Van Deventer, C. S.Ranthamane, Matla Martin2017-06-192017-06-192001-12http://hdl.handle.net/11660/6374English: The general objectives of this research were to study the genetic variability for nitrogen use efficiency components, to identify suitable inbred parental lines with out standing nitrogen efficiency characteristics, to calculate the inheritance of nitrogen use efficiency (NUE) components and to develop a strategy for the development of nitrogen efficient maize hybrids. Four parental lines (AC8342, CML394, K64R and M162W) were individually crossed to each tester (CML351, CML202 and CML216) in a Line x Tester fashion to produce FI hybrids seed. The FI hybrids were evaluated in two different environments each under two different nitrogen levels. Six agronomic and yield characteristics and three nitrogen use efficiency components were measured. The data were analysed using the computer program' AGROBASE 2000'. Analyses such as Line x Tester, additive main effects and genetic correlations were performed. In the combined ANOVA, significant differences between locations were found for all characters measured. The nitrogen levels differed significantly for PLHT and GNC. The FI hybrids differed significantly for PLHT, GY, SDW, SDN and GNC. Significant differences were also found among the FI hybrids for PLHT, GY, SDW, SDN, HI, GNC and SNC at Doompan. Similar significant differences were observed at Bethlehem except for HI and SNC. Significant variability between FI hybrids was observed for yield efficiency, recovery efficiency and physiological efficiency. There was a large'" environmental difference between locations for the nitrogen use efficiency components. In the simple ANOVA, significant differences between FI hybrids were observed for yield efficiency, recovery efficiency and physiological efficiency at Doompan. Significant differences were also . found between the FI hybrids for yield efficiency and recovery efficiency at Bethlehem. With a few exceptions in the Bethlehem trial, the selection indices of the F, hybrids for PLHT were less than one. The selection index for GY exceeds the value of one in three and nine of the F, hybrids in the Doornpan and Bethlehem trials respectively. For SOW three of the F, hybrids in the Doornpan trial had values above one and nine of the F, hybrids in the Bethlehem trial. The selection index values for SDN were lower than one in the Doornpan trial. In the Bethlehem trial the values of three of the crosses were larger than one. The selection indices for HI in both trials were relatively high. At Ooornpan the F, hybrids responded significantly different to the two N-Ievels for PLHT, GY, SDW, SDN, HI and GNC. Significant differences between the F, hybrids at the low N-Ievel were found for all characters measured except for SNC. At the high N-level the F, hybrids differed significantly for PLHT, GY, SDW, SDN, HI and GNC. At Bethlehem, FI hybrids responded significantly different to the two N-levels for GY, SON and HI. Significant differences were found between the F, hybrids at both N-levels for PLHT, GY, SDW, SDN and GNC. At Doornpan significant differences existed between the F, hybrids for yield efficiency, recovery efficiency and physiological efficiency. At Bethlehem significant variability was found between the FI hybrids for all three nitrogen use efficiency components. The two N-Ievels had a significant effect on the GCA-values of the lines and testers for PLHT and SDN in the Doornpan trial. Significant variability was also found between the GCA-values for PLHT, GY and SDN at both N-levels. The GCA-values of the inbred lines in the Bethlehem trial responded differently to the two N-Ievels for GY and SON. Significant differences were found between the GCA-values of the inbred lines for PLHT at both N-Ievels and for GY only between the testers at the high N-Ievel. At Doornpan significant differences between the GCA-values of the lines were found only for physiological efficiency and between the testers for yield efficiency and recovery efficiency. At Bethlehem the GCA-values for testers differed significantly for yield efficiency and recovery efficiency. No significant differences were found between. the GCA-values of the lines for nitrogen use efficiency components at Bethlehem. The FI hybrids responded differently with regard to their SCA-values for GY, SOW. HI, GNC and SNC in the Doornpan trial. Significant differences for SCA-values were found for PLHT, GY, SOW, SON and SNC at both N-Ievels. In the Bethlehem trial the two N-levels had only an effect on the SCA-values of a few of the hybrids for SON and GNC. Significant differences were found between the SCA-values of the FI hybrids for PLHT, GY, SOW, SON and GNC at both the low and the