Image_1_Dissecting the Genetic Basis Underlying Combining Ability of Plant Height Related Traits in Maize.TIF

<p>Maize plant height related traits including plant height, ear height, and internode number are tightly linked with biomass, planting density, and grain yield in the field. Previous studies have focused on understanding the genetic basis of plant architecture traits per se, but the genetic basis of combining ability remains poorly understood. In this study, 328 recombinant inbred lines were inter-group crossed with two testers to produce 656 hybrids using the North Carolina II mating design. Both of the parental lines and hybrids were evaluated in two summer maize-growing regions of China in 2015 and 2016. QTL mapping highlighted that 7 out of 16 QTL detected for RILs per se could be simultaneously detected for general combining ability (GCA) effects, suggesting that GCA effects and the traits were genetically controlled by different sets of loci. Among the 35 QTL identified for hybrid performance, 57.1% and 28.5% QTL overlapped with additive/GCA and non-additive/SCA effects, suggesting that the small percentage of hybrid variance due to SCA effects in our design. Two QTL hotspots, located on chromosomes 5 and 10 and including the qPH5-1 and qPH10 loci, were validated for plant height related traits by Ye478 derivatives. Notably, the qPH5-1 locus could simultaneously affect the RILs per se and GCA effects while the qPH10, a major QTL (PVE > 10%) with pleiotropic effects, only affected the GCA effects. These results provide evidence that more attention should be focused on loci that influence combining ability directly in maize hybrid breeding.</p

Maize kernel zein accumulation of liao2345/<i>o2</i>-1, liao2345/<i>o2</i>-2, liao2345, and CA339 in mature seeds, detected by SDS/PAGE.

<p>Total zein loaded in each lane is equal to 1 mg of mature seed endosperm, and the relative molecular weights of proteins are marked at the right side, the unit is kDa.</p

Table_1_Dissecting the Genetic Basis Underlying Combining Ability of Plant Height Related Traits in Maize.DOCX

<p>Maize plant height related traits including plant height, ear height, and internode number are tightly linked with biomass, planting density, and grain yield in the field. Previous studies have focused on understanding the genetic basis of plant architecture traits per se, but the genetic basis of combining ability remains poorly understood. In this study, 328 recombinant inbred lines were inter-group crossed with two testers to produce 656 hybrids using the North Carolina II mating design. Both of the parental lines and hybrids were evaluated in two summer maize-growing regions of China in 2015 and 2016. QTL mapping highlighted that 7 out of 16 QTL detected for RILs per se could be simultaneously detected for general combining ability (GCA) effects, suggesting that GCA effects and the traits were genetically controlled by different sets of loci. Among the 35 QTL identified for hybrid performance, 57.1% and 28.5% QTL overlapped with additive/GCA and non-additive/SCA effects, suggesting that the small percentage of hybrid variance due to SCA effects in our design. Two QTL hotspots, located on chromosomes 5 and 10 and including the qPH5-1 and qPH10 loci, were validated for plant height related traits by Ye478 derivatives. Notably, the qPH5-1 locus could simultaneously affect the RILs per se and GCA effects while the qPH10, a major QTL (PVE > 10%) with pleiotropic effects, only affected the GCA effects. These results provide evidence that more attention should be focused on loci that influence combining ability directly in maize hybrid breeding.</p

Table_2_Dissecting the Genetic Basis Underlying Combining Ability of Plant Height Related Traits in Maize.DOCX

