Van Deventer, C. S.Blokpoel, Ian Hendrik Christiaan2017-06-092017-06-091998-09http://hdl.handle.net/11660/6354English: The main objective of this study was to determine the combining ability of several tomato genotypes, the heritability of various yield and quality characteristics and the expression of heterosis in the F1 hybrids. 2. Six inbred tomato genotypes were used as parental lines in the diallel cross. Crosses were made in glasshouses at the University of the Orange Free State. The F1 hybrids and their parental lines were planted at the ARC - Roodeplaat Vegetable and Ornamental Plant Institute. Various yield and quality characteristics were analysed. 3. Significant differences among the six parental lines were recorded for total yield, marketable yield, green yield and average fruit mass. The 15 F1 hybrids showed significant differences for total yield, marketable yield, unmarketable yield, green yield and average fruit mass. 4. Significant genetic variation among the SIX parental genotypes was recorded for fruit pH. The 15 F1 hybrids show no significant differences for soluble solid content and fruit pH. 5. A significant positive phenotypic correlation (r=0.95) was found between total yield and marketable yield. 6. Inbred line p88/120 was the best general combiner for most of the yield characteristics while p88/120 and p88/192 is the best general combiners for most of the quality characteristics. Crosses p881l40 x UC82B, P881l20 x p88/192 and p881l40 x p881l92 were the best specific combiners for total and marketable yield. The best specific combination was the cross between p88/164 and UC82B, which had 7 positive SCA values. 8. A GCA:SCA ratio of 85:1 was recorded for average fruit mass indicating that additive genes are involved. 9. Narrow sense heritability were relatively high for average fruit mass (H2n= 74.38%), green yield (H2n=55.01 %) and fruit colour (H2n= 50.04%). The breeder can select effectively for larger fruited genotypes as well as selecting against green yield to increase the total yield. 10. The average level of heterosis over the best parent exceeds 10% for total and marketable yield between all the F1 hybrids. Heterosis of the F1 hybrids over mid-parent value (Hmp), heterosis over the better parent (Hbp) and superiority over the best parent (Scm) was mostly negative for all the quality characteristics.Afrikaans: Die doel van hierdie studie was om die kombineervermoeë van verskeie kultivars, die oorerflikhede van verskeie opbrengs en kwaliteit karakteristieke en die uidrukking van heterose in die F1 basters te bepaal. 2. Ses ingeteelde tamatie genotiepes was gebruik as die ouer lyne in 'n dialeel kruising. Kruisings was gemaak in glashuise by die Universiteit van die Oranje Vrystaat. Die F1 basters en hulouer lyne is uitgeplant by die Instituut vir Groente en Sierplante (LNR-Roodeplaat). Verskeie opbrengs en kwal iteits karakteristieke is bepaal. 3. Betekenisvolle verskille was gekry tussen die ses ouer lyne vir totale opbrengs, bemarkbare opbrengs, groen opbrengs en gemiddelde vrug massa. Die 15 F1 basters het betekenis van mekaar verskil t.o.v. totale opbrengs, bemarkbare opbrengs, onbemarkbare opbrengs, groen opbrengs en gemiddelde vrug massa. 4. Betekenisvolle genetiese vanaste was verkry tussen die ses ouer genotiepes vir vrug pH. Die 15 F1 basters toon geen betekenisvolle verskille tussen oplosbare vastestowwe en vrug pH. 5. 'n Betekenisvolle positiewe fenotiepiese korrelasie (r=0.95) is gevind tussen totale opbrengs en bemarkbare opbrengs. Die ingeteelde lyn p88/l20 was die beste algemene kombineerder vir meeste van die opbrengs karakteristieke terwyl p88/120 en p88/l92 die beste algemene kombineerders was vir die meeste van die kwaliteit karakteristieke. 7. Die kruisings p88/l40 x UC82B, p881l20 x p88/192 en p88/140 x p881l92 was die beste spesifieke kombineerders vir totale en bemarkbare opbrengs. Die beste spesifieke kombinasie was die kruising tussen p88/164 en UC82B wat 7 positiewe spesifieke kombineer waardes gehad het. 8. 'n Algemene tot spesifike kombineervermoeë verhouding van 85:1 was behaal vir gemiddelde vrug massa wat aandui dat additiewe gene betrokke is. 9. Noue sin oorerflikheid was relatief hoog vir gemiddelde vrug massa (H2n= 74.38%), groen opbrengs (H2 n=55.0l%) en vrugkleur (H2n= 50.04%). Die teler kan effektief selekteer vir groter vrugte asook selekteer teen groen opbrengs om sodoende die totale opbrengs te verhoog. 10. Die gemiddelde vlak van heterose oor die beste ouer oorskry 10% vir totale opbrengs en bemarkbare opbrengs tussen al die F1 basters. Heterose van die F1 basters oor middel-ouer waarde, heterose oor die beter ouer en heterose oor die beste ouers was meestal negatief gewees vir die kwaliteits karakteristieke.enTomatoes -- BreedingTomatoes -- GeneticsDissertation (M.Sc.Agric. (Plant Breeding))--University of the Free Statte, 1998DissertationUniversity of the Free State