Rapid and high-precision marker assisted backcrossing to introgress the <Emphasis Type="Italic">SUB1</Emphasis> QTL into BR11, the rainfed lowland rice mega variety of Bangladesh |
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| Authors: | K M Iftekharuddaula M A Newaz M A Salam H U Ahmed M A A Mahbub E M Septiningsih B C Y Collard D L Sanchez A M Pamplona D J Mackill |
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| Institution: | (1) Bangladesh Rice Research Institute, Gazipur, 1701, Bangladesh;(2) Bangladesh Agricultural University, Mymensingh, 2202, Bangladesh;(3) NSW Department of Primary Industries, Tamworth, NSW, 2340, Australia;(4) International Rice Research Institute, DAPO Box 7777, Metro Manila, Philippines |
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| Abstract: | Flooding is one of the major hazards of rice production for the rainfed lowland rice ecosystem, and tolerant cultivars are
urgently needed to help protect farmers from submergence damage. A quick and efficient strategy was implemented to introgress
SUB1, a major QTL for submergence tolerance, into a rainfed lowland mega variety BR11 of Bangladesh by only two backcrosses and
one selfing generation. In marker-assisted backcrossing (MABC), one tightly-linked simple sequence repeat (SSR) and two gene-based
markers, four flanking SSR and 116 background SSR markers were used for foreground, recombinant and background selection,
respectively, in backcrosses between a SUB1 donor IR40931-33-1-3-2 and BR11. BR11-Sub1, identified in a BC2F2 plant, possessed BR11 type SSR alleles on all fragments analyzed except the SUB1 QTL. The introgression size in BR11-Sub1 was 800 Kb indicating approximately 99.8% identity to BR11. BR11-Sub1 along with
other introgression lines showed submergence tolerance similar to the tolerant parent. Yield, yield-component parameters and
grain physico-chemical properties showed successful recovery of the BR11 traits in BR11-Sub1, with yield potential ranging
from 5.2 to 5.6 t/ha, not significantly different from the recurrent parent mega variety BR11. Producing a large number (~1000)
of backcross F1 plants was considered essential to achieve recombination on both sides of the gene, limiting linkage drag with only two backcrosses.
A large number of background markers ensured proper recovery of the recurrent parent genome in the BC2F2 generation. The study demonstrates a rapid and highly precise strategy to introgress a major QTL by BC2F2 generation into a modern rice variety using an unadapted donor. The variety can replace BR11 on more than 2 million of ha
in Bangladesh and provide major increases in rice production. |
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