By HC Sharma, MK Dhillon, G Pampapathy and BVS Reddy

1. Cytoplasmic Male-Sterility Influences the Expression
of Resistance to Insects in Sorghum
HC Sharma, MK Dhillon, G Pampapathy and BVS Reddy
International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Patancheru 502 324, Andhra Pradesh, India
Introduction
Cytoplasmic male-sterility has been used to exploit heterotic potential of hybrids for increasing crop
production. Large-scale cultivation of crop cultivars based on a single source of cytoplasmic male-
sterility (CMS) may have disastrous consequences for sustainable crop production, and may render
the entire crop vulnerable to outbreaks of insect pests and diseases (Yang et al. 1989). It is therefore
important to understand the interactions between insect pests and CMS to develop appropriate
strategies for the development and deployment of insect-resistant hybrids.
Material and Methods
A diverse array of insect-resistant and -susceptible male-sterile (A-lines), maintainer (B-lines), and
restorer (R-lines) lines were used to understand the influence of CMS on expression of resistance
to sorghum shoot fly (Atherigona soccata), shoot bug (Peregrinus maidis), yellow sugarcane aphid
(Melanaphis sacchari) and sorghum midge (Stenodiplosis sorghicola). Twelve A and B pairs were
evaluated for resistance to shoot fly and shoot bug, while 35 pairs were evaluated for resistance to
yellow sugarcane aphid, and four pairs for resistance to sorghum midge. Data were recorded on
percentage of plants with shoot fly deadhearts at 14 days after seedling emergence. Shoot bug and
aphid damage were recorded visually on a 1 to 9 damage rating scale (1 = <10% leaf area damaged,
and 9 = >80% leaf area damaged). Resistance to sorghum midge was measured in terms of number
of midges emerging per panicle when infested with 40 midge females for 2 consecutive days using a
headcage technique.
Larva Adult Adults
Sorghum shoot fly damage. Shoot bug damage.
Adult
Yellow sugarcane aphid. Sorghum midge damage.
midge damage in the resistant x resistant hybrids ranged from 5.73 to 18.80%, while those based on
resistant x susceptible parents suffered 13.07 to 33.33% midge damage (Fig. 2b). The susceptible
x resistant hybrids suffered 16.63 to 44.03% midge damage, and susceptible x susceptible hybrids
suffered 33.73 to 68.30% midge damage. The male-sterile lines showed a greater influence on the
expression of resistance/susceptibility to shoot fly and sorghum midge than the restorer lines.
0
1
2
3
4
5
6
7
8
9
10
Overall
ShootbugDR
Resistant Susceptible
Lines
A B
0
1
2
3
4
5
6
Overall
AphidDR
Resistant Susceptible
Lines
A B
0
5
10
15
20
25
30
35
Overall
Midgesemerged(√N)
Resistant Susceptible
Lines
A B
0
20
40
60
80
100
120
Overall
Shootflydeadhearts(%)
Resistant Susceptible
Lines
A B
Fig. 1. Effect of cytoplasmic male-sterility on expression of resistance to insects. A: shoot
fly, b: shoot bug, c: yellow sugarcane aphid, and d: sorghum midge. Overall = Mean insect
infestation/numbers across A- and B-lines tested, Resistant = Mean across insect-resistant
A- and B-lines, and Susceptible = Mean across insect-susceptible A- and B-lines tested.
70
60
50
40
30
20
10
0
R
MR1xR
MR2xR
MS1xR
MS2xR
MR1xS
MR2xS
MS1xS
MS2xS
S
Midgedamage(%)
R
FR1xR
FR2xR
FS1xR
FS2xR
FR1xS
FR2xS
FS1xS
FS2xS
S
Shootflydeadhearts(%)
120
100
80
60
40
20
0
Fig. 2. Insect damage/numbers in sorghum hybrids based on resistant (R) and susceptible (S)
male-sterile and restorer lines. a: shoot fly (FR1 = SPSFR 94006, FR2 = SPSFR 94007, FS1
= Tx623A and FS2 = CK 60A). b: sorghum midge (MR1 = ICSA 88019, MR2 = ICSA 88020,
MS1 = 296A and MS2 = ICSA 42).
Results and Discussion
Deadheart formation in the shoot fly-resistant A- and B-lines was 64.8 and 49.5%, while the shoot
fly-susceptible A- and B-lines suffered 86.6 and 88.1% deadhearts, respectively (Fig. 1a). Shoot bug
damage rating in the resistant A-lines was 6.7 as compared to 5.4 in the B-lines. The susceptible
genotypes suffered a damage rating of 7.7 in the A-lines and 7.5 in the B-lines (Fig. 1b). Yellow
sugarcane aphid-resistant genotypes suffered a damage rating of 3.2 in the A-lines and 2.0 in the
B-lines, while the susceptible genotypes showed a damage rating of 5.0 in the A-lines and 4.9 in the
B-lines (Fig. 1c). Midge emergence was significantly lower in panicles of midge-resistant B-lines than
in the A-lines (Fig. 1d), but no differences were apparent among susceptible A- and B-lines. Hybrids
based on resistant x resistant parents showed 60.6 to 62.3% shoot fly deadhearts compared to 90.3
to 95.1% deadhearts in the hybrids based on susceptible x resistant and susceptible x susceptible
parents (Fig. 2a). The resistant x susceptible hybrids suffered 80.8 to 82.8% deadhearts. Sorghum
Conclusion
• Insect-resistant A-lines were more susceptible to insects than the corresponding B-lines, perhaps
due to factors associated with male-sterility or fertility restoration cytoplasm in sorghum (Sharma
2001).
• Resistance to insects is largely governed by additive gene action, and resistance is needed in both
parents to produce insect-resistant hybrids (Sharma et al. 1996; Dhillon et al. 2006).
• The female parent has a greater influence on expression of resistance or susceptibility to insects.
These findings have an important bearing for development and deployment of insect-resistant
hybrids for sustainable crop production.
References
Dhillon MK, Sharma HC, Reddy BVS, Ram Singh and Naresh JS. 2006. Inheritance of resistance to sorghum
shoot fly, Atherigona soccata. Crop Science 46: 1377-1383.
Sharma HC. 2001. Cytoplasmic male-sterility and source of pollen influence on the expression of resistance to
sorghum midge, Stenodiplosis sorghicola. Euphytica 122: 391-395.
Sharma HC, Abraham CV, Vidyasagar P and Stenhouse JW. 1996. Gene action for resistance in sorghum to
midge, Contarinia sorghicola. Crop Science 36, 259-265.
Yang RC, Lu HR, Zhang XB, Xia YH, Li WM, Liang KJ, Wang NY and Chen QH. 1989. Study of the susceptibility of
CMS WA cytoplasm in rice to blast and bacterial blight. Acta Agronomica Sinica, 15, 310-318.
For more information write to: HC Sharma, Principal Scientist - Entomology, ICRISAT, Patancheru 502 324, Andhra
Pradesh, India. Email: h.sharma@cgiar.org or M.Dhillon@cgiar.org
a b
c d
a b
Nov 2009