Allozyme variation among populations of the groundnut seed
Contents
1. C sieberiana samples Adh2 1 for the clustering of T indica 84 M SEMBENE et al samples Got1 1 and Got2 3 for the grouping of P reticulatum and groundnut samples Pfi and Afi did not cluster with the other P reticulatum and groundnut samples DISCUSSION AND CONCLUSION With 1 8 alleles per locus C serratus populations show a rather low enzyme polymorphism The percentage of polymorphic loci 44 8 is similar to percentages commonly reported for other groups of insects 56 in Phlebotomus papatasi Kassem etal 1993 53 6 in Hypera postica Hsiao and Stutz 1985 37 7 in Dacus cucurbitae Yong 1992 and 35 in Yponomeuta spp Menken 1982 The comparison of polymorphism rates between different insect species is however not straightforward as it depends not only on the criterion 95 or 99 used to determine polymorphism but also on the enzyme systems used Polymorphism is maintained in laboratory samples of C serratus Samples Bou and Cfi which were reared for one generation from a small number of females have rates of polymorphism equal to or even higher 50 0 and 62 5 respectively than most of the other samples In these samples one might have expected low genetic variability resulting from a founding effect Hartl 1994 Kassem et al 1993 The persistence of high variability suggests a low degree of consanguinity in field collected individuals at least in these two2. 0 100 0 025 0 265 0 237 0 630 0 897 0 000 0 000 0 300 0 325 0 411 0 398 0 282 0 197 0 000 0 300 0 117 0 349 0 152 0 37 0 000 0 075 0 095 0 117 1 00 0 371 0 000 0 12 0 325 0 325 0 410 0 322 Pth 0 050 0 139 0 647 0 007 0 150 0 304 0 516 0 000 0 225 0 340 0 349 0 000 0 000 0 075 0 117 0 371 0 12 0 300 0 489 Tth 0 000 0 000 0 000 0 000 0 275 0 247 0 103 mn 0 000 0 000 _ 0 000 0 000 0 275 0 447 0 219 0 002 0 397 0 396 0 24 0 59 0 02 0 03 0 125 0 175 0 133 0 092 0 216 0 237 0 231 0 116 0 584 0 323 0 456 0 146 T8 Te P ANHANAS NW Seed beetle population genetics 83 Goti 2 Pgmi 2 Goi2 2 CF2 22 1 var Pgm1 3 Adhi t 0 1 2 CF1 50 9 var Fig 3 CFA scattergram of seed beetle samples from the different localities in Senegal See Materials and Methods for naming codes Alleles are numbered according to their migration speed for example Adh1 1 is the slowest allele of Adh 1 Genetic analysis Parameters of genetic variability ofthe 17 samples are given in Table 1 The number of alleles varied from 1 5 to 2 2 mean 1 8 The difference between allele frequencies at a given locus was lower between geographically distant samples from the same host plant than between sympatric samples from different host plants except for P reticulatum and g
3. 162 166 Johnson C D 1986 Caryedon serratus Olivier Bruchidae established in northern and southern America with additional host and locality recorded from Mexico Coleopt Bull 40 264 Kassem H A Fryauff D J Shehata M G and El Sawaf B M 1993 Enzyme polymorphism and genetic variability of one colonized and several field populations of Phlebotomus papatasi Diptera Psychodidae J Med Entomol 30 407 413 Krafsur E S Obrycki J J and Flanders R V 1992 Gene flow in populations of the seven spotted lady beetle Coccinella septempunctata Heredity 83 440 444 Lebrun P and Chevallier M H 1990 Starch and Polyacrilamide Gel Electrophoresis of Hevea brasiliensis A Laboratory Manual I R C A C LR A D Publisher France 55 pp Matokot L Mapangou DivassaS and Delobel A 1987 Evolution des populations de Caryedon serratus Ol dans les stocks d arachide au Congo Agron trop 42 69 74 Menken S B J 1982 Biochemical genetics and systematics of small ermine moths Lepidoptera Yponomeutidae Zool Syst Evolut Forsch 20 131 143 Moretti J Broussier G and Jayle M F 1957 R alisation technique et premi res applications de l lectrophor se sur gel d amidon Bull Soc Chim Biol 39 593 605 Ndiaye S 1991 La bruche de l arachide dans un 86 gt _ M SEMBENE et al agrosyst me du centre ouest du S n gal Contribution l tude de la contamination en plein champ e
