Insecticides of Plant Origin - American Chemical Society

Chapter

14

Downloaded by PENNSYLVANIA STATE UNIV on August 23, 2013 | http://pubs.acs.org Publication Date: February 23, 1989 | doi: 10.1021/bk-1989-0387.ch014

Insect Growth Inhibitors from Petunia and Other Solanaceous Plants C. A. Elliger and A. C. Waiss, Jr. Agricultural Research Service, U.S. Department of Agriculture, 800 Buchanan Street, Albany, CA 94710 From Petunia and Physalis species were obtained a number of steroidal compounds that contribute to plant resistance against insect feeding. Petuniasterones from P. hybrida and the ancestoral species P. parodii and P. axillaris varied in larval growth inhibiting activity toward Heliothis zea depending on structure with the most active materials having a bicyclic orthoester system on the steroid side chain. Physalis peruviana contained numerous withanolides, among which highly glycosylated derivatives appeared to be most active against H. zea. These allelochemicals are discussed in relation to the eventual transfer of the substances into economically significant crops to provide an expanded basis for insect resistance. For many years chemists have been isolating and identifying substances from plants that are more or less effective in suppressing insects. The investigation of these substances among which are antifeedants, growth inhibitors, antihormones, and other toxicants is justified on the basis of finding on the one hand a new class of "natural pesticides** for commercial application or on the other a relationship between these phytochemicals and **host plant resistance** in appropriate cases. At the present time, however, after a l l these efforts, only the old well known and established, pyrethrins, rotenoids and nicotine are used as "insecticides** in commercially significant quantities (1). There are, of course, a number of promising candidates whose acceptance would depend upon economic considerations other factors being equal. A difficulty with compounds showing anti-insect activity is that they are not toxic enough, in general, to be commercially satisfactory for external application, and this then leads to the basic question of host plant resistance. Why do these substances confer a selective advantage to the plant? We feel that these agents do provide just this advantage when they are presented by This chapter not subject to U.S. copyright Published 1989 American Chemical Society

In Insecticides of Plant Origin; Arnason, J., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1989.


