Chapter 12
Aphicidal Activity of Cuticular Components from Nicotiana tabacum Downloaded by UNIV OF CALIFORNIA SAN DIEGO on April 13, 2016 | http://pubs.acs.org Publication Date: December 20, 1993 | doi: 10.1021/bk-1994-0551.ch012
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R. F. Severson , R. V. W. Eckel , D. M. Jackson , V. A. Sisson , and M. G. Stephenson 4
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Phytochemical Research Unit, Richard B. Russell Agricultural Research Center, Agricultural Research Service, U.S. Department of Agriculture, P.O. Box 5677, Athens, GA 30613 Department of Entomology, North Carolina State University, Raleigh, NC 27695 Crops Research Laboratory, Agricultural Research Service, U.S. Department of Agriculture, P.O. Box 1555, Oxford, NC 27565 Nematodes, Weeds and Crops Research, Coastal Plain Experiment Station, Agricultural Research Service, U.S. Department of Agriculture, P.O. Box 748, Tifton, GA 31793 2
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Most Nicotiana species have multicellular, glanded leaf trichomes which may produce chemical secretions containing diterpenes and/or sugar esters with C to C acyl moieties. These components affect tobacco aphids, Myzus nicotianae Blackman, in several ways, including influencing the acceptance or rejection of plants for colonization by alate migrant aphids, and the survival and fecundity of alate and apterous aphids. Cuticular diterpenes and sucrose esters were isolated from the cuticular extracts of aphid resistant and susceptible Ν. tabacum genotypes. These compounds were applied topically to the backs of apterous aphids. LC 's (dose per aphid which kills 50% of the test population after 48 hrs.) of the isolates were; α- and β-4,8,13-duvatriene-l,3diols, 15.7 μg; α- and β-4,8,13-duvatrien-l-ols, 6.4 μg; cisabienol, 7.5 μg; sucrose esters (6-O-acetyl-3,3,4-tri-O-acylsucrose with C3 to C7 acyl groups), 0.25μg;and cis-abienol plus α- and β-4,8,13-duvatrien-1-ols (1:3), 6.0 μg. 2
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Aphids are insect pests of fruit, vegetable, grain and row crops. They cause economic losses by reducing yield and quality, and by transmitting certain plant viral diseases (1). Some aphid species, such as the blackmargined aphid, Monellia caryella (Fitch), are host specific, while others, like the green peach aphid, Myzus persicae (Sulzer), have a wide range of host plants (2). The selection of the host plant is usually made by winged (alate) adults which may use physical or cuticular chemical leaf traits to accept or reject the plant as a suitable host. If found acceptable, the aphid will probe into the leaf and feed on 0097-6156/94/0551-0172$06.00/0 © 1994 American Chemical Society Hedin et al.; Natural and Engineered Pest Management Agents ACS Symposium Series; American Chemical Society: Washington, DC, 1993.
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12. SEVERSON ET AL.
Aphicidal Activity of N. tabacum Components
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the phloem sap (3, 4). An aphid on an acceptable host plant may produce several nymphs per day. Thus, plant colonization begins an exponential population growth which is difficult to control with insecticides or biological agents. Persistent use of synthetic aphicides to control aphid population explosions has resulted in the development of resistance to these compounds. Aphid species have developed resistance to several classes of insecticides (7). Recently, a change from a green to a red morph has occurred in the tobacco aphid, Myzus nicotianae Blackman. Although, the red morph of the tobacco aphid is often associated with an increase in insecticide resistance, this color change has not been directly linked to use of insecticides. However, since the red aphid develops faster, has a higher reproduction rate and tolerates higher temperatures, it is more difficult to control than the green form (5). Thus the dependence on synthetic aphicides for the control of M. nicotianae is undesirable, and other insect management methods must be developed. One part of aphid management should be the use of natural plant chemicals which deter host plant acceptance (nonpreference host plant resistance) by the adult aphid, or are toxic to adults and nymphs (6). For the past 30 years, the U.S. tobacco, Nicotiana tabacum L., and Nicotiana species germplasm collections have been evaluated for tobacco aphid infestations in small field plots in North Carolina, South Carolina, Kentucky, Tennessee and Georgia (7, 13). Aphid resistance observed with some tobacco genotypes may be due to high levels of pyridine alkaloids (8). In 1982 Johnson and Severson (77) reported that chemicals produced by leaf trichomes played an important role in determining resistance of different tobacco introductions (TI) to the green morph of the tobacco aphid. In this paper we report on the effect of different leaf surface chemistries of N. tabacum germplasm on the colonization of tobacco by the red morph of the tobacco aphid, and discuss studies conducted to determine mechanisms of resistance. We also discuss the effects of specific cuticular isolates on the survival and fecundity of adult tobacco aphids. Materials and Methods In 1990, 1991 and 1992, eighteen N. tabacum genotypes were grown in replicated field plots (3 replications of 12 plants) under typical flue-cured tobacco production practices at the Crops Research Laboratory, Oxford, NC and at the University of Georgia Coastal Plain Experiment Station, Tifton, GA. Six weeks after transplantation, five leaves (12-18 cm in length) were collected from each tobacco type from two of the replications. One 2-cm diameter disc was cut from the center of each leaf and the discs were dipped 8 times into a scintillation vial containing 10 ml of methylene chloride (Burdick and Jackson distilled in glass grade). The vial was sealed with a teflon lined cap, cooled in dry-ice, and stored in the freezer (-18°C) until analysis. Subjective ratings (0, no aphids to 7, maximal infestation) were made of natural aphid infestations on all three replications (10). The cuticular component extracts were analyzed by capillary gas chromatography using a slightly modified method of Severson et al. (75). An internal standard (92.5 μg of tricosanol) was added to the vial containing the cuticular extract and the sample was mixed. About a 0.75 cm equivalent of the sample from tobaccos with secreting trichomes or 1.5 cm from tobaccos with 2
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Hedin et al.; Natural and Engineered Pest Management Agents ACS Symposium Series; American Chemical Society: Washington, DC, 1993.
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NATURAL AND ENGINEERED PEST MANAGEMENT AGENTS
nonsecreting trichomes was transferred to a 1-ml tapered reacti-vial. The solvent was removed under a stream of nitrogen, 50 μΐ of 1:1 N-Obis(trimethylsilyl)-trifluroacetamide: dimethylforamide (Pierce Chemical Company) was added, the vial was capped, and was heated at 76°C for 45 min to convert hydroxylated components to trimethylsilylethers. After cooling, the sample was transferred to a 100 μΐ micro autosampler vial and the vial was capped. A 1 μΐ portion was analyzed on a Hewlett Packard 5890 gas chromatograph equipped with a splitless injector (purged activation time 1.0 min; injector temp. 250° C), flame ionization detector (detector temp 350° C), and a 7673A auto sampler using a 0.5 mm id X 20 m bonded SE54 fused silica capillary column (hydrogen flow rate 18 ml/min). A temperature program of 100° C to 160° C at 15° C/min and 160° C to 300° C at 5° C/min was used. Internal standard methodology was used to calculate component levels. Cuticular extracts used for the isolation of components were obtained from different M tabacum genotypes that were grown in blocks of 100 plants. Cuticular components were extracted from plant tops using methylene chloride as previously described (75). The extracts from the following tobaccos were used to isolate specific components using the methodology reported by Severson et al.(7
