Study On Rapeseed Ideal Canopy Structure In High Plant Density

In this study, two experiments were designed. First was that setting five planting densities-150,000plantsperhm2,300,000plants per hm2,450,000plantsperhm2,600,000plants per hm2and750,000plants per hm2,15double-low rapeseed varieties (lines) with different genetic background were used tostudy the dynamic changes of yield traits such as high yield population density and yield components,and investigate canopy structure of rapeseed high yield population in high plant density. The second wasthat three rapeseed varieties (lines) of different plant types were chosen as the materials in four plantingdensity levels of300,000plants per hm2,600,000plants per hm2,900,000plants per hm2and1,200,000plants per hm2, changing the inherent plant type by manual removal of the main raceme and axillarybuds, to research the effect of artificially altering plant types on the yield component traits. Through theabove two experiments, study on rapeseed ideal canopy structure in high plant density could providetheoretical guidance and reduce blindness for rapeseed high yield breeding.The results were as follows:1. Rapeseed high yield population densityIn five planting density levels of150,000plants per hm2,300,000plants per hm2,450,000plantsper hm2,600,000plants per hm2and750,000plants per hm2, the yield of15double-low rapeseedvarieties (lines) first increased and then decreased with planting density increasing consistently, just theoptimal density for the highest yield value of different plant type varieties was different. But among the15rapeseed varieties, the high yield population density distributed between300,000-600,000plants perhm2, and the yield of7,3and5varieties was the highest in the density of300,000plants per hm2,450,000plants per hm2and600,000plants per hm2, respectively.2. Research on the importance of each agronomic character for rapeseed yield under high yieldconditionsThrough grey relational grade analysis of yield per plot of15varieties in high yield populationdensities of300,000-600,000plants per hm2and each agronomic character, the importance order of eachcharacter to rapeseed yield was: effective branches number>length of main raceme>siliques number ofbranches>plant height>seeds per silique>1000-seed weight of branches>seed weight per silique>branchheight>racemes per unite area>branch yield per plant>density>siliques of main raceme>1000-seedweight of main raceme>yield of main raceme per plant.3. The trend of yield component traits of rapeseed with densityFor15varieties in the densities of150,000-750,000plants per hm2, the increasing trend of racemesper unite area (the sum of branch racemes and main racemes) and siliques per unite area slowed with theincrease of density, when the maximum of which the density distributed between600,000-750,000plants per hm2. The maximum of racemes per unite area of Guangyuan58and Huaza6was in thedensity of600,000plants per hm2, of other13varieties in the density of750,000plants per hm2. Themaximum of siliques per unite area of9varieties was in the density of600,000plants per hm2, of other6varieties in the density of750,000plants per hm2. With the density increasing, seeds per silique and 1000-seed weight of rapeseed decreased slightly, and seed weight per silique declined.4. The effect of artificially altering canopy structure on the yield and yield component traits ofrapeseedIn the densities of300,000-1,200,000plants per hm2, the yield of three rapeseed varieties ofdifferent plant types first increased and then decreased consistently with the density increasing, and themaximum yield appeared in the range of densities of600,000-900,000plants per hm2. The optimaldensity for the maximum yield after different altering plant type treatment was different. When reachingthe highest yield, the density was600,000plants per hm2and900,000plants per hm2after manualremoval of the main raceme and axillary buds, respectively.In the average density level of750,000plants per hm2, when artificially altering plant typescompared with CK, the effect on the yield and yield component traits was as follows: after retainingonly main raceme,1000-seed weight of main raceme, seeds per silique, seed weight per silique andyield of main raceme were higher than CK, whereas the average yield per plot of three varieties waslower than CK. When retaining only branches after manual removal of the main raceme, branchesnumber and1000-seed weight of branches increased compared with CK. However, siliques per unitearea, seeds per silique and yield per plot of different varieties fluctuated differently, only branchesnumber, racemes per unite area, siliques number of branches and yield of branches per plant of Huaza9with relatively better branching advantages significantly increased, the yield of which was4.02%higherthan CK.5. Rapeseed ideal canopy structureThe potential to improve the density of rapeseed is limited with existing leaf structure. To obtainhigh-yielding rapeseed still has to mainly rely on branches number and siliques number of branches,consideration to seeds per silique and1000-seed weight, and maximize the potential of yield componenttraits. The theoretical yield value of rapeseed could reach up to697kg per667m2, relying solely onsingle stem or less branching type unfeasibly. To achieve the yield potential of ultra-high density ofrapeseed, the leaf structure must be optimized to increase photosynthetic efficiency, and synchronouslyimproved with canopy structure.