Bruchid Species Research Articles

Why Callosobruchus rhodesianus causes limited damage during storage of cowpea seeds in a tropical humid zone in Togo

AbstractThe sympatric bruchids Callosobruchus rhodesianus (Pic) and Callosobruchus maculatus (F.) (Coleoptera: Bruchidae) colonize cultures of cowpea, Vigna unguiculata (Walp.) (Papilionaceae), in Togo at the end of the rainy season. Seeds containing larvae of the two bruchid species were introduced into the storage systems. Callosobruchus rhodesianus adults emerged from the seeds at the beginning of storage, but this species disappeared quickly and C. maculatus became dominant. Analysis of the reproduction of females collected at the beginning of storage made it possible to distinguish between four groups of females differing in their reproductive activity. Three groups were sexually active but they differed in their fecundity and the duration of the latency period before the first oviposition phase. The fourth group of females was in reproductive diapause. In interspecific competition, the presence of C. maculatus larvae reduced the survival chances of C. rhodesianus and therefore is disadvantageous for this species. The main factors explaining the rapid decrease of the C. rhodesianus populations under storage conditions were the variability of female reproductive activity with the emergence of insects in reproductive diapause and the significant larval mortality in interspecific competition with C. maculatus.

Extracts from Tephrosia vogelii for the protection of stored legume seeds against damage by three bruchid species

AbstractAliquots of powdered dried leaves of Tephrosia vogelii (Leguminosae – Papilionoideae) were extracted with hexane, acetone and ethanol. The extracts were tested for their potential to protect stored legume seeds from damage by the bruchids Acanthoscelides obtectus, Callosobruchus maculatus and Callosobruchus chinensis (Coleoptera – Bruchidae). While the acetone and ethanol extracts were ineffective except for a significant but low effect on A. obtectus, the hexane extract had a relatively high efficacy, providing similar control of all three bruchid species. This effect was manifested in slowly‐reduced adult survival within 7 days and in reduced numbers of eggs laid and of F1 progeny produced, resulting in seed damage averaging 7.1% compared to 99.8% in the untreated controls after one generation. These findings are discussed in the context of previously identified constituents of T. vogelii, the rotenoids rotenone, tephrosin and deguelin.

Ancient and recent evolutionary history of the bruchid beetle, Acanthoscelides obtectus Say, a cosmopolitan pest of beans

Acanthoscelides obtectus Say is a bruchid species of Neotropical origin, and is specialized on beans of the Phaseolus vulgaris L. group. Since the domestication and diffusion of beans, A. obtectus has become cosmopolitan through human-mediated migrations and is now a major pest in bean granaries. Using phylogeographic methods applied to mitochondrial DNA (mtDNA) and nuclear microsatellite molecular markers, we show that the origin of this species is probably further south than Mesoamerica, as commonly thought. Our results also indicate that A. obtectus and its Mesoamerican sister species Acanthoscelides obvelatus, two morphologically close species differing principally in voltinism, speciated in allopatry: A. obtectus (multivoltine) arising in Andean America and A. obvelatus (univoltine) in Mesoamerica. In contrast to Mesoamerica where beans fruit once yearly, wild beans in Andean America fruit year-round, especially in regions showing little or no seasonality. In such habitats where resources are continuously present, multivoltinism is adaptive. According to existing hypotheses, multivoltinism in A. obtectus is a new adaptation that evolved after bean domestication. Our data suggest the alternative hypothesis that multivoltinism is an older trait, adapted to exploit the year-round fruiting of wild beans in relatively aseasonal habitats, and allowed A. obtectus to become a pest in bean granaries. This trait also permitted this species to disperse through human-mediated migrations associated with diffusion of domesticated beans. We also show that diversity of Old World A. obtectus populations can be quite well explained by a single colonization event about 500 bp. Human-mediated migrations appear not to be rare, as our results indicate a second more recent migration event from Andean America to Mexico.

