The effect of seed quality (seed colour variation) on storability, germination temperature and field performance of radicchio

The possible role played by seed colour (uniformly light-L, slightly black variegated-LB, widely black variegated-BL, uniformly black-B, purple-P) in the seed quality of 'Rosso di Treviso precoce' and 'Rosso di Chioggia' radicchio was investigated. The effect of seed-storage length (two, seven months) was also studied in 'Rosso di Treviso precoce'. For better evaluation of seed quality, germination tests were carried out at 12, 20 and 28°C. The influence of seed characteristics on crop yield was then investigated in the field. Germinability and seed vigour were linked to colour. Reduced germination was observed with L seeds. Moreover, when germinated, L seeds gave rise to plants with reduced ability to form heads, thus reducing the marketable yield. As colour became increasingly darker, seeds germinated faster and more uniformly, and germinability was higher. The differences apparently resulted from incomplete seed development, as shown by the close relationship between germinability and seed weight, and by the smaller embryos of lighter seeds. Sensitivity to temperature changed with seed colour and radicchio type. The L seeds of both types germinated poorly whatever the temperature. The other lots germinated best at 28°C, excluding the LB and P seeds of 'Rosso di Chioggia' which gave better results at 20°C. The negative effect of 12°C was more evident in P seeds of 'Rosso di Chioggia'. Only germinability at 12°C decreased during storage but, whatever the temperature, germination rate decreased with time.