INFLUENCE OF PHOTOPERIOD, SHORT-DAY VERNALIZATION, AND COLD VERNALIZATION ON DAYS TO HEADING IN AVENA SPECIES AND CULTIVARS

Abstract

Exposure of 19 accessions belonging to nine species of Avena to constant daily photoperiods of 9, 12, 15, 18, and 24 hr showed that heading was promoted by the longer photoperiods, except in A. abyssinica, which headed first on 15-hr days. Some accessions headed sooner in 9-hr than in 12-hr photoperiods. An interrupted night treatment suggested that photoperiodic control of heading date is exercised by the length of the dark period. A second experiment demonstrated a short-day vernalization response in two of the six accessions initially grown in 9-hr days and later in 12-hr days. In a third experiment (19 entries) cold vernalization (7.2 C for 39 days) strongly promoted heading in seven wild species from the Mediterranean region and in A. abyssinica and the winter oat Landhafer (from 21 to 60 days earlier in 18-hr days). Weaker but significant (P <.05) responses were evident in A. strigosa and three of the remaining nine cultivated hexaploids. The responses to cold vernalization were greater in plants growing in 12- and 18-hr days than in 9-hr days. For the three experiments, regression analysis of days to heading on hours of photoperiod showed that A. byzantina C.W. 544, A. sativa Rapida, A. abyssinica, A. vaviloviana, and A. barbata were the least sensitive to differences in photoperiod (1–3 days earlier per hour longer). Avena strigosa and related diploid wild species showed intermediate sensitivity. Northern spring oat cultivars and Ottawa breeding lines were very sensitive (6–10 days earlier per hour longer). The implications that these findings have for oat breeding are discussed.