To determine the resistance of cotton species and cultivars to the herbicide diuron, a green house test was conducted in Viçosa, Minas Gerais. Genotypes of the species Gossypium: hirsutum latifolium Hutch. ( cv IAC 17 and BR 1) , G. hirsutum marie galante Hutch. (cv Veludo C 17) , and G. barbadense brasiliense Hutch. (cv rim-de-boi ) were studied . A split plot in a randomized complete block design was utilized in this experiment. The main plots were the herbicid e dosage (0,0 0, 0,0 48, 0,0 96, 0, 35 7, 0, 71 4 an d 1, 42 8 kg a. i. /h a) applied to the sand subs trat when the plants had one or two true leaves, and the subplot were the genotypes. Each plot was represented by a wood bos (3 7 x 47 x 11/cm) filled with washed sand. The seeds were acid deslinted before planting. To measure the resistance several parameters were observed such as: Phitotoxicity level 15 days after application, plant height, fresh and dry weight of plants, rate of stem elongation and rate of relative growth of aerial part. The results showed that cv IAC 17 and BR -1 were the most resistant to the chemical stress of the herbicide, the cv Veludo C 71 had in termediate resistance being the cv Rim de Boi the kg a . i . /ha was ha rmful to the plants of this cultivar. The results indicates that one should consider the specie and cultivar, before recommend ingthe application of diuron to a cotton field.
Resistance; genotypes; cotton; diuron