Reference "Development of submergence-tolerant rice cultivars: the Sub1 locus and beyond"

Reference ID

25508

Title

Development of submergence-tolerant rice cultivars: the Sub1 locus and beyond

Source

Ann Bot (Lond), 2008, vol. , pp. -

Authors (8)

Septiningsih-E-M	Pamplona-A-M
Sanchez-D-L	Neeraja-C-N
Vergara-G-V	Heuer-S
Ismail-A-M	Mackill-D-J

Abstract

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 F(1) 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.