Developmental Characteristics And Genetic Analysis Of High-grain Weight Traits In Brassica Napus

Rapeseed is the first source of edible vegetable oil in my country.Its oil production accounts for about 55%of the oil production of domestic oil crops.However,the level of oilseed rape production in my country is still low,which affects farmers’enthusiasm for planting.Suitable for light and simplified mechanized selection of high-yield rapeseed varieties is the fundamental strategy to improve farmers’planting benefits.Research has shown that increasing the thousand-seed weight is an effective way to achieve breakthroughs in yields on the basis of stabilizing the number of siliques and siliques per plant.The thousand-seed weight of rape is not only restricted by the two yield elements of siliques per plant and siliques per plant,but also severely affected by the maturity period.In this study,the high-grain weight early-flowering line GRG177 of Brassica napus and the low-grain late-flowering high-yielding line GRD328 of Brassica napus were used as research materials to study the cytological and physiological basis of rapeseed morphology and development,and to conduct genetic analysis and analysis of large-grain traits.Gene mapping.The main results are as follows:1.Comparative analysis of the development characteristics of high-grain weight grains.The dry grain weight,fresh grain weight,grain volume,silique surface area and filling rate of the high-grain weight line GRG177 of Brassica napus were significantly higher than those of the low-grain weight and high-grain product line GRD328.GRG177 is 1.0～3.5 times of GRD328respectively.The single cotyledon cell of GRG177 grain was larger than GRD328 in the same period.The concentration of zeatin nucleoside（ZR）in GRG177 was significantly higher than GRD328 during the period from flowering to 26 days,the abscisic acid（ABA）content was significantly higher than GRD328 after 38 days of flowering,and the concentration of IAA during the period from flowering to 41 days was significantly lower than GRD328,GRG177 ZR/IAA was significantly higher than GRD328 during the period from flowering to 29d.2.The main gene+polygene model was used to analyze the genetic segregation of 1000-seed weight and related traits.the result shows:Thousand-seed weight is controlled by 2 pairs of additive-dominant-epistatic majorgenes+additive-dominant-epistatic polygene（MX2-ADI-ADI）genetic model,and at the same time,and the number of angular grains,blooming duration were also controlled by the same genetic model.The initial blooming and the number of siliques per plant are controlled by 2 pairs of additive-dominant-epistatic major genes+additive-dominant polygene（MX2-ADI-AD）genetic model,and the final blooming stage is controlled by 1 pair of additive-dominant genes Major gene+additive-dominant-epistatic polygene（MX1-AD-ADI）genetic model control.The major gene heritability of 1000 grain weight was 54.7397%,26.243%and 71.7121%in the segregation generation（B₁,B₂ and F₂）,and the polygene heritability was0.0022%,22.4166%and 4.3712%,respectively.The heritability of the major genes of the number of siliques and the number of siliques per plant was higher than 41%,and the heritability of polygenes was lower than 20%.The heritability of the three segregating generations at the beginning,blooming duration and final blooming was relatively high（51.79%～96.81%）.3.QTL of GRG177 was initially located by F₂ segregation and BSA.There are 200 genes in this region,including 7 candidate genes for 1000 kernel weight.Bna A03g53970D encodes a protein containing a tetrapeptide repeat domain,which is similar to transcription inhibitors in other organisms.It participates in mediating effects and triggers immunity.The function of Bna A03g54530D is unknown.Bna A03g53870D belongs to the Myb-R2R3 gene family.Bna A03g53920D is involved in cytochrome synthesis and is regulated by Bna A03g54150D.The core cell cycle and nuclear replication are quantitative trait genes.The expression products of Bna A03g54220D and Bna A03g54550D genes are related to protein synthesis and metabolism.