Checklist of the Bruchidae (Insecta: Coleoptera) of Mexico

Johnson and Kingsolver (1981) estimated that there were 140 species of Bruchidae in Mexico. We now know that there are at least 334 species in 23 genera of Bruchidae in Mexico. This increase is due to research that has produced new distribution records and new species. In the checklist the species are listed by genus and distribution records are given for each species. Brief histories on the work of researchers in the New World and estimates of numbers species of bruchids in the New World and worldwide are given. Four names are excluded from a checklist of bruchids of the New World for a variety of reasons. Bruchus ingae Fåhraeus (1839) has only been found in southern South America and the original designation from Mexico is considered to be in error. Bruchus serraticornis (Fabricius) was published by Fabricius (1775) on page 65 with a locality as “Habitat in Oriente.” Blackwelder (1946) indicated that serraticornis was published by Fabricius (1775) on page 66 (erroneously) and was from “Mexico, Old World.” In several recent papers European entomologists (Decelle and Lodos 1989; Borowiec and Anton 1993; Anton et al. 1997) indicated that serraticornis (Fabricius) was in the Old World genus Bruchidius. The name is therefore excluded. Bruchus triangularis Say (1831:1) and B. oculatus Say (1831:2), both from Mexico, were among the species described by Say (1831) whose types were apparently lost. These names cannot be applied to any species with any degree of certainty because of inadequate descriptions by Say. They continue to appear on checklists but not in the literature, so after 170 years we consider them to be nomina dubia and therefore they were removed from the checklist.

Infochemical‐mediated preference behavior of the parasitoid Microctonus hyperodae when searching for its adult weevil hosts

AbstractInfochemicals are the most important cues used by parasitoids for host location. The attractiveness of infochemicals in a tritrophic context is expected to be determined by the degree of specialization of the parasitoid and its host(s). Microctonus hyperodae Loan (Hymenoptera: Braconidae) is an oligophagous parasitoid that attacks adult Curculionidae of the Brachycerinae subfamily, especially Listronotus bonariensis Kuschel, on Gramineae. In 1996, a new host–parasitoid association between the carrot weevil Listronotus oregonensis LeConte and M. hyperodae was created in the laboratory. In this study, the infochemicals used by M. hyperodae when searching for its adult weevil hosts were determined using a Y‐shaped olfactometer. Three curculionid species (L. oregonensis, Listronotus sparsus Say, and Neydus flavicaudis Boheman) and one bruchid species [Callosobruchus maculatus (Fabricius)], and their feces, were tested. It was expected that hosts phylogenetically and ecologically close to L. bonariensis would be more attractive than species less related but in fact, M. hyperodae responded only to L. oregonensis and its feces. When feces and host insects were tested separately, M. hyperodae responded to the odors emitted by L. oregonensis adults but not to their feces, suggesting that most of the kairomones came from the host itself. Host plants were also tested, but M. hyperodae responded neither to Lolium multiflorum Lamark (Gramineae) nor to Daucus carota L. (Umbelliferae) leaves.

Determinants of oviposition inAcanthoscelides obtectus: a nonconformist bruchid

Abstract.Acanthoscelides obtectusis atypical of bruchids found in stored seeds because females do not attach eggs individually to host seeds but scatter them irregularly among potential hosts. In other respects, its life history resembles that of other species and comparison provides evidence for the adaptive nature of their behaviour. Individual females differ dramatically in the temporal pattern of their oviposition. The hypothesis is proposed that this is an adaptation to life in heterogeneous habitats. Oviposition is not regulated by host availability to the same extent as in other bruchids, providing evidence that regulation of the number of eggs laid by species which stick eggs to host seeds is an adaptation to the abundance of hosts. The continued presence of males and opportunity for multiple matings does not affect fecundity or egg viability. Females preferentially lay on clean seeds when provided with a choice between them and seeds previously exposed to other adult beetles. However, they do not appear to be deterred by, or cannot detect, the presence of larvae infesting seeds. Other bruchid species avoid such seeds that they can identify by the occurrence of egg cases and pheromones. The number of eggs laid is influenced by the host cultivar available for oviposition. Oviposition byA. obtectusappears to be an adaptation to both storage environments and the heterogeneous environment of a growing crop or uncultivated land. Its behaviour suggests an ancestral condition in bruchids and the changes which might have occurred in the ecology of other bruchid species as they have adapted to become pests of human seed stores.

