LAUSR

Quantitative differences in tuber bulking of 100 genotypes in a segregating F1 population, their parents (SH, RH) and five contrasting cultivars of potato (Solanum tuberosum) grown in six environments were analysed using a piece-wise expolinear function. Tuber bulking was characterised by three parameters: cm, ED and wmax, where cm and ED were growth rate and effective duration, respectively, of the linear phase of tuber bulking, and wmax was the final tuber dry weight at the end of the linear phase (tE). We also analysed radiation (RUET) and nitrogen use efficiency (NUET), and their relationships with the model parameters. Values of cm and RUET were highest for early-maturing genotypes. Late-maturing genotypes had largest ED and NUET. As a result, wmax was higher in late genotypes than in early genotypes. Most traits exhibited high heritability and high genetic correlations with wmax. Path analysis showed that RUET, cm and a previously quantified parameter for total canopy cover Asum, had a major influence on wmax. Sixteen QTLs were detected for all traits explaining the phenotypic variance by up to 66%. One particular QTL on paternal linkage group V was detected for all traits with a major additive effect and maximum total phenotypic variance. Additional QTLs mostly associated with RH (cm, tE and ED) or both SH-RH linkage groups (NUET, wmax). Our study demonstrates that there are opportunities for improving tuber dry matter yield by selecting an optimal combination of important physiological traits.