem length, branching or fibre bundle appearance. These were analysed with the novel fibre extraction procedure utilising short autoclave treatment in 0.05 M EDTA as calcium complexing agent. Since 1999, cultivars selected for the core were grown around Wageningen on sandy soils. The fibre content was determined by different methods and a correlation was found between the values obtained by warm water retting and the autoclave procedure. However, the data obtained by green decortication show up to 20% and on average 15% higher fibre content values. This higher value roughly corresponds to the weight of the cuticula and remaining xylem tissue that is more efficiently removed by retting and autoclave treatments. The reproducibility of this fibre content determination method for small straw sample analysis (25 g) is a promising tool for accelerated breeding protocols.

RAPD analysis of genetic variability of regenerated seeds in the Canadian flax cultivar CDC Normandy

Genetic variability of the original breeder seeds and twice regenerated seeds of the Canadian flax cultivar CDC Normandy was analyzed using RAPD markers. It was found that two (out of 98) RAPD loci derived from 16 informative UBC RAPD primers were polymorphic, confirming a narrow genetic variation for CDC Normandy. No off-types from the other flax accessions being simultaneously regenerated were found in the 48-seed sample of the 1998 regeneration, but one off-type in the 1999 regeneration was revealed at seven fixed recessive RAPD loci. The G-statistics calculated for the change in genotypic frequencies at two polymorphic RAPD loci over the two regeneration cycles were not statistically significant at the 0.05 level, suggesting no significant genetic change occurred in the regenerated accessions. These findings have practical implications for flax germplasm management, breeding program and commercial seed production.

Genetic diversity within a range of cultivars and landraces of flax (Linum usitatissimum L.) as revealed by RAPDs

Analysis of the extent and distribution of genetic diversity incrop plants is essential for optimizing sampling and breedingstrategies. We used random amplified polymorphic DNA (RAPD)markers to assess genetic diversity and relationships in 22 Canadiancultivars, 29 selected world cultivars and 10 landraces of flax(Linum usitatissimum L.). RAPDvariation was generally low and more variation was detected among,than within, the investigated flax accessions. Based on 53 variableRAPD loci observed for the 61 accessions, the landraces had a lowerproportion of fixed recessive RAPD loci (0.427) (i.e.,more genetic variation) than all of the flax cultivars examined(0.492). The linseed cultivars had a lower proportion ofrecessive loci (0.469) than the fiber flax cultivars(0.529). Canadian linseed cultivars had a lower proportionof recessive loci (0.465) than the selected world flaxcultivars (0.512). A trend was also observed that the rateof loss in genetic variation in Canadian flax breeding programs overthe last fifty years was approximately two variable loci per 100 lociper 10 years. Clustering analyses based on similarity estimatesshowed that the fiber cultivars were more related (or similar toeach other) and were classified as a homogeneous group. All ofthe linseed cultivars were clustered in diverse groups with the ninelandrace accessions. Implications of these findings for flax breedingand germplasm management are discussed.

Comparison of genetic diversity of flax (Linum usitatissimum L.) between Canadian cultivars and a world collection

AbstractThis study reports results of phenotypic measurements of genetic diversity in the world collection of flax maintained by Plant Gene Resources of Canada (PGRC) and compares the range of diversity in the world collection with the diversity observed in 19 Canadian registered flax cultivars. Morphological and seed‐oil characters were used to describe the phenotypic diversity in 2331 flax accessions. The plants were grown by PGRC at Saskatoon, Saskatchewan, Canada, in 1998 and 1999. The comparison between the Canadian cultivars and the world collection was based on single characters, as well as on character complexes by application of an existing intraspecific classification for the species. Considering single quantitative or qualitative character expressions, the Canadian cultivars represented a wide range in diversity for the species. The variation of characters Canadian plant breeders have selected for (e.g. plant height, seed weight, seed colour, petal colour, oil content) was reduced further than those characters not focused on by plant breeders (e.g. dotting of the sepals, style colour, ciliation of capsule septa, oil quality characters). A comparison of diversity based on the intraspecific classification proposed for flax by Kulpa and Danert, who described 28 botanical varieties, showed that all Canadian cultivars belong to two botanical varieties. This study demonstrates the usefulness of agrobotanical characterization of genebank collections for plant breeding and illustrates the application of the traditional method of intraspecific classification for comparison of gene pools.