14. ELLIGER & WAISS

Insect Growth Inhibitors

189

the p l a n t to i t s herbivores v i a an e f f i c i e n t d e l i v e r y system. Generally, dosage o f d e l e t e r i o u s substances takes p l a c e during i n s e c t f e e d i n g on an o t h e r w i s e v u l n e r a b l e p l a n t p a r t o r r e p e l l e n c y i s manifested i n close proximity to that part. I t i s not i n p r i n c i p l e necessary, therefore, f o r the p l a n t to cover i t s e n t i r e structure or i t s vicinity with potent insecticides. It is s u f f i c i e n t f o r t h e p u r p o s e o f d e f e n s e i f exposure t o a compound o f moderate b i o l o g i c a l a c t i v i t y be s e l f - i n f l i c t e d by t h e a t t a c k i n g insect. F o r t h i s r e a s o n t h e r e a r e v e r y few s u b s t a n c e s from p l a n t s t h a t a r e p o t e n t enough t o be termed " i n s e c t i c i d e s " . A feature of host plant resistance exists that l i m i t s i t s usefulness i n crop p r o t e c t i o n . Such r e s i s t a n c e i s n o t a c t u a l l y e f f e c t i v e enough a g a i n s t the pests t h a t a r e o f major economic concern. T h i s i s n o t a s u r p r i s e t o t h e e c o l o g i s t who r e a l i z e s t h a t our present observations r e l a t e to a co-evolutionary stalemate where c e r t a i n i n s e c t s have c a r v e d o u t t h e i r own n i c h e s by e v o l v i n g t o l e r a n c e t o s u b s t a n c e s t h a t may once have been e f f e c t i v e a g a i n s t them. Thus, f o r example, g o s s y p o l i n c o t t o n s e r v e s t o ward o f f a t t a c k o f many i n s e c t s b u t a c t u a l l y a t t r a c t s t h e b o l l w e e v i l ( 2 ) . S i m i l a r l y , t h e c u c u r b i t a c i n s , s e r v i n g t o r e p e l most i n s e c t s , a r e kairomones f o r s p e c i a l i s t b e e t l e s ( 3 ) . The attempts by t h e p l a n t breeder to u t i l i z e host plant resistance have been toward i n c r e a s i n g the content o f a c t i v e substances already present w i t h i n a p a r t i c u l a r c r o p (4, 5) o r t o i n t r o d u c e r e s i s t a n c e f a c t o r s found i n c l o s e l y r e l a t e d p l a n t v a r i e t i e s ( 6 ) . However, t h e amount o f v a r i a b i l i t y a v a i l a b l e i n t h i s manner i s l i m i t e d by t h e g e n e t i c p o o l o f a g i v e n p l a n t s p e c i e s and may, i n many i f n o t most c a s e s be insufficient to a f f o r d protection e s p e c i a l l y i n view of the co-evolutionary process mentioned above. At best, i t may be e x p e c t e d t h a t s e l e c t i v e b r e e d i n g would be s i m p l y a b l e t o r e s t o r e t o a s p e c i f i c c r o p t h a t degree o f r e s i s t a n c e which a l r e a d y e x i s t e d i n i t s wild progenitors. T h i s then i s a q u a n t i t a t i v e e f f e c t , but the putative resistance factors will not i n these cases differ q u a l i t a t i v e l y from t h o s e t o which t h e p e s t i n s e c t s have a l r e a d y developed t o l e r a n c e . To c i r c u m v e n t t h e l i m i t a t i o n s o f c l a s s i c a l h o s t p l a n t r e s i s t a n c e a new means o f i n t r o d u c i n g r e s i s t a n c e f a c t o r s must be found. T h i s means i s now a v a i l a b l e w i t h i n t h e t e c h n i q u e s o f modern c e l l b i o l o g y and m o l e c u l a r g e n e t i c s . We s h a l l e v e n t u a l l y be able to provide the e s s e n t i a l q u a l i t a t i v e transformations of h o s t p l a n t r e s i s t a n c e by t r a n s f e r r i n g s o u r c e s o f r e s i s t a n c e n o t m e r e l y between s p e c i e s w i t h i n t h e same genus b u t u l t i m a t e l y between genera w i t h i n a p l a n t f a m i l y . We have chosen t h e tomato p l a n t ( L y c o p e r s i c o n esculentum) as an e x p e r i m e n t a l s u b j e c t upon which t o t e s t t h i s c o n c e p t . The tomato was chosen b e c a u s e o f i t s economic s i g n i f i c a n c e and because i t s complement o f e x i s t i n g r e s i s t a n c e f a c t o r s has been w e l l studied (1-9). A d d i t i o n a l l y , t h e l i n k a g e maps o f n u c l e a r chromosomes i n tomato a r e among t h e most w e l l e s t a b l i s h e d ( 1 0 ) . As an example o f a s i g n i f i c a n t i n s e c t p e s t o f t h i s p l a n t , we p i c k e d t h e polyphagous l e p i d o p t e r a n H e l i o t h i s z e a (Boddie) t h e l a r v a e o f w h i c h a r e known synonymously as tomato f r u i t w o r m , c o r n earworm, c o t t o n b o l l w o r m and soybean podworm. E x p e r i m e n t a l advantages o f t h i s i n s e c t i n c l u d e i t s ready a d a p t a t i o n t o a r t i f i c i a l d i e t s and i t s b r o a d h o s t range which render i t a very severe t e s t of p o t e n t i a l p l a n t defense


190

INSECTICIDES OF PLANT ORIGIN

systems. Before we could begin to explore advanced genetic techniques i t was necesary to screen various candidates among various solanaceous plants that appeared suitable on the basis of other considerations (such as lack of known substances deleterious to humans). We examined a number of species i n several genera within the Solanaceae (Table I) i n an exploratory screening f o r a c t i v i t y against H. zea and selected a number of active species for further study.


Table I. Species Examined within the Solanaceae for A c t i v i t y Against H e l i o t h i s zea Species

Genus

esculentum, hirsutum, pervianum lycopersicoides, tuberosum, melongena annuum tabacum alkakengi, ixocarpa, peruviana hybrida, a x i l l a r i s , p a r o d i i , violacea suaveolens betacea sinuata

Lycopersicon Solanum Capsicum Nicotiana Physalis Petunia Brugmansia Cyphomandra Salpiglossis

Table II presents the results of a feeding study using foliage of a few of these species. Four-day old larvae of H. zea were placed Table I I . Survival of 4-Day Old H. zea on Several Solanaceous Species

Larvae

Percent Survival Days after Application

L. esculentum (Ace) L. hirsutum, f. glab. Physalis ixocarpa P. peruviana Petunia hybrida (Blue Cloud) Control D i e t * b

a. b.

a

1 Day

2 Days

4 Days

6 Days

Weight of Survivors After 6 Days + s.d.