4. 3 segregates far from other samples This could be explained by the fact that Afi was collected in a farmer s store This storage population may have originated from a very small initial infestation with a high consanguinity level as a result Fimela data also suggest that infestation of P reticulatum may at times originate from T indica and or B rufescens The generally strong association of C serratus genotypes with particular hosts plants would indicate the existence of relatively isolated populations or biotypes Seed beetles associated with P reticulatum exhibit strong geneticsimilarity with those associated with groundnut indicating a close relationship between these two groups of insects The peculiarity of C sieberiana associated forms questions the accuracy of the present classification of this group ofinsects Hybridisation experiments are underway to elucidate its taxonomic status Acknowledgments The authors thank Michel Ribodeau ENSA Thi s and St phane Bombard Institut Pasteur Dakar for help with statistical treatment of data and Philippe Borsa ORSTOM Paris for helpful comments and suggestions REFERENCES Ali Diallo B 1991 Biologie de Caryedon serratus OL en pr sence de ses plantes h tes sur le terrain et en conditions exp rimentales Th se de Doctorat Universit de Niamey Anonymous 1991 STAT ITCF Manuel d utilisation Institut Technique des C r ales et des Fourrages Paris Boro
5. Gagnepain et al 1986 Delobel and Matokot 1991 Food plant selection and larval development studies Robert 1984 Ali Diallo 1991 as well as morphometry Semb ne and Delobel 1996 provide support to the hypothesis that there exists some genetic isolation between C serratus populations with different feeding habits andin particular between groundnut feeding and Caesalpiniaceae feeding forms Sound control methods based on principles other than destruction by costly and dangerous chemicals cannot be developed without an understanding of the population biology of the pest For example females laying eggs on pods shortly after harvest are known to be responsible for primary field infestation of groundnut Matokot et al 1987 Ndiaye and Jarry 1990 personal observations Prevention will differ according to whether these females originate from groundnut stores from wild hosts or whether they emerge from quiescence or diapause at the end of the rainy season Questions such as whether stored groundnuts constitute a reservoir for the reinfestation of wild hosts at certain periods of the year and the range over which such areinfestation is possible need to be answered In order to determine the degree of isolation between wild forms and those feeding on groundnuts we analysed the genetic variability of Senegalese populations of C serratus feeding on seeds of five host plants species Piliostigma reticulatum Bauhinia
6. arachides au s n gal M m Comit Etudes Hist Scient A O F 1 363 438 Semb ne M and Delobel A 1996 Identification morphom trique de populations soudano sah liennes de bruche de l arachide Caryedon serratus Olivier Coleoptera Bruchidae J Afr Zool 110 357 366 Swofford D L and Selander R B 1981 Biosys 1 A Fortran program for the comprehensive analysis of electrophoretic data in population genetics and systematics J Heredity 72 281 283 Terranova A C 1981 Polyacrylamide gel electrophoresis of Anthonomus grandis Boheman proteins USDA SEA Agronomical Research Results ARR S 9 Ward R D Skibinski D O F and Woowark M 1992 Protein heterozygosity protein structure and taxonomic differentiation Evolution Biol 26 73 159 Yong H S 1992 Allozyme variation in the melon fly Dacus cucurbitae Insecta Diptera Tephritidae from peninsular Malaysia Comp Biochem Physiol 102 B 367 370
