Genetic variability for yield and quality characteristics in South African pumpkin (Cucurbita maxima Duch.)

English: The objective of this study was to study the inheritance of agronomic and quality characteristics in South African pumpkin germplasm and to identify characteristics that could be improved through hybrid breeding. 2. Six parental lines were crossed. The parents with the 15 F1-crosses were planted in Greytown as a randomized block design with six replications. Three of the replications were used for destructive measurements at the flowering stage, while the other three were used to evaluate yield and quality characteristics at a mature harvesting stage. 3. Significant phenotypic differences were found among the parental lines and their F1-offsprings for all the characteristics evaluated. C was the superior parent in nine of the 19 characteristics measured. For yield, fruit number, LPL, LBL and MBT parents in general tend to have a lower ranking than the crosses. The opposite was noticed for ST where the pure breeding parents performed better. 4. Specific combining abilities were calculated to be significant for all the characteristics, indicating that general combining ability predicted performances deviated from the observed performances for some of the crosses. 5. The calculated percentage variation due to GCA indicated that for most of the characteristics mostly additive variance influenced the expression of the characteristic. For LPL, yield, fruit mass, fruit number, ST, TT and MBT a large percentage (>25%) of the variation were influenced by non-additive gene action. Very high broad sense heritabilities were calculated for all the traits. The lowest value was calculated for OBES (0.81). Very high narrow sense heritabilities were calculated for W, ML, TL, W:ML, SHT, BT, density, OW:L, OTT and OST. Heritabilities for fruit mass, LBL, ST, TT and OBES were calculated to be high. Moderate heritabilities were calculated for yield, fruit number, LPL and MBT. 7. Ovary and leaf morphology showed strong phenotypic and genotypic correlations with fruit characteristics expressed at a mature stage. OW:L and OST had respectively genetic correlations of 0.87 and 0.91 with SHT. OTT had a genetic correlation of 0.90 with density. Density had negative correlations with LPL (-0.94) and LBL (-0.85). 8. The highest direct response to selection was calculated for fruit mass, which showed a 122.88% improvement on the population mean. Direct selection response for density was calculated to be 98.74%. For most characteristics it was concluded that gain through indirect selection could be as successful as with direct selection. 9. Positive mid-parent heterosis and high parent heterosis were calculated for all characteristics except ST that showed only negative HPH. Yield (-11.30 to 88.21 %), fruit mass (-58.90 to 94.05%), fruit number (-57.12 to 11.56%) and density (-41.64 to 93.81 %) were identified to express the highest heterosis in the trial.