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Legume Genomics and Genetics (online), 2010, Vol. 1, No.4, 18-23
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19
Arshad, 2002). Among the grain legumes, dry peas
(
Pisum sativum
) ranks first in production in Europe,
while in Pakistan the production of peas Kgs/ha is
almost static from the past 15 yeas (Anonymous, 2007).
Development of new pea cultivars for Pakistan pulse
growers is a critical component in the effort to ensure
that the cost of production remains competitive and the
crop retain its high quality. Breeding, mutation, genetic
engineering, indigenous and exotic germplasm evalua-
tion and conservation are very essential to develop high
yielding genotype and to broaden the gene pool (Gha-
foor et al., 2003).
Due to the contradictory reports on powdery mildew
resistance gene inheritance and divesting effect of the
pathogen on yield, a study was made to confirm the
exact nature of the powdery mildew resistant gene and
select high yielding powdery mildew resistance lines.
The efforts were extended to select morphological mar-
kers to be used in Marker Assisted Selection (MAS)
breeding program.
1 Results
1.1 Inheritance of powdery mildew disease
In the present investigation plant response to
Erysiphe
pisi
appeared to be under the control of two alleles
(susceptible and resistant) of single gene. All the F
1
were susceptible indicating the recessive expression of
the
er-1
gene. Similarly, F
1
generation showed that an-
thocyanin pigmentation present, flower colour purple,
pod colour purple, tendril type normal, leaf type
leaflet present, seed texture rough were the dominant
alleles over anthocyanin pigmentation absent, flower
colour creamy, pod colour green, tendril type bushy,
leaf type leafless and seed texture smooth (Table 1 ).
1.2 Analysis F
2
generation
For F
2
population, the observed value count of sus-
ceptible was 33/46 and resistant 13/46. Chi squire (χ
2
)
for the expected value 3:1 ratio was calculated (0.2)
and was fit for goodness by χ
2
(p>0.65), indicated the
monogenic inheritance for powdery mildew disease
(Table 1). Anthocyanin pigmentation, flower colour,
pod colour, tendril type, leaf type and seed texture showed
3:1 ratio, which was fit for goodness by χ
2
(p >0.07)
method and also indicates monogenic inheritance
(Table 1). In likelihood ratio analysis, out of seven
qualitative contrasting traits; anthocyanin pigmen-
tation high significantly linked with (P<0.00) with
flower colour, seed colour and pod colour with like-
Table 1 Segregation for eight qualitative contrasting traits in F
2
generation of in
Pisum sativum
No.
Contrasting traits Dominates X Recessive
Observed value
Expected value χ
2
P at 5%
PP, Pp
pp
Present
Absent
1
Anthocyanin
pigmentation
PP X pp
29
17
3:1
3.22
0.07
CC, Cc
cc
Purple
Creamy
2
Flower colour
CC X cc
29
17
3:1
3.22
0.07
GG, Gg
gg
Green
Purple
3
Pod colour
GG X gg
31
14
3:1
1.24
0.26
NN, Nn
nn
Normal
Bushy
4
Tendril type
NN X nn
37
8
3:1
1.41
0.21
LL, Ll
ll
Leaf present
Leafless
5
Leaf type
LL X ii
39
7
3:1
2.64
0.1
SS, Ss
ss
Rough
Smooth
6
Seed texture
SS X ss
33
13
3:1
0.2
0.64
RR, Rr
rr
Susceptible
Resistant
7
Sensitivity to pow-
dery mildew
er-1
gene
RR X rr
33
13
3:1
0.2
0.64