7. samples The overall average expected heterozygosity 0 184 of C serratus in Senegal is somewhat lower than reported in most other Coleoptera 0 160 in Coccinella 7 punctata Krafsur et al 1992 0 206 in Leptinotarsa decemlineata Jacobson and Hsiao 1983 0 231 in Hypera postica Hsiao and Stutz 1985 0 236 in Anthonomus grandis Terranova 1981 all of which belong to the same superfamily Phytophagoidea as C serratus It is however higher than in most insects mostly non Phytophagoidea 0 074in 23 insects species Nevo 1978 0 083 in Yponomeuta spp Menken 1982 0 116 in Phlebotomus papatasi 0 137 in 170 insect species Ward et al 1992 Higher genetic variability is expected in species exploiting variable environments than those restricted to more stable environments In the case of the Senegalese population of C serratus with five hosts having distinct phenologies one may expect a rather high variability It should also be mentioned that scoreable and informative enzyme systems vary from one insect species to the other Sample Tkb exhibits a homozygote deficiency which suggests an open genetic system in which females mate preferentially with heterozygous males In all other samples mean heterozygosity is lower than expected under Hardy Weinberg predictions which indicates a preferentially assortative reproductive behaviour In spite of this high heterozygote deficiency only A hypogaea and P reticul
8. 38 0 275 0 387 Samples Keur Baka Ckb 0 000 0 000 0 000 0 000 m 0 150 0 349 0 578 0 000 0 000 0 425 0 335 0 258 0 16 0 100 0 139 Pkb 0 027 0 073 0 649 0 38 0 075 0 322 0 772 0 000 0 200 0 381 0 485 0 000 0 000 0 050 0 095 0 483 0 007 0 250 0 420 0 301 0 291 0 415 0 09 0 18 0 01 Tkb 0 000 0 000 0 000 0 000 0 300 0 266 0 114 0 000 0 000 0 000 0 000 0 550 0 439 0 242 0 16 0 108 0 113 0 100 0 142 0 215 0 117 0 562 0 203 0 560 0 209 0 137 0 178 Aou 0 050 0 095 0 483 0 75 0 100 0 304 0 678 0 000 0 300 0 434 0 313 0 000 0 000 0 025 0 072 0 661 0 038 0 300 0 399 0 259 0 12 Ouarak Bou 0 000 0 000 0 050 0 219 0 777 0 000 0 325 0 355 0 098 0 275 0 237 0 147 1 00 0 125 0 117 0 054 1 00 0 325 0 316 Pou 0 060 0 095 0 475 0 75 0 125 0 355 0 655 0 000 0 350 0 440 0 216 _ 0 000 0 000 _ 0 050 0 095 0 483 0 007 0 225 0 387 Tou 0 000 0 000 0 000 0 000 0 000 0 175 0 538 0 681 0 025 0 025 0 000 1 00 0 000 0 000 0 225 0 462 0 016 0 429 0 522 1 00 0 01 0 01 0 129 0 183 0 133 0 071 0 217 0 207 0 229 0 171 0 478 0 131 0 453 0 601 Thi s Ath Bth 0 025 0 000 0 117 0 000 0 791 0 002
9. 712 0 775 0 750 0 850 0 000 0 000 0 000 0 000 0 000 0 000 0 125 0 250 0 000 0 063 0 800 0 825 0 750 0 800 0 863 0 063 0 013 0 075 0 250 0 188 0 200 0 063 0 000 0 225 0 000 0 000 0 725 0 750 0 788 0 863 0 025 0 275 0 138 0 262 0 162 0 700 0 788 0 700 0 625 0 025 0 075 0 038 0 213 0 013 0 000 0 013 0 075 0 000 0 000 0 000 0 000 0 200 0 050 0 000 0 200 0 075 1 2 3 Lap 1 1 000 0 775 1 000 1 000 0 000 0 138 0 000 0 013 1 000 0 863 1 000 0 988 1 000 0 000 1 000 1 000 0 962 0 213 0 950 1 000 0 320 0 138 0 000 0 000 0 000 0 680 0 863 0 000 1 000 1 000 1 2 1 Adh 1 0 950 0 938 0 938 1 000 0 962 0 938 0 525 0 962 1 000 0 038 0 063 0 475 0 038 0 000 Adh 2 0 050 0 063 0 063 0 000 0 287 0 112 0 425 0 338 0 712 0 813 0 575 0 663 0 000 0 075 0 000 0 000 0 962 0 938 0 950 1 000 0 038 0 063 0 050 0 000 0 038 0 788 0 050 0 000 0 262 0 075 0 300 0 325 0 275 0 150 0 262 0 363 0 725 0 813 0 738 0 637 0 000 0 038 0 000 0 000 0 000 0 000 0 000 0 000 2 2 0 738 0 925 0 700 0 675 37 5 0 338 0 150 0 075 0 338 0 338 0 563 0 813 0 925 0 563 0 663 0 100 0 038 0 000 0 100 0 000 81 1 5 25 0 22 62 5 27 2 2 62 5 62 5 1 7 25 0 2 2 62 5 2 2 62 5 22 50 0 1 5 25 0 2 2 50 0 1 5 37 5 1 5 25 0 1 7 25 0 2 2 1 7 50 0 62 5 1 7 P 95 criterion 37 5 Table 2 Observed mean heterozygosity Ho expected mean he
