A 6 × 6 diallel cross was conducted in spring-planted oilseed rape (Brassica napus L.) in 1983 at Elora and Dundalk, Ontario. The F1 hybrids exhibited positive heterosis for seed yield, of up to 72%, over the higher-yielding parent in the hybrid crosses. Heterosis for 1000 seed weight, percent oil, plant height, and lodging resistance was nonsignificant; negative heterosis for percent protein was observed with some hybrids. Generally, the hybrids were intermediate to the parents in flowering date and physiological maturity. Specific combining ability was more important than general combining ability for seed yield, percent oil, percent protein, plant height (Dundalk), and lodging resistance (Elora); specific combining ability was as important as general combining ability for 1000 seed weight, physiological maturity, plant height (Elora), and lodging resistance (Dundalk). The cultivars 'Topas' and 'Regent' were the best general combiners for seed yield. The best specific combinations for seed yield heterosis, 'Westar' × 'Hanna', 'Regent' × 'Liné', and 'Regent' × 'D-1', exhibited average high-parent heterosis values of 50, 38, and 30%, respectively. The results demonstrated that considerable potential exists for producing high-yielding single-cross hybrids of oilseed rape. Commercial exploitation of this heterosis will depend on the successful development of suitable pollination control mechanisms.Key words: Brassica napus, oilseed rape, F1 hybrid, heterosis, combining ability.
Rapid isolation of oilseed rape (Brassica napus L.) microspores was accomplished by mechanical homogenization of whole racemes with buds no longer than 4.5 mm. After filtration and multiple washes, spores were incubated overnight in liquid medium at 30 °C in the dark, before plating in fresh medium at a density of 100 000 spores/mL. After 14 days in culture, gentle agitation on a shaker improved the rapid development of normal embryos and later, when transferred to light and liquid B5G medium (B5 + 0.1 mg/L gibberellic acid), further agitation enhanced the rate of maturation and germination. With this method 200–400 million spores can be processed in one batch, resulting in a final yield of several hundred thousand embryos within 3 weeks. Applications of the system for mutation–selection in B. napus are outlined.
Chloroplast (ct) DNA from the three elementary Brassica species (B. nigra (L.) Koch, B. oleracea L. and B. campestris L.) and the three amphiploid Brassica species (B. carinata A. Br., B. napus L. and B. juncea (L.) Czern.) was digested with fifteen restriction endonucleases. In all species restriction sites for enzymes with GC-rich recognition sequences were less frequent and not as variable as for those with AT-rich sequences. Comparisons between species revealed two distinct groups of ct DNA fragment patterns: complex one, composed of B. oleracea, B. napus, B. campestris and B. juncea and complex two, composed of B. nigra and B. carinata. The patterns of B. carinata were virtually identical to those of B. nigra and those of B. juncea were virtually identical to those of B. campestris indicating not only where the ct genomes of B. carinata and B. juncea originated, but also how little these genomes have been altered since the origin of these amphiploids. Ct DNA in B. napus shows more homology with that of B. oleracea than with that of B. campestris, but the ct genome of this amphiploid has diverged more from that of its putative parent than have those of the other two amphiploids.
An understanding of the genetics of the long daylength response of soybean [Glycine max (L.) Merrill] would facilitate the development of cultivars adapted to the long days of the northernmost growing areas of North America and Europe. The objective of this study was to determine the genetic control of soybean response to extension of the natural daylength to 20h using incandescent lamps. Three pairs of near‐isogenic lines (NIL) plus a long daylength insensitive check were grown outdoors and rated visually for response to incandescent long day (ILD). The same entries were further grown indoors and rated for response to extension of the natural daylength to 20h using cool white fluorescent lamps (FLD). Based on these results, entries were classified for alleles at the E3 and E4 maturity loci. Check OX619 and ILD‐insensitive NILs X2398, X2403, and X2396 were classified genotypically as e3e3 e4e4. The respective recurrent parents were all ILD‐sensitive and were classified: Evans‐e3 and Harosoy‐e3 as e3e3 E4E4 and ‘Maple Arrow’ as E3E3 e4e4. Analyses of F2 and F2:3 populations from five crosses revealed that only the e3e3 e4e4 genotype is ILD‐insensitive. Consequently, a model of two (E3 and E4), each with two alleles, each with dominance, plus epistasis of E3 on e4> is proposed to explain the ILD‐insensitivity. It was concluded that E3 is the major locus conferring long daylength insensitivity in soybean, but both E3 and E4 have to be considered when breeding for insensitivity to long daylength using ILD.
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