Study On The Effect Of Brace Root Traits On Lodging Resistance And Genetic Research Of Maize Brace Root Traits

Lodging is one of the main factors reducing maize production and farmers’ harvest, andalso a restricting factor of the development of corn mechanization. There is an anchor forceon the plant provided by maize root combining with soil and brace root,which is the importantpart of maize root. So it is worth to analysis the effect of the Architecture and quality of braceroot on lodging resistance. In this paper, the maize brace root was divided into brace rootangle, brace root number, brace root diameter and buried brace root depth. The Correlationbetween brace root angle, brace root number of190maize inbred lines and lodging grade wasconducted by contingency analysis method.At the same time, The brace root angle,brace rootnumber, brace root diameter and buried brace root depth of two groups of inbred lines withdifferent lodging resistance was compared, finally combined the results of the two experimentto demonstrate the relationship between brace root traits and lodging resistance; after definingthe important influence brace root traits on lodging resistance,8inbred lines with differentbrace root traits was used to do the analysis of combining ability and genetic analysis inGriffing diallel pattern II, and combined analysis of six generations were used to analysis thegenetic model of the brace root traits，The results are listed below:1.The results of the relationship between brace root traits and lodging resistance showedthat: The Chi-square value of brace root angle, brace root number and lodging grades werehighly significant; The comparison of the two groups of inbred lines with different typelodging resistance in two regions indicated that:excepted for inbred line R1,all the brace rootangle of lodging-resistant inbred lines were significantly wider than lodging-sensitive ones.The brace root number of all lodging-resistant inbred lines was significantly more thanlodging-sensitive ones. The lodging-resistant inbred lines were generally larger than thelodging-sensitive ones. So the brace root angle and brace root number had closely positivecorrelation with lodging resistance. Brace root diameter and buried brace root depth hadcertain positive correlation with lodging resistance.2. The heterosis analysis results of brace root traits indicated that most crosses’ High-parent heterosis and Mid-parent heterosis of brace root number were Negative.Mostcrosses’ heterosis of brace root angle and buried brace root depth were positive. buried braceroot depth had the highest heterosis, then the brace root angle，and brace root number in thelast. So buried brace root depth and brace root angle were more likely to combine excellentcrosses, but the brace root number was more likely to perform negative heterosis, whichdemand strict conditions, should strengthen the selection of parents3. Combining ability analysis results showed that: The highest GCA parents of brace rootangle, brace root number, brace root diameter and buried brace root depth were2355,2353,2355.Inbred lines2353and2355had good performance in the three brace root traits ongeneral combining ability. The highest SCA of brace root angle,brace root number and braceroot depth were2353×2333(6.998),2339×2334(1.407) and2334×2333(5.030). Cross2339×2334showed high special combining ability in3traits.4. Genetic estimation results of brace root traits showed that brace root angle was mainlycontrolled by additive gene effect,one should pay attention to the selection of parents withwide brace root angle in selecting parents,. There was a similar dominance variance andadditive variance in brace root number, illustrated brace root number was influenced by bothof the additive and non-additive gene effect. In the combination, consideration should begiven to parents and its hybrid’s combination performance. There was a bigger dominantvariance than additive variance in buried brace root depth, illustrated buried brace root depthwas mainly controlled by non-additive gene effect. The accuracy of the expected of futuregenerations from parents was low, the the selection criteria of parents could be relaxed.Heritability estimation analysis of the brace root results showed that the heritability of braceroot number and buried brace root depth were low, which was more likely to be influenced byenvironmental factors, should not be selected in early generation. Both of the broad-senseheritability and narrow-sense heritability were high in brace root angle, which mean braceroot angle can be selected in the early generation.5. The test results of genetic mixed major gene and polygene model for brace root angle，brace root number and buried brace root depth showed that: Additive-dominance-epistasispolygene model was the most suitable genetic model for brace root angle, combine the resultsthat brace root angle was controlled by the additive effect of multiple gene, we can know thatadditive gene effects dominated the effect of multiple genes. One additive-dominance majorgene plus additive-dominance-epistasis polygene mixed inheritance mode was the mostsuitable genetic model for brace root number, the dominate effect and addictive effect of the major gene in brace root number were both negative. The heritability of multiple genes washigher than the heritability of major genes. So the brace root number should be selected inmore generations in order to accumulate multiple genes. The most suitable model for buriedbrace root depth was Additive-dominance-epistasis polygene model, indicated that buriedbrace root depth was mainly controlled by dominant effect of genes. In the effects of multiplegenes, dominate effects played an important role. Therefore relaxed criteria in choosingparents should be used to improve buried brace root depth.