Evolutionary aspects of host plant specialisation – a study on bruchids (Coleoptera: Bruchidae)

We have studied the relationship of bruchids and their legume hosts by extensive field sampling throughout Hungary over 17 years and by rearing the beetles from the samples in the laboratory. The value of the system lies in the accuracy of host affiliations. A total of 138 species and subspecies of plants were sampled, representing approximately 87% of the Leguminosae in Hungary. Only 51 legume species (37.0%) harboured bruchids (12 Bruchus spp. and 15 Bruchidius spp). Bruchids occurred in 38.3% of the host plant samples. Thirty‐seven plant species congeneric with bruchid host species were unoccupied by bruchids.The degree of host specificity ranged from monophagy (at least ecological monophagy) to oligophagy. On the basis of presence/absence data we tested the null hypothesis assuming that plant taxa and seed consuming bruchid species form congruent phyletic relations at the species level. We argue that the case for coevolution between the beetles and their hosts is weak. A comparison of the available taxonomic relationships (and presumed phylogenies) best fits a case of sequential evolution, with stronger phylogenetic conservatism in Bruchus species than in Bruchidius species. Bruchid and host plant taxa showed rough congruence only at the tribe level. We suggest that host shifts are best explained by the changes in the bruchids’ chemosensory system that determines the females’ host selection behaviour.

Characterization of resistance to three bruchid species (Callosobruchus spp., Coleoptera, Bruchidae) in cultivated rice bean (Vigna umbellata).

Resistance of wild and cultivated rice bean (Vigna umbellata [Thunberg] Ohwi and Ohashi) to three bruchid species, Callosobruchus chinensis L., Callosobruchus maculatus F., and Callosobruchus analis F., was evaluated. All but three accessions of cultivated, and all wild rice bean accessions tested, exhibited complete resistance to all three bruchid species. Rice bean seeds with seed coat removed also showed complete resistance to the three bruchid species. Results indicate that physical attributes and/or chemical(s) present in the seed coat of rice bean are not the main factors responsible for resistance. Feeding tests were performed by using artificial beans prepared with varying proportions of rice bean (resistant) and azuki bean (susceptible) flour. Number of bruchid adults that emerged decreased, and larval developmental period (days) was extended, when artificial beans with an increasing proportion of rice bean flour were used. These tests revealed that a chemical compound(s) contained in the cotyledon of rice bean has an inhibitory effect on the growth of these bruchid species. The results also indicate that the chemical(s) in rice bean cotyledon is most effective against C. maculatus.

Effect of a trypsin inhibitor from Dimorphandra mollis seeds on the development of Callosobruchus maculatus

Bruchid larvae cause major losses in grain legume crops throughout the world. Some bruchid species, such as the cowpea weevil, are pests that damage stored seeds. Plants synthesize a variety of molecules, including proteinaceous proteinase inhibitors, to defend themselves against attack by insects. In this work, a trypsin inhibitor (DMTI-II) isolated from Dimorphandra mollis seeds was tested for anti-insect activity against Callosobruchus maculatus larvae. The inhibitor produced ca. 67% mortality to this bruchid when incorporated into an artificial diet at a level of 1%. The doses necessary to cause 50% mortality (LD 50) and to reduce weight by 50% (ED 50) for DMTI-II were ca. 0.50% and 0.60%, respectively. The action of DMTI-II on C. maculatus larvae may involve the inhibition of trypsin-like activity of larval midgut extracts, the absence of digestion by midgut preparations or with a mixture of pepsin and papain, and its association with a chitin column and chitinous structure in the midgut of this insect.

Insects Associated with Seeds of Lonchocarpus muehlbergianus Hassl. (Fabaceae) in Tres Barras, Parana, Brazil

To find the insects associated with seeds of a Brazilian native leguminous plant, Lonchocarpus muehlbergianus Hassl., fruits were collected from isolated trees in Tres Barras, Parana, Brazil. A sample of 500 g of fruits with 2353 seeds was evaluated in the laboratory. It was found that 77.4% of the seeds were not damaged by insects, 12.4% of the seeds were damaged and 10.2% of the seeds were empty. The bruchid species Ctenocolum crotonae (Fahraeus) was detected for the first time in this plant. This species was recorded in Mato Grosso, Brazil and, in this paper, the geographical distribution is amplified to include Parana State. Horismenus missouriensis Ashmead (Hymenoptera: Eulophidae) was also observed in the sample and it is probably a parasitoid of the bruchid larva or pupa. Of the 2353 seeds, 4.9% were damaged by C. crotonae and 4.6% had emergence holes of H. missouriensis. Larvae of Tenebrionidae and Curculionidae were also detected feeding on the seeds, representing 2.8% of the total number of the seeds.

