Inheritance of nitrogen use efficiency components in South African irrigated wheat - Otto, Willem Morkel (University of the Free State, 2007)
In a second experiment, the NUE components of seven parental irrigation cultivars and their F2-offspring were studied in 2004 at a cooler (Bethlehem) and a warmer (Vaalharts) irrigation environment. The genotypes were tested at two N treatments; a control (LN) and 180 kg N/ha (HN) applied. Agronomic characteristics, N uptake and NUE components were measured. From the analysis of variance, the agronomic characteristics (BM, grain yield, HM, TKM and GP) showed significant genotypic variation. Harvest index, BM, HM and TKM showed no significant genotypic variation at the N treatment. The N uptake and NUE components showed significant genotypic variation with the exception of NutEYld. The HN treatment resulted in significant variation in Ngrain, Ntotal NHI, NUEYld and NutEYld. The HN treatment increased BM, grain yield and GP values, but reduced the HM, TKM, HI and NHI values of the genotypes. The NUE components NupE%, NUEYld and NutEYld were also reduced by the HN treatment. Cultivars responded differently at the two N treatments in measured and calculated agronomic and NUE components. Olifants, Kariega and Marico showed good responses for the agronomic components at the HN treatment. Inia, SST 806, SST 822, Olifants, Kariega and Marico showed high values for NUE components. The crosses Olifants x Steenbras, SST 806 x SST 822, Marico x Steenbras, Olifants x SST 822 and Marico x SST 806 showed positive responses in the measured agronomical and NUE components. The correlation coefficients were calculated to study the phenotypic resemblance between characteristics. The calculated correlation matrixes for the environments indicated positive correlation coefficients between several of the agronomic and calculated components. Biomass and grain yield was highly correlated with the NUE components, NupE%, NUEYld, Ngrain and Ntotal at both environments. Grain protein was negatively correlated to NutEYld, while NHI was positively correlated to this component. This points to the first order importance of grain yield production before grain protein under limiting N availability conditions. The correlation coefficients of components BM, grain yield, NPE, NRE and NUEYld increased at the HN treatment. The effect of N treatments on the calculated GCA and SCA effects was studied from a diallel analysis. Significant GCA effects for the parental cultivars were found for the majority of the agronomic and NUE components at both N treatments. Significant SCA effects for the tested hybrids were also found at BM, grain yield, Ngrain, Ntotal, NupE%, NUEYld, NAEYld, PHE and NRE. The application of N fertilizer (LN versus HN treatments) affected the significance of the calculated combining abilities. For the agronomic characteristics that were measured at Bethlehem, GCA effects for BM, HM, TKM, GP and HI were significant at the HN treatment. Significant GCA effects were found at the LN treatment for TKM and GP. The N uptake components Ngrain, Ntotal and NHI showed significant GCA effects at the HN treatment. For the NUE efficiency components significant GCA effects were calculated for NupE%, NUEYld and NutEYld at the HN treatment. No significant cultivar differences were found for the N uptake and NUE components at the LN treatment. For the agronomic components SST 822, Inia and Kariega generally had the highest GCA values. The cultivars Marico, Olifants, SST 806 and Inia showed the highest GCA values at the HN treatment for the agronomic, N uptake and NUE components. At Vaalharts significant variability for GCA effects for the agronomic components BM, grain yield, HM, TKM and HI were found at both N treatments. For the N uptake components, significant GCA effects were calculated for Ngrain and Ntotal at both N treatments and for NHI at the HN treatment. Significant GCA effects were found for the NUE components NupE%, NUEYld at both N treatments and for NutEYld at the HN treatment. The cultivars Kariega, Olifants, Inia, Steenbras and SST 806 had the highest GCA values for the agronomic, N uptake and NUE components at the LN treatment. At the HN treatment Olifants, SST 806 and Inia had the highest GCA values for these components, as well as for the N uptake and NUE components. The calculated SCA effects at Bethlehem were significant for BM, grain yield, Ngrain, Ntotal, NUEYld at both N treatments, and for NAEYld, NPE, NRE, HM and NupE% at the HN treatment. At Vaalharts significant SCA effects were calculated for BM, grain yield, Ngrain, Ntotal, NupE%, NUEYld at both N treatments and for NHI at the HN treatment. The calculated GCA:SCA ratios for the respective components at Bethlehem showed that the values for most of the components increased at the HN treatment, with only grain yield, Ngrain and NUEYld at values less than one. The calculated NUE components NAEYld, NPE and NRE also showed non-additive gene action. At Vaalharts all the components showed additive gene action at both the LN and HN treatments, except for GP, NHI and NutEYld at the LN treatment. Also, in contrast to the response calculated at Bethlehem, the calculated NAEYld, NPE and NRE showed additive gene action. These differences in responses between the two environments can be attributed to the different growing conditions and N availability scenarios inducing the changes in response of agronomic and NUE components. High broad-sense heritabilities were calculated for BM, grain yield, HM, TKM and HI at the LN and HN treatments at both environments. At Vaalharts the heritability value for GP was high at the HN treatment, and at Bethlehem at both the LN and HN treatments. Broad-sense heritability estimates improved at the HN treatment except for TKM compared to the LN treatment. The heritability values for the N uptake components, Ngrain, Ntotal and NHI were high, and were increased at the HN treatment. With the exception of the NutEYld component at the LN treatment at Vaalharts, the broad-sense heritability values of all the NUE components were high and increased by the HN treatment. At Bethlehem the narrow-sense heritability value of TKM was high at both N treatments, and values of GP, NHI and NutEYld at the HN treatment. At Vaalharts high narrowsense heritability values were found for HM, TKM, NAEYld and NPE at the LN treatment. All the agronomic characteristics and calculated components showed increased narrowsense heritability values at the HN treatment. These responses indicate that the estimation of heritability of the studied components were improved when N were sufficiently available.

