ANNUAL REPORT - Department of Biotechnology

Magnaportha grisea, showed significant difference
th
in the amount of product amplified at 35 cycle of the
reaction. The quantity of amplified product was more
in Tetep than in HP2216. Gall midge resistance
genes Gm1 and Gm4 are being fine mapped to within
10cM of 2 MB region of the genome. Candidate
genes within the region are being identified through
resistance gene analogue based primer
development and through RTPCR approach using
primers designed for the known resistance pathway
genes. Simple sequence repeat markers are being
developed for the rice gall midge as biotype
diagnostic tools. Rice resistance against brown plant
hopper has been characterized in several of the
genotypes and using these genotypes, mapping
populations have been developed to track down the
resistance genes. A large number of polymorphic
markers have been identified to develop linkage map
as a pre-requisite for this.
Development of varieties with durable resistance
to leaf and stripe rusts using molecular marker
technology in bread wheat
During 2005-06, progeny of 1117 selected F , F , F
3 4 5
and F plants derived from the crosses of
6
PBW343/Yr16//PBW343/Lr24 or Lr28 or Lr37 were
sown at three locations and evaluated for disease
resistance. A set of these lines were also grown under
net house conditions for screening with linked
molecular markers. In addition, 32 F /F bulks from
5 6
the crosses PBW343/Yr16//PBW343/Lr24 or Lr28 or
Lr37 were evaluated for agronomic and economic
traits in a randomized block design with three
replications during normal season 2005-06. Nine
F /F bulks outperformed the parent and the checks
5 6
for one or more of the yield contributing traits or yield
itself. All the 196 families selected during 2005-06
were sown at off-season nursery in Wellington during
May-Sept. 2006. Further selections were made on
the basis of marker data, rust reaction and plant type.
On molecular tagging of Lr37 and Yr16 genes,
molecular analysis of Thatcher and Tc.Lr37 differing
in presence and absence of Lr37 was carried out
using 105 SSR (gwm, gdm, barc, wmc, cfa and cfd)
and 17 EST-SSR (cfe, cwem, ksum) primer pairs
specific to 2A chromosome. Of these, nine
polymorphic primers namely gwm512, gwm382,
gwm296, gwm359, gdm5, barc212, wmc382,
wmc407 and cfd36 alongwith VentriUp/LN2, a
DBT Annual Report 2006-07
44
marker linked to Yr17 were analyzed on a complete
population (109 lines) derived from the cross Tc X
Tc.Lr37. The rust response of the mapping
population (Tc X Tc.Lr37) using PBW343 isolate
2
showed monogenic inheritance at Lr37 locus ( 3:1 =
0.0120, P= 0.950 - 0.900). Linkage analysis using
this data revealed that VentriUp/LN2, Xgwm359 and
Xgdm5 formed a linkage group with Lr37 (Figure 2).
Rest of the primers failed to show an association with
a gene and formed a separate linkage group.
The primer pair VentriUp/LN was used for validation
2
on F populations derived from the cross PBW343
2
XTc.Lr37. Linkage analysis of the data using
Mapmaker revealed co-segregation of the marker
(VentriUp/LN ) with Lr37. Whereas, F population
2 2
derived from the cross Tc X Tc.Lr37 showed a linkage
distance of 33.5 cM and eliminated the possibilities of
using this marker for MAS in this population.
Molecular analysis of these genotypes was carried
out using 104 SSRs, 28 EST-SSRs mapped on
wheat chromosome 2D and 200 SSRs spanning rest
of the wheat genome. Combine analysis of all 61
polymorphic primers formed a linkage group around
the locus Yr16. The marker cfd50 and Xgwm 47
flanked Yr16 at 35.7 and 38.8 cM respectively (LOD
4.0).
Development of molecular markers for wheat
quality improvement.
Under wheat quality improvement programme,
genotyping of RILs has been completed with ~200
SSRs for grain weight (GW) population and with 180
SSRs for the pre-harvest sprouting tolerance (PHST)
population; framework maps will become available
soon. An earlier SSR map of the grain protein
content (GPC) population prepared by Meerut
University had a few large gaps. Within these gaps,
41 new SSR markers were placed and a revised map
with 214 SSR loci was prepared. Three hundred
sixty (360) EST-derived SSR/STS markers specific
for a bin of 2DL containing an important QTL for GPC
were developed. Out of these, 96 markers were so far
tested for polymorphism; seven markers that were
polymorphic are being used for high density
mapping. Similarly, for a major QTL for PHST on 3AL,
144 arm specific SSR/STS markers were developed.
In both cases, homozygous recombinants (30
containing QTL for GPC and 98 containing the major