10. _ Insect Sci Applic Vol 18 No 1 pp 77 86 1998 0191 9040 98 3 00 0 00 Printed in Kenya All rights reserved 1998 ICIPE ALLOZYME VARIATION AMONG POPULATIONS OF THE GROUNDNUT SEED BEETLE CARYEDON SERRATUS OL IN SENEGAL M SEMBENE J P BRIZARD AND A DELOBEL 1 Laboratoire de Protection des Stocks ITA ORSTOM B P 2765 Dakar S n gal Laboratoire de G n tique et d Am lioration des Plantes ORSTOM B P 1386 Dakar S n gal Accepted 4 May 1998 Abstract Starch gel electrophoresis was used to compare eight loci in six enzymatic systems of 17 samples of the groundnut seed beetle Caryedon serratus Ol Coleoptera Bruchidae bred on five different host plant species Arachis hypogaea Bauhinia rufescens Cassia sieberiana Piliostigma reticulatum and Tamarindus indica The rate of polymorphism was 44 8 The average genetic diversity Hw was 0 184 Allozyme variability analysis indicated that seed beetles associated with P reticulatum and groundnut Arachis hypogaea were genetically similar whereas other samples clustered according to their host plant species Geographical distances less than 400 km were not decisive for the genetic structuring of samples associated with a given host plant Key Words Caryedon serratus seed beetle groundnut population genetics electrophoresis allozyme variation R sum L lectrophor se sur gel d amidon a permis de comparer huit loci appartenant six syst mes enz
11. atum samples exhibited a significant deviation from Hardy Weinberg expectations On Piliostigma reticulatum the population dynamics of C serratus seems to depend on the succession of a shorter period November to February when ripe pods are abundant in the field and a longer period March to October when they become progressively less available then absent When the first pods reach maturity after the rainy season in November C serratus population levels are usually very low Infestation rates on P reticulatum at that time are not higher than 2 to 4eg s per 1000 pods which suggests that P reticulatum samples consist in a mixture of the F1 of a limited number of founding females On newly harvested groundnut infestation rates are similarly low inthe order of 1 egg per 10 000 seeds Matokot et al 1987 in Congo personal observations in Senegal This partly explains why A hypogaea samples are not panmictic On the contrary B rufescens trees bear pods all year round Infestation rates do not exhibit the wide fluctuations observed on P reticulatum a situation which is more favourable to panmixia Tamarindus indica fruition reaches a peak in March April Inter tree variability is high so that a few ripe tamarind pods may be found in a given area at any time of the year Ndiaye 1991 Moreover tamarind seeds are a common by product of several local meals in Senegal They are potential reservoirs for C serr
12. atus before new pods mature As indicated earlier C sieberiana samples were collected late in the season after the C serratus population had undergone several generations in the field This precludes the development of an artificial founding effect and certainly explains the absence of deviation from Hardy Weinberg expectations The relative genetic isolation between these populations is best explained by the fact that they feed on different host plants samples from B rufescens which are all very similar are characterised by allele frequencies which are different from other samples The same is true for samples from T indica and C sieberiana These Seed beetle population genetics 85 convergent results seemtoindicatethathostplants play a major part in the genetic structuring of the C serratus population in Senegal To the contrary A hypogaea samples cannot be differentiated from P reticulatum samples by their allele frequencies These samples show morphological similarities as indicated by morphometric analysis Sembene and Delobel 1996 Geographic distances in the order of 200 to 400 km do not seem to play a decisive role in this structuration except for groundnut and P reticulatum associated forms samples from the same locality show a low degree of relatedness Fig 3 In this respect samples collected in Fimela Pfi and Afi clearly stand out Afi with an unusually high frequency of Adh1 1 and Lap1
