Rice bean (Vigna umbellata Thunb. Ohwi and Ohashi) protection against Callosobruchus maculatus F.” by presence of protein profile

To identify defence responses of rice bean against Callosobruchus maculatus, 10 genotypes of rice bean and a mungbean variety, PAU 911 as susceptible check were evaluated. The rice bean genotypes were found to restrain the growth and development of C. maculatus at different larval stages. To justify these results, seeds of different test genotypes were examined for the presence of plant protease inhibitors which inhibit insect proteases causing reduction in the availability of amino acids necessary for their growth and development. Trypsin, chymotrypsin and cysteine protease inhibitor content was significantly higher in rice bean genotypes which ranged from 299.99 to 342.97 TIU g⁻¹ seeds, 235.07 to 251.45 CIU/g seeds and 1060.70 to 1574.99 CPIU/g seeds, respectively as compared to mungbean variety, PAU 911 (235.52 TIU/g seeds, 217.91 CIU/g seeds and 499.99 CPIU/g seeds, respectively). The protein profile showed a polypeptide band of 25–30 kDa corresponding to presence of protease inhibitors in rice bean genotypes except PAU 911. The results indicate that protease inhibitors in different genotypes of rice bean are very effective against C. maculatus.     

Identification,biochemical characterization and biological role of defense proteins from common bean genotypes seeds in response to Callosobruchus maculatus infestation

Common bean is a legume of significant socioeconomic importance and is cultivated worldwide. This crop is affected by several pests and diseases, which cause considerable economic losses and reduce yield. In recent years, several studies have demonstrated the role of proteins and peptides with activity against a wide range of insects and pathogens. The objective of this work was to identify defense proteins, such as antimicrobial peptides, protease and amylases inhibitors in common bean genotypes and evaluate the relationship of these proteins with Phaseolus vulgaris seed resistance to Callosobruchus maculatus infestation. Nineteen common bean genotypes were subjected to protein extraction, pH 5.4, and precipitation with ammonium sulfate at 70% saturation. The obtained extracts were separated by tricine gel electrophoresis. Experiments were carried out with natural seeds of common beans and artificial seeds (Vigna unguiculata seeds covered with seed coats of common beans) to evaluate the rate of oviposition and development of the insect species Callosobruchus maculatus. Lipid-transfer proteins were identified in nine genotypes whereas defensins were present in all genotypes. The inhibitory activity of α-amylases and trypsin and fungal development were determined in crude extracts (50 μg mL⁻¹). The results also indicated that the extracts from all bean genotypes inhibited the activity of human salivary α-amylase and C. maculatus larval α-amylase. Except for the extracts of four genotypes, all other extracts inhibited trypsin activity. None of the extracts from the evaluated bean genotypes inhibited the growth of tested fungi. Natural seeds from all genotypes did not inhibit insect oviposition, however, the larvae did not survive after feeding on these seeds. Artificial seeds containing seed coat flour of all genotypes inhibited the oviposition of C. maculatus, indicating that the seed coat was also repellent to insect.     

Seed coat phytochemistry of both resistant and susceptible seeds affords some protection against the granivorous beetle Callosobruchus maculatus

The seed coat lies at the interface between the internal structures of the seed and the external environment and thus represents a key arena in the study of seed-herbivore interactions. Callosobruchus maculatus is a cosmopolitan pest of legume seeds, and under post-harvest conditions, females interact directly with the seed testa prior to laying their eggs. Here we investigate the effect of chemical extracts of the seed coat of the resistant Phaseolus vulgaris and the susceptible Vigna unguiculata beans on egg laying preferences and larval development of C. maculatus. Seed coat extracts contained phenolic, glycoside and alkaloid compounds. Upon re-incorporation of extracts into artificial host beans it was found that that several seed coat extracts from both the resistant and susceptible varieties reduced female oviposition and disrupted larval growth and development. However, none of the extracts assayed resulted in complete ovipositional or developmental failure suggesting that complete resistance in P. vulgaris is derived from other physical or chemical properties of the seed and/or seed coat that function either alone or synergistically. Further work is required to elucidate the importance of synergistic interactions between different physiological defence mechanisms on overall plant (seed) resistance.     

Deterrent and insecticidal properties of bean seed (Phaseolus vulgaris L.) whole meal or protein extract incorporated into the diet of Callosobruchus maculatus (F.) (Coleoptera: Bruchidae)

Callosobruchus maculatus, a pest that causes serious damage to chickpea Cicer arietinum, cannot develop in the seeds of Phaseolus or Vigna spp. which contain lectins. The insecticidal activity towards C. maculatus in these seeds is attributed both to lectins with specific affinity to N-acetylglucosamine, the major component of insect chitin, and to alpha-amylase inhibitors (lectin-like proteins). The insecticidal properties of bean meal or bean protein extracts from different sources towards different pest species are variable and need to be experimentally evaluated. The main objective of this study was to determine through a feeding trial on artificial chickpea seed the potential of bean seed meal from a wild bean Vigna caracalla, four varieties of Phaseolus vulgaris, and of a protein extract of P. vulgaris seed, to alter different life history traits of C. maculatus. The chickpea weevil was set up on artificial chickpea seeds containing different amounts of bean meal to observe the effects on female oviposition, percentage of development to adulthood and juvenile development time. These traits were combined in a composite index measuring the alteration of the multiplication rate of C. maculatus fed on artificial seed. The activity of lectin-like extracts was observed on chickpea artificial seed spiked with bean seed extract. Incorporation of bean flour at a rate of 10 and 20% in chickpea artificial seed significantly decreased C. maculatus female fecundity, percentage of adult emergence, and greatly increased the development time. Feeding trials with protein extracts of P. vulgaris reduced fecundity and survival of C. maculatus. Incorporation of 10% V. caracalla bean seed meal in chickpea artificial seed, reduced the multiplication potential of C. maculatus by over 90% showing that bean seed lectin extracts are worthy of further investigation for post-harvest infestation control.     

