Qu CHEN,Muheng ZENG,Feng JIANG,Chengwei HUANG,Xiaoming WANG,Pengfei LIU

College of Agronomy,Zhongkai University of Agriculture and Engineering,Guangzhou 510225,China

Analysis on Genetic Characteristics of Leaf Angle in Waxy Corn

Qu CHEN,Muheng ZENG,Feng JIANG,Chengwei HUANG,Xiaoming WANG*,Pengfei LIU*

College of Agronomy,Zhongkai University of Agriculture and Engineering,Guangzhou 510225,China

The leaf angle in waxy corn is a significant trait for breeding corn with compact plant type,which is beneficial to improve yield.According to the Griffing method II,the GCA(general combining ability)and SCA(specific combining ability) of leaf angle trait in the 7 waxy corn inbred lines and 21 combinations were estimated,and the genetic characteristics of leaf angle in corn were also analyzed.The results showed that among the 7 inbred lines,the GCA values ranked as N22＞N8＞N28＞N7＞N23＞N27＞N4.The GCA of N27 showed great negative effect,and the genetic variance of its SCA was lower.It suggested that the N27 can be used as an ideal parent for breeding excellent combinations with small leaf angle and compact plant type.The inheritance of leaf angle trait in waxy corn is in accordance with the model of"additive-dominant-epistatic".The efficiency of leaf angle trait is controlled by recessive genes.The broad heritability of leaf angle trait in waxy corn is relative low(68.5%),but its narrow heritability is relatively high (72.62%).In the breeding practices,the early-generation selection is more suitable for the leaf angel trait.

Waxy corn;Leaf angle;Combining ability;Genetic characteristics

L eaf angle is an important trait affecting the corn plant type,and it is also an important indicator determining the spatial distribution of leaf population.The leaf angle is directly and closely related to the high density resistance of corn[1].Duncan et al.[2]considered that the smaller the leaf angle is,the higher the light intensity in the middle and lower parts of population is.Thus,the population density can be further increased so as to increase population yield.At present,there are rare researches on the genetic background of leaf angle in corn[3].Ma et al.[4]found that under conditions of spring sowing and summer sowing,the leaf angle above spikes was in accordance with the E-1 model(additive-dominant-epistatic major gene+additive-dominant multigene mixed inheritance model),and it was controlled by two pairs of major genes;the leaf angle below spikes was all in accordance with the D-2 model(additive major gene+additivedominant multi-gene model),and one pair of major genes was detected.The research of Lu et al.[5]showed that the main ways of leaf angle-related genes are additivity and partial dominance, and the epistatic interaction also played an important role in the inheritance of leaf angle.Su et al.[3]found that in the quantitative inheritance of leaf angle above spikes,the additive gene effect was dominant in the inheritance of leaf angle;the GCA of inbred lines with straight-up and erect leaf types showed a negative effect.In this study,using the 7 fresh waxy corn inbred lines with different leaf angles,a total of 21 combinations were developed according to the Griffing method

Materials and Methods

Materials

In this study,the 7 waxy corn inbred lines,bred by the corn research group of Zhongkai University of Agriculture and Engineering,were selected as parents.According to the Griffing method II,a total of 21 hybrid combinations were bred,and they were treated as the test materials.

Field design

The sowing was performed in the dryland of Zhongcun Farm,Zhongkai University of Agriculture and Engineering in September of 2013.The inbred line parents were planted according to the combinations arranged by the Griffing method II.The arranged hybrid combinations of inbred lines were planted in March of 2014.The randomized block design was adopted. There were two rows,with length of 5 m and row spacing of 0.65 m,in each of the plots.A total of 15 plants were cultivated in each of the rows.There were three replicates for each of the treatments.

Measurement of leaf angle

At the grain-filling stage of corn,a total of 10 central plants were selected from each of the plots.The angles between the spike leaves(spike leaf and its inferior three leaves and superior three leaves)and the vertical direction of stem,referred as leaf angles,were measured.

Data processing and statistics

The data was processed with Excel 2010 and then analyzed with DPS 7.05.

Results and Analysis

Analysis of combining ability of leaf angle in waxy corn

As shown in Table 1,there were no significant differences in leaf angle in waxy corn among same blocks(P＞0.05),but there were significant different differences among different treatments(P＜0.01),indicating the presence of real genetic differences among different treatments.The further variance analysis showed that the GCA differed significantly among different parents(P＜0.01),and the SCA also differed significantly among different hybrid combinations(P＜0.01).It was suggested that the variation of leaf angle trait among different combinations was caused by both additive and nonadditive genes.

