Biology Reference
In-Depth Information
Resistance is present in
A. hypogaea
, with
most of the resistant accessions being of sub-
species
fastigiata
(Subrahmanyam et al. 1989).
Inheritance studies indicated the presence of
two or three recessive genes in some crosses,
with evidence for epistatic interactions, and
with resistance being accompanied by slowing
down of disease development (Subrahmanyam
et al. 1983b). Many wild peanut species were
found to have strong resistance or immunity to
rust, with evidence for dominance and additive
epistatic interactions for resistance (Singh et al.
1984). In section
Arachis
, 11 diploid species
accessions were immune and 3 were highly
resistant; in sections
Erectoides
,
Extranervosae
,
Rhizomatosae
, and
Triseminate
, 37 of 38 acces-
sions tested were immune (Subrahmanyam et al.
1983a). The tetraploid
A. monticola
was scored
as susceptible. Further screening of 74 section
Arachis
accessions indicated that all had very
low leaf damage, except for
A. monticola
,
A.
ipaensis
, and some accessions of
A. stenosperma
(Pande and Rao 2001). Breeding has resulted in
release of some germplasm lines and varieties
with improved rust resistance, sometimes also
possessing resistance to late leaf spot (Gorbet
and Shokes 2002a, 2002b; Singh et al. 2003).
et al. 2011) derived from the cross TG 26
×
GPBD-4. Furthermore, the partial genetic link-
age maps (TAG 24
×
GPBD-4 with 67 marker
loci and TG 26
GPBD-4 with 53 marker
loci) were both saturated to over 180 loci (Sujay
et al. 2011). The populations were subjected to
further phenotyping for seven to eight seasons.
Final analysis detected a total of 15 QTLs for
rust and 28 QTLs for LLS resistance (Sujay
et al. 2011). These QTLs included a major QTL
for LLS (QTLLLS01; linked markers GM1573
and pPGPseq8D09), which was detected across
all the environments and explained between
10.27% and 62.34% of the phenotypic variation.
In addition, three new SSR markers (GM1536,
GM2301, and GM2079) significantly associated
with the major rust QTL (QTLrust01) were iden-
tified (Sujay et al. 2011).
In parallel, the validated SSR marker (IPAHM
103) was deployed in initiating introgression of
rust QTL into three elite groundnut varieties
(ICGV 91114, JL 24, and TAG 24) using the
donor GPBD-4 through marker-assisted back-
crossing. Later, the newly identified linked mark-
ers (GM2079, GM2301, and GM1536) in the
same QTL region have been used together with
IPAHM103 for foreground selection to identify
heterozygous plants at backcrossed F
1
genera-
tions (BC
1
F
1
,BC
2
F
1
and BC
3
F
1
) and homozy-
gous plants at backcrossed F
2
(BC
2
F
2
and
BC
3
F
2
) generations by S. Nigam and P. Janila
of ICRISAT. As a result, 76 homozygous BC
3
F
2
and 158 BC
2
F
3
lines have been generated and
screened for disease resistance during the rainy
season of 2011 (Pandey et al. 2012). This ini-
tial screening has been encouraging and has
lead to the identification of several promising
lines showing remarkable reduction in disease
symptoms.
×
Markers
Markers for rust in general have been discovered
in the same populations analyzed for LLS men-
tioned earlier in this chapter. ICRISAT, in collab-
oration with University of Agricultural Sciences-
Dharwad (UAS-D) in India, had identified and
validated markers linked with these two foliar
diseases. QTL analysis using a partial genetic
map of a mapping population with 67 marker
loci derived from the cross TAG 24
GPBD-4
and multiple season phenotyping data on both
the foliar diseases detected a total of 12 QTLs
explaining between 1.7% and 55.2% of the phe-
notypic variation each (Khedikar et al. 2010).
The SSR marker tightly linked to the major
QTL (IPAHM103; QTLrust01) was then vali-
dated among a diverse set of genotypes as well
as another mapping population (Sarvamangala
×
Resistance to Other Diseases and Pests
Aphids
The aphid-transmitted groundnut rosette virus
is an important pathogen of peanut in Africa
and Asia. Groundnut rosette virus causes severe
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