Identification of QTL associated with nitrogen metabolism in a maize (Zea mays L. ssp. mays) testcross population

Maize is a widely cultivated crop in the world and its production relies heavily on nitrogen (N) fertilization. N is an essential mineral nutrient for plant growth and development. However, during the last decades excessive quantities of N have been applied by farmers, a surplus to what maize plants can uptake, and several problems have arisen, such as pollution of the ecosystem and an economic loss to farmers. Breeding maize hybrids that are more efficient in the use of N is a long term goal for plant breeders. Nonetheless, previous to breeding, the genetic basis of N-metabolism in maize would need to be elucidated. Herein, maize testcrosses (TC), derived from the IBMSyn10-DH crossed by an elite inbred, were: 1) Grown in hydroponic condition and several physiological traits related to N-metabolism were assessed on leaf and root tissues. After performing statistical analyses, quantitative trait loci (QTL) were identified; 2) Grown in field conditions under low and high N, several agronomic traits were determined, and statistical and QTL analyses were implemented. A novel statistical approach was implemented to differentiate experimental errors from truthful phenotypic records in order to remove them for further genetic analysis. This automated method for outlier determination helped to focus the analysis on real data and obtain more reliable QTL mapping results. Several QTL associated with N-metabolism were determined and numerous candidate genes underlying QTL genomic regions are proposed for further analysis. At least one rich QTL region, presenting three or more overlapping confidence intervals for QTL, were determined at each of the ten chromosomes. These genomic regions may be valuable in the determination of N-metabolism in maize TC

Genetic and agronomic assessment of cob traits in corn under low and normal nitrogen management conditions

With rising energy demands and costs for fossil fuels, alternative energy from renewable sources such as maize cobs will become competitive. Maize cobs have beneficial characteristics for utilization as feedstock including compact tissue, high cellulose content, and low ash and nitrogen content. Nitrogen is quantitatively the most important nutrient for plant growth. However, the influence of nitrogen fertilization on maize cob production is unclear. In this study, quantitative trait loci (QTL) have been analyzed for cob morphological traits such as cob weight, volume, length, diameter and cob tissue density, and grain yield under normal and low nitrogen regimes. 213 doubled-haploid lines of the intermated B73 × Mo17 (IBM) Syn10 population have been resequenced for 8575 bins, based on SNP markers. A total of 138 QTL were found for six traits across six trials using composite interval mapping with ten cofactors and empirical comparison-wise thresholds (P = 0.001). Despite moderate to high repeatabilities across trials, few QTL were consistent across trials and overall levels of explained phenotypic variance were lower than expected some of the cob trait × trial combinations (R2 = 7.3–43.1 %). Variation for cob traits was less affected by nitrogen conditions than by grain yield. Thus, the economics of cob usage under low nitrogen regimes is promising

Identification of QTL associated with nitrogen metabolism in a maize (Zea mays L. ssp. mays) testcross population

Maize is a widely cultivated crop in the world and its production relies heavily on nitrogen (N) fertilization. N is an essential mineral nutrient for plant growth and development. However, during the last decades excessive quantities of N have been applied by farmers, a surplus to what maize plants can uptake, and several problems have arisen, such as pollution of the ecosystem and an economic loss to farmers. Breeding maize hybrids that are more efficient in the use of N is a long term goal for plant breeders. Nonetheless, previous to breeding, the genetic basis of N-metabolism in maize would need to be elucidated. Herein, maize testcrosses (TC), derived from the IBMSyn10-DH crossed by an elite inbred, were: 1) Grown in hydroponic condition and several physiological traits related to N-metabolism were assessed on leaf and root tissues. After performing statistical analyses, quantitative trait loci (QTL) were identified; 2) Grown in field conditions under low and high N, several agronomic traits were determined, and statistical and QTL analyses were implemented. A novel statistical approach was implemented to differentiate experimental errors from truthful phenotypic records in order to remove them for further genetic analysis. This automated method for outlier determination helped to focus the analysis on real data and obtain more reliable QTL mapping results. Several QTL associated with N-metabolism were determined and numerous candidate genes underlying QTL genomic regions are proposed for further analysis. At least one rich QTL region, presenting three or more overlapping confidence intervals for QTL, were determined at each of the ten chromosomes. These genomic regions may be valuable in the determination of N-metabolism in maize TC.</p

Genetic and agronomic assessment of cob traits in corn under low and normal nitrogen management conditions

With rising energy demands and costs for fossil fuels, alternative energy from renewable sources such as maize cobs will become competitive. Maize cobs have beneficial characteristics for utilization as feedstock including compact tissue, high cellulose content, and low ash and nitrogen content. Nitrogen is quantitatively the most important nutrient for plant growth. However, the influence of nitrogen fertilization on maize cob production is unclear. In this study, quantitative trait loci (QTL) have been analyzed for cob morphological traits such as cob weight, volume, length, diameter and cob tissue density, and grain yield under normal and low nitrogen regimes. 213 doubled-haploid lines of the intermated B73 × Mo17 (IBM) Syn10 population have been resequenced for 8575 bins, based on SNP markers. A total of 138 QTL were found for six traits across six trials using composite interval mapping with ten cofactors and empirical comparison-wise thresholds (P = 0.001). Despite moderate to high repeatabilities across trials, few QTL were consistent across trials and overall levels of explained phenotypic variance were lower than expected some of the cob trait × trial combinations (R2 = 7.3–43.1 %). Variation for cob traits was less affected by nitrogen conditions than by grain yield. Thus, the economics of cob usage under low nitrogen regimes is promising.This article is published as Jansen, Constantin, Yongzhong Zhang, Hongjun Liu, Pedro J. Gonzalez-Portilla, Nick Lauter, Bharath Kumar, Ignacio Trucillo-Silva et al. "Genetic and agronomic assessment of cob traits in corn under low and normal nitrogen management conditions." Theoretical and applied genetics 128, no. 7 (2015): 1231-1242. 10.1007/s00122-015-2486-0. Posted with permission.</p

Genetic and agronomic assessment of cob traits in corn under low and normal nitrogen management conditions

AbstractKey message Exploring and understanding the geneticbasis of cob biomass in relation to grain yield undervarying nitrogen management regimes will help breedersto develop dual-purpose maize.Abstract With rising energy demands and costs for fossilfuels, alternative energy from renewable sources suchas maize cobs will become competitive. Maize cobs havebeneficial characteristics for utilization as feedstock includingcompact tissue, high cellulose content, and low ashand nitrogen content. Nitrogen is quantitatively the mos