Analysis of combining ability effect of leaf angle in waxy corn

General combining ability effect

The GCA value differed from-7.846 9 to 5.483 4.There were great differences in GCA effect among parents, and the additive effect also differed among parents.The GCA values of N22,N8,N28 and N7 were all positive, so the GCA showed positive effect on leaf angle;while the GCA effects of the other three parents on leaf angle were negative.Among the 7 inbred lines, the GCA values ranked as N22＞N8＞N28＞N7＞N23＞N27＞N4.There were significant(P＜0.05 or P＜0.01)differences in GCA value among all the seven inbred lines except between N22 and N8 and N28 and N7,indicating the presence of differences in additive effect of genes affecting leaf angle among different parents.The N4 showed the greatest negative effect, followed by N27.They could be treated as excellent parents for breeding corn varieties with compact plant type and small leaf angle.

Specific combining ability effect

In order to effectively utilize the heterosis of inbred lines,the SCA of leaf angle in the 21 hybrid combinations was analyzed.Table 3 showed that the SCA value of leaf angle in waxy corn differed among different hybrid combinations,ranging from-8.164 to 6.199.It was indicated that the effects of genes affecting the leaf angle in waxy corn were non-additive.During the matching of hybrid combinations with inbred lines,the interactions among genes and the related trait variations were different.Among the 21 hybrid combinations,there were 15 combinations of which the SCA showed negative effect,accounting for 71.43%;the N7×N23 hybrid combination showed the lowest SCA effect. The N22 showed the positive and greatest GCA effect(Table 2).However,among the 3 hybrid combinations containing N22,the SCA effects were all negative.The N4 showed the most negative GCA effect.But the N4×N28 combination showed the highest SCA value(6.199).

The SCA reflects the non-additive effects of genes during the matching of hybrid combinations,and it is determined by the epistatic and dominant effects of genes and the interactions among genes.These kinds of effects can promote or cancel out each other.They are finally reflected SCA values[6-10].It showed that there are non-additive effects of genes existing in the inheritance of leaf angle trait in waxy corn.In breeding practices, more attention should be paid to the utilization of SCA.

Table 2GCA effect on leaf angle in waxy corn inbred lines

Table 3SCA effect on leaf angle in waxy corn inbred lines

Table 4Genetic variance estimation of leaf angle in 8 waxy corn inbred lines

Comprehensive evaluation of utilization value of inbred lines

To understand the variation degrees of SCA of a certain waxy corn parent in different combinations,the genetic variances of SCA of each of the parents were estimated(Table 4). As shown in Table 4,the GCA effect of leaf angle in N27 was relatively negative,but its genetic variance of SCA was the smallest.It was suggested that the N27 can transmit stably the traits of compact plant type and small leaf angle to all the combinations.

Analysis of genetic parameters of leaf angle

The analysis of genetic parameters(Table 5)showed that the additive variance of leaf angle in waxy corn was much higher than the dominant variance.It indicated that the additive effects of genes are dominant in the inheritance of leaf angle trait in waxy corn.The broad inheritability of leaf angle trait was 68.50%,so only 68.50% of the variation of leaf angle trait was controlled by genes.Therefore,the degree of genetic determination of leaf angle trait is not very high,and it may be affected by environmental factors. The narrow inheritability of leaf angle trait was relatively high(72.62%).It suggested that the leaf angle trait can be selected at early generation.

Variance analysis ofWr+VrandWr-Vr

The differences in Wr+Vr and Wr-Vr among the common parents were tested.The results showed that there were significant differences in Wr+Vr and Wr-Vr values of leaf angle among the common parents(P＜0.01).Therefore,significant dominant and epistatic effects exist in the inheritance of leaf angle trait in waxy corn,and it is not in accordance with the Hayman“additive-dominant”model.

Regression analysis ofWr/Vr

As shown in Fig.1,the regression equation of relationship between Wr (covariance of leaf angle among noncommon parents)and Vr(array variance)was as follows:

It indicated that the recessive gens of leaf angle trait are additive genes,while its dominant genes are reductive genes.The regression intercept(a)was-893.54,which showed significant(P＜0.01)difference with 0 (Sa=48.76,t=18.32).It suggested that the inheritance of leaf angle trait is not suitable for the additive-dominant model.In addition to additive and dominant effects,epistatic effect also existed.So the inheritance of leaf angle trait in waxy corn is suitable for the“additive-dominant-epistatic”model.

With Wr as the ordinate and Vr as the abscissa,the standard curve was drawn(Fig.1).According to the position of each parent on the standard curve,the distribution of recessive genes in parents can be inferred.The parents near the origin contained more dominant genes,while the parents far from the origin contained more recessive genes.As shown in Fig.1,the inbred lines N8,N22 and N28 contained more recessive genes controlling the inheritance of leaf angle trait,and their leaf angle values were 61.52°,65.78° and 51.45°,respectively.The inbred lines N4 and N27 near the origin contained more dominant genes controlling the inheritance of leaf angle trait, and their leaf angle values were relatively low(34.42°and 42.84°).The numbers of recessive genes in N7 and N22 ranked middle among the top 5 parents.It can be speculated that the inbred lines with large leaf angle contain more recessive genes controlling the inheritance of leaf angle trait,and the inbred lines with small leaf angle contain more dominant genes controlling the inheritance of leaf angle trait.

