A model-based approach to analyse genetic variation in potato using standard cultivars and a segregating population. I. Canopy cover dynamics

We designed a model to quantify the canopy cover dynamics in potato (Solanum tuberosum L.). It describes the dynamics during the build-up phase, maximum cover phase, and decline phase of canopy development through five parameters defining timing of three phases and maximum canopy cover (v_max). These five parameters were estimated for 100 individuals of an F1 population, their parents, and five standard cultivars, using data from six field experiments, and used to estimate secondary traits, related to duration and area under the canopy cover curve for the three phases. The duration of the canopy build-up phase (D_P1) was rather conserved, but the duration of maximum canopy cover (D_P2) and the decline phase (D_P3) varied greatly, with late maturing genotypes having longer D_P2 and D_P3 and thus a higher area under the canopy cover curve (A_sum). High genetic variability coupled with high heritability was recorded for end of canopy senescence (t_e), D_P2 and A_sum. Strong positive phenotypic and genetic correlations were observed between D_P2 and t_e, v_max or A_sum indicating that genotypes with longer D_P2 could be indirectly obtained by selecting for these traits. Several quantitative trait loci (QTLs) were detected for model traits explaining the variance by up to 74%. Clustering of many QTLs were found on position 18.2 cM on paternal linkage group V with major additive effects. Many additional QTLs with minor effects were mostly associated with maternal linkage groups. Our model approach could be used to exploit available genetic variability in canopy cover dynamics of potato.