QTL mapping of pearl millet rust resistance using an integrated DArT- and SSR-based linkage map
Abstract
Rust, caused by the fungus Puccinia
substriata var. indica, is one of the most important
production constraints of pearl millet worldwide,
leading to grain yield losses of up to 76 % as well as
major losses in fodder yield and quality. Here, we
report the development of a linkage map integrating
Diversity Arrays Technology (DArT) markers and
simple sequence repeat (SSR) markers, using this to
identify quantitative trait loci (QTLs) for pearl millet
rust resistance. Genotyping data from 256 DArT and
70 SSR markers on 168 F7 recombinant inbred lines
from cross 81B-P6 9 ICMP 451-P8 were used to
construct a linkage map comprised of 286 loci (229
DArT and 57 SSR markers) spanning a total length of
740.3 cM (Haldane) with an average adjacent marker
distance of 2.7 cM. Linkage group 7 (LG7)
(153.5 cM) was the longest and LG6 the shortest (45.0 cM). The map was used to identify a major QTL
for rust resistance with an LOD score of 27 on LG1,
which explained 58 % of the observed phenotypic
variation. In addition, two putative modifiers of small
effect were detected, one each on LG4 and LG7. The
novel rust resistance QTL identified on LG1 is thought
to confer a durable slow-rusting phenotype, which is
still effective in India more than 20 years after it was
first deployed in the previously popular single-cross
hybrid MH 179 (ICMH 451). The flanking markers
reported here provide a framework for marker-assisted
selection and possible future map-based cloning of
this resistance gene.