| The main germplasm used in this study was a dwarf mutant named Ds-1 with zhongshuangNO.4 (ZD4) and HuashuangNO.3 (HD3) as control. Characters of the young seedling of Ds-1 were investigated under light and dark conditions, and its other growing habits and agronomic characters were identified in field. The reactions of its hypocotyl and stem to different phytohormone treatments were observed. The inheritance of the gene for the short stem of Ds-1 and the allelic relationship with another dwarf germplasm Ds-2 were studied. RAPD technique and candidate gene approach were adapted to detect molecular markers linked to the dwarf gene (Dsl). The main results were as follows:1. Hypocotyl length of Ds-1 grown under light condition was shorter than that of ZD4, but no obvious difference under dark; Ds-1 was lower significantly than ZD4 in plant height, branching position, number of elongated nodes, length of intemode and main inflorescence; but as to the number of total nodes there was no significant difference between the dwarf and the normal varieties. It showed that the dwarf phenotype was due to fewer numbers of elongated nodes, shorter length of internode and main inflorescence, lower branching positions. In comparison with the control, Ds-1 had fewer siliques per plant, lower yield per plant and higer 1000 seeds weight, but no significant difference existed in branch numbers, pods of main infloresence and seeds per pod.'2. Phytohormone 6-E^ BR had no significant effects to the hypocotyl length of Ds-1; IAAand GA3 enhanced hypocotyl elongation significantly, but only 100mg/L GAS could elongate its hypocotyl to normal length; 6-BA> IAA, NAA, GA3> 920> BRhad no obvious effects to the stem elongation of Ds-1, while 600mg/L PP333 reduced the stem length, and 600mg/L GA3 could partially enhance the stem length reduced by PP333 but not to normal. These results indicated that the signal transduction for GA3 in Ds-1 was normal.3.Genetic analysis showed that the plant heights of Fl population was intermediate of two parents, but partial to dwarf parent, Fl and RF1 had no significant difference. The segregation ratio of tall plants: short plants in F2 population accorded with 1:3 and with 1:1 in BC1 population, all BC2 plants were dwarf. So, a partial dominant dwarf gene, dominant degree was 0.25-0.31, controlled the plant height of Ds-1.4. Both the broad sense heritability(h2B) and narrow sense heritability(h2N) of plant heights were high, and the h B were higher than h2N in two crosses. So besides additive effect, dominant and environmental effect also affected this character.5. The Fl family of Ds-1xDs-2 was dwarf, and in F2 population high plants were observed, which indicated the dwarf gene of Ds-2 wasn't allelic to that of Ds-1.6. Bulked segregant analysis (BSA) was adapted to identify RAPD markers linked to dwarf gene Dsl. Totally 1041 primers were screened and only one polymorphic band S470.416 was found linked to the Dsl locus with a map distance of 9.2 cM. Primers based on GA insensitive gene (GAP), GA20-oxidase gene (GA20ox) and phytochromeA (PhyA) didn't amplified polymorphic bands linked to Dsl. |
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