Characterization of Root Traits in Response to Phosphorus Deficiency and Identification of QTL for Phosphorus Efficiency in Two Culture Systems in Brassica napus

Phosphorus (P) is an essential mineral element required in large quantities by plants. The modifications of root morphology and architecture are considered as important strategies of plants tolerance to P deficiency. However, the effect of various culture systems on the changes of root traits in response to P deficiency is not well documented. In this study, different responses of root traits to P deficiency were observed in a Brassica napus double haploid (DH) population consisted of 182 lines using an agar system and a ‘pouch and wick’ system. A larger fraction of the DH lines was found to have an increase in total root length, primary root length, total lateral root length, mean lateral root length except for lateral root density in a ‘pouch and wick’ system compared with agar system. The relative root traits (ratio of the value of a trait observed when plants are grown at a reduced P supply to that grown at an optimal P supply) were exploited to identify quantitative trait loci (QTLs) for P efficiency in the two culture systems. Ten and two QTLs were detected for these relative root traits in agar system and ‘pouch and wick’ system, respectively. The QTL for the same trait in the agar system was not overlapped with that in the ‘pouch and wick’ system, which was consistent with the poor correlation of these traits between the two systems. BnaA09g50010D, BnaA09g50650D and BnaC04g03990D were identified as the putative candidates for 3 QTL clusters detected in agar system. These results will contribute to the understanding of the effect of growth environments on the root traits and the QTLs in respond to P deficiency.

Key words: root traits, QTL, phosphorus deficiency, agar system, ‘pouch ad wick’ system, Brassica napus