Inheritance Of Seed Colour, Erucic Acid Content And Flower Colour In Artificially Resynthesized Brassica Napus L.

As one of the most important oilcrops, rapeseed was planted 7.0 ×106 hectares in China which took the first place in planting area and yield in rapeseed-yielded countries (Fu, 2000). Recently, consumption of rapeseed oil has been 35% of edible oil and consumption of rapeseed meal has been 25% of plant meal in China (Liao, 2002). Plant oil was consumed about 1.1 ×107t in China in 2003. It will need 2.0 × 107t plant oil to meet consumption of 1.5 billina people in 2020, based on average consumption 13.6 kg per person of one year (Wang, 2004). It is essential for us to greatly develop rapeseed to meet need. Many countries are developing high quality rapeseed, in detail, further decreaseing content of erucic acid, linenice acid, fibre and glucosinolate and increasing content of oleic acid and protein in seed. Most of cultivars are black seeds and not yellow seeds. Compared with black seed, yellow seed has higher oil content in seed of the same genetic background and thinner seed coat that is associated with higher protein and lower fiber contents in the meal. It will be nice to develop high quality rapeseed with yellow-seeded character in the futher. However unfortunitelly there exist no spontaneous yellow-seeded variant in the B. napus germplasm in contrast to Brassica rapa, Brassica carinata and Brassica juncea. People obtained some yellow-seeded B. napus but yellow-seeded character was unstable and its seed coat colour was not purely yellow. So breeders employed a number of strategies to develop steadily yellow-seeded B. napus such as interspecifical hybridizations, radicalization and artificial resynthesis and so on. The white-flowering and yellow-seeded line No.2127-17 is a doubled haploid (DH) derived from the resynthesized B. napus line No.7076 through interspecific hybridizations between B. alboglabra Bailey and B. rapa (syn. campestris) L. with the objective to develop yellow-seeded B. napus germplasm (Chen et al., 1988). The seed colour of No.2127-17 is purely yellow and has stable genetic behavior. It was employed to cross with two spring canola B. napus variety Quantum2 and Sprint which are black seed and yellow-flowering from western Canada in order to study inheritance of seed colour and identify its QTLs on linkage groups. The flower colour and erucic acid are also included in the present study. It is possible for us to develop a double-low and yellow-seeded B. napus from their offspring of the crosses. The results of this study are summarized as follows:1. Microspore cultureThe F1 plants derived from a cross of Quantum2 x No.2127-17 was used to make the microspore culture. The yield of embryogenesis was increased and reached 38.3 embryos per plate in NLN-13 media with 0.1 mg/L 6-BA. However, abnormal embryos were more frequent than the CK without 6-BA. Abnormal embroy was decreased when 0.05% activated carbon was added. Of the three chromosome doubling methods, the doubling frequency was the highest with 50 mg /L colchicine and reached 67.6%. The plantlets reached a survival frequency of 87.6% when theshade-net covered plantlet instead of film. About six hundred doubled haploid (DH) plants were obtained.2. Inheritance of seed colour, erucic acid content and flower colourThe inheritance analysis of flower and erucic acid indicated that white flower was dominant over yellow flower and under monogenic control; and erucic acid exhibited a pair of addictive effect genes difference. The results of joint segregation pattern of the two characters revealed that white flower tightly linked to high erucic acid with a recombination frequency of 5.9% in DH line progeny. The inheritance analysis of seed colour indicated that yellow seed was partially dominant over black seed, and could be due to two pairs of genes differeence (Y and B) in a cross of Quantum2 x No.2127-17, and could be due to three pairs of genes difference (Y, B and C) in Sprint x No.2127-17. Y suppresses over B and C, and independent duplicating effect between B and C.3. Development of molecular markersSSR (simple sequence repeat), SRAP (sequence relatived amplified polymorphism) and RAPD (random amplified polymorphic DNA) techniques and BSA strategy were employed to develop molecular markers linked to seed colour and erucic acid. A total of 757 RAPD primers, 330 pairs of SSR primers and 170 pairs of SRAP primers were selected to detecte polymorphisms between two bulks. One RAPD marker BS28.400 and two SRAP markers me4em5e and me4em5f were tightly linked to black seed; further a marker-analysis revealed that BS28^too, me4em5e and me4em5f could explain 39.9%-51.2%, 40.2%-57.5% and 31.7%-38.7% of the total phenotypic variation of seed colour in 2002-2004, respectively. BS28.400 was converted into a dominant SCAR marker. Erucic acid at one side was tightly linked to a dominant RAPD marker BS92.Moo and a co-dominant SSR marker TPSO39.2oo at genetic distance 7.1 cM and 2.2 cM, respectively.4. Linkage mapping and QTL analysis of seed colour and erucic acidPolymorphic RAPD, SSR and SRAP primers were selected to construct linkage groups of Brassica napus using 121 DH lines. A total of 255 markers were detected that comprised 107 random amplified polymorphic DNA (RAPD) markers, 100 simple sequence repeat (SSR) markers, 46 SRAP markers and two morphological marker i.e. the flower colour and erucic acid. These markers were assembled into 19 main linkage groups (LG1 - LG19) and five minor ones (A - E). The total map length is 1438.2 cM with an average distance of 5.6 cM between two markers. The marker loci with distorted segregation accounted for 32.7% and tended to cluster in six linkage groups. The composite interval mapping was used to localize the putative QTL for erucic acid using WinQTL Cart program. The composite interval mapping was used to localize the putative QTL for seed colour. The results revealed that onemajor QTL was detected on LG18 in 2002-2004. The QTL was responsible for 40.5%-62.4% of the phenotypic variation of seed colour. One putative major QTL controlling the erucic acid was revealed in the intervals between marker loci TPSO39₂o