13. eters were estimated 1 genetic variability allele frequencies mean number of alleles per locus and rates of polymorphism and heterozygosity A locus 80 M SEMBENE et al was consideredas polymorphicifthe frequency of its most common allele was less than 95 2 genetic equilibrium deviation from Hardy Weinberg equilibrium absence of linkage disequilibrium Genotype frequencies were tested against Hardy Weinberg expectations with panmixia as the null hypothesis The value of the consanguinity Leucine aminopeptidase Migration Loci Allele 3 Lap 1 0 Genotype Alcohol dehydrogenase Migration Loci Allele Adh 2 1 Adh 1 22 Genotype WP Adh 2 21 Glutamate oxalo acetate transaminase Migration Loci Allele 2 EE I 1 1 2 3 Got 1 22 Genotype Got 2 33 Phosphoglucomutase Migration Loci Allele Pgm 1 0 Genotype WE Heterodimer 3 EE Allele i interlocus heterodimer coefficient Fis represents the heterozygote deficiency of each population at each locus In the test of linkage disequilibrium the null hypothesis was independence between genotypes at different loci In both cases Fisher s exact test available in Genepop was used Correspondence factor analysis CFA was performed using STAT ITCF V5 Anonymous 1991 Degradation band Fig 2 Genetic interpretation of polymorphic zymograms of Caryedon serratus enzyme systems Seed beetle population ge
14. netics to ascertain seed beetle groupings and their relationships with allele frequencies at the various loci RESULTS Enzyme systems Six enzyme systems ENDO PGD GPI DIA HK and EST failed to stain reliably or did not show clear bandings Two of them ICD and MDH proved to be monomorphic Only LAP ADH GOT and PGM showed scoreable polymorphic loci Polymorphic loci LAP E C 3 4 1 1 the profiles showed numerous migration zones which could be interpreted as two loci of a monomeric enzyme a slow locus Lap 1 coding for an active enzyme with three electromorphs and a fast migrating highly polymorphic locus with numerous bands of low intensity The latter was not used ADH E C 1 1 1 1 zymograms exhibited two cathodally migrating activity zones each with two alleles The activity of the slowest enzyme ADH 1 coded by Adh 1 was low At both loci heterozygotes had three well defined bands The presence of inter locus heterodimers suggested the existence of a dimericenzyme with a duplicated gene and a post translational and or post transcriptional modification ADH 1 was not observed in samples from C sieberiana GOT E C 2 6 1 1 anodally migrating GOT 1 had two alleles The fast allele which was the most frequent showed two electromorphs the slowest of which was a degradation band Cathodally migrating and dimeric GOT 2 was coded by Got 2 with three alleles Heterozygotes appeared as more or les
15. reticulatum and Tkb from T indica In Ouarak Aou from A hypogaea Bou from B rufescens Pou from P reticulatum and Tou from T indica In Thi s Ath from A hypogaea Pth from P reticulatum and Tth from T indica Cfi and Bou were reared in the laboratory for one generation on their usual host Pods were collected as soon as they reached maturity when new infestations started except for C sieberiana samples which were collected at a period when seed beetle populations reached their highest levels after at least one generation in the pods Groundnut samples were collected from the field during drying except Afi which was taken from a farmer s store For each host plant species enough pods were collected to obtain at least 40 C serratus adults Insects were used as soon as they emerged Seventeen samples total 680 individuals of both sexes were analysed In case of doubt genitalia were examined in order to avoid any confusion with Caryedon crampeli Pic a species which also feeds on B rufescens C sieberiana and P reticulatum Voucher specimens including genital parts are kept in the LF A N Institut Fondamental d Afrique Noire Cheikh Anta Diop Dakar collections Starch gel electrophoresis Sample preparation Live individual seed beetles were crushed in an ice bath in 100 ul of buffer pH 7 4 made of 0 1M Tris 0 04M L cystein and 10 Triton X100 Homogenates were collected in Eppendorf tubes and cen