Marker-assisted rationalisation of genetic resource collections: a case study in flax using AFLPs

Removing redundant germplasm from collections is one of the options for genebanks to increase the efficiency of their genetic resource management. Molecular characterisation of germplasm is thereby becoming more and more important to verify suspected duplication. AFLPs were used to characterise 29 flax accessions of material derived from research activities (hereafter termed ’’breeder’s line”). Based on similar accession names, the breeder’s lines could be classified into three series (’M 25’, ’Ru’ and ’Rm’) that were expected to contain redundancies. In addition, 12 reference cultivars were analysed. A total number of 144 polymorphic bands (59.8%) were scored among the 164 individuals investigated. In general, relatively high levels of intra-accession variation were found, even for the cultivars examined. This finding was not in line with the low outcrossing rates reported for flax. A cluster analysis grouped the ’Ru’ and ’Rm’ series together, indicating their close genetic relationship. An analysis of molecular variance (AMOVA) showed a significant group effect (fibre/oil flax) only for ’M 25’, explaining 34% of the variation observed within this series. For the cultivars 40.5% of the variation was distributed among accessions within groups and all pairwise comparisons were significantly different, except for one case. Both for the series of breeder’s lines and the cultivars the major part of the variation was distributed among individuals within accessions. This component constituted 80.7% and 83.6% of the total variation for the ’Ru’ and ’Rm’ series, respectively. Pairwise comparisons of accessions were performed by AMOVA in order to identify redundant germplasm. Stepwise bulking of accessions until all remaining accessions were significantly different showed that the 29 accessions of breeder’s lines could be reduced to 14. Only a small negative effect of this bulking approach on the among-population component of variance was observed, showing a reduction of 2.6%. Results are discussed in relation to improving the efficiency of collection management.

Histology of quantitative resistance in flax to the flax rust fungus (Melampsora lini)

Macroscopical and histological research is useful to characterize quantitative resistance. Analysis of histological components of the resistance to the flax rust fungus (Melampsora lini) was carried out on seedlings of seven flax (Linum usitatissimum) accessions: five fibre flax accessions with various levels of quantitative resistance and two near-isogenic lines of linseed with gene K or NI. Flax seedlings were inoculated with uredospores. Collected leaves of the flax accessions were stained with Chlorazol Black E. It was found that in the pathosystem flax - M. lini, a lower number of pustules (lower infection frequency) on quantitatively resistant accessions did not result from mechanisms acting before stomatal penetration by the fungus. Reduced infection frequency was associated with increased rates of early abortion of the rust fungus but rates of this abortion were not large enough to explain the low infection frequency on the quantitatively resistant accessions Afganistan and Solido. In both of the accessions the number of haustoria formed 2 days after inoculation and the size of established colonies after 5 days were reduced. Hyphae of the fungus in the accession Solido stained intensely, and appeared stunted and crinkled. Most of the established colonies in the quantitatively resistant accessions were associated with plant cell necrosis, and at the macroscopic level, pustules were interspersed with some necrotic flecks. This indicates that quantitative resistance of flax to flax rust was caused by incomplete hypersensitivity. Various intensities of the hypersensitive reaction were involved with the resistance of some wild Linum species against M. lini, although in some other accessions it was based on prehaustorial arrestment of the infection units.

RESISTANCE TO THE FLEA BEETLE PHYLLOTRETA CRUCIFERAE (COLEOPTERA: CHRYSOMELIDAE) IN FALSE FLAX, CAMELINA SATIVA (BRASSICACEAE)

AbstractFeeding damage by the crucifer flea beetle, Phyllotreta cruciferae (Goeze), was assessed on 51 accessions of false flax, Camelina sativa L., and compared with damage to seven other crucifer species. Three experiments were conducted on seedlings in laboratory arenas infested with field-collected beetles. Feeding damage was estimated visually at daily intervals for up to 7 days. Natural infestation of false flax and other crucifers was observed in the field. Flea beetles fed little (0–10% consumption) on cotyledons or true leaves of any of the false flax accessions, and fed more (59–100% consumption) on the other crucifers. Flea beetles were observed sitting on false flax in the field, sometimes in high numbers, but they did not feed. In the laboratory, beetles eventually fed on cotyledons and leaves and once feeding was initiated, it tended to continue. Resistance in false flax may result from the absence of cues that initiate feeding, rather than a feeding deterrent. The high level of resistance in false flax would likely be economically beneficial if this species is developed as an oilseed crop. False flax could also be useful experimentally for identifying the cues that attract flea beetles to plants and stimulate their feeding.