100 95 95 90

90 90 95 90

90 90 95 80

90 90 95 55

261 mg + 120 40 103 10 20 6 1

75 100

50 100

35 100

35 100

90 700

59 78

20 larvae i n i t i a l l y applied. A r t i f i c i a l diet used i n bioassays and insect rearing containing no additive compounds (14).

upon leaves i n p e t r i dishes provided with moist f i l t e r paper to maintain freshness. As feeding progressed, leaves were changed



14. ELLIGER & WAISS


191

d a i l y and the larvae were allowed to feed for a t o t a l of s i x days on the leaves (ten days o v e r a l l ) . I t can be seen that none of the experimental sets had larvae that grew to a size approaching that of control animals. This i s a manifestation of the presence of growth i n h i b i t i n g factors which are known to be present i n even the standard susceptible plant tested (Ace tomato) (1-9). This e f f e c t i s even more pronounced with neonate larvae for which mortality i s high and stunting i s so severe that individual weights were not p r a c t i c a l to obtain. Exposure of plant material to older larvae i s a more severe test of plant defenses inasmuch as these older animals are more tolerant i n general to allelochemicals (11). The two Physalis species and the Petunia horticultural variety possessed sufficient additional resistance over Ace tomato (Lycopersicon esculentum) to merit consideration as sources of transgenic resistance factors. The other Lycopersicon species, L. hirsutum. F. Rlabratum i s amenable to standard techniques of plant crossing (12). I t may be noted that i n the l a t t e r case, the responsible agent for enhanced resistance, 2-tridecanone, has already been described (13). Physalis and Petunia, of course, d i f f e r greatly from tomato i n plant c h a r a c t e r i s t i c s with the former producing a large b e r r y - l i k e f r u i t within an expanded fused calyx and the l a t t e r being known for i t s flowers. I t may be admitted at t h i s time that transgenic combinations of these with Lycopersicon w i l l probably produce a range of plant types which may or may not have desirable properties from an economic standpoint. Our concern i s with host plant resistance, however, and we f e e l that any enhancement of resistance within progeny of these combinations would be of great importance. We established that the resistance factors i n Physalis and Petunia are chemical i n nature by s e r i a l extraction of leaf material with successively more polar solvents followed by incorporation of material from these extracts into artificial diets. Fractions obtained from extraction of plant material (and eventually solutions of pure compounds) were evaporated onto c e l l u l o s e powder and incorporated into modified Berger diet (14). Newly hatched larvae of H e l i o t h i s zea were applied to each of ten r e p l i c a t e diets and were allowed to feed for ten days. Larval weights were obtained and were compared to the weight of control larvae that were grown on diets containing as additive only c e l l u l o s e powder. Generally, we have expressed l a r v a l growth as precent of control values, and the term ED50 ( e f f e c t i v e dosage) i s defined as that concentration of additive required to reduce l a r v a l growth to f i f t y percent of control weights. Thus, we found that active material i n Petunia i s found i n hexane and ethyl acetate fractions (or i n chloroform), but not i n subsequent extracts of higher p o l a r i t y . The active substances of the Physalis species are s u b s t a n t i a l l y more polar and appear i n acetone and methanol extracts. Identification of the respective active components of these extracts i s of substantial importance, f i r s t i n order to follow t h e i r appearance i n the transgenic progeny and secondly to explore t h e i r toxicology. Petuniasterones. Further f r a c t i o n a t i o n of chloroform extracts from Petunia hybrida i n a sequence of chromatographic procedures yielded