Talisia esculenta lectin and larval development of Callosobruchus maculatus and Zabrotes subfasciatus (Coleoptera: Bruchidae)

Bruchid larvae cause major losses in grain legume crops throughout the world. Some bruchid species, such as the cowpea weevil and the Mexican bean weevil, are pests that damage stored seeds. Plant lectins have been implicated as antibiosis factors against insects, particularly the cowpea weevil, Callosobruchus maculatus. Talisia esculenta lectin (TEL) was tested for anti-insect activity against C. maculatus and Zabrotes subfasciatus larvae. TEL produced ca. 90% mortality to these bruchids when incorporated in an artificial diet at a level of 2% (w/w). The LD 50 and ED 50 for TEL was ca. 1% (w/w) for both insects. TEL was not digested by midgut preparations of C. maculatus and Z. subfasciatus. The transformation of the genes coding for this lectin could be useful in the development of insect resistance in important agricultural crops.

Differences in midgut serine proteinases from larvae of the bruchid beetles Callosobruchus maculatus and Zabrotes subfasciatus.

Proteinase activities in the larval midguts of the bruchids Callosobruchus maculatus and Zabrotes subfasciatus were investigated. Both midgut homogenates showed a slightly acidic to neutral pH optima for the hydrolysis of fluorogenic substrates. Proteolysis of epsilon-aminocaproil-Leu-Cys(SBzl)-MCA was totally inhibited by the cysteine proteinase inhibitors E-64 and leupeptin, and was activated by 1.5 mM DTT in both insects, while hydrolysis of the substrate Z-ArgArg-MCA was inhibited by aprotinin and E-64, which suggests that it is being hydrolysed by serine and cysteine proteinases. Gel assays showed that the proteolytic activity in larval midgut of C. maculatus was due to five major cysteine proteinases. However, based on the pattern of E-64 and aprotinin inhibition, proteolytic activity in larval midgut of Z. subfasciatus was not due only to cysteine proteinases. Fractionation of the larval midgut homogenates of both bruchids through ion-exchange chromatography (DEAE-Sepharose) revealed two peaks of activity against Z-ArgArg-MCA for both bruchid species. The fractions from C. maculatus have characteristics of cysteine proteinases, while Z. subfasciatus has one non-retained peak of activity containing cysteine proteinases and another eluted in a gradient of 250-350 mM NaCl. The proteolytic activity of the retained peak is higher at pH 8.8 than at pH 6.0 and corresponds with a single peak that is active against N-p-tosyl-GlyGlyArg-MCA, and sensitive to 250 microM aprotinin (90% inhibition). The peak contains a serine proteinase which hydrolyzes alpha-amylase inhibitor 1 from the common bean (Phaseolus vulgaris). Arch.

The effect of arcelin-1 on the structure of the midgut of bruchid larvae and immunolocalization of the arcelin protein

Some wild accessions of the common bean ( Phaseolus vulgaris) contain a family of proteins called arcelins, that are toxic to the larvae of certain bruchid species. Among the six allelic variants of arcelin tested so far, arcelin-5 and arcelin-1 confer the highest level of resistance against the Mexican bean weevil, Zabrotes subfasciatus. The same proteins are not toxic to the bean weevil, Acanthoscelides obtectus, which is also a serious pest of cultivated beans. Arcelins belong to the bean lectin family that includes phytohemaggutinins and α-amylase inhibitors. Although homologous to lectins, arcelins are themselves only very weak lectins, and their binding properties have not been clearly established. The toxic properties of arcelins may be related to their recognition of and interaction with the glycoproteins and other constituents of the membranes along the digestive tract of insects. Since arcelin-1 was shown to have growth inhibitory effects for the larvae of Z. subfasciatus but not of A. obtectus, we examined the effect of an arcelin-1 containing diet on the structure of the cells that line the intestinal tract of the larvae of these two bruchid species, and used antibodies against arcelin to examine the distribution of arcelin within the cells and tissues. Here we show that dietary arcelin-1 caused an alteration of the gut structure and the penetration of arcelin into the haemolymph in Z. subfasciatus but not in A. obtectus. These results lead us to suggest that arcelins exert their toxic effect by severely damaging the epithelial cells.