<p>Maize plant height related traits including plant height, ear height, and internode number are tightly linked with biomass, planting density, and grain yield in the field. Previous studies have focused on understanding the genetic basis of plant architecture traits per se, but the genetic basis of combining ability remains poorly understood. In this study, 328 recombinant inbred lines were inter-group crossed with two testers to produce 656 hybrids using the North Carolina II mating design. Both of the parental lines and hybrids were evaluated in two summer maize-growing regions of China in 2015 and 2016. QTL mapping highlighted that 7 out of 16 QTL detected for RILs per se could be simultaneously detected for general combining ability (GCA) effects, suggesting that GCA effects and the traits were genetically controlled by different sets of loci. Among the 35 QTL identified for hybrid performance, 57.1% and 28.5% QTL overlapped with additive/GCA and non-additive/SCA effects, suggesting that the small percentage of hybrid variance due to SCA effects in our design. Two QTL hotspots, located on chromosomes 5 and 10 and including the qPH5-1 and qPH10 loci, were validated for plant height related traits by Ye478 derivatives. Notably, the qPH5-1 locus could simultaneously affect the RILs per se and GCA effects while the qPH10, a major QTL (PVE > 10%) with pleiotropic effects, only affected the GCA effects. These results provide evidence that more attention should be focused on loci that influence combining ability directly in maize hybrid breeding.</p

Structure of the <i>O2</i> gene and specific site of each sequence primer.

<p>Structure of the <i>O2</i> gene and specific site of each sequence primer.</p

Examination of the <i>O2</i> gene transcript abundance in developing endosperm (18 DAP) by RT-PCR.

<p>O2RT1 and O2RT2 are two specific primers spanning the third and the fifth exon of the <i>O2</i> gene, the amplified region of ORT2 is larger than that of O2RT1; GAPDH is the reference gene. The templates of RT-PCR are labeled in each line, H₂O represents the blank control; RNA represents the negative control; cDNA is used to detect abundance of the <i>O2</i> transcript.</p

Maize kernel phenotypes of liao2345/<i>o2</i>-1, liao23455/<i>o2</i>-2, and liao2345; <i>o2o2</i>, <i>o2o2</i>, <i>O2O2</i>.

<p>A: Photographs of intact kernels taken under normal light on light box. B: Photographs of intact kernels taken with transmitted light. C: Photographs of decapped kernels taken under normal light.</p

Test of three SSR markers inside the <i>O2</i> gene by PAGE.

<p>phi112, umc1066, and phi057 can distinguish the three genotype of the <i>O2</i> gene. The amplified region of phi112 located in the promoter of <i>O2</i> the gene; and umc1066 in the first exon of the <i>O2</i> gene; and phi057 in the sixth exon of the <i>O2</i> gene.</p

Analysis of chromosome segments introgression of <i>O2</i> based on SSR markers mapping to bin7.01.

<p>The positions of SSR markers are based on a map from IBM2 2008 Neighbors 7. The red fragments (A) are of recurrent parent origin, blue fragments (B) are of donor origin, and gray fragments (U) represent markers that have no polymorphism between the two parents, and have no information for that genotype.</p

Image_3_Dissecting the Genetic Basis Underlying Combining Ability of Plant Height Related Traits in Maize.TIF

<p>Maize plant height related traits including plant height, ear height, and internode number are tightly linked with biomass, planting density, and grain yield in the field. Previous studies have focused on understanding the genetic basis of plant architecture traits per se, but the genetic basis of combining ability remains poorly understood. In this study, 328 recombinant inbred lines were inter-group crossed with two testers to produce 656 hybrids using the North Carolina II mating design. Both of the parental lines and hybrids were evaluated in two summer maize-growing regions of China in 2015 and 2016. QTL mapping highlighted that 7 out of 16 QTL detected for RILs per se could be simultaneously detected for general combining ability (GCA) effects, suggesting that GCA effects and the traits were genetically controlled by different sets of loci. Among the 35 QTL identified for hybrid performance, 57.1% and 28.5% QTL overlapped with additive/GCA and non-additive/SCA effects, suggesting that the small percentage of hybrid variance due to SCA effects in our design. Two QTL hotspots, located on chromosomes 5 and 10 and including the qPH5-1 and qPH10 loci, were validated for plant height related traits by Ye478 derivatives. Notably, the qPH5-1 locus could simultaneously affect the RILs per se and GCA effects while the qPH10, a major QTL (PVE > 10%) with pleiotropic effects, only affected the GCA effects. These results provide evidence that more attention should be focused on loci that influence combining ability directly in maize hybrid breeding.</p