In die studie is die N verbruiksdoeltreffendheid (NUE) van koringcultivars onder besproeiing ondersoek deur graanopbrengs, N opname, agronomiese en fisiologiese NUE komponente te meet. De algemene (GCA) en spesifieke kombineervermoë (SCA) van die genotipes vir NUE komponente is bereken, asook die fenotipiese korrelasie koëffisiënte en oorerflikheidswaardes. Vyf Suid Arikaanse besproeiingscultivars is evalueer vir verskille in agronomiese en NUE komponente in reaksie op N bestuurstrategieë by die Rietrivier en Loskop besproeiingskemas. Die N bestuursbehandelings het ‘n geen (N0) en optimum N bemestingstoediening ingesluit, waarvan laasgenoemde verdeel is in vier N bestuursstrategieë, en is toegepas in 2000 en 2001. Die twee besproeiingsskemas het verskil in residuele minerale N in die grond met planttyd in 2000 and 2001. Die variansie analises vir graanopbrengs, Ngraan, Ntotaal, NHI, NAE, NRE en NPE toon dat die hoofeffekte cultivar en N behandeling en die interaksie tussen die hoofeffekte nie konstant reageer het by die twee besproeiingskemas oor die twee seisoene nie. Die effek van residuele minerale N in die grond het tot lae graanopbrengste by die N0 behandeling gelei by Rietrivier in 2000 in vergelyking met 2001. In ooreenstemming hiermee was die graanopbrengs van die N0 behandeling by Loskop met ‘n verlaagde residuele minerale N met plant laer in 2001 in vergelyking met 2000. Betekenisvolle genotipiese variasie is gevind vir die agronomiese eienskappe (BM, graan opbrengs, HM, DKM en GP). Oesindeks, BM, HM en DKM toon geen betekenisvolle genotipiese variasie vir die N behandelings nie. Die N opname en NUE komponente toon betekenisvolle genotipiese variasie met die uitsondering van NutEYld. Die HN behandeling het betekenisvolle variasie in Ngraan, Ntotaal, NHI en NutEYld tot gevolg gehad. Die HN behandeling verhoog BM, graanopbrengs en GP, maar verlaag die HM, DKM, HI en NHI waardes van die genotipes. Die NUE komponente NupE%, NUEYld en NutEYld word ook verlaag deur die HN behandeling. Die cultivars reageer verskillend in agronomiese en NUE komponente. Olifants, Kariega en Marico toon goeie reaksie in agronomiese eienskappe by die HN behandeling. Inia, SST 806, SST 822, Olifants, Kariega en Marico toon verhoogde NUE komponente. Die kruisings Olifants x Steenbras, SST 806 x SST 822, Marico x Steenbras, Olifants x SST 822 en Marico x SST 806 toon ook positiewe reaksie in agronomiese en NUE komponente. Korrelasiekoëffisiënte is bereken om die fenotipiese ooreenstemmings tussen komponente te bepaal. Die berekende koëffisiënte vir die twee omgewings toon positiewe korrelasies tussen verskeie van die agronomiese en berekende komponente. Biomassa en graanopbrengs is hoogs gekorreleer met die NUE komponente, NupE%, NUEYld, Ngraan en Ntotaal. Graanproteïen is negatief gekorreleerd met NutEYld, terwyl die komponent positief met NHI gekorreleer is. Dit dui op die voorkeur van graanopbrengsvorming bo graanproteïen onder beperkte N beskikbaarheidstoestande. Die korrelasie koëffisiënte van die komponente BM, graanopbrengs, NPE, NRE en NUEYld is verhoog by die HN behandeling. Die effek van N behandelings op die GCA en SCA waardes is met ‘n diallel-analise bestudeer. Betekenisvolle GCA effekte vir die ouer cultivars is gevind vir die meerderheid gemete agronomiese en NUE komponente by albei N behandelings. Betekenisvolle SCA effekte is ook gevind vir BM, graanopbrengs, Ngraan, Ntotaal, NupE%, NUEYld, NAEYld, PHE en NRE. Die toediening van N bemesting (LN versus HN behandelings) het die betekenisvolheid van die berekende effekte beïnvloed. Die GCA effekte vir die agronomiese eienskappe BM, HM, TKM, GP en HI was betekenisvol by die HN behandeling op Bethlehem. Betekenisvolle GCA effekte vir DKM en GP is by die LN behandeling gevind. Die N opname komponente Ngraan, Ntotaal en NHI het betekenisvolle GCA effekte by die HN