Correlation among traits as criterion of cotton genotypes indirect selection
The cotton crop has notable importance for Brazilian and worldwide economy. Relationships knowledge among characters allows developing alternatives that increase the genetic progress with simultaneous selection of several traits. The use of correlation estimates for use in indirect selection helps the breeder in the selection of characters and facilitates progress in the selection. This work evaluates the phenotypic correlation and unfolding of the direct and indirect effects of morphological and technological fiber traits as criterion of indirect selection in cotton genotypes. The experiment was carried out at Fazenda Capim Branco, a research station of Universidade Federal de Uberlândia, 2014/2015 season. 21 genotypes were evaluated, 19 commercial genotypes F3 proceeding from the Programa de Melhoramento Genético Algodoeiro (PROMALG) and two commercial control: FM 966 and DP 555. The experimental design was the randomized complete block with four replications. The experimental parcel was made of four rows of 5 meters cotton plants length, spaced of 0.9 meters. The morphological and agronomic traits evaluated were: a) chlorophyll content (TCA and TCB); b) number of fruiting branches (NFB); c) 1st fruit node height (NH); d) first, second and third-position bolls percentage (FPB, SPB, TPB); e) leaf Area Index (LAI); f) cotton seed yield (CSP); g) lint yield (LP); and h) Lint yield (LY). The fiber quality traits evaluated with HVI (High Instrument Volume): i) Fiber Length average (UHML); ii) Uniformity of length (UI); iii) Short fiber Index (SFI); iv) Fiber Strengh (STR); v) Elongation (ELG); vi) Micronaire (MIC), and vii) Fiber Maturity (MR). Statistical analyses and multicollinearity diagnosis were carried out with the software GENES. The intrinsic traits of fiber quality, according to correlations, influenced cotton seed yield and also morphological traits. Based on phenotypic correlations and according to path analysis, the higher micronaire index of favorable effect on cotton seed yield was identified due to a positive correlation and direct effect. Thus, micronaire index can be an indirect selection criterion of cotton genotypes.