The importance of photoperiodic response for the breeding of glasshouse spinach

Summary

Very quick-growing spinach material has been raised for winter cropping in glasshouses by crossing some glasshouse varieties with an extremely quick-bolting parent and subsequent selection in winter glasshouse crops. The resulting material gave increased leaf production in winter cropping under glass and did not bolt too rapidly.

The procedure used was based on the observation that leaf growth is optimal under a daylength corresponding with the critical daylength for bolting. The critical daylength of the current spinach varieties is longer than the daylengths under which winter crops are grown, so the rate of growth is not optimal.

This paper also demonstrates how any other growth-accelerating properties than a particular critical daylength can be traced and used for breeding purposes.

The importance of this ecological basis for breeding, growing and variety testing is pointed out and exemplified.