Embriogênese somática indireta de duas variedades RB de cana-de-açúcar

Abstract

The sugar cane (Saccharum officinarum L.) is cultivated in about 80 countries around the world, which is responsible for supplying approximately 70% of world demand for sugar and for being an alternative to produce renewable fuel. Somatic embryogenesis is a valuable tool for breeding programs, which could benefit studies of physiology, genetics and biochemistry. This work aimed to establish the best concentrations of sucrose, 2,4-D and activated charcoal in the somatic embryogenesis of two varieties (RB92579 and RB99395) of sugar cane. The variables evaluated were: percentage of embryogenic calli, quality of embryogenic calli and number of regenerated plants from somatic embryos. The soft-end stem of 8 to 10 months-old plants were collected, disinfested and excised to obtain the apical meristem surrounded by few leaves primordia. In the first experiment, it was evaluated the effect of four concentrations of sucrose: 10, 20, 30 and 40 g L-1; in the second experiment, the effect of four concentrations of 2,4-D: 0, 3, 6 and 9 mg L-1; and in the third experiment, the effect of four concentrations of activated charcoal: 0; 0,75; 1,50 and 2,25 g L-1. The concentration of 30 g L-1 sucrose in the culture medium was indicated as the most feasible for the varieties in the development of embryogenic callus in the dark phase. The explants cultured in absence of 2,4-D were brown, did not produce callus and died after three weeks in vitro. The concentration of 3 mg L-1 of 2,4-D added to the culture medium was designated as the best treatment to formation and quality of embryogenic calli, as well as the number of regenerated plants in both varieties. The activated charcoal stimulated an abnormal early germination of the embryos in the dark inducing root formation on the callus and reducing their quality. There was a high positive correlation between the quality of callus and the number of regenerated plants. The response to somatic embryogenesis of the variety RB99395 was significantly better thanin the variety RB92579.