192


a large number of s t e r o i d a l ketones of unusual f u n c t i o n a l i t y that vary i n t h e i r potency toward i n h i b i t i n g development of H. zea larvae. We have termed these petuniasterones (15) and have categorized them into several groups which are shown here. A l l of these compounds are derived from a 28 carbon steroid and have a carbonyl group at C-3 with either a hydroxy- or acetoxy- group at C-7. The side chain possesses oxygenated functionality at positions -22, -24, and -25. Among the members of the various series are Α-ring dienones and 1-acetoxyenones. Further oxygenation may be found at C-12, C-17 and upon the position ot to the t h i o l e s t e r moiety which i s present i n some cases as a substituent on a b i c y c l i c orthoester system. The side chain may have orthoester substitution, hydroxy or ester groups flanked by oxirane f u n c t i o n a l i t y , three hydroxy groups, or a c y c l i c ether with a hydroxy substituent. The orthoesters and oxirane containing compounds are much more abundant i n plant extracts than the l a s t two substances mentioned. We have observed that f a c i l e conversion of one type to another can occur i n v i t r o . Thus, elimination of the 1-acetoxy group i n series Β, Ε and Η takes place under mild conditions to afford the corresponding dienones. Also, i t was noted that the bridged orthoester systems of the A, D and Ε series may be formed under a c i d i c c a t a l y s i s from the corresponding petuniasterones Β or C whereby the carboxylate ester attached to C-22 i s converted to orthoester and the epoxy ring i s opened (Equation 1). PS-F, -G^ and - G 2 were formed when unesterified PS-C was treated with aqueous acid (Equation 2). We suspect that similar conversions occur naturally within the plant from appropriately substituted 24,25-oxirane containing precursors. As mentioned above the petuniasterones d i f f e r i n i n h i b i t o r y a c t i v i t y toward H. zea. Tables III and IV show the results of feeding studies i n which dietary levels of added petuniasterones were presented to larvae at concentrations up to 800 ppm. Table I I I .

Growth Inhibitory A c t i v i t y of Petuniasterone Toward Heliothis zea

Compound Petuniasterone A (I) Petuniasterone A Acetate Methyl Ester from PS-A Petuniasterone D (XIII) 12-Acetoxypetuniasterone D Acetate (XIV) a.

MW

PPM

Microraoles/Kg

558 600 542 484

130 144 35 130

233 237 65 269

584

135

231

ED50 is defined as dietary concentration of additive s u f f i c i e n t to reduce growth to 50% of control subjects grown on a r t i f i c i a l diet with no additive. Growth period was ten days.

Of these compounds, only those having the b i c y c l i c orthoester system were s i g n i f i c a n t l y active i n reducing l a r v a l growth (Table I I I ) . We had o r i g i n a l l y suspected that the Α-ring dienone system



14. ELLIGER & WAISS

193


V

R =CHOHCOSCH , R =H, R =Ac 1

3

2

3

Petuniasterone A Series




Petuniasterone D Series

XV

XVI

Petuniasterone E

Petuniasterone F


ELLIGER & WAISS



14.


195


196


XVI

XVII


14. ELLIGER & WAISS

197

Insect Growth Inhibitors Table IV.

Inactive Substances'

Compound

Max.

Level Tested

Growth at Level

Max.


b

A l l Petuniasterone Β (VI-VIII) A l l Petuniasterone C (IX-XII) Petuniasterone F (XVI) 30-Hydroxy PS-A (IV) 17-Hydroxy PS-Α (II) 17-Hydroxy PS-Α, Acetate (III) Testosterone 4-Cholesten~3-one 1-Dehydrotes tos terone a. b.

800 800 800 400 400 800 800 800 800

PPM PPM PPM PPM PPM PPM PPM PPM PPM

70-95% 80-94% 89% 91% 69% 6 7% 102% 84% 104%

Materials not reducing growth of H. zea larvae to 50% of control values at maximum l e v e l tested after ten days. Growth expressed as percent of control wts. f o r larvae grown on diets without additive.

