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Phosphorous(P) deficiency is a major restraint factor for crop production and plants have developed several mechanisms to adapt to low P stress.In this study,a set of 271 introgression lines(ILs) were used to characterize the responses of seedlings to low P availability and to identify QTLs for root traits,biomass,and plant height under P-deficiency and P-sufficiency conditions.Plant height,total dry weight,shoot dry weight,and root number were inhibited under P-deficiency,whereas maximum root length(MRL) and root-shoot ratio(RS) were induced by P-deficiency stress.Relative MRL(RMRL,the ratio of MRL under P-deficiency to MRL under P-sufficiency con-dition) and relative RS(RRS) were used to evaluate P-deficiency tolerance at the seedling stage.A total of 24 additive QTLs and 29 pairs of epistatic QTLs were detected,but only qRN4 was detected in both conditions.This suggested that different mechanisms may exist in both P supply levels.QTLs for adaptive traits(RMRL,RRS,RRV,and RRDW) and qRN4 consistently expressed to increase trait stabil-ity may contribute to P-deficiency tolerance.Twelve intervals were cluster regions of QTLs for P-deficiency tolerance,and one QTL(qRRS8) showed pleiotropic effects on P-deficiency tolerance and drought tolerance.These interesting QTLs can be used in marker-assisted breeding through the target ILs.
Phosphorous (P) deficiency is a major restraint factor for crop production and plants have developed several mechanisms to adapt to low P stress.In this study, a set of 271 introgression lines (ILs) were used to characterize the responses of seedlings to low P availability and to identify QTLs for root traits, biomass, and plant height under P-deficiency and P-sufficiency conditions. Plant height, total dry weight, shoot dry weight, and root number were inhibited under P-deficiency, MRL) and root-shoot ratio (RS) were induced by P-deficiency stress. Relative MRL (RMRL, the ratio of MRL under P-deficiency to MRL under P-sufficiency condition) and relative RS evaluate P-deficiency tolerance at the seedling stage. A total of 24 additive QTLs and 29 pairs of epistatic QTLs were detected, but only qRN4 was detected in both conditions. This suggested that different mechanisms may exist in both P supply levels. QTLs for adaptive traits (RMRL, RRS, RRV, and RRDW) and q RN4 consistently expressed to increase trait stabil-ity may contribute to P-deficiency tolerance. Population-of-clusters were cluster regions of QTLs for P-deficiency tolerance, and one QTL (qRRS8) showed pleiotropic effects on P-deficiency tolerance and drought tolerance. QTLs can be used in marker-assisted breeding through the target ILs.