16. roundnut samples The proportion of polymorphic loci varied between 25 0 and 62 5 Observed Ho and expected Hw heterozygosities together with deviations from Hardy Weinberg expectations are shown in Table 2 for each locus and each sample Over all loci highly significant P lt 0 001 deviations from Hardy Weinberg expectations were observed in all groundnut and P reticulatum samples while C sieberiana samples were in slight disequilibrium P lt 0 05 No significant deviation was found in samples from B rufescens and T indica A slight excess of heterozygotes was however detected in Tkb Fis multilocus 0 242 Observed deviations were caused by a strong heterozygote deficiency 0 13 lt Fis multilocus lt 0 60 Over all loci deviations from Hardy Weinberg expectations occurred in populations from the same locality P lt 0 01 Finally over all loci and samples probability of deviation from Hardy Weinberg expectations was highly significant y 622 5 df 32 No linkage disequilibrium was found among any pair of allozymes for any sample P gt 0 05 Correspondence factorial analysis separated samples according to their host plants Fig 3 The most discriminating loci were Adh 1 and 2 and Got 1 and 2 The slow allele of Adh 1 Adh1 1 and the fastest allele of Pgm 1 Pgm1 3 were responsible for the clustering of B rufescens samples Adh2 2 for the clustering of
17. rufescens Tamarindus indica F 100 km p oo eae 16 N Ouarak Sahelian zone 14N Mo wale oa A J pe Guinean zone 12N D 4 16 W 14 W 12 W Fig 1 Map of Senegal showing the geographical origin of Caryedon serratus samples A Seed beetle population genetics 79 Cassia sieberiana and groundnut Arachis hypogaea Bauhinia tomentosa an uncommon and introduced ornamental host and Piliostigma thonningit absent from the northern part of Senegal were excluded from this study MATERIALS AND METHODS Study site In Senegal phytogeographic regions are basically determined by rainfall Parallel isohyetes define from north to south the sahelian less than 800 mm rainfall soudanian 800 to 1000 mm rainfall and guinean more than 1000 mm rainfall regions Fig 1 Samples originated from Ouarak 16 04 W 15 33 N Thi s 16 56 W 14 48 N Fimela 16 41 W 14 08 N and Keur Baka 15 57 W 13 56 N all within the sahelian zone C serratus samples Beetles used in this study were bred as eggs larvae or pupae from pods collected on different hosts species Samples were named after their host plant and geographic origin in Fimela sample Afi was obtained from Arachis hypogaea Bfi from Bauhinia rufescens Cfi from Cassia sieberiana Pfi from Piliostigma reticulatum and Tfi from Tamarindus indica InKeur Baka Akb was obtained from A hypogaea Ckb from C sieberiana Pkb from P
18. s oval bands PGM E C 5 4 2 2 two groups of well separated electromorphs were distinguished The faster was faint and could not be regularly scored It was not used in the analysis The slower enzyme PGM 1 was coded by amonomericlocus with three alleles The genotype which was homozygote for the median allele showed two close electromorphs the slower of which was faint The existence of double electromorphsin phosphoglucomutase has also been reported by Ouazzani et al 1993 Figure 2 shows the electrophoretic profiles of the four enzymatic systems and their genetic interpretation Samples Table 1 Allelic frequencies mean number of alleles A and percentage of polymorphic loci P for 17 samples of Caryedon serratus Thi s Ouarak Bou Keur Baka Akb _ Ckb Fimela Pth Tth 0 063 0 000 0 075 0 000 0 938 1 000 0 925 1 000 Ath Bth 0 100 0 138 0 075 0 000 Tou Pou Tkb Aou Pkb Tfi Cfi Bfi Afi 0 000 0 000 0 000 0 000 0 000 Allele 1 Loci 0 050 0 000 0 050 0 000 0 038 0 000 0 038 0 000 Got 1 0 950 1 000 0 950 1 000 0 100 0 125 0 138 0 000 0 825 0 875 0 788 1 000 0 962 1 000 0 962 1 000 0 100 0 000 0 100 0 000 0 825 1 000 0 813 1 000 1 000 1 000 1 000 1 000 1 000 0 000 0 112 0 075 0 000 0 000 1 000 0 887 0 925 1 000 1 000 1 Got 2 0 850 0 863 0 825 1 000 0 050 0 000 0 100 0 000 0 075 0 000 0 075 0 000 0 075 0 000 0 087 0 000 0 275 0 225 0 237 0 075 0
