Simultaneous gene silencing of both FAD2 genes in high linoleic acid flax leads to high level of oleic acid, which is stable across multiple generations. High oleic oil is one of the preferred traits in oil crop engineering due to its stability and multiple applications as an industrial feedstock. Flax possesses two isoforms of FAD2 enzymes that desaturate monounsaturated oleic acid to polyunsaturated linoleic acid. These two enzymes are encoded by two FAD2 genes. By simultaneous gene silencing both FAD2 genes in high linoleic acid flax, Linola, high level of oleic acid up to 80% was achieved in 69 silencing lines. The high oleic trait was stable across multiple generations with oleic acid reaching up to 77% in homozygote T3 progeny. The RNAi-mediated gene-silencing approach generated high oleic linseed oil, as well as a high oleic platform that can be exploited for further fatty acid engineering.

The effects of induction medium compositions on flax anther culture were investigated in order to improve the efficiency of callus induction and plant regeneration. Anthers were inoculated onto the modified MS medium supplemented with five different combinations of plant growth regulators. The medium containing the combination of 2mg/l 2,4-dichlorophenoxy-acetic acid (2,4-D) and 1 mg/1 6-benzylaminopurine (BAP) produced a significantly higher number of calli forming shoots/100 responded anthers and a significant increase in overall efficiency of regeneration than the same basal medium containing 1 mg/1 a-naphthalene-acetic acid (NAA) and 2 mg/1 BAP (CK). Among the five levels of thiamin hydrochloride tested, the modified MS medium containing 10 mg/1 thiamin hydrochloride significantly increased the number of calli forming shoots/100 responded anthers and the overall efficiency of regeneration compared with the same basal medium containing 0.1 mg/1 thiamin hydrochloride. Maltose concentration had a significant effect on the percentage of anthers producing calU, the number of calli forming shoots/100 responded anthers and the overall efficiency of regeneration. The medium containing 6% or 9% maltose produced the highest overall efficiency of regeneration among the five levels of maltose evaluated. Sucrose concentration significantly affected the number of calli forming shoots/100 responded anthers and the overall efficiency of regeneration, and dramatically affected the frequency of microspore-derived plants and the frequency of spontaneous chromosome doubhng in microspore-derived plants. The efficiency of doubled haploid line production obtained in this study appears adequate for applied breeding programmes.

Identification of responsive genotypes and development of efficient protocols are the prerequisite to an effective doubled haploid production system in applied breeding programs. Evaluation of 16 low linolenic flax (Linola) genotypes/populations with diverse genetic backgrounds from a Linola breeding program using A 22 C medium containing 9% sucrose (A 22 C-9) led to the identification of a number of responsive genotypes. For 96-3-F 1 hybrid, callus induction was greater in modified NLN medium containing 12% sucrose (NLN-12) than in A 22 C-9. But there was no difference in shoot regeneration between NLN-12 and A 22 C-9. For 96-45-F 1 hybrid, there was no difference in callus production between the two media. However, A 22 C-9 had a greater shoot regeneration than NLN-12. In comparison to sucrose, lactose was found to increase callus induction from anthers for all three genotypes tested. However, the effect of lactose on shoot regeneration appeared to be genotype-dependent.Keywords Anther culture · Carbohydrate · Doubled haploid · Linum usitatissimum L.Abbreviations A 22 C-6: A 22 C medium containing 6% sucrose · A 22 C-9: A 22 C medium containing 9% sucrose · BAP: 6-Benzyl-amino-purine · 2,4-D: 2,-4-Dichlorophenoxyacetic acid · NLN-12: Modified NLN medium containing 12% sucrose · PPFD: Photosynthetic photon flux density Communicated by S. Gleddie

No abstract

P. 1999. Quality changes occurring in stored solin, high linolenic acid and standard flaxseed (Linum usitatissimum L.). Can. J. Plant Sci. 79: [35][36][37][38][39][40][41][42]. Changes occurring in stored solin/flax cultivars over 6 mo at temperatures ranging from 10 to 35°C and moisture contents of 8.0, 9.5, 11.0 and 12.5% were observed. The cultivars were NorLin, McGregor, FP1001 (high linolenic acid), Linola™ 947 (solin) and Linola™ 989 (solin). Oil composition in all cultivars changed only slightly over 6 mo with a significant increase in palmitic acid. Doubling of free fatty acid levels was considered an indicator of quality deterioration. The deterioration occurred in 6 mo at 8% MC and 20°C in FP1001 and in NorLin, McGregor, and Linola™ 947 at 25°C; Linola™ 989 could be stored at 30°C. Linola™ 989 could be safely stored at moderately higher temperatures at a given moisture level than Linola™ 947. Visible mold with corresponding germination loss was usually associated with Aspergillus glaucus group infection. Stored-product insects that could survive and develop on the solin/flax were the red flour beetle, Tribolium castaneum (Herbst), the confused flour beetle, T. confusum J. du Val, the sawtoothed grain beetle, Oryzaephilus surinamensis (L.) and the merchant grain beetle, O. mercator (Fauvel).In general, Linola™ 947 and FP1001 were slightly more difficult to store than the other cultivars but there was no consistent difference between solin and flaxseed. Flax (Linum usitatissimum L.) cultivars grown in Canada have traditionally had their oil used for the manufacture of paints, varnishes, putty, plastics and linoleum (Daun 1982; White and Jayas 1991). Since the mid-sixties, however, demand for linseed oil as an industrial oil has remained static due to increased use of synthetic drying agents. This trend has led to the search for new uses of flax such as edible oils (Haumann 1990; Flax Council of Canada 1996). Several cultivars with low linolenic acid levels and high linoleic acid levels are suitable for cooking oil and margarine (Dribnenki and Green 1995;Dribnenki et al. 1996). They are now available in Australia, Canada and Europe. In Canada, producers grow both standard brown cultivars for industrial oils, and yellow-seeded cultivars (solin) for edible oils. The two types of flax can easily be separated by color within the grain handling system. Storage guidelines have been developed for canola Sinha 1980), wheat (Hyde andBurrell 1973;Wallace et al. 1983), yellow mustard (Mills et al. 1994) and other crops. However, few studies have been conducted on safe storage of flaxseed. White and Jayas (1991) For personal use only. CANADIAN JOURNAL OF PLANT SCIENCEand RH is used to define levels of seed moisture content where spoilage will not occur, since fungi do not grow at relative humidities below 65% (Wallace 1973). Flaxseed is designated "dry" at 10% MC by the Canadian Grain Commission (1996) and can be safely stored for long periods at cool temperatures. Ten percent moisture in flax would be the equiva...