| Popis: |
High nitrate content is considered a negative quality trait in lettuce ( Lactuca sativa L.) and breeding efforts have been directed towards obtaining cultivars with reduced nitrate accumulation. Previous research has shown that with respect to the nitrate content in fresh matter, lettuce genotypes responded differently to changes in environmental conditions between experiments. To study the inheritance and characteristics associated with genotype × environment (GE) interaction for nitrate content, two lettuce genotypes known to show large GE interaction, and 25 F 3 lines from a cross between them were studied in four successive experiments. GE interactions were observed both for nitrate content and for dry matter content: with increasing daylength one parent showed nearly constant nitrate content and decreasing dry matter content, while with the other parent the reverse was true. Similarly, under increasing daylength, F 3 line means showed a high and negative correlation between the rate of change of nitrate and dry matter content, suggesting that these are pleiotropic effects. None of the F 3 lines had a transgressive low nitrate content in all experiments, but some F 3 lines had significantly lower nitrate relative to the lowest nitrate parent in some experiments, while they were not significantly different from the lowest nitrate parent in the other experiments. This suggests that a recombination of genes for low nitrate content from both parents, resulting in a further reduction of nitrate content is possible. |