19. t dans les stocks de l arachide Arachis hypogaea L par Caryedon serratus OL Coleoptera Bruchidae r le des l gumineuses h tes sauvages dans le cycle de cette bruche Th se de Doctorat Universit de Pau et des Pays de l Adour Ndiaye S and Jarry M 1990 Importance de certaines l gumineuses arbor es et arbustives au S n gal dans le cycle de Caryedon serratus OL et influence sur la contamination en plein champ de l arachide Arachis hypogea L Proc 5th Int Work Conf Stored Prod Prot Bordeaux 1990 vol 3 1663 1669 Nevo E 1978 Genetic variation in natural populations Patterns and theory Theor Popul Biol 13 121 177 Ouazzani N Lumaret R Villemur P and Di Giusto F 1993 Leaf allozyme variation in cultivated and wild olives trees Olea europaea L J Heredity 84 34 42 Pasteur N Pasteur G Bonhomme F Catalan J and Britton Davidian J 1987 Manuel Technique de G n tique par Electrophor se des Prot ines Lavoisier Technique et Documentation Paris _ Raymond M and Rousset F 1995 Genepop V 1 2 A population genetics software for exact tests ecumenicism J Heredity 86 248 249 Robert P 1984 Contribution l tude de l cologie de la bruche de l arachide Caryedon serratus Ol Col opt re Bruchidae sur ses diff rentes plantes h tes Th se de Doctorat Universit Fran ois Rabelais Tours Roubaud E 1916 Les insectes et la d g n rescence des
20. ted in Africa and southern Asia Johnson 1986 About 60 years after its first record as a pest of groundnut in West Africa Roubaud 1916 C serratus has recently _ becomeamajor primary groundnut pestin Central Africa Matokot et al 1987 and Asia Dick 1987 Itis also recorded in Central and South Americain the seeds of ornamental Bauhinia Commonly Fonds Documentaire Cote B18 474 deux ee ota ORSTOM Ex d m 78 M SEMBENE et al known as the groundnut seed beetle C serratus is nowadays responsible for heavy weight losses in stored groundnuts in Senegal up to 83 losses after four months storage have been reported Ndiaye 1991 Caryedon serratus larvae consume the seeds of wild Caesalpiniaceae belonging to asmallnumber of species in four genera Bauhinia Cassia Piliostigma and Tamarindus Borowiec 1987 The larvae bore through groundnut hulls which favours attack by secondary pests such as Oryzaephilus mercator Tribolium confusum Ephestia cautella or Corcyra cephalonica as well as the spread of Aspergillus flavus a mould which produces a toxic substance aflatoxin Gillier and Bockel e Morvan 1979 Groundnutinfestation by the seed beetle raises the question of the mechanisms by which A hypogaea a plant of the family Fabaceae became part of the insect s range of hosts It is interesting to note that C serratus is not a pest of stored groundnuts in all groundnut growing regions in Africa
21. terozygosity Hw heterozygosity deficit Fis and deviation tests from Hardy Weinberg equilibrium for each locus of seed beetle samples from the different localities in Senegal The deviations compared with expected values are determined by the x test P lt 0 01 P lt 0 05 Loci Got 1 Got 2 Lap 1 Adh 1 Adh 2 Pem 1 Ho Hw Fis P Ho Hw Fis P Ho Hw Fis P Ho Hw Fis P Ho Hw Fis P Ho Hw Fis P Overall Ho Hw Fis 0 164 Afi 0 000 0 000 0 000 0 000 au Bf 0 000 0 025 0 000 0 200 0 878 0 000 0 000 0 200 0 320 0 301 0 000 0 275 0 000 0 237 0 147 1 00 0 075 0 125 0 072 0 117 0 02 0 054 1 00 1 00 0 560 0 325 0 475 0 316 0 016 0 019 1 00 Fimela Cfi 0 000 0 000 0 000 0 139 1 000 0 000 0 250 0 375 1 00 0 347 0 345 0 000 0 000 0 700 0 499 0 393 0 02 0 150 0 139 Pfi 0 000 0 000 0 000 0 000 0 000 0 320 1 00 0 000 0 000 nus 0 075 0 072 0 026 1 00 0 475 0 560 0 068 0 164 1 00 0 019 Tfi 0 000 0 000 0 000 0 000 0 275 0 247 0 103 0 000 0 000 0 000 0 000 0 275 0 447 0 396 0 029 0 092 0 158 0 183 0 092 0 092 0 159 0 195 0 192 0 379 0 201 0 221 0 374 0 146 0 161 0 116 Akb 0 025 0 072 0 661 0 38 0 050 0 304 0 839 0 000 0 275 0 417 0 351 0 000 0 000 0 025 0 072 0 661 0 0
