Characterization of root traits for phosphorus deficiency tolerance using chromosome segment substitution lines

Phosphorus (P) acquisition, a key factor in rice productivity, is related to morphological and anatomical root traits. In this study, we examined the root traits of rice that contribute to P acquisition under low P conditions using chromosomal segment substitution lines (CSSLs) grown under non-flooded conditions. Rice plants were grown under low- and high- P conditions in a growth chamber. We tested 39 CSSLs and the parent varieties 'Sasanishiki' and 'Habataki.' Four out of the five selected genotypes from 39 CSSLs had larger root surface areas than that of Sasanishiki due to long fine root and/or coarse roots. The root surface area and shoot P uptake were significantly and positively correlated. Two of the genotypes had higher P use efficiency and shoot dry weight compared to that of Sasanishiki under low P conditions, and nodal root cross-sectional areas were larger in the two genotypes than in Sasanishiki under low P conditions. The root cortical aerenchyma in the nodal roots was well developed in all observed genotypes, which may have reduced the metabolic cost. These results suggest that the thick nodal roots with aerenchyma in contribution to the increase in root surface area are the advantage for growth under low P levels in non-flooded conditions.