Journal Article

Development of submergence-tolerant rice cultivars: the <i>Sub1</i> locus and beyond

Endang M. Septiningsih, Alvaro M. Pamplona, Darlene L. Sanchez, Chirravuri N. Neeraja, Georgina V. Vergara, Sigrid Heuer, Abdelbagi M. Ismail and David J. Mackill

in Annals of Botany

Published on behalf of The Annals of Botany Company

Volume 103, issue 2, pages 151-160
Published in print January 2009 | ISSN: 0305-7364
Published online October 2008 | e-ISSN: 1095-8290 | DOI: http://dx.doi.org/10.1093/aob/mcn206
Development of submergence-tolerant rice cultivars: the Sub1 locus and beyond

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  • Ecology and Conservation
  • Evolutionary Biology
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Background and Aims

Submergence is a recurring problem in the rice-producing rainfed lowlands of south and south-east Asia. Developing rice cultivars with tolerance of submergence and with agronomic and quality traits acceptable to farmers is a feasible approach to address this problem. The objectives of this study were to (a) develop mega varieties with Sub1 introgression that are submergence tolerant, (b) assess the performance of Sub1 in different genetic backgrounds, (c) determine the roles of the Sub1A and Sub1C genes in conferring tolerance, and (d) assess the level of tolerance in F1 hybrids heterozygous for the Sub1A-1-tolerant allele.

Methods

Tolerant varieties were developed by marker-assisted backcrossing through two or three backcrosses, and their performance was evaluated to determine the effect of Sub1 in different genetic backgrounds. The roles of Sub1A and Sub1C in conferring the tolerant phenotype were further investigated using recombinants identified within the Sub1 gene cluster based on survival and gene expression data.

Key Results

All mega varieties with Sub1 introgression had a significantly higher survival rate than the original parents. An intolerant Sub1C allele combined with the tolerant Sub1A-1 allele did not significantly reduce the level of tolerance, and the Sub1C-1 expression appeared to be independent of the Sub1A allele; however, even when Sub1C-1 expression is completely turned off in the presence of Sub1A-2, plants remained intolerant. Survival rates and Sub1A expression were significantly lower in heterozygotes compared with the homozygous tolerant parent.

Conclusions

Sub1 provided a substantial enhancement in the level of tolerance of all the sensitive mega varieties. Sub1A is confirmed as the primary contributor to tolerance, while Sub1C alleles do not seem important. Lack of dominance of Sub1 suggests that the Sub1A-1 allele should be carried by both parents for developing tolerant rice hybrids.

Keywords: Oryza sativa; Sub1; marker-assisted backcrossing; mega varieties; submergence tolerance; recombinant; hybrid; abiotic stress

Journal Article.  6999 words.  Illustrated.

Subjects: Ecology and Conservation ; Evolutionary Biology ; Plant Sciences and Forestry

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