ICRISAT Archival Report 2006 - The seedlings of success in the ...

The phenotyping of F 6 inbred progenies of the mapping population developed between 841B (tolerant) and 863B
(sensitive) has been initiated and the harvesting is underway.
Vincent Vadez and CT Hash
Milestone 5B.2.1.2: Putative QTLs for salinity tolerance based on 35 BC 6 F 3 contiguous segment introgression
lines identified (CTH/SS/VV, 2010)
Funding to complete development of the contiguous segment introgression line set, and initiate its assessment, was
received from DBT in December 2006, so work towards this milestone on this will recommence in 2007.
Milestone 5B.2.1.3: New F 6 RIL mapping populations for salinity tolerance available in pearl millet for
phenotyping and genotyping (CTH/BVSR/KNR/VV, 2009)
The existing (ICMB 841-P3 x 863B-P2)-derived pearl millet mapping population was advanced to F6 RILs. The
new RILs are being skeleton mapped as part of an exercise to create a more informative pearl millet consensus
linkage map. Seed of approximately 150 progenies of this RIL mapping population are now available for salinity
tolerance screening while new pearl millet RIL mapping populations are being generated for this target trait. Crosses
were made between several selected pairs of sorghum parental lines exhibiting substantial pair-wise dissimilarity
(>70%) at 67 SSR loci distributed across all 10 sorghum linkage groups, as well as substantial phenotypic
differences for salinity tolerance based on pot screens of 30 candidate parental lines. F1 hybrids from several such
crosses were sown for advance to the F2 generation by selfing during the 2006/07 postrainy season.
Output target 5B.3: Breeding value of putative terminal drought tolerance QTLs in pearl millet documented
(2009)
Activity 5B.3.1: Publication of earlier results on drought tolerance QTL and gene pyramiding
Milestone 5B.3.1.1: Publication of results from marker-assisted selection for the linkage group 2 drought
tolerance QTL into the genetic background of two parental lines (CTH/FRB, 2008)
QTL for improved grain yield across variable grain-filling moisture environments: Previous molecular work
on drought tolerance in pearl millet has focused on QTL for the ability to maintain yield under post-flowering
drought stress, which can be easily transferred to otherwise well-adapted hybrid parents to improve the performance
of their hybrids under this type of stress. Pearl millet breeding programs targeting adaptation to variable postflowering
moisture environments would benefit from QTLs that improve grain yield across the full range of postflowering
moisture conditions, rather than in just some specific drought-stressed environments. We reanalyzed an
extensive (12 environment) phenotyping data set that included both stressed and non-stressed post-flowering
environments, to identify QTLs for improved yield over the whole range of moisture environments. Genetic
materials were testcrosses of 79 F 2 -derived F 4 progenies from a mapping population based on a widely adapted
maintainer line (ICMB 841) × a post-flowering drought tolerant maintainer (863B). Three QTLs (on LG 2, LG 3,
LG 4) were identified as primary candidates for MAS for improved grain yield across variable post-flowering
moisture environments. QTLs on LG 2 and LG 3 (the most promising) explained a useful proportion (13 to 25%) of
phenotypic variance for grain yield across environments. They also co-mapped with QTLs for harvest index across
environments, and with QTLs for both grain number and individual grain mass under severe terminal stress. Neither
had a significant QTL × environment interaction, indicating their predicted effects should occur across a broad range
of available moisture environments. Finally, both are linked to SSR markers so they are amenable to efficient MAS.
The remaining QTL (LG 4) is of secondary interest as it has a less consistent performance across individual
moisture environments and a less clear effect on secondary traits. Responses to MAS predicted for each of the
identified grain yield QTLs ranged from 70 to 100 kg ha -1 across environments and as much 160 kg ha -1 in
individual moisture environments.
FR Bidinger, T Nepoleon and CT Hash
Improvement of the post-flowering drought tolerance of ICMB 841 by MABC: We completed the evaluation of
13 BC 5 F 3 segmental introgression lines targeting the LG 2 QTL (for post-flowering drought tolerance) from 863B in
the background of widely adapted seed parent ICMB 841. These segmentally near-isogenic lines were evaluated in
testcross hybrid form (with both drought-tolerant and drought-susceptible testers) in multiple years in both the
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