cytoplasmic male-sterility influences the expression of resistance to insects in sorghum
TRANSCRIPT
Cytoplasmic Male-Sterility Influences the Expression of Resistance to Insects in Sorghum
HC Sharma, MK Dhillon, G Pampapathy and BVS ReddyInternational Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Patancheru 502 324, Andhra Pradesh, India
IntroductionCytoplasmic 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 MethodsA 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.
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Sorghum shoot fly damage. Shoot bug damage.
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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.
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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.
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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 DiscussionDeadheart 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.
ReferencesDhillon 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: [email protected] or [email protected]
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Nov 2009