Abstract
The purpose of this study was to estimate the phenotypic correlations between 14 traits obtainedin a thematic core collection of upland rice for drought tolerance and partition them into direct and indirect effects by path analysis. Two experiments were carried out (with and without water stress). One hundred samples were evaluated in a triple 10x10 lattice design. The plot was formed by four rows, 3.0 metres long, spaced at 0.35 m. The plot useful area was constituted by two central rows of 2.0 m in length, totalling 1.4 m2, where data from 14 traits were collected, five from the root system and nine from the aerial part of the plant. Of the evaluated traits, spikelet sterility was the main grain yield determinant, presenting relevant negative correlations of -0.77 and -0.59 in environments with and without drought stress, respectively. The partitioning of spikelet sterility correlations presented negative direct effects on grain yield in environments with (-0.60) and without (-0.62) water stress, corroborating the negative correlations between these traits. The obtained data confirmed that spikelet sterility is an important variable for the selection of rice strain submitted to water deficit. Partial correlation coefficients indicated that only 70.33% in the environment with stress and 50.30% in the environment without stress of grain yield variation were phenotypically explained by variables considered in path analysis, thereby showing the complexity of the selection for drought-tolerant rice.
Highlights
Rice is one of the main cereals cultivated in the world and its evolution process led it to adapt to the most varied soil and climate conditions
An improvement in yield stability in environments with water deficit is essential for this cultivation, and can be carried out by identifying the traits that may contribute to drought resistance (BABU et al, 2003)
This shows that spikelet sterility in panicles is the main determinant of grain yield
Summary
Rice is one of the main cereals cultivated in the world and its evolution process led it to adapt to the most varied soil and climate conditions. The stress caused by water deficit has long caused yield reduction in several crops, and this has recently been aggravated due to climate changes. Under this type of stress, the plant generally shows an increase in diffusive resistance to water vapour, thanks to stomatal closure, a reduction in transpiration and carbon dioxide supply for the photosynthetic process, reduced cellular growth and increased photorespiration (SHINOZAKI; YAMAGUCHI-SHINOZAKI, 2007), thereby reducing the photosynthesis rate and, having undesirable effects on vigour and plant height, pollen grain fertility and yield (BOTA et al., 2004). An improvement in yield stability in environments with water deficit is essential for this cultivation, and can be carried out by identifying the traits that may contribute to drought resistance (BABU et al, 2003)
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