Grain and shoot iron (Fe) content and root phytosiderophore release are the major determinants of Fe-deficiency tolerance index (FeDTI) and the reliable screening markers to breed Fe-efficient rice (Oryza sativa L.)

Abstract

There is a need to exploit the genetic variability in rice to improve the Fe deficiency tolerance, particularly under aerobic conditions, and to improve the Fe uptake and accumulation in the grain to facilitate biofortification. The present research was conducted to ascertain the regulators and determinants of Fe-deficiency tolerance in rice. Fifty-seven diverse genotypes were investigated under Fe-deficient (1 µM, FDS, -Fe) and Fe-sufficient (100 µM, FSS, +Fe) nutrient solution cultures for growth and physiological attributes, Fe uptake and accumulation and root release of phytosiderophores (PS), etc., and Fe-deficiency tolerance index (FeDTI). A strong positive correlation was observed between root traits and the PS release. Further, a higher release of PS was evidenced as a major determinant of shoot Fe and grain Fe in rice particularly under Fe deficiency. Based on FeDTI, a total of ten rice genotypes were identified, and their Fe deficiency response was further validated on Fe deficient (∼2.1 ppm Fe, FeDS) and Fe-sufficient soils (∼10 ppm Fe, FeSS) in pot culture. Maintenance of high active Fe content and consequently a higher leaf chlorophyll content throughout the plant growth were extremely important determinants of grain yield and grain Fe fortification in rice under Fe deficiency than under the Fe sufficient condition. Based on the FeDTI, this study further identifies the Fe-deficiency tolerant rice genotypes which can be exploited through conventional and molecular breeding approaches to improve the Fe uptake efficiency and grain Fe content of the high-yielding rice genotypes.

Keywords:

• Aerobic rice
• Fe biofortification
• Fe-deficiency tolerance index (FeDTI)
• Fe translocation efficiency (FeTE)
• phytosiderophore release
• root characteristics

Acknowledgment

The award of JRF by the University Grant Commission (UGC), New Delhi, India, to Pooja Tamuk is gratefully acknowledged.

Author contributions

PT: investigation, validation, data curation, formal analysis, writing—original draft, and review. RNP: supervision, data curation, and formal analysis. TJP: investigation and formal analysis. MB: investigation and formal analysis. DC: investigation and formal analysis. BG: formal analysis, data curation, and validation. SC: data curation and formal analysis. AT: investigation and formal analysis. BS: supervision, data curation, formal analysis, writing—review and editing.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The in-house funding received by the Division of Soil Science and Agricultural Chemistry from ICAR—Indian Agriculture Research Institute, New Delhi was utilized.