Effect of temperature and daylength on the phenological development of oats (Avena sativa L.)

Content Partner: Lincoln University. The abiotic factors, temperature and daylength, are mainly responsible for phonological development in cereals. They influence the time of panicle development on the shoot apex, panicle emergence, anthesis and grain-filling which contribute to crop yield and quality. The objective of the research presented in this thesis was to investigate the influence of temperature and daylength on the phenological development of oats. The study was based on two approaches. The first was the traditional photothermal approach which describes the interval between phenological events as influenced by thermal and photothermal time. The second was a more mechanistic approach based on the co-ordinated processes of initiation and expansion of leaves and floral structures on the main shoot apex. To compare both approaches, phenological events of field grown oat crops, and the number of leaves and floral structures initiated and expanded on the main shoot apex were recorded from three genotypes (Cashel, Drummond and CF435). These were sown (SO) on eight dates (23/04/1996,21/05,06/08,20/09,25/11,22/01/1997, 20/05, and 25/11), at the Crop & Food Research Experiment Station at Lincoln, New Zealand (latitude 43°36'S, altitude 12m). The experiment was a split-plot design with sowing date as the main plot, and genotypes as the subplots, with three replicates. Ten plants per subplot were marked at emergence (EM), and the number of visible leaf tips, the length of the emerged leaf laminae, the emergence of the flag leaf ligule (FL), and anthesis (AN) were recorded. On each sampling date five plants per subplot were removed and dissected under a microscope to record the number of primordia, and the developmental stages of flag leaf primordium (FP), double ridge (DR), and initiation of the terminal spikelet (TS). Using the traditional photothennal approach, the interval between SO and AN, and intennediate phases (SO-EM, EM-FP, FP-DR, DR-TS, TS-FL, FL-AN), were estimated based on the accumulation of thermal (Tt) and phothermal time (Pt) above a base temperature of 0°C and a base photoperiod of 7h. For each genotype the phases SO-EM (CV between 8 and 10%) and FL-AN (CV between 6 and 15%) were nearly constant in Tt among sowing dates. Using Pt minimized the variation (CV between 6 and 9%) in the interval EM-AN among sowing dates, and also the variation of intermediate phases. It was found that EM could be predicted within an error of 2 days using Tt based