Studies On The Creation And Genetics Of A Dwarf Mutant And An Apetalous Flower Mutant And Development Of New Hybrids In Brassica Napus L.

A dwarf mutant, NDF-1, approximately 70 cm high, was derived from a 200-cm high doubled haploid (DH) Brassica napus line '3529' , seeds of which were jointly treated with chemical inducers and bombardment of fast neutron. The leaves of the 'NDF-1' mutant were wrinkled and thicker compared with the wild-type control. Dwarfism couldnot be rescued by feeding exogenous GA3 during germintaion and seedling periods. The mutant had much lower values than its original parents for all agronomic traits, except for its seed weight. 'NDF-1' maturated approx a week earlier than the tall parent '3529'. A genetic analysis revealed that dwarfism is under the control of a major gene (designated as ndfl) with a mainly additive effect and non-significant dominance effect. The broad and narrow heritability was 91.9 (%) and 85.7 (%) respectively, which presented high reliability for selection of the dwarf in spite of the existence of the enviroment influence. Because of the high level of resistance to lodging, breeding programmes for double low dwarf oilseed rape and heterosis utilization were initiated. Some new dwarf strains with improved agronomic performance were developed. The hybrid of the cross between the tall parent and the dwarf line showed increased harvest index and significantly higher seed yield than the tall parent or the control variety 'Zhongyou 821'and presented an estimated heterosis vigour rate as high as 30-40%. The dwarf trait will be a promising marker for a simple, economic and efficient way to control the purity of F₁ hybrid varieties in hybrid production of B. napus.Dwarf double-purpose recessive genetic male sterile (rGMS) line was obtainedby introducing an artificially mutated dwarfing gene to a normal rGMS line. A half dwarf hybrid, HDB-4, was subsequently developed with the dwarf rGMS line as female parent and a normal elite line as male. Results of a fertilization trial and a planting density trial indicated that the better yielding performance of the half dwarf hybrid depended on relatively high fertilizing level and high planting density, and only up to 300 kg/hm2 N applied and 30 plants / m2 planted respectively could HDB-4 yield higher oilseed than the normal hybrid control, Shuza No.6. In optimum conditions the half dwarf hybrid presented a seed yield vigor rate as high as more than 20%-30% by the control. Fertilizer promoted plant pods the per and the 1000-seed weight while the productivity per plant kept rather stable than the control. High level fertilization and planting density endurance for the half dwarf hybrid was closely related to its lodging resistance. Combination of the dwarf and heterosis is significant for the super-high yielding breeding strategy in B.napus.Backward suppression subtractive library of mature leaves in dwarf mutant DDF-1 and its wild type 3529 was constructed by suppression subtractive hybridization (SSH), in which the tip part from plants of dwarf mutant DDF-1 and wild type 3529 were respectively used as tester and driver. These clones in the backward subtractive library were verified by colony PCR. The recombined efficiencies of the backward subtractive library were 90%. The size of inserted fragments was between 100 bp-1000 bp. One hundred clones in the backward subtractive library were verified by dot blot again, thirty-two positive clones were found. All the lones were selected for sequence determination and homology analysis by BLAST online. Some of these clones were placed into several functional categories, including signaling, secondary messenger, photosynthesis, fatty acid metabolizability and senescence. The successful construction of subtractive cDNA library has provided a foundation for further study of the mechanism of dwarfing in plant development for the stem.A spontaneous mutant with apetalous flowers (Apet33-1) was also obtained from a hybrid progeny in Brassica napus. The result of genetic analysis showed that the apetalous character was controlled by only one gene locus, petalous flower exhibited incomplete dominance over apetalous flower and that its expression wasnot affected by cytoplasmic factors. Sixteen agronomically important characteristics of the apetalous line Apet33-10 were compared with those of its petalled near-isogenic line Pet33-10. Results from four years of tests indicated that there was no difference between Apet33-10 and Pet33-10 in all tested agronomic characteristics, except for the pod number of main inflorescence and second order branches at low sclerotinia disease incidence. The Sclerotinia sclerotiorum disease severity index of Apet33-10 was significantly lower than that of Pet33-10, and correspondingly, the plot yield of Apet33-10 was increased obviously in comparison to that of Pet33-10 if sclerotinia disease was serious. The pod number of main inflorescence of Apet33-10 was significantly lower than that of Pet33-10. On the other hand, the pod number of second order branches of Apet33-10 was significantly higher than that of Pet33-10, hence no overage difference of the pod number per plant was observed between the two lines.Moreover, hybrid breeding projects have been conducted. Polima CMS lines and corresponding maintainers were developed. Accordingly, 'Shuza No. 10' and 'Shuza No.9', both CMS 'three-line' Brassica napus hybrid with moderate maturity, had been obtained. 'Shuza No.9' presented high yielding (20-30% higher than the non-double-low CK c.v. 'Zhongyou 821' , and about 10% higher than the double-low hybrid 'Shuza No.6'), and good quality with oil content of 41.47% and both low erucic acid content (0.02%) and low glucosinolate content(23.03 u mol/g) as well. Shuza No.9 was approved and released by National Crop Variety Approval Committee of P R China in 2003. 'Shuza No. 10' showed 20-30% higher yielding than the traditional CK c.v. 'Zhongyou 821', and about 10-20% higher than the double-low hybrid 'Shuza No.6'. And 'Shuza No.10' also possessed good quality with relatively high oil content (39.87%) and both low erucic acid content (0.20%) and low glucosinolates content(<40 u mol/g). 'Shuza No. 10' was approved and released by Sichuan Province Crop Variety Approval Committee in 2002.