Agronomic performance associated with the incidence of frost on wheat cultivars in Brazil.

The subtropical environments, are the regions with the largest area of wheat cultivation in Brazil, however, events, such as frost formation in the period of flowering and grain filling negatively influence the production, due to direct loss in grain formation. Identifying cultivars, which have a higher genetic resistance to frost damage, can provide strategies for maintaining the productive potential in commercial crops in subtropical region in Brazil. The study aimed to evaluate the linear relationships among characters and the agronomic performance of wheat cultivars of different cycles, under the influence of frost stress in a subtropical low altitude region. The experiment was conducted in a subtropical climate triticultural region in the South of Brazil (Santa Maria, RS). A randomized block design with seven cultivars and four repetitions was used, totaling 28 experimental units. The cultivar cycle from the emergence stage to physiological maturity was recorded, as was the recording of the phenological stage on the day of frost formation. The characters evaluated were: plant height, number of fertile tillers, number of spikelets per plant, number of grains per plant, whole grains in the main stem, damaged grains in the main stem, whole grains in the tillers, damaged grains in the tillers, thousand-grain mass, hectoliter weight, grain yield, harvest index, and number of spikes per m². Analysis of variance, test for comparison of means between treatments with significant effect, Pearson linear correlation analysis, and trail analysis were performed. The results show that the cultivars and phenological stages of the plants have different degrees of sensitivity to frost damage, with the early anthesis stage being less sensitive to frost damage than the late milky grain stage. Therefore, the linear relationships indicate that the characters plant height, number of fertile tillers, number of grains per plant, whole grains and hectoliter weight, have positive relationship with grain yield. There is a genetic effect for tolerance to frost damage. The use of cultivars with similar cycle behavior are not indicated, as they increase the risk of frost losses when sowing in only one growing season. [ABSTRACT FROM AUTHOR]