behandeling getoon. Betekenisvolle GCA effekte is bereken vir die NUE komponente NupE%, NUEYld en NutEYld by die HN behandeling. Geen betekenisvolle cultivarverskille is gevind vir N opname en NUE komponente by die LN behandeling nie. Die cultivars SST 822, Inia en Kariega het die hoogste GCA effekte vir die agronomiese eienskappe gehad. Die cultivars Marico, Olifants, SST 806 en Inia het die hoogste GCA gehad vir agronomiese, N opname en NUE komponente by die HN behandeling. Betekenisvolle GCA effekte is vir die agronomiese eienskappe BM, graanopbrengs, HM, DKM en HI bereken vir albei N behandelings op Vaalharts. Betekenisvolle GCA effekte is ook bereken vir die N opname komponente Ngraan en Ntotaal vir albei N behandelings, en vir NHI by die HN behandeling. Die NUE komponente NupE% en NUEYld het betekenisvolle GCA effekte getoon by albei N behandelings, en vir NutEYld by die HN behandeling. Die cultivars Kariega, Olifants, Inia, Steenbras en SST 806 het die hoogste GCA waardes gehad vir die agronomiese, N opname en NUE komponente by die LN behandeling. Olifants, SST 806 en Inia het die hoogste GCA waardes gehad vir die agronomiese, N opname en NUE komponente by die HN behandeling. Die berekende SCA effekte vir BM, graanopbrengs, Ngraan, Ntotaal, NUEYld was betekenisvol op Bethlehem by albei N behandelings, en vir NAEYld, NPE, NRE, HM en NupE% by die HN behandeling. Betekenisvolle SCA effekte is op Vaalharts bereken vir BM, graanopbrengs, Ngraan, Ntotaal, NupE% en NUEYld by albei N behandelings, en vir NHI by die HN behandeling. Die verhouding GCA:SCA is bereken vir die gemete komponente en vir Bethlehem het die waardes van die meerderheid komponente toegeneem by die HN behandeling, met slegs graanopbrengs, Ngraan en NUEYld met waardes onder een. Die berekende NUE komponente NAEYld, NPE en NRE het ook nie-additiewe geenwerking getoon. Vir Vaalharts het al die komponente additiewe geenwerking getoon by die LN en HN behandelings, met die uitsonderings van GP, NHI en NutEYld by die LN behandeling. In teenstelling met die reaksie gemeet op Bethlehem, het die berekende NAEYld, NPE en NRE komponente additiewe geenwerking getoon. Die verskille tussen die twee omgewings kan toegeskryf word aan die verskille in groeitoestande en N beskikbaarheid wat gelei het tot verskillende reaksies in agronomiese en NUE komponente. Hoë meer algemene oorerflikheidswaardes is bereken vir BM, graanopbrengs, HM, TKM en HI vir die LN en HN behandelings vir beide omgewings. Vir Vaalharts was die oorerflikheid hoog vir GP by die HN behandeling, en vir Bethlehem by beide die LN en HN behandelings. Die meer algemene oorerflikheidwaardes is verhoog by die HN behandelings behalwe vir DKM in vergelyking met die LN behandeling. Die algemene oorerflikheidswaardes vir die N opname komponente, Ngraan, Ntotaal en NHI was hoog, en is verder verhoog by die HN behandeling. Met die uitsondering van die NutEYld komponent by die LN behandeling op Vaalharts, was die algemene oorerfliheidswaardes van al die NUE komponente hoog en is verder verhoog by die HN behandeling. Vir Bethlehem was die meer spesifieke oorerflikheidswaarde van DKM hoog by beide N behandelings, terwyl oorerflikheidswaardes vir GP, NHI en NutEYld hoog was by die HN behandeling. Vir Vaalharts is hoë meer spesifieke oorerflikheidswaardes bereken vir HM, DKM, NAEYld en NPE by die LN behandeling. Al die agronomiese en berekende komponente het verhoogde meer spesifieke oorerflikheidswaardes getoon by die HN behandeling. Hierdie reaksies dui daarop dat die skatting van oorerflikheid van die komponente wat ondersoek is verhoog is onder toestande waar N voldoende beskikbaar was.
Thesis (Ph.D. (Plant Sciences (Plant Breeding)/Soil Sciences)--University of the Free State, 2007
Keywords: Nitrogen fertilizers; Wheat -- Fertilizers -- South Africa; Wheat -- Yields -- South Africa; Crops and nitrogen