Yield determination in triticale as affected by radiation in different development phases

The critical period for grain yield determination has not been determined for triticale. We aimed to identify it, determining the relative importance of both the major yield components and the dry matter acquisition by the spikes at anthesis. A field experiment was carried out with two triticales, differing in tillering capacity, subjected to shading treatments at five different timings from early tillering to maturity. Results showed that reductions in grain yield were more significant when shading was imposed during 3 weeks before and 1 week after anthesis. Reductions in grain yield by shading treatments were associated with lower number of grains per m² more than with changes in the average grain weight. Reductions in grains per m² were due to reductions in the number of fertile florets per spike, affecting grains per spike. The assimilate acquisition by the spikes during the critical period was a key determinant of floret survival. Grain number per m² was related with photothermal quotient during 30 days before anthesis and spike dry weight at anthesis, though the goodness of the prediction compared with wheat, was lowered by poorer grain setting percentage.