high N-Ievels. The F I hybrids showed significant differences between the SCA-values for all three nitrogen use efficiency components in the Doornpan trial and only for yield efficiency and recovery efficiency in the Bethlehem trial. The GCA:SCA ratios differed significantly at the two N-levels for PLHT in the Doornpan trial. With the exception of SON the additive variance components of SOW, GNC and SNC were higher at the high N-level. In the Bethlehem trial the GCA:SCA ratios for PLHT, SDW and GNC were higher at the high N-level. SOW had the largest GCA:SCA ratios under both N-levels. The GCA:SCA ratios for recovery efficiency was larger than that of yield efficiency. In the Doornpan trial the narrow-sense heritabilities for PLHT and GNC were the largest under the high N-level. The narrow-sense heritabilities for nitrogen use efficiency components were very low. The narrow-sense heritabilities of PLHT, GY, SOW, GNC and SNC were much larger at the high N-Ievel at Bethlehem. Again the heritabilities obtained for nitrogen use efficiency components were very low. Significant phenotypic correlation coefficients were found between GY and PLHT at the high N-Ievel in the Doompan trial. Significant correlation coefficients were also found between GY and SDN at both N-Ievels. In the Bethlehem trail significant correlation coefficients existed between GY and PLHT and between GY and SON at both N-levels. GNC was significant but negatively correlated with GY at the high N-level. The genotypic correlation coefficients in the Doompan trial were significant between GY . and SDN and between GY and SNC at both N-Ievels. HI and GY were significantly correlated at the high N-Ievel. In the Bethlehem trial SDN was highly correlated with GY at both N-levels. GY was significantly correlated with PLHT at the high N-level, negatively correlated with SDW at the low N-Ievel and negatively correlated with GNC at the high N-Ievel. In the Doompan trial GY at the low arid the high N-levels was significantly correlated with yield efficiency. It was also significantly correlated with recovery efficiency at the high N-level. In the Bethlehem trial GY was significantly correlated with the three nitrogen use efficiency components at the high N-level. Recovery efficiency was significantly correlated with GY at the low N-level.Afrikaans: Die algemene doel van hierdie studie was die bestudering van die genetiese variabiliteit vir stikstof gebruik effektiwiteit, die identifisering van geskikte ingeteelde ouerlyne met uitstaande stikstof gebruik eienskappe, asook die bepaling van die oorerflikheid van die stikstof gebruik effektiwiteit en die ontwikkeling van 'n strategie vir die ontwikkeling van stikstof effektiewe mielie basters. Vier ouer lyne (AC8342, CML394, K64R, en M162W) is elk individueel gekruis met die toetsers (CML351, CML202 en CML216). 'n Lyn x toetser model is gebruik om die FI baster saad te produseer. Die F I basters is in twee verskillende omgewings, elk met twee verskillende stikstof vlakke geëvalueer. Ses agronomiese en opbrengs eienskappe en drie stikstof gebruik komponente is gemeet. Die data is geanaliseer deur die rekenaar program 'Agrobase 2000'. Analises vir lyn x toetser, additiewe hoof effekte en genetiese korrelasie is uitgevoer. Volgens die gekombineerde ANOVA is betekenisvolle verskille tussen die lokaliteite waargeneem vir alle eienskappe wat gemeet is. Die stikstof vlakke het vir PLHT en GNC betekenisvol verskil. Die F I basters het betekenisvolle verskille getoon vir PLHT, GY, SDW, SDN en GNC. Betekenisvolle verskille is ook gevind vir die FI basters by Doompan vir PLHT, GY, SDW, SDN Hl, GNC en SNC. Dieselfde betekenisvolle verskille is ook waargeneem vir die FI basters by Bethlehem behalwe vir Hl en SNC. Betekenisvolle variabiliteit tussen FI basters IS waargeneem vrr opbrengsvermoë, herstelvermoë en fisiologies prestasie. Daar was 'n groot omgewings verskil tussen lokaliteite vir die effektiewe stikstof gebruik komponente. In die eenvoudige ANOV A, was daar betekenisvolle verskille tussen die FI basters by Doompan vir opbrengsvermoë, . herstelvermoë en die fisiologies prestasie waargeneem. Betekenisvolle verskille is ook in die proefby Bethlehem gevind tussen die FI basters vir opbrengsvermoë en herstelvermoë Met 'n paar uitsonderings in die Bethlehem proef, was die seleksie indeks vir die FI basters vir PLHT minder as een. Die seleksie indeks vir GY was groter as een in drie en nege van die FI basters in die Doompan en Bethlehem proewe onderskeidelik. Vir SDW het drie van die F, basters in die Doornpan proef waardes bo een getoon en nege van die F, basters in die Bethlehem proef. Die seleksie indeks waardes vir SDN was laer as een in die Doornpan proef. In die Bethlehem proef was die waardes