AUTHOR=Rakotondramanana Mbolatantely , Wissuwa Matthias , Ramanankaja Landiarimisa , Razafimbelo Tantely , Stangoulis James , Grenier Cécile 

TITLE=Stability of grain zinc concentrations across lowland rice environments favors zinc biofortification breeding

JOURNAL=Frontiers in Plant Science

VOLUME=Volume 15 - 2024

YEAR=2024

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2024.1293831

DOI=10.3389/fpls.2024.1293831

ISSN=1664-462X

ABSTRACT=One-third of the human population consumes insufficient zinc (Zn) to sustain a healthy life. Zn deficiency can be relieved by increasing the Zn concentration ([Zn]) in staple food crops through biofortification breeding. Rice is a poor source of Zn and in countries predominantly relying on rice without sufficient dietary diversification, such as in Madagascar, Zn biofortification is a priority. Multi-environmental trials were performed in Madagascar over two years, 2019 and 2020, to screen a total of 28 genotypes including local and imported germplasm. The trials were conducted in the highlands of Ankazomiriotra, Anjiro and Behenji, and in Morovoay, a location representative of the costal ecosystem. Contributions of genotype (G), environment (E) and G by E interactions (GEI) were investigated. The grain [Zn] of local Malagasy rice varieties was similar to the internationally established [Zn] baseline of 18-20 μg g-1 for brown rice. While several imported breeding lines reached 50% of our breeding target set at +12 μg g-1, only few met farmers' appreciation criteria. Levels of grain [Zn] were stable across E. The G effects accounted for a main fraction of the variation, 76% to 83% of the variation for year 1 and year 2 trials, respectively, while GEI effects were comparatively small contributing 23% to 9%. This contrasted with dominant E and GEI effects for grain yield. Our results indicate that local varieties tested contained insufficient [Zn] to alleviate Zn malnutrition and developing new Zn-biofortified varieties should therefore be a priority. GGE analysis did not distinguish mega-environments for grain [Zn], whereas at least three mega-environments existed for grain yield, differentiated by the presence of limiting environmental conditions and responsiveness to improved soil fertility. Our main conclusion reveals that grain [Zn] seems to be under strong genetic control in the agro-climatic conditions of Madagascar. We could identify several interesting genotypes as potential donor for the breeding program, among those BF156, with a relatively stable [Zn] (ASV=0.89) reaching our target (>26 μg g-1 ). While selection for grain yield, general adaptation and farmers' appreciation would have to rely on multi-environment testing, selection for grain [Zn] could be centralized in earlier generations.