gave r i s e to i n h i b i t o r y a c t i v i t y , but our observations that the C-series compounds (IX-XII) and PS-F (XVI) were inactive showed that this was not true. The model compound, 1-dehydrotestosterone, also having an Α-ring dienone actually proved to be mildly stimulatory to growth. Presence of the t h i o l e s t e r moiety was not essential for activity. PS-D (XIII) with i t s unsubstituted orthoacetate was just as active as PS-A (I) and the methyl ester formed from the t h i o l e s t e r by trans-ester i f i c a t i o n of PS-Α was the most active compound tested. Acetylation of the hydroxyl group at p o s i t i o n -7 does not appear to influence a c t i v i t y ; however, our preliminary observations on PS-Ε (XV) indicate that a c t i v i t y i s reduced when the Α-ring dienone system i s not present. Only a small amount of XV was available f o r testing, and bioassay was conducted on concentrations up to 150 ppm i n this case. Larval growth was 69% of control weight at t h i s level. Further substitution of hydroxyl at position -17 (II & III) or at position -30 (IV) of the orthoester appears to eliminate i n h i b i t o r y a c t i v i t y . A l l of these observations taken together do not point to a s p e c i f i c mode of action. I t i s tempting to speculate, however, that some disruptive action upon the insect's hormonal system i s occurring because of the s t e r o i d a l nature of these compounds. In another case involving the e f f e c t of diterpene r e s i n acids upon lepidopterans i t was shown that cholesterol at high dietary levels could reverse i n h i b i t i o n caused by the acids (16). In the present study, cholesterol at levels of up to 4000 ppm had no e f f e c t upon the action of petuniasterone A. We have noted that f o r dietary levels of active substances i n the range of approximately the ED50 most larvae survive even though stunted, whereas f o r larvae on petunia leaves or on diets containing crude extracts many larvae die. In fresh leaves of Royal Cascade petunia the highest l e v e l of PS-Α (I) was about 120 ppm and that of PS-D (XIII) and 12-acetoxypetuniasterone D, 7-acetate (XIV) was 30 and 100 ppm respectively. We found that



198


i n h i b i t o r y a c t i v i t y of PS-Α (I) and PS-D (XIII) was additive and not synergistic (this may be true f o r a l l active compounds). The a c t i v i t y of PS-A was not changed by the presence of the inactive PS-B, 22-hemithiomalonate (VI), and i t may be assumed that the other inactive substances do not s i g n i f i c a n t l y enhance or decrease the e f f e c t of the i n h i b i t o r y petuniasterones. The l e v e l of active compounds i n the petunia c u l t i v a r studied i s thereby about 250 ppm or approximately twice the ED50 and this amount t y p i c a l l y reduces l a r v a l growth to about 25% of control weights with nearly 100% survival. The greater a c t i v i t y of crude material suggests that additional, s i g n i f i c a n t l y active substances have not been isolated. Among commercial v a r i e t i e s of Petunia hybrida, the content of petuniasterones i s quite variable. We have observed, for example, Table V.

Survival of 3-Day Old Larvae of H. zea upon Petunia and Lycopersicon Leaves a

Plant L. P. P. P. P. P. a.

esculentum (Ace) hybrida (Blue Cloud) hybrida (Royal Cascade) violacea parodii axillaris

Number of Surviving Larvae one day two days 15 7 6 15 2 7

15 3 1 13 0 3

15 Larvae applied i n i t i a l l y .

that the variety "Blue Jeans" has almost no PS-A i n i t s leaves. I t was of interest to examine the putative ancestors of the hybrids both with respect to insect resistance i n general and to the various petuniasterones i n p a r t i c u l a r . There i s some disagreement concerning the actual species of Petunia that have given r i s e to the present hybrids, but i t i s f e l t that P. violacea, P. p a r o d i i , P. a x i l l a r i s and P. i n f l a t a are l i k e l y ancestors (17). We were able to acquire seed of a l l but the l a s t mentioned and grow plants for evaluation. Table V compares l a r v a l survival on leaves of these three Petunia species with that of larvae on two commercial v a r i e t i e s and on leaves of a commercial tomato. The difference between plants i s impressive and suggests that there may be a q u a l i t a t i v e difference f o r the toxic agents contained within P. parodii. This difference i s confirmed by comparison of the h.p.l.c. p r o f i l e s f o r extracts of these petunias (Figure 1). One can e a s i l y see that the insect susceptible P. violacea has a very low content of petuniasterones whereas P. a x i l l a r i s more nearly resembles the hybrid already studied. The highly resistant P. p a r o d i i appears to contain d i f f e r e n t compounds. We have performed preliminary workups of P. p a r o d i i and a x i l l a r i s and have isolated several new petuniasterones from the former species, only one of which was abundant within extracts of the l a t t e r . Our proposed structures are shown here (XIX-XXIII), but i n c e r t a i n cases the assignment of stereochemistry i s not rigorously established. I t i s




