RA 00110.pdf - OAR@ICRISAT

Table 6. Performance of third phase pearl millet hybrids based on different male sterile lines in coordinated trials.
Hybrid
M B H 110
M B H 118
C M 46
X5
BJ 104
Local
1977
-
-
2445
-
-
Susceptible control
-
1978
Grain yield (kg ha -1 )
1979
1970 2160
2320a 2140
1790 1960
- -
1920 2020
1490 1650
1980
2550
7660
2070
-
2080
1510
1981
2370
7470
-
2270
2160
1690
1982
2420
7470
-
2130
2380
2060
1983 Mean
2060
2170
-
1910
1620
-
2260
2360
2070
2100
2030
1680
%
BJ 104
111
116
98
104
100
83
1977
_
_
0.8
-
-
-
Downy mildew (%)
1978
1.7
4.6
-
.
9.8
1979
1.5
_
0.9
-
13.7
1980
0.3
2.4
3.2
-
8.7
1981
7.3
_
_
1.7
8.1
1982
1.8
2.1
_
1.6
14.9
-
1983 Mean
1.9
5.6
-
4.5
21.3
2.4
3.7
1.6
2.6
12.8
61.8 2 58.9 2 57.8
Trial mean - 1880
2002
2109
2184
2328
2049
2093
103
1. HB 3
2. NHB 3
Current Phase
New hybrids were needed to replace 5141A and its
hybrids. New hybrids using seed parents other than
5141A were released during 1981-84 (Table 2). They
performed well agronomically and were downy mildew
resistant, e.g., CM 46, PHB 47, M B H 110, X5,
and M B H 118 are recommended for cultivation in
the immediate future.
Four new hybrids, highly resistant to downy mildew
with good productivity, were released in 1986
(Table 2). These hybrids are expected to have a
longer life because they all have different seed parents,
and both male and female parents are resistant
to downy mildew.
Problems in Hybrid Breeding
From the discussion of the different hybrid phases, it
is evident that disease susceptibility is a major problem.
It is downy mildew that has necessitated frequent
changes in the most popular hybrids. The
susceptibility of hybrids to downy mildew has diluted
the impact of hybrids on Indian pearl millet
production. The seed parents and their respective
hybrids which were identified and released as resistant,
have succumbed to downy mildew after 3-5
years of cultivation. Hybrids become susceptible to
downy mildew because essentially they are a single
genotype. Moreover, the hybrids released during the
first three phases had a narrow genetic base which
did not fully exploit the available genetic diversity.
In the 20 hybrids released during the first three
phases, male-sterile line 23A was used in five combinations,
5071A was used in three, and 5141A in
eight. Thus, these three lines were seed parents of 16
of the 20 hybrids.
Similarly, the same pollinators were also repeatedly
used in combination with different male-sterile
lines. J 104 was used in four different hybrids, K
560-230 was used in three different hybrids, and K
559 in two.
The limited genetic resources used in the first three
phases led to an early breakdown of downy mildew
resistance. Diversification of hybrid breeding material
is essential. Three different sources of cytoplasm,
A 1 , A 2 , and A 3 are identified and available,
but so far all male-sterile lines which have been used
in released hybrid combinations are on A 1 , cytoplasm.
It may be necessary to exploit the other two
cytoplasm sources. Work at the Punjab Agricultural
University, Ludhiana, is investigating the use of new
male-sterile lines which incorporate these other
sources of cytoplasm. New male-sterile lines bred at
different centers in India are at present showing a
high degree of downy mildew resistance, and are
being used to produce experimental hybrids. The
restorer lines which are used as male parents, need to
be diversified using material showing a high degree
of downy mildew resistance. The present stock of
restorer lines in use by different centers is promising
and showing a high degree of downy mildew resistance.
So far the resistance in seed parents, restorer lines,
and hybrid combinations has only been successful
against downy mildew. The other two important
diseases of pearl millet, ergot and smut, now need
attention. Scientists at ICRISAT have bred some
restorer lines with resistance to ergot and smut, but
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