Multiple Small-Effect Alleles of Indica Origin Enhance High Iron-Associated Stress Tolerance in Rice Under Field Conditions in West Africa.

Giovanni Melandri,Francisco J Agosto-Peréz,Alhassan T Maji,Afeez Shittu,Anthony J Greenberg,Venuprasad Ramaiah,Yuxin Shi,Susan R Mccouch,Juan D Arbelaez,Steven A Ngaujah,Vishnu Govindaraj,Kadougoudiou A Konaté,Inoussa Akintayo,Gary Atlin,Mouritala Sikirou,Vimal K Semwal

doi:10.3389/fpls.2020.604938

Abstract

Understanding the genetics of field-based tolerance to high iron-associated (HIA) stress in rice can accelerate the development of new varieties with enhanced yield performance in West African lowland ecosystems. To date, few field-based studies have been undertaken to rigorously evaluate rice yield performance under HIA stress conditions. In this study, two NERICA × O. sativa bi-parental rice populations and one O.sativa diversity panel consisting of 296 rice accessions were evaluated for grain yield and leaf bronzing symptoms over multiple years in four West African HIA stress and control sites. Mapping of these traits identified a large number of QTLs and single nucleotide polymorphisms (SNPs) associated with stress tolerance in the field. Favorable alleles associated with tolerance to high levels of iron in anaerobic rice soils were rare and almost exclusively derived from the indica subpopulation, including the most favorable alleles identified in NERICA varieties. These findings highlight the complex genetic architecture underlying rice response to HIA stress and suggest that a recurrent selection program focusing on an expanded indica genepool could be productively used in combination with genomic selection to increase the efficiency of selection in breeding programs designed to enhance tolerance to this prevalent abiotic stress in West Africa.

Highlights

High iron-associated (HIA) stress, often referred to as iron (Fe)toxicity in the literature, is a nutritional disorder that affects rice production in many cultivated areas of the world, including Africa, Asia and South America (Fageria et al, 2008)
Under HIA stress conditions, stress-induced leaf bronzing (LBS) symptoms were always negatively correlated with grain yield (GY), positively correlated with grain yield loss (GY-loss), and similar values were observed in the two populations (Figures 1A,B)
The only marked difference between the two populations was that Pop 2 displayed a negative correlation between FLW and GY under stress (Figure 1B), while the correlation was positive in Pop1 (Figure 1A)

Summary

Introduction

High iron-associated (HIA) stress, often referred to as iron (Fe)toxicity in the literature, is a nutritional disorder that affects rice production in many cultivated areas of the world, including Africa, Asia and South America (Fageria et al, 2008). Critical to its occurrence are soil conditions of low pH (typical of acid soils), low cation exchange capacity (low clay content) and the presence of high amounts of Fe. HIA stress affects only lowland rice production (irrigated or rainfed) when prolonged waterlogging results in anaerobic conditions that promote the microbial reduction of insoluble ferric (Fe3+) into soluble ferrous (Fe2+) iron. In West Africa, HIA stress is a widespread nutritional disorder and it was recently estimated that rainfed lowland rice grown on Fe-rich soils represents approximately 20% of the total rice area of the region (van Oort, 2018). The typical visual symptom associated with HIA stress in rice is the appearance of necrotic brown spots on the leaves (bronzing), accompanied by broad variation in yield loss, ranging from 10% to 100%, depending on the sensitivity of the rice variety and the intensity of the stress (Audebert and Fofana, 2009)

Methods

Results

Conclusion