Quantitative genetic analysis of seed vigour and pre-emergence seedling growth traits in Brassica oleracea

The ability of seeds to germinate and establish seedlings in a predictable manner under a range of conditions has a direct contribution to the economi c success of commercial crops, and should therefore be considered in crop i mprovement. We measured traits associated with seed vigour and pre-emergenc e seedling growth in a segregating population of 105 doubled haploid Brassi ca oleracea lines. The germination traits measured were: mean germination t imes for unstressed germination; germination under water stress or germinat ion after a heat treatment; and conductivity of seed leachate. The seedling growth traits measured were: seed weight; seedling growth rate; and seedli ng size at the end of the exponential growth phase. There were some correla tions, notably among germination traits, and between seed weight and pre-em ergence seedling growth. Heritability of the various traits was typically i n the 10-15% range, with heritability of conductivity and mean germination time under water stress 25 and 24% respectively. Collectively the results i ndicate that germination and pre-emergence seedling growth are under separa te genetic control. Quantitative trait loci analyses were carried out on al l measurements and revealed significant loci on linkage groups O1, O3, O6, O7 and O9. We suggest that genes at these loci are important in determining predictable seed germination and seedling establishment in practice.