EVALUATION AND GROUPING OF SUGARCANE GENOTYPES IN AGREEMENT WITH THEIR PHYSIOLOGIC CHARACTERISTICSOTYPES

Resumo

Abstract

The objective of this work was to evaluate physiological characteristics of sugar cane genotypes, as well as characterize them in groups according to their similarity, checking the ability of ecological adaptability of these genotypes. The work was performed in field conditions, being assessed ten sugarcane genotypes (RB855113, RB835486, RB867515, SP80-1816, RB72454, RB925345, RB855156, RB937570, RB947520 and RB925211) in a randomized block design with three repetitions. It were evaluated the stomatal gas flow rate (U - μ mol s^-1), the concentration of under-stomatal CO₂ (Ci - μmol mol^-1), the photosynthetic rate (A - μmol m^-2 s^-1), the CO₂ consumed (Δ C - μmol mol^-1), the stomatal conductance (Gs - mol m^-1 s^-1), the temperature gradient between leaf and air (Δ T), and the transpiration rate  (E - mol H₂O m^-2 s^-1), being also calculated the water use efficiency (WUE - mol CO₂ mol H₂O^-1) from the values of the amount of CO₂ fixed by photosynthesis and amount of water transpirated. Both univariate and multivariate data analysis were made. The genotype SP80-1816 showed better water use efficiency, combined with low stomatal conductance and transpiratory rate. The cultivar RB855113 stood out by having high photosynthetic rate, and high consumption of CO₂. The cultivar RB867515, in addition to showing high water use efficiency, also showed high photosynthetic rate. With respect to the multivariate analysis, the biotypes RB925345, RB925211, RB855156 and RB855113 are situated in different groups when compared to the others as to the physiological characteristics with respect to other genotypes with isolation in separate groups.

Keywords: Saccharum spp. photosynthesis. Transpiration. Cultivars.