Tolerância de cana-de-açúcar (Saccharum spp.) a herbicidas utilizando plantas micropropagadas

Abstract

Two experiments were conducted at the UFRRJ - Campos dos Goytacazes, whose aim is to evaluate new methodologie to early differentiation of sugarcane cultivars tolerance subjected to treatment with herbicides. Two experiments were installed, one in vitro culture system on stage multiplication and another on ex vitro, while acclimatization micropropagated plants phase. The variables to experiment in vitro evaluated were number of tillers, symptoms of phytotoxicity and dry weight. The experiment ex vitro evaluated was number of tillers, symptoms of phytotoxicity and height. The followind sugarcane cultivars were used RB951541, RB966928, RB98710, RB969017, RB979088 and SP79-1011. The herbicides used were clomazone, MSMA, diuron, diuron+hexazinona and 2,4-D with three different doses and a further control plant without application. The experimental design was full randomized with ten repetitions. In the in vitro experiment there were used, the cultivars RB951541, RB966928 and SP79-1011 and the herbicides clomazone, MSMA, diuron, the results showed that there were a significant difference in the tolerace to herbicides between the cultivars and the RB951541 was the most sensible. To evaluate the tolerance of sugarcane cultivars to the herbicides clomazone and diuron in in vitro culture, the lowest doses of 1,0kg a.i./ha and 2,4 kg a.i./ha allowed the distinction to the notes of fitotoxicity syntoms and dry matter weight characteristics. The results showed the possibility of the application of this methodology to to early detect the tolerance of sugarcane cultivars to herbicides, being the notes of fitotoxicity syntoms and dry matter weight characteristics the ones with better results. The second experiment evaluated all mentioned cultivars, on the acclimatization plants phase, at 50 days after transplant to pots. The evaluations of this experiment resulted in the indication of 21 DAT and the dose 1 of the herbicides as the most indicated parameters to differenciate the cultivars. The proposed methodology, in the used doses, was not efficient to select sugarcane cultivars to the tolerance to diuron and diuron + hexazinona, because these products caused the death of all plants, in all the doses. The cultivar RB951541 was the most sensible to the herbicides, in all the characteristics evaluated and in both experiments, showing that the methodologies used detected the same sensibility. The same happened in the distinction of the tolerant cultivars, with the cultivars RB966928 and SP79-1011 beeing the most tolerants.