Assessing lodging resistance in rice: A comparison of two indirect testing methods

Abstract

Rice lodging is still a problem in many countries, as all rice-growing countries have some varieties that get lodged. Direct evaluation of lodging resistance requires visual estimates in plots, but is not feasible in early generations of breeding programs, where genetic variability is too high. The aim of this study was to compare two methods for indirect evaluation of lodging resistance, especially in field conditions: the recovery ability after bending (measured as the tiller angle difference before and after bending); and, to test the sturdiness of the lower part of the plant, we have measured its resistance to pulling. Sixteen rice varieties and two F(5) breeding lines were grown in plots and rows; 20 additional F(5) breeding lines were only tested in rows. Visual estimates of plot lodging were significantly correlated with their tiller angle difference (r = 0.56*), but not with plant height or pulling resistance, although the latter was also correlated with visual lodging when only susceptible accessions were considered (r = -0.72*). Tiller angle difference was not significantly correlated with pulling strength, but it correlates with plant height (r = 0.56*). The scoring of tiller angle difference is simpler and less dependent on the evaluator than pulling resistance. It is concluded that it can be a valuable trait to select for resistance to lodging in early segregating generations of a pedigree breeding program.