Discussion

Combining ability analysis is a theoretical basis for parent selectionand combination[10].During the breeding,the size of GCA reflects genetic transfer capability,while the size of SCA reflects the strength of interaction among parents in hybrid combinations[7-10].In this study,there were significant differences in GCA of leaf angle among the 7 parents,and the GCA values of the 7 inbred lines ranked as N22＞N8＞N28＞N7＞N23＞N27＞N4.The GCA effects of leaf angle in N4,N27 and N23 were all negative,which was consistent with the straight-up leaf type.The study results were basically the same with those of Su et al[7].

Table 5Genetic parameters of leaf angle

Table 6Variance analysis ofWr+VrandWr-Vr

In current researches,it is commonly considered that both the additive and non-additive effects play important roles in inheritance of leaf angle in waxy corn.However,the relative importances of additive and non-additive effects are still controversial.The results of this study show that the inheritance of leaf angle trait in fresh waxy corn is in accordance with the“additive-dominant-epistatic”genetic model.Under the additive and non-additive combined effects,the additive variance of leaf angle trait in waxy corn is much larger than the non-additive variance(dominance variance).It is indicated that the additive effect plays the dominant role in the inheritance of leaf angle trait in waxy corn.The results of this study also show that the efficiency of leaf angle trait is controlled by recessive genes.All the results above are partly consistent with the study results of Ma et al.[4]and Lu et al[5].But there are still some differences,which may be caused by the differences in leaf angle measurement method and tested populations.

The broad inheritability generally reflects the effects of genetic variation and environmental variation,while the narrow inheritability reflects the strength of additive genetic effect.In this study,the broad inheritability of leaf angle trait in fresh waxy corn is relative low,indicating low degree of genetic determination of leaf angle variation and weak environmental effect on leaf angle variation;but the narrow inheritability is relatively high,indicating better selection effect of leaf angle trait at early generation.

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Responsible editor:Tingting XU

Responsible proofreader:Xiaoyan WU

糯玉米葉夾角遺傳特性分析

陳趣，曾慕衡，蔣鋒，黃成威，王曉明*，劉鵬飛*
（仲愷農(nóng)業(yè)工程學(xué)院農(nóng)學(xué)院作物研究所，廣東廣州510225）

按雙列雜交GriffingⅠⅠ估算了7個糯玉米自交系及21個組合葉夾角性狀的配合力，并對玉米葉夾角遺傳特性進(jìn)行分析。結(jié)果表明：7個自交系葉夾角性狀的GCA值大小順序為N22＞N8＞N28＞N7＞N23＞N27＞N4，N27的GCA值表現(xiàn)為較大的負(fù)效應(yīng)，其特殊配合力遺傳方差較小，說明N27可作為培育葉夾角較小、株型緊湊的優(yōu)良組合的理想親本。糯玉米葉夾角性狀的遺傳符合"加性-顯性-上位性"模型，葉夾角性狀的增效受隱性基因控制，葉夾角性狀的廣義遺傳率較低，為68.50%，狹義遺傳率較高，為72.62%，在育種實踐中，宜早代選擇。

糯玉米；葉夾角；配合力；遺傳特性II.The combining ability effect and genetic parameters of leaf angle trait in fresh waxy corn were analyzed,and the genetic characteristics of leaf angle in corn were discussed,providing theoretical basis and reference for the breeding of high density-resistant waxy corn inbred lines and compact hybrids.

國家農(nóng)業(yè)部公益性農(nóng)業(yè)科研專項（201303008）；廣東省級現(xiàn)代農(nóng)業(yè)科技創(chuàng)新、推廣與信息化建設(shè)專項資金——現(xiàn)代種業(yè)提升工程項目（財農(nóng)［2014］492號）廣東省科技計劃項目（2012B020301006）；廣東省農(nóng)業(yè)廳特用玉米育種攻關(guān)專項（B3071328）。

陳趣（1989-），男，廣東湛江人，碩士研究生，主要從事玉米遺傳育種研究，E-mail：774990480@qq.com。*通訊作者。王曉明，教授，博士生導(dǎo)師，主要從事玉米遺傳育種研究，E-mail：wxm1724@sina.com；劉鵬飛，講師，博士，主要從事玉米遺傳育種研究，E-mail：lpf2004buildit@aliyun.com。

2015-04-21

修回日期 2015-05-26

Supported by Special Fund for Agro-scientific Research in the Public Interest of China (201303008);Special Funds for Modern Agricultural Science and Technology Innovation,Promotion and Information Construction in Guangdong Province(YCN[2014] 492);Science and Technology Plan Project of Guangdong Province(2012B020301006); Key Breeding Project for Special Maize of Department of Agriculture of Guangdong Province(B3071328).

*Corresponding author.E-mail:wxm1724@sina.com;lpf2004buildit@aliyun.com

Received:April 21,2015 Accepted:May 26,2015