22. trifuged at 26 000 rpm for 20 min The extract was collected between the resulting supernatant lipid and the deposit solid with a syringe It was then transferred to filter paper wicks 15x6mm which wereimmediately loaded into gels Running conditions and staining Electrophoresis was performed ina17x17x1cm 12 potato starch gel Gel preparation and migration techniques were those described by Moretti et al 1957 and Pasteur et al 1987 Gel buffer was made of Tris 0 02M and maleic acid 0 01M Gel slabs were run for 15 hina 0 02M Tris and 0 01M maleic acid buffer of pH 7 3 under a constant 120 V potential Specific staining solutions were prepared according to Lebrun and Chevalier 1990 To stop enzymatic activity the staining solution was replaced by a 7 acetic acid solution for 1 hour Gels were then kept for 12 h in the refrigerator in a 15 glycerol solution then dried at 60 C for 4 h Twelve enzymatic systems were tested alcohol dehydrogenase ADH diaphorase DIA endopeptidase ENDO esterases EST glutamate oxalo acetate transaminase GOT glucose phosphate isomerase GPI hexokinase HK isocitrate dehydrogenase ICD leucine aminopeptidase LAP malate dehydrogenase MDH 6 phosphogluconate dehydrogenase PGD and phosphoglucomutase PGM Statistical analyses Data were analysed using Genepop V1 2 Raymond and Rousset 1995 and Biosys 1 V1 7 Swofford and Selander 1981 The following param
23. wiec L 1987 The genera of seed beetles Coleoptera Bruchidae Polsk Pismo Entomol 57 3 207 Davey P M 1958 The groundnut bruchid Caryedon gonagra F Bull Entomol Res 49 385 404 Delobel A 1995 The shift of Caryedon serratus OL from wild Caesalpiniaceae to groundnuts took place in West Africa Coleoptera Bruchidae J stored Prod Res 31 101 102 Delobel A and Matokot L 1991 Control of groundnut insect pests in African subsistence farming Proc 5th Int Work Conf Stored Prod Prot Bordeaux vol 3 1599 1607 Dick K M 1987 Losses caused by insects to groundnuts stored in a warehouse in India Trop Sci 27 65 75 Gagnepain C Gillon Y and Leroux M 1986 Caryedon serratus Col Bruchidae principal insecte consommateur des gousses de Piliostigma thonningti Caesalpiniaceae en savane de Lamto C te d Ivoire Ann Soc Entomol Fr 22 457 467 Gillier P and Bockel e Morvan A 1979 La protection des stocks d arachide contre les insectes Ol agineux 3 131 137 Hartl D L 1994 G n tique des Populations M decine Sciences Flammarion Paris 305 pp Hsiao T H and Stutz J M 1985 Discrimination of alfalfa weevil strains by allozyme analysis Entomol exp appl 37 113 121 Jacobson J W and Hsiao T H 1983 Isozyme variation between geographic populations of the Colorado potato beetle Leptinotarsa decemlineata Coleoptera Chrysomelidae Ann Entomol Soc Amer 76
24. ymatiques chez dix sept chantillons de bruche de l arachide provenant de cinq plantes h tes diff rentes Arachis hypogaea Bauhinia rufescens Cassia sieberiana Piliostigma reticulatum et Tamarindus indica Le taux de polymorphisme est de 44 8 La diversit g n tique moyenne Hw est de 0 184 L analyse de la variabilit allozymique montre que les bruches inf od es a P reticulatum et l arachide sont g n tiquement tr s proches alors que les autres chantillons se regroupent en fonction de leur esp ce h te Les distances g ographiques inf rieures 400 km ne sont pas d terminantes dans la structuration g n tique des chantillons d une plante h te donn e Mots Cl s Caryedon serratus bruche arachide population g n tique lectrophor se allozyme INTRODUCTION roundnut Arachis hypogaea L was introduced from South America to Africa towards the end of the sixteenth century Its cultivation in West Africa remained low well into the early part of the nineteenth century With the intensification of edible oil refining which occurred durii3 tfie last third of the nineteenth century groundnut farming experienced a ae dramatic increase particularly in Senegal The PL author MS 77 first infestations of stored groundnuts by the bruchid Caryedon serratus Olivier were reported in Senegal at the turn of the twentieth century Davey 1958 Delobel 1995 Caryedon serratus is widely distribu
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