Molecular characterization of Rickettsia sp. in a bruchid beetle, Kytorhinus sharpianus (Coleoptera : Bruchidae)

An endosymbiotic/parasitic bacterial associate was detected by diagnostic PCR experiments in the bruchid beetle, Kytorhinus sharpianus. Molecular phylogenetic analysis of the 16S rDNA sequence demonstrated that the bacterium is a new member of the genus Rickettsia. Among four bruchid species of three subfamilies examined, the Rickettsia was detected only in K. sharpianus.Not all in viduals of K, sharpianus possessed the Rickettsia, suggesting that the microbe is likely to be a facultative companion of the host insect, rather than an obligate symbiont.

Genetic engineering with α-amylase inhibitors makes seeds resistant to bruchids

AbstractSeeds of the common bean,Phaseolus vulgaris, contain two inhibitors of mammalian and insect α-amylases (αAls) that show specificity towards the amylases of different insect species. Expression in pea (Pisum sativum) and azuki bean (Vigna angularis) of a chimeric gene consisting of the cDNA of bean αAl-1 and a seed-specific promoter makes the seeds of these legumes resistant to three species of Old World bruchids whose amylases are inhibited by αAl-1. This was the first successful genetic engineering of insect resistance in seeds. To understand the basis of the specificity between amylases and inhibitors we cloned a second bean inhibitor (αAl-2) with different specificity, and we cloned the cDNA of the New World bruchid,Zabrotes subfasciatus. The amylase of this bruchid is inhibited by αAl-2, but not by αAl-1. Knowledge of the amino acid sequences and of the three-dimensional structure of the pancreatic α-amylase–αAl-1 complex allows us to predict the peptide domains and amino acids of the proteins that are important for protein–protein recognition and inhibition of enzyme activity.

Molecular cloning of bruchid ( Zabrotes subfasciatus) α-amylase cDNA and interactions of the expressed enzyme with bean amylase inhibitors

α-Amylases are important digestive enzymes in weevils that infest starchy seeds, and plants have evolved proteinaceous α-amylase inhibitors (αAI) for protection. To gain a better understanding of the interaction between weevil α-amylases and αAIs, we cloned the α-amylase cDNA of Zabrotes subfasciatus larvae. Larvae of this bruchid infest seeds of cultivated varieties of the common bean, Phaseolus vulgaris, although the seeds contain high levels of an αAI. The α-amylase cDNA, called ZsAmy, encodes a mature protein of 466 amino acids with a signal peptide of 17 amino acids. This protein has 50–60% amino acid identity with the other five known insect α-amylases. Three amino acid residues known to be important for catalysis and three histidine residues involved in substrate binding are conserved in the derived amino acid sequence of ZsAmy. Expression of ZsAmy with a baculovirus vector in cultured insect cells resulted in the production of active α-amylase. αAI-1, the form of the inhibitor found in cultivated beans, does not inhibit larval or expressed bruchid α-amylase, but αAI-2, a form of the inhibitor found in certain wild bean accessions, does inhibit the larval, as well as the expressed bruchid α-amylase. These and other observations lead to the conclusion that ZsAmy encodes the major larval amylase of this bruchid species.

Potential of four vegetable oils and ten botanical powders for reducing infestation of cowpeas by Callosobruchus maculatus, C. chinesis and C. rhodesianus

The possible use of ten botanicals and four vegetable oils in managing the bruchid beetles of legumes, Callosobruchus chinesis, C. maculatus and C. rhodesianus, was investigated. All four oils tested (corn, groundnut, sunflower and sesame) significantly reduced the oviposition of all three bruchid species at 10 ml/kg and also significantly reduced the longevity of adults of C. maculatus and C. chinensis at this dose. Only corn and sunflower oil caused a significant reduction of longevity of C. rhodesianus at 10 ml/kg. The number of eggs laid by all three bruchid species was significantly reduced in treatments to which powders of Cymbopogon citratus, Cinnamomum camphora, Derris inudata, Monodora myristica, Zingiber spectabile or A. zerumbet had been added.

