Development And Genetic Analysis Of Novel Quality Resources And Polima CMS Restorer Line In Brassica Napus

Oilseed rape is one of the most important oil crops in China. China has the iargest total planting area and the highest total product in the world. In rapeseed oil, oleic acid (C₁8: 1) is the main nutrition which can be absorbed by human body. And linolenic acid is necessary for brain development. But it can not be produced by ourselves. So it only can be absorbed from the vegitable oil. How ever, the high ratio of linolenic acid can be easily oxidized and lead the oil rancid thus shortens the shelf life. So in the lipid industry, it is hybrogenated into oleic acid. But the reaction companied the production of Vans-fatty acid which is harmful to human health. It is the most economical and heathy way for low linolenic acid breeding. And the most suitalbe linolenic acid concentration in variety is 3%.It will be impossible for novel fatty acid breeding without special quality resources. Unfortunately, Brassica napus has a narrow genetic basis, even more narrow for quality resources. Until now, the Polish spring oilseed rape 'Bronowski' is the unique low glucosinolate gene resource. And 'Oro' is the unique low erucie acid gene resource. ' Stellar' (and the sister line 'Apollo') and 'Wotan' are often used as the low linolenic acid and high oleic acid breeding resource, respectively. Further pedigree investigation indicated that 'Stellar', 'Apollo' and 'Wotan' were mutated from 'Oro'. New quality gene resources are desired.Besides the quality improvement, the goal of oilseed rape breeding includes high yield. Oilseed rape (Brassica napus L.) shows so high levels of heterosis that the worldwide breeders are interested in the development of F₁ hybrid eultivars. There several efficient pathways to utilize the heterosis, such as cytoplasmic male sterility(CMS), genie male sterility(GMS), genie male sterility and cytoplasmic male sterility(GCMS), ecotypical male sterity(EMS), chemical hybriding agents(CHA) and self incompatibility(SI). In China, Polima cytoplasmic male sterility(Pol CMS) is currently the most pollination control system. It can be divided into three categories according to the sensitivity of male sterility to temperature: high temperature CMS lines, low temperature CMS lines and stable CMS lines. For the stable Pol CMS lines, maintainer lines are essential for the multiplication ofpol CMS lines while being used as a female parent in hybrid seed production.Later, a new Pol CMS resource, temperature-sensitive Polima cytoplasmic male sterility(Pol TCMS) line was found in segregating progenies of Pol CMS line 'Xiangai A'×restorer line. The novel resource is partially fertile at Wuhan in spring, but stable sterile in Kunming or Xi'ning in summer. So it can be multiplied without the utilization of maintainer line in the autumn-sowing area. In the spring-sowing-area, it can be used to produce hybrid seeds. But in practice, the climate might be a problem in limited situation. Under abnormal temperature condition, trace pollen can result in self-pollination within the CMS lines, which will lead to the yield loss for low hybridity. So, in some cases, the proportion of selfed seed was so high that the yield of the hybrid variety was significantly decreased in a large area. Therefore, a new pollination control system that should be more convenient and less risky is desired to carry out the production of hybrid seeds. The selection of novel gene resources related to fertility could be a way to resolve such a problem.New gene resources can be found ether in current resources(such as Pol TCMS) or by interspecies hybridization(including resynthesizing oilseed rape). The U's triangle indicated that B. napus is derived from the hybridization between B. campestrsis and B. oleracea. Different from B. napus, the genetic variations in B. campestrsis and B. oleracea are abundant. Furthermore, B. campestrsis originated in China. So, it is practicable to broaden the genetic basis by utilization of resynthesized B. napus.This study evaluated the quality resources in the resynthesized B. napus lines. Based on the evaluation, low linolenic acid resynthesized B. napus was selected out and was used to QTLs analysis. On the other hand, it developed a novel temperature-sensitive Pol restorer line which never reported before. Primary genetic analysis was carried out in this study. The follgwing were the main results:1. Evaluation of quality traits in resynthesized B. napus and integration of increased oleic acid, low linolenic acid and low glucosinolate traits The present study was to evaluate seed fatty acids of 139 RB lines. Neither high erucic(＞55%, for industrial, breeding) lines nor high oleic acid(＞72%, for nutritional purpose) lines was found. However, zero erucic acid lines, low linolenic acid(＜3%) lines and increased oleic acid(69.23%) lines were selected. Moreover, we found that a line 'R1-2' had many novel quality traits(increased oleic acid and double-low). Thus the line 'R1-2' was crossed with another line 'R15-4' which had low linolenic, zero erucic acid and high glucosin01ate. An individual in the F₃ progeny was selected out because of integrating four quality traits(increased oleic acid, low linolenic acid, zero erucic acid and low glucosinolate).2. Genetic analysis and QTLs of low linolenic acid in resynthesized B. napusThe resynthesized B.napus line 'R15-4' was reciprocally crossed with a cultivated B. napus line 'L1745'. In the F₂ populations linolenic acid content segregated and the genetics fitted a continuous distribution model. The segregation indicated it was possible to introgress the gene(s) into oilseed rape. Meanwhile, the population means between reciprocal cross were remarkable different at the level ofα=0.05. It indicated that the cytoplasm may influence the genetic model of linolenic acid.A genetic linkage map for B. napus was constructed using the (L1745×R15－4) F₂ population. Total 303 markers including SSR, AFLP and SRAP were distributed on 18 main linkages, 3 minor linkages. The map covered 2723.6cM genome length with an average interval of 8.99cM. By SSR markers, it was compared with the France map reported by Piquemal et al in 2005. As a result, 39 SSR markers were common in both maps. Only the 12^th linkage in our map can not found common SSR markers.After constructing the mapping population and linkage group, linolenic acid was tested to the mapping population '(L1745×R15－4) F₂'. Four QTLs were detected for lin01enic acid trait by Composite Interval Mapping (CIM) method with LOD=2.5. The 4 QTLs distributed on 3 linkages. The 6^th linkage detected one QTL explaining 23.65% variation. The 7^th linkage detected two QTLs explaining 19.62% an 9.51% variation, respectively. And the 14^th linkage detected one QTL explaing 14.06% variation. 3.Development and primary genetic analysis of a fertility-temperature-sensitive polima CMS restorer in Brassica napus'7-6' was a double-low pol CMS restorer of the hybrid cultivar 'Huaza No.13'. It is normally fertile in Wuhan. But by observing for several years, we found '7-6' was partially sterile. A DH line 'L1815' was crossed with '7-6'. Microspore was gathered from the F1 plants thus a DH population with 63 genotypes was constructed. The population was investigated fertility in Wuhan and Gansu in 2003 and 2004. A line named 'FL-204' was selected out. It was completely fertile in Wuhan in spring vs. sterile in Gansu in summer. The experiments in growth chamber indicated the fertility of 'FL-204' was influenced by temperature. So it was named fertility-temperature-sensitive polima CMS restorer(FTSR) in this study.And F2, BC₁ as well as Double Haploid populations were constructed to determine the inheritance of fertility by evaluating in different locations. The deviations from Mendelian genetics were observed. It was hypothesized that: The change of fertility was the result of the interaction between the nuclear genes (restoring gene (Rf) and temperature-sensitive gene (ts)) and the cytoplasm. For the Rfgene in 'FL-204', the ability to restore the fertility ofpol CMS could be inactivated by the ts in Gansu. However, the ts gene(s) could be nonfunctional, which lead 'FL-204' fertile in Wuhan. And only in the pol sterile cytoplasm the ts gene(s) could be active. Therefore, a practical method for the application of FTSRs was proposed.