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2001; Singh et al. 2003; Mathews et al. 2007),
several with high yield as well as resistance
to leafspots. Substantial progress has also been
made in Ghana with collaboration between the
Savanna Agricultural Research Institute (SARI)
and ICRISAT, which has resulted in the release
of three varieties, Edorpo-Munikpa, Nkatiesari,
and Kpaniele (Frimpong et al. 2006; Padi et al.
2006). These are bunch-type, medium-to-late
maturing (120 days) with resistance to both leaf
spots.
Resistance has different components, includ-
ing percent defoliation, incubation (time from
inoculation until the appearance of lesions)
period, latency (time from inoculation until
sporulation) period, lesion number and diameter,
sporulation, and pod yield (Green and Wynne,
1986; Chiteka et al. 1988a, 1988b; Anderson
et al. 1993; Waliyar et al. 1993, 1995). Some
have argued that as yield is the primary objective
in any resistance program, selection based on
defoliation would probably be the most appro-
priate due to its high heritability and the fact
that reductions in yield are attributed in large
part to premature defoliation in diseased fields
(Anderson et al. 1991). Reports by Aquino et al.
(1995) suggested that latency period and maxi-
mum percentage of lesions that sporulated were
the components of resistance most highly corre-
lated with late leaf spot disease development and
suggested that using either component may facil-
itate more rapid selection of lines with improved
levels of rate-reducing resistance in germplasm
evaluations.
Wynne and Halward (1989) and Simpson
(1991) suggested multigenic type resistance for
the two leaf spot diseases with a strong possi-
bility of each under the control of two or more
genes. Available evidence indicates resistance to
both early and late leaf spot to be quantitatively
inherited (Sharief et al. 1978; Kornegay et al.
1980; Walls et al. 1985), with a large additive
effect possibly with the involvement of cytoplas-
mic factors (Coffelt and Porter 1986). Resistance
to late leaf spot is reported to be governed by five
loci (Nevill 1982).
Breeding
Some wild peanut species have consider-
able resistance to leafspots. Subrahmanyam
et al. (1989) evaluated 96 accessions of wild
Arachis
species for reactions to late leaf spot
and observed that lesions were formed on
all accessions, but lesions were small and
nonsporulating on all accessions of sections
Erectoides
,
Triseminatae
,
Extranervosae
,
Rhi-
zomatosae
, and
Caulorrhizae
. Lesions with
diameters ranging from 0.16 to 1.0 mm were,
however, found in section
Arachis
. In section
Arachis
it was further observed that 15 acces-
sions had no sporulating lesions, and sporulation
was slight to extensive in other accessions. In
A. stenosperma
, the failure of late leaf spot and
rust pathogens to infect has been shown to be
due to inability of the fungal hyphae to penetrate
the stomata of peanut leaves (Leal-Bertioli et al.
2010). Rao et al. (2003) list seven wild species
(held at The International Crops Research Insti-
tute for the Semi-Arid Tropics, ICRISAT) that
have resistance to early leaf spot (ELS), nine to
late leaf spot (LLS), and twelve to rust that have
been exploited to develop breeding lines with
some degree of resistance (Simpson et al. 1993;
Stalker et al. 2002a). In Brazil, IAC-Caiapo, a
runner-type cultivar, shows moderate resistance
to foliar diseases and high productivity (Godoy
et al. 1999).
All commercially grown cultivars used to
be susceptible to some extent to both diseases
(Shokes and Culbreath 1997), suffering yield
losses of around 50% in the absence of fungi-
cide sprays (Smith 1984; McDonald et al. 1985;
Waliyar et al. 2000). It was not until 1984 that the
first commercial U.S. cultivar (Southern Runner)
with an appreciable level of resistance to late leaf
spot was released (Holbrook and Stalker 2003).
Cultivars with moderate levels of resistance such
as Florida MDR 98 and C-99R (Gorbert and
Shokes 2002a, 2002b) were later released. These
have medium-to-late maturity. ICRISAT has also
released several
A. hypogaea
accessions with
some resistance to leafspots (Upadhyaya et al.
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