14. ELLIGER & WAISS


199



200


14. ELLIGER & WAISS



R

XXII R=CH COSCH 2

3

XXIII


201



202

interesting that although we have not yet performed insect bioassays on pure substances the increased i n s e c t i c i d a l a c t i v i t y of this plant i s correlated with further oxygenation of the petuniasterone system. Also of note, and perhaps not surprising i n view of the enhanced t o x i c i t y of the plant i s that the r a p i d i t y of action of crude extracts permits observation of acute effects upon the larvae treated. We have seen rapid onset of uncontrolled diuresis for these larvae a f t e r consumption of only a few b i t e s of a r t i f i c i a l d i e t containing these extracts. The animals immediately stop feeding, lose body turgor and become moribund due to dehydration. Such action makes the compounds of P. p a r o d i i of special interest to the insect physiologist. From a standpoint of plant breeding i t i s i r o n i c that a r t i f i c i a l s e l e c t i o n for color (from violacea) may a c t u a l l y have resulted i n a loss of insect resistance f o r the r e s u l t i n g hybrids which formerly had been present in the white flowered Petunia p a r o d i i . a

Table VI. Growth of H. z e a on A r t i f i c i a l Containing P. peruviana Extracts

Diets

b

Hexane Ethyl acetate Acetone Methanol a. b.

102 30 9 0.6

±6 ±6 ±5 ±0.6

Expressed as % of control wts. + s.d. after ten days. Extracts were incorporated into a r t i f i c i a l diets on a wt. basis equivalent to o n e - f i f t h the amount o r i g i n a l l y present i n fresh plant leaves.

Inhibitory agents of Physalis. Growth i n h i b i t i o n of H. zea larvae by Physalis peruviana extracts i s shown i n Table V I . The methanol and acetone f r a c t i o n s were examined further by i n i t i a l p a r t i t i o n i n g of their constituents between water and the macroreticular, nonionic r e s i n XAD-2. The insect i n h i b i t o r y a c t i v i t y of both fractions was associated with material that underwent sorption to the r e s i n . Subsequent chromatographic separations of the materials released from the XAD-2 by desorption with methanol were carried out on Sephadex LH-20 (Methanol as eluent) to give i n each case broad zones showing b i o l o g i c a l a c t i v i t y . Further chromatographic examination by h.p.l.c. using Dynamax C-18 columns with acetonitrile/water gradients showed that considerable overlap of components occurred between the acetone and methanol extracts. The n.m.r. spectra of the s t i l l crude mixtures indicated the presence of a number of substances within the withanolide family, a group of s t e r o i d a l lactones long known to be present in Physalis species as well as i n other genera within the Solanaceae (18, 19). Further chromatographic workup on preparative Dynamax C-18 of the LH-20 active zones gave a number of pure or highly enriched substances having a range of b i o l o g i c a l potency from completely inactive to highly i n h i b i t o r y at dietary levels below 100 ppm. Most of these compounds remain u n i d e n t i f i e d , but the ^-H n.m.r. and n.m.r. spectra show that aglycones, mono-, d i - , and t r i g l y c o s i d e s are




ELLIGER & WAISS

XXIV

OH OH :

1

GlucO

XXV



204

represented with the most polar of these occurring in the methanol extract. Two substances, XXIV and XXV have been identified. Compound XXIV, 4-B-hydroxy withanolide E, has already been reported to have anti-insect activity (20, 21) against larvae of the lepidopteran, Spodoptera ν littoralis. Our preliminary results indicate an ED50 of ça. 250 ppm for XXIV toward H. zea. The 3-B-glucoside of perulactone (XXV) has not been previously reported although the, aglucone has been described (22). Initial results shown an ED of 150 ppm (ca. 220 micromolal) in H. zea bioassays. Several of the more highly glycosylated compounds appear to be at least an order of magnitude more active. It is possible that dietary uptake and transport within the insect are enhanced by the increased water solubility of these derivatives.


50

Conclusion The purpose of this investigation has been to facilitate the transfer of genetic characteristics related to insect resistance into plants having economic usefulness. The source of this genetic material can profitably lie within plants which are distantly related now that modern methods exist to carry out intergeneric hybridization. The role *of the chemist in this process s t i l l consists in isolation and structure determination of biologically active substances. In this instance chemistry serves to provide genetic markers for analyses of hybrid progeny. Here the chemist is concerned with the eventual delivery system as well as with the individual components that contribute to insect resistance. At the present time we are conducting experiments on protoplast fusion which should lead to production of many hundreds of plant types. It can be seen that chemical analysis is much more practical for this large number than is recourse to artificial infestation by insect pests, etc. We expect the eventual intergenerically transformed tomato plants (e.g. Lycopersicon χ Physalis) to have a longer lasting or more durable resistance in the face of evolutionary change of the insect pests. Insects that have become adapted to or tolerant toward resistance factors of tomato may not develop detoxification mechanisms for the Physalis chemicals or those of Petunia. Multigenic resistance in plants would have to be met by more complex biochemical evolution for a given pest insect. Evolution of tolerance toward pesticides by insects is rapid as we a l l know; even such an advanced agent such as Bacillus thurensensis toxin can lose effectiveness under certain circumstances (23.24)· We hope to avoid this problem by presenting the pest with an array of phytochemicals that will place a more severe burden upon the evolutionary capability of insects. Thus, multigenic resistance factors will require multiple enzyme systems for detoxification and will place an unacceptable load upon the insect. Literature Cited 1. Jacobson, Μ., Botanical Pesticides: Past, Present and Future; This Volume. 2. Maxwell, F. G.; Lafever, Η. N.; Jenkins, J. N. J. Econ. Entomol., 1966, 59, 585-588.



