Growth response of Eucalyptus clones to different soils in a nursery environment

Issufo, Alima A. K. (1998-12)

Thesis (M. Sc.) -- University of Stellenbosch, 1998.

Thesis

ENGLISH ABSTRACT: A nursery clonal test of 20 clones was established at the University of Stellenbosch on eight soil treatments consisting of combinations of four soil types and two lime levels. One clone was from first-generation and 15 were from second-generation Eucalyptus grandis selected in 13 different open pollinated family trials and two full-sib trials. Three hybrid clones were selected from two E. grandis x E. camaldulensis and one E. grandis x E. urophylla families. Soil collection was done in four different places in the Western Cape, specifically Lourensford near Somerset West, Pampoenvlei near Malmesbury and Grabouw and Helshoogte near Stellenbosch. The yellowish soil from Grabouw and the reddish soil from Helshoogte were clayey while the black and light soils from Lourensford and Pampoenvlei respectively were sandy soils. Two lime levels, with or without lime application, on these soils generated eight soil treatments. Results are firstly presented in tables and the delineation of significant differences between the rankings of clones, replications, soil types, soil treatments for selected variables given by Duncan's New Multiple Range Test is included. Graphical presentations are used to illustrate some of the trends over all the single effects, that is soil types, lime levels and clones. Analysis of variance for the simplified model detected a highly significant difference for soil treatments, which is the combination of different soil types and lime levels. Quite strong correlations between the soil treatments were also evident. Assessments of height, diameter, root and shoot mass were made at age 12, 18 and 24 weeks. Number of branches was assessed at 24 weeks. All the single effects were found to be statistically different for most variables at all ages. The most outstanding on the two-way interactions is the general insignificance of clone x soil type, clone x lime and soil type x lime interaction, for height and diameter growth but indeed not for shoot mass and root mass. This might mean that height and diameter alone are not sensitive enough but when leaves are induded in mass (like a volume) then more expression is obtained justifying the interaction found at 24 weeks for root and shoot mass for all two-way interactions. Generally the three-way interaction seems insignificant. Once again, shoot mass shows some sensitivity being perhaps an indication of "whole tree" response to environment. Analysis of variance for the simplified model showed that soil treatment (soil type x lime), results were highly significant for all the variables studied. When diameter and height means were studied in terms of phenotypic correlations between sites (soil treatments), quite strong correlations were evident between the soil treatments. Clone x soil treatment interaction, was also detected by means of regression coefficients. Some clones were found to be stable for variable shoot mass, for instance, AG I, AG3-B, AG6, AGl2 and AGI4. Average stability clones were GUI, GCI and GC2 while unstable clones were identified as AG5, AG8, AGII, AG13 and AGI5. The magnitude of genotype x environment interaction is low implying that it will not affect broad sense heritability ( there are too few clones to reliably estimate) as well as genetic gain. It is noted that genotype x environment interaction tends to disappear for height and diameter over time, while it remains for shoot mass (volume of the tree) and number of branches at age 24 weeks. The results from this study are encouraging for further research aimed at developing techniques for early prediction of genotype x environment interaction in eucalypt trees.

AFRIKAANSE OPSOMMING: 'n Kwekeryproefmet 20 verskillende klone is aan die Universiteit van Stellenbosch voltooi. Die proef het uit grondbehandelings bestaan wat verskeie kombinasies van vier verskillende gronde met twee vlakke van kalkbehandeling ingesluit het. Die gronde is in die Wes-Kaap (Lourensford, naby Somerset Wes) , Pampoenvlei (naby Malmesbury), Grabouw en Helshoogte (naby Stellenbosch) gevind. Die geel gekleurde grond van Grabouw en die rooi gekleurde grond van Helshoogte het beide 'n hoe klei inhoud terwyl die swart en ligte gekleurde gronde van Lourensford en Pampoenvlei 'n sanderige geaardheid het. Twee vlakke van bekalking (met of sonder kalk) het agt verskillende behandelings tot gevolg gehad. Resultate word eers in getabuleerde vorm aangegee en die afbakening van statistiese rangorde verskille van klone, herhalings, grondsoorte, grondbehandelings word vir verskeie veranderlikes deur Duncan's New Multiple Range Test aangedui. Grafieke is gebruik om die algemene neiging van die enkelvoudige effekte naamlik gronde, kalkvlakke en klone aan te dui. Analise van variansie vir die vereenvoudige model het baie beduidende statistiese verskille tussen grondbehandelings aangedui wat 'n kombinasie van die verskillende grondsoorte en bekalkingsvlakke is. Sterk korrelasie is tussen die verskillende grondbehandelings waargeneem. Die meting van hoogte en stamdeurnee en die bepaling van wortel en starn massa, is gemaak op ouderdom 12, 18 en 24 weke. Die aantal takke is op 24 weke getel. Al die enkelvoudige effekte het statisties beduidende verskille vir die meeste van die veranderlikes op aIle ouderdomme aangedui. Die mees opvallende twee rigting interaksie is die algemene onbeduidenis van die kloon x grondsoort, kloon x bekalking en grondsoort x bekalking interaksies waar hoogte en deursnee as veranderlikes gebruik is. Die effek was egterbeduidend waar starn en wortel massa as veranderlikes gebruik is. Die gebruik van gemiddelde hoogte en deursnee as veranderlikes is egter nie sensitief genoeg nie, maar die gebruik van blaarmassa (as volume) wat by stammassa ingesluit word, gee'n beter aanduiding van interaksie op 24 weke. Die analise van varlanSle VIr die vereenvoudigde model het getoon dat die grondbehandelings (grondsoort x bekalking) resultate baie beduidend was vir die onderskeie veranderlikes wat gemeet is. By die bestudering van deursnee en hoogte gemiddeldes (in terme van fenotipiese korrelasie tussen grondbehandelings), is sterk korrelasie gevind tussen die verskeie grondbehandelings. Kloon x grondbehandeling interaksie is opgemerk deur gebruik te maak van regressle koeffisiente. Verskeie klone (AG1, AG3-B, AG6, AG12 en AG14) het stabiliteit getoon ten opsigte van starn massa as veranderlike. Die gemiddelde stabiele klone was GU1, GC1 en GC2 terwyl die onstabiele klone AG5, AG8, AG 11, AG 13 en AG 15 was. Die grootte van die genotipe x omgewing interaksie was klein en impliseer dat dit nie oorerfbaarheid ( daar is te min klone vir betroubare skattings) en genetiese verbetering veel sal beYnvloed nie. Die genotipe x omgewing interaksie neig om onbeduidend te word vir die hoogte en deursnee veranderlikes terwyl dit beduidend bly vir starn massa ( boom volume) en aantal takke op 24 weke. Die resultate van hierdie studie is bemoedigend vir verdere navorsing wat gemik is daarop om tegnieke te ontwikkel vir vroee voorspelling van genotipe x omgewing interaksie van gombome.

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