“LINKAGE AND QTL MAPPING FOR DOWNY MILDEW RESISTANCE IN PEARL MILLET (Pennisetum glaucum (L.) R. Br.)”
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Date
2014-10
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jau,junagdh
Abstract
Present experiment on “LINKAGE AND QTL MAPPING FOR DOWNY MILDEW
RESISTANCE IN PEARL MILLET (Pennisetum glaucum (L.) R. Br.)” was conducted at
Department of Biotechnology, Junagadh Agricultural University, Junagadh, The study was
formulated to improve the yield potential of hybrids of J-2372, which is one of the elite and
important restorer lines used in hybrid breeding programs in Gujarat. Identification of downy
mildew resistance genomic regions was set as an objective.
Downy mildew of pearl millet is one of the most important devastating
diseases limiting pearl millet productivity. DNA-based marker tools facilitated better
understanding of the inheritance and expression of downy mildew. To fulfill the objectives,
the two pearl millet inbred parental lines were crossed to F1, and the F1 progenies were selfed
to produced 125 segregating F2 mapping population progenies for generating marker data
using 24 SSR out of 80 markers exhibiting clear polymorphism between parental lines. The
downy mildew screening of segregating F2 population progenies based on J-2480 x J-2372
against downy mildew was done at JAU., Jamnagar.
R QTL interval mapping method identified two downy mildew QTLs on Linkage
Group 1 and Linkage Group 6. This best single-QTL model detected by interval mapping on
Linkage Group 1 (M1 marker) recorded a high LOD score of 6.3 with map position 14.8 and
explained 46.4 % of recorded phenotypic variation in downy mildew incidence among 125 F2
progenies and Linkage Group 6 (M44 marker) recorded a LOD score of 1.6 with map
position 56.07 and explained 36 % of recorded phenotypic variation in downy mildew
incidence among 125 F2 progenies against Sclerospora graminicola pathogen
The confidence interval detected that the position between 10-15 cM on linkage group
1 was responsible for the resistance against downy mildew in pearl millet. The effect plot for
marker M1 indicated that the resistance against the downy mildew was governed by
dominant inheritance and can be easily used for the transfer of trait though marker assisted
selected using marker M1.
In present study, downy mildew resistance QTLs detected exhibited over-dominant
modes of inheritance, and DMR resistant QTLs come from resistant male parent J-2480.
These identified DMR QTLs from J-2480 can now be transferred to genetic backgrounds of
elite pearl millet hybrid parental lines (J-2372) through marker-assisted backcrossing
programs. Flanking markers of the identified QTLs can facilitate selection of resistant
progenies during the backcrossing process, where as other marker loci can be used in
reducing the length of the donor segments carried along with the introgressed DM resistance
genes and/or selecting for recovery of recurrent parent alleles on non-carrier chromosomes
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BIOTECHNOLOGY