Abstract
ABSTRACT The aim of the current study is to estimate the correlation coefficients and the consequence of genotypic correlations on direct and indirect effects through path analysis between agronomic traits of maize hybrids used for silage production. Eight (8) topcross hybrids and seven (7) checks were analyzed in completely randomized blocks, with six replications, in two environments: Campos do Goytacazes and Itaocara counties – Rio de Janeiro State, in the crop year 2015/2016. The following agronomic traits were assessed: plant height, first ear height, culm diameter, number of ears, ear yield with straw at silage maturity, ear yield without straw at silage maturity, grain yield at silage maturity, grains ratio in the fresh matter and fresh matter yield. The highest correlation estimates were found between the variables ear yield without straw and grain yield, and between ear yield with straw and ear yield without straw, with magnitudes 0.95 and 0.92, respectively. The coefficient of determination was high, which indicates that the assessed components explain most of the existing variation in fresh matter yield. According to the path analysis, the trait showing the strongest direct effect on fresh matter yield was the ear yield with straw at silage maturity, in association with the high correlation (r = 0.91), which showed the possibility of achieving significant gains through indirect selection.
Highlights
The existing relations between traits are assessed through phenotypic, genotypic and environmental correlations
The following agronomical traits were assessed: plant height (PH); soil level measurements up to the insertion node of the plant tassel; the mean insertion height of the first ear (TH); soil level measurements up to the basis of the upper ear on the culm; mean culm diameter (CD), which is measured in the first internode above the plant’s culm; total number of harvested ears (NT); ear yield with straw at silage maturity (TPS); ear yield without straw at silage maturity (TPWS); grain yield at silage maturity (GY); grain yield in fresh matter (GFM); and fresh matter yield (FMY)
The total correlations between traits such as plant height, ear height, culm diameter, ear yield with straw at silage maturity, ear yield without straw at silage maturity, grain yield at silage maturity were all above 0.62, except for the number of ears and for the grain yield in fresh matter, which have presented 0.34 and 0.08 correlation, respectively
Summary
The existing relations between traits are assessed through phenotypic, genotypic and environmental correlations. The phenotypic correlation has genetic and environmental causes, whereas the genetic correlations present association of inheritable nature, they can be used to guide breeding programs. The correlation coefficients are used to quantify the magnitude and direction of factors influencing the determination of complex traits, they do not allow making cause/effect conclusions and inferring the type of association ruling the pair of traits Y/X (Coimbra et al 2005). Such studies, per se, do not allow inferring the direct and indirect influences determining a main trait, such as yield. Studies concerning consequences of the correlation coefficient are conducted through path analysis
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