Abstract
Pyramiding useful QTLs into an elite variety is a promising strategy to develop tolerant varieties against multiple abiotic stresses. However, some QTLs may not be functionally compatible when they are introgressed into the same variety. Here, we tested the functional compatibility of Pup1 and Sub1, major QTLs for tolerance to phosphorus (P)-deficiency and submergence conditions, respectively. Phenotypic analysis revealed that IR64-Pup1+Sub1 (IPS) plants harboring both Pup1 and Sub1 QTLs show significant tolerance to submerged conditions, similarly to IR64-Sub1, while IPS failed to tolerate P deficiency and mild drought conditions; only IR64-Pup1 showed P deficiency tolerance. In submerged conditions, Sub1A and OsPSTOL1, major genes for Sub1 and Pup1 QTLs, respectively, were expressed at the same levels as in IPS and IR64-Sub1 and in IPS and IR64-Pup1, respectively. On the other hand, in P-non-supplied condition, crown root number, root length, and OsPSTOL1 expression level were significantly lower in IPS compared to those of IR64-Pup1. However, there was no significant difference in P content between IPS and IR64-Pup1. These results imply that Pup1 does not compromise Sub1 function in submerged condition, while Sub1 suppresses Pup1 function in P-non-supplied condition, possibly by regulating the transcript level of Pup1. In conclusion, Pup1 and Sub1 are regarded as functionally compatible under submergence condition but not under P-non-supplied condition. Further study is needed to elucidate the functional incompatibility of Pup1 and Sub1 QTLs in IPS under P-non-supplied condition.
Highlights
Rice (Oryza sativa L.) is one of the major staple food crops with high agronomic and nutritional importance, and it is widely cultivated in tropical and temperate regions of the world
There was no significant difference in P content between IPS and IR64-Phosphorus uptake 1 (Pup1)
Further study is needed to elucidate the functional incompatibility of Pup1 and Sub1 quantitative trait locus (QTL) in IPS under P-non-supplied condition
Summary
Rice (Oryza sativa L.) is one of the major staple food crops with high agronomic and nutritional importance, and it is widely cultivated in tropical and temperate regions of the world. More than 40% of the rice cultivation area is subject to abiotic stresses such as phosphorus (P) deficiency, submergence, drought, and salinity. Development of a rice cultivar with tolerance to P deficiency and submergence with desirable agronomic traits is an attainable approach to address these problems [3]. P deficiency and submergence are considered to be serious problems limiting crop productivity throughout the world [1,4]. Flooding is one of the most hazardous natural disasters and a major stress constraint to rice production throughout the world, especially in Southeast Asia, which results in huge economic losses. 25% of the global rice croplands are submerged by periodic flash floods, including those in Northeast Asia, which are unpredictable and can occur several times a year
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