Acacia Seed Predation by Bruchids in an African Savanna Ecosystem

1. Acacia tortilis, A. nilotica and A. mellifera seeds on the ground suffered greater bruchid infestation than seeds within canopy held pods. 2. Seeds of indehiscent and dehiscent Acacia species showed no difference in the rate of bruchid infestation. More bruchid species attacked seeds of indehiscent (A. nilotica, A. tortilis, A. hebeclada and A. robusta) than dehiscent (A. karroo, A. mellifira and A. caffra) species. 3. Bruchid infestation differed between A. tortilis trees, and for A. tortilis and A. hebeclada, differed between years. There was no difference in bruchid attack on A. nilotica between years. 4. Stored Acacia seeds were infested more than fresh seeds. 5. The results of this research have important implications for re-afforestation programmes with Acacia trees in Africa. Pods should be collected from the canopies of Acacia exhibiting low bruchid infestation, the length of seed storage should be minimized and seeds susceptible to the same bruchid species should not be stored together.

Influence of two successive learning processes on the response ofEupelmus vuilleti Crw (Hymenoptera: Eupelmidae) to volatile stimuli from hosts and host plants

Eupelmus vuilleti (Crw) is a solitary ectoparasitoid of several bruchid species which develop inside Leguminosae seeds. In this hymenopteran a preemergence learning process is responsible for a specific response of females toward the host and host-plant volatiles. This learning occurs after the imaginal molt, while the adult remains in the larval chamber of its host. The persistence of the response toward host and host-plant volatiles of females reared onBruchidius atrolineatus (Pic) larvae developing inVigna unguiculata (Walp) seed was investigated in this study. In the absence of any reinforcement, the response towardB. atrolineatus larvae persisted for 6 days after female emergence from the seeds, whereas the response towardV. unguiculata seed volatiles was maintained for 7 days. Our experiments showed that a later learning process also takes place inE. vuilleti. An ovipositional experience on a given plant-host complex enabled females to learn the stimuli from that complex. This learning occurred even if the complex experienced during oviposition differed from the one on which females were reared. After an ovipositional experience on a new plant-host complex, the response acquired through preemergence learning was maintained. These experiments demonstrate that theE. vuilleti females can memorize cues from several species during successive learning processes. The adaptive significance of these learning capacities, which confer an important behavioral plasticity to this generalist parasitoid, is discussed.

Bean [alpha]-Amylase Inhibitor Confers Resistance to the Pea Weevil (Bruchus pisorum) in Transgenic Peas (Pisum sativum L.).

Bruchid larvae cause major losses of grain legume crops through-out the world. Some bruchid species, such as the cowpea weevil and the azuki bean weevil, are pests that damage stored seeds. Others, such as the pea weevil (Bruchus pisorum), attack the crop growing in the field. We transferred the cDNA encoding the [alpha]-amylase inhibitor ([alpha]-AI) found in the seeds of the common bean (Phaseolus vulgaris) into pea (Pisum sativum) using Agrobacterium-mediated transformation. Expression was driven by the promoter of phytohemagglutinin, another bean seed protein. The [alpha]-amylase inhibitor gene was stably expressed in the transgenic pea seeds at least to the T5 seed generation, and [alpha]-AI accumulated in the seeds up to 3% of soluble protein. This level is somewhat higher than that normally found in beans, which contain 1 to 2% [alpha]-AI. In the T5 seed generation the development of pea weevil larvae was blocked at an early stage. Seed damage was minimal and seed yield was not significantly reduced in the transgenic plants. These results confirm the feasibility of protecting other grain legumes such as lentils, mungbean, groundnuts, and chickpeas against a variety of bruchids using the same approach. Although [alpha]-AI also inhibits human [alpha]-amylase, cooked peas should not have a negative impact on human energy metabolism.