14. ELLIGER & WAISS


205

3. Metcalf, R. L.; J. Chem. Ecol. 1986, 12, 1109-1124. 4. Juvik, J. A.; Stevens, M. A. J. Amer. Soc. Hort. Sci. 1982, 107, 1061-1065. 5. Maxwell, F. G.; Jennings, P. R., Eds. Breeding Plants Resistant to Insects; Wiley-Interscience: New York, 1980; 683p. 6. Gibson, R. W. Amer. Potato J. 1978, 55, 595-599. 7. Elliger, C. A.; Wong, Y.; Chan, B. G.; Waiss, A. C., Jr. J. Chem. Ecol. 1981, 7, 753-758. 8. Isman, M. B.; Duffey, S. S. Entomol. Exp. Appl. 1982, 31, 370-376. 9. Campbell, B.C.;Duffey, S. S. J. Chem. Ecol. 1981, 7, 927-946. 10. Tanksley, S. D.; Bernatzky, R. Molecular Markers for the Nuclear Genome of Tomato, In Tomato Biotechnology; ARL: New York, 1987; pp 37-44. 11. Shaver, T. N.; Parrott, W. L. J. Econ. Entomol. 1970, 63, 1802-1804. 12. Rick, C. M. Genetic Resources in Lycopersicon, In Tomato Biotechnology; ARL: New York, 1987; pp 17-26. 13. Williams, W. G.; Kennedy, G. G.; Yamamoto, R. T.; Thacker, J. D.; Bordner, J. Science 1980, 207, 777-889. 14. Chan, B. G.; Waiss, A. C., Jr.; Stanley, W. L.; Goodban, A. E. J. Econ. Entomol. 1978, 71, 366-368. 15. Elliger, C. Α.; Benson, M. E.; Haddon, W. F.; Lundin, R. E.; Waiss, A. C., Jr.; Wong, R. J. Chem. Soc. Perkin Trans. 1 1988, 711-717. 16. Elliger, C. Α.; Zinkel, D. F.; Chan, B. G.; Waiss, A. C. Jr.; Experentia 1976 32, 1364-1365. 17. Sink, K. C. in Petunia; Sink, K. C., Ed.; Springer: Berlin 1984; pp. 3-9. 18. Kirson, I.; Glotter, E. J. Nat. Prod. 1981, 44, 633-647. 19. Glotter, E.; Kirson, I.; Lavie, D.; Abraham, A. In Bioorganic Chemistry; Van Tamelen, Ε. E., Ed.; Academic Press: New York, 1978; Vol. II pp. 57-95. 20. Ascher, K. R. S.; Nemny, N. E.; Eliyahu, M.; Kirson, I.; Abraham, Α.; Glotter, E. Experentia 1980, 36, 998-999. 21. Ascher, K. R. S.; Eliyahu, M.; Glotter, E.; Goldman, Α.; Kirson, I.; Abraham, Α.; Jacobson, M.; Schmutterer, H. Phytoparasitica 1987, 15, 15-29. 22. Gottlieb, H. G.; Kirson, I.; Glotter, E.; Ray, A.; Sahai, M.; Ali, A. J. Chem. Soc. Perkin Trans. I 1980, 2700-2704. 23. McGaughey, W. H. Science 1985, 229, 193-195. 24. McGaughey, W. H.; Beeman, R. W. J. Econ. Entomol. 1988, 81 28-33. RECEIVED November 2, 1988


Insecticides of Plant Origin - American Chemical Society

Recommend Documents