The possibility to estimate the mean fiber strength by correcting Pressley 1/8" determinations through Fibrograph measures is demonstrated. The intrinsic strength (RI) of fibers of a homogenized sample may be obtained by the following expression: RI =15 x 0.11383 (P/p2) (p1/L x L2.5%) where P is the Pressley reading, p2 is the weight of the bundle of fbers, L, L2.5% and p, are the amount reading, the 2.5% staple length and the weight of fibers on the comb of the Fibrograph. Comparative studies carried out by the authors in the Laboratory of Fiber Technology of the "Instituto Agronomico" at Campinas, State of São Paulo, Brazil, about the two measures of number strenght showed that, whereas the Pressley 1/8" índices had no correlation with Micronaire and maturity, in the abscence of genetic variations, the RI values where highly correlated with both characters. Among the main fiber characters, maturity had the highest contribution to variations of RI in multipie regression analysis. The study of 22 regional variety testes showed that data of intrinsic strength yielded higher discrimination among varieties than those of Pressley 1/8".
cotton; intrinsic resistance; corrected Pressley