vir drie van die kruisings groter as een. Die seleksie indeks vir Hl was relatief hoog vir albei proewe. By Doornpan het die F, basters betekenisvol verskillend gereageer op die twee N-vlakke vir PLHT, GY, SDW, SDN, Hl en GNC. Betekenisvolle verskille tussen die F, basters by die lae N-vlak is gevind vir alle eienskappe wat gemeet, behalwe vir SNC. By die hoë Nvlak het die F, basters betekenisvol verskil vir PLHT, GY, SDW, SDN, Hl en GNC. Die F, basters by Bethlehem het betekenisvolle verskille getoon by die twee Nvvlakke vir GY, SDN en Hl. Betekenisvolle verskille is gevind tussen die F, basters by albei N-vlakke vir PLHT, GY, SDW, SDN en GNC. By Doornpan het betekenisvolle verskillle bestaan tussen die F, basters VIr opbrengsvermoë, herstelvermoë en fisiologiese effektiwiteit. By Bethlehem het betekenisvolle verskille voorgekom tussen die F, basters vir al drie stikstof verbruik effektiwiteit komponente. Die twee Nvvlakke het 'n betekenisvolle effek op die GCA-waarde vir die lyne en toetsers vir PLHT en SDN by die Doornpan proef getoon. Betekenisvolle variabiliteit is ook tussen die GCA-waardes vir PLHT, GY, en SDN by albei N-vlakke gevind. Die GCA-waarde vir die ingeteelde lyne in die Bethlehem proef het verskillend gereageer vir die twee N-vlakke vir GY en SDN. Betekenisvolle verskille is tussen die GCA-waarde vir die ingeteelde lyne vir PLHT by beide N-vlakke en vir GV slegs tussen die toetser by hoë N-vlakke gevind. By Doornpan is betekenisvolle verskille tussen die GCA-waardes v,ir die lyne slegs vir die fisiologiese persentasie gevind en tussen die toetsers vir opbrengsvermoë en herstelvermoë. By Bethlehem het die GCA-waarde vir die toetsers betekenisvol verskil vir opbrengsvermoë en herstelvermoë. Geen betekenisvolle verskil is tussen die GCAwaardes van die lyne vir effektiewe stikstof gebruik komponente by Bethlehem gevind nie. Die F, basters het verskillend gereageer ten opsigte van die SCA-waarde vir GY; SDW, Hl, GNC en SNC in die proef by Doornpan. Betekenisvolle verskille vir die SCA-waarde vir PLHT, GY, SDW, SDN en SNC by albei Nvvlakke is waargeneem. In die Bethlehem proef het die twee Nvvlakke slegs 'n effek getoon tussen die SCA-waardes van 'n paar basters vir SON en GNC. Betekenisvolle verskille is tussen die SCA-waardes van die F, basters vir PLHT, GY, SOW en GNC by beide hoë en lae N-vlakke gevind. Die F, basters het betekenisvolle verskille getoon vir SCA-waardes vir al drie die effektiewe stikstof gebruik komponente in die Doompan proef en selgs vir die opbrengsvermoë en herstelvermoë in die Bethlehem proef. Die GCA:SCA verhouding het betekenisvol verskil by die twee N-vlakke vir PLHT in die Doompan proef. Met die uitsondering van SON, was die additiewe afwykings komponente vir SDW, GNC en SNC ook hoër by die hoë N-vlak. In die Bethlehem proef was die GCA:SCA verhouding vir PLHT, SDW en GNC weer hoër by die hoë N-vlak. SOW het die grootste GCA:SCA verhouding vir beide N-vlakke getoon. Die GCA:SCA verhouding vir herstelvermoë was groter as die vir opbrengsvermoë. In die Doompan proef was die smal sin oorerflikheid vir PLHT en GNC die grootste onder die invloed van die hoë N-vlak. Die smal sin oorerflikheid vir die effektiewe stikstof gebruik komponente was baie laag. Die smal sin oorerflikheid vir PLHT, GY, SOW, GNC en SNC was baie groter by die hoë N-vlak in die Bethlehem proef. Die oorerflikheid verkry vir die effektiewe stikstof gebruik komponente was baie laag. 'n Betekenisvolle fenotipiese korrelasie koëffisient is gevind tussen GY en PLHT by die hoër N-vlak in die Doompan proef. Betekenisvolle korrelasie koëffisiente is ook tussen GY en SDN by beide Nvvlakke gevind. In die Bethlehem proef het betekenisvolle korrelasie koëffisiente bestaan tussen GY en PLHT en tussen GY en SON vir beide Nvlakke. GNC was betekenisvol maar negatief gekorreleer met G1" by die hoë N-vlak. Die genotipiese korrelasie koëffisient in die Doompan proef was betekenisvol tussen GY en SDN en tussen GY en SNC vir albei die N-vlakke. Hl en GY was betekenisvol gekorreleer by die hoë N-vlak. In die Bethlehem proefwas SON sterk gekorreleer met GY by beide N-vlakke. GY was betekenisvol gekorreleer met PLHT by die hoë Nvvlak, maar negatief gekorreleer met SDW by die lae N-vlak en negatief gekorreleer met GNC by die "hoë N-vlak. In die Doompan proefhet GY by die lae en hoë N-vlakke betekenisvol gekorreleer met die opbrengsvermoë. Dit was ook betekenisvol gekorreleer met herstelvermoë by die hoë Nvlak. In die Bethlehem proef was GY betekenisvol gekorreleer met die drie effektiewe stikstof gebruik komponente op 'n hoë N-vlak. Herstelvermoë was ook betekenisvol gekorreleer met GY op 'n lae N-vlak.enThesis (Ph.D. (Plant Breeding))--University of the Free State, 2001ThesisUniversity of the Free State