Crescimento e desenvolvimento de cultivares de cana-de-açúcar tolerantes ao frio na região central e noroeste do RS

Abstract

The objective of this study was to evaluate the growth and development of cold tolerant sugarcane genotypes in the northwest and central regions of Rio Grande do Sul. For this, experiments were installed in a greenhouse and in the field. The greenhouse experiment was installed in June 2018, at the Federal University of Santa Maria, Frederico Westphalen campus. were used fifteen genotypes of sugarcane: UFSM XIKA FW, UFSM LUCI FW, UFSM PRETA FW, UFSM DINA FW, UFSM MARI FW, RB855156, RB966928, RB946903, RB925345, RB965902, RB867515, RB925268, RB935744, RB845210, IAC87-3396. The UFSM genotypes come from the process of mutation of the breeding program of the Federal University of Santa Maria campus of Frederico Westphalen and have tolerance to low temperatures. The RB genotypes are from the Ridesa program and the IAC genotype comes from the breeding program of the Agronomic Institute of Campinas, and the RB genotypes are recommended for cultivation in Rio Grande do Sul. The experimental design was a randomized complete block design with four replications. Was calculated the necessary thermal sum of the planting up until the emergency of the sugarcane and the necessary thermal sum of the emergency until the emission of the fourth leaf. In addition, two other experiments were installed in September 2017 at the field, in Frederico Westphalen, northwest region, and Cruz Alta, central region of the state. The sugarcane genotypes used were: UFSM XIKA FW, UFSM LUCI FW, UFSM PRETA FW, UFSM DINA FW, UFSM MARI FW, IAC87-3396. In Frederico Westphalen were used two spacings of 0,5 and 0,33 meters between plants, and Cruz Alta only a spacing of 0,5 meters between plants. The spacing between cultivation lines in both experiments was 1,5 meters. The experimental design in both experiments was a randomized block design with four replications. At 38, 73, 103, 147, 175, 224 and 266 days after transplantation were measured a stem diameter, height of plant, number of stems per linear meter and leaf area. At the end of the cycle, yields of stems per hectare were determined. These data were correlated with the meteorological data. It concluded that the smaller spacing between plants provides higher productivity of tons of stems per hectare. The morphological characters that most interfere with productivity are the number of stalks per meter of furrow and the height of the plant. The accumulated thermal sum and the minimum temperature are the main variables that interfere in the growth and development of the culture, being the UFSM genotypes the ones with lower thermal requirement.