Evaluating the combination of a parasitoid and a predator for biological control of seed beetles (Chrysomelidae: Bruchinae) in stored beans

The two seed beetle species Acanthoscelides obtectus and Callosobruchus maculatus are among the economically most important pests of stored legume seeds world-wide. Insect natural enemies for biological control were considered in IPM strategies to control bean weevils in store. In this contribution, the control effect by a combination of the parasitoid Anisopteromalus calandrae and the predator Xylocoris flavipes on both seed beetle species was evaluated in a laboratory study on black eyed beans Vigna unguiculata. The combination of parasitoid and predator was most effective against both species of seed beetles. However, in C. maculatus the combination was not significantly more effective compared to A. calandrae alone, suggesting a poor effect on adults and no effect on eggs and larvae by X. flavipes. In the case of A. obtectus, the suppressive effect by the combination of the parasitoid and the predator was high. For C. maculatus, germination of black eyed beans was approximately three times higher when both natural enemies were present. The combination of A. calandrae and X. flavipes is considered a promising component for integrated control of A. obtectus.     

Resistance screening of 14 Cajanus cajan (L.) Millsp. cultivars to Callosobruchus maculatus (F.) (Coleoptera:Bruchidae)

Pigeonpea, Cajanus cajan, is a rich source of human dietary protein and carbohydrate as well as an income generator for farmers especially in developing countries. However, a major limiting factor to the viable production and post-harvest preservation of pigeonpea is infestation by the cowpea weevil, Callosobruchus maculatus. An experiment to screen for resistance in 14 newly developed C. cajan cultivars from The University of the West Indies (UWI) was conducted. The experiment compared oviposition preference based on eight parameters, namely, testa thickness, testa hardness, seed sphericity, surface area, total adult emergence, larval + pupal mortality, seed hardness and surface roughness. Four of the pigeon pea cultivars screened were resistant and could be ranked in the order of decreasing resistance as: A16 = A66PL1> A112 > A196PL2. Seed surface roughness, seed testa hardness and seed grain hardness were all found to play a major role in oviposition deterrence with seed roughness being the most effective deterrent. The results suggest that breeding for pigeonpea cultivars with rougher seed coats, harder seed testa and harder grains could enhance pigeonpea seed resistance to C. maculatus by reducing infestation and damage while in storage.     

Genetics of bruchid (Callosobruchus maculatus Fab.) resistance in cowpea (Vigna unguiculata (L.) Walp.)

Bruchid resistance has been measured using a variety of techniques. Mean development period (MDP) and percentage adult emergence (PAE) are two of the more important traits measuring bruchid (Callosobruchus maculatus Fab.) resistance in cowpea. The objective of the study was to evaluate the genetic relationship between MDP and PAE in C. maculatus resistant cowpea. Seventy-two F₂ population plants were developed from the cross between C. maculatus resistant TVu-11953 (with delayed MDP and low PAE) and C. maculatus susceptible Ife Brown (with early MDP and high PAE) which were evaluated for resistance to cowpea C. maculatus. MDP at 45 days after infestation (DAI) and PAE at 60 DAI were taken as analysed measures for resistance to C. maculatus infestation. Data generated were subjected to chi-square analysis. Varied resistant response to C. maculatus infestation was observed among the F₂ generation plants but their responses showed inclination to the susceptible parent. A 15:1 ratio for susceptible to resistant genotypes was observed with MDP among the F₂ genotypes evaluated which is an indication of the presence of two recessive genes that control of MDP. The segregation of PAE also showed a 15:1 ratio goodness of fit (P > 0.05) for susceptible to resistant genotypes. Test of independence between MDP and PAE was not significant (χ² = 2.19, P = 0.19). This study revealed that the recessive genes controlling these two traits (MDP and PAE) were independently assorted and showed no linkage. This was also evident in the observed F₂ genotypes with C. maculatus resistance expressing either delayed MDP or low PAE and not both in the study.     

Free fatty acids from Lathyrus sativus seed coats acting as short-range attractants to Callosobruchus maculatus (F.) (Coleoptera: Bruchidae)

Lathyrus sativus L. (Leguminosae) seed, commonly known as khesari, is an important legume in India, Pakistan, Bangladesh, China, and Ethiopia. Ten free fatty acids were identified in seed coat waxes of four varieties of L. sativus with total fatty acids accounting for between 10.5 and 17.4 mg per 100 g of seed depending on the variety. Palmitoleic acid (C16:1) was the predominant free fatty acid in two of the varieties; whereas palmitic (C16:0) and lauric (C12:0) acids were the predominant free fatty acids in the two other varieties. Attraction of free fatty acids from seed coat waxes of the four varieties were tested for attractiveness to females of Callosobruchus maculatus (F.) (Coleoptera: Bruchidae) at 2–8, 2–8, 4–8, and 4–8 μg concentrations, respectively, in Y-tube olfactometer bioassays. The attractiveness of synthetic mixtures comparable to the fatty acid compositions of the four varieties were also tested. Individual synthetic myristic, palmitic, palmitoleic, and stearic acids at 0.66, 1.18, 1.36, and 1.18 μg, respectively, elicited attraction of the insect. A synthetic blend of 0.93, 1.68, 1.82, and 1.18 μg of myristic, palmitic, palmitoleic, and stearic acids, respectively, was most attractive to the insect. At present, C. maculatus are controlled with insecticides, which are harmful to human health and environment. Hence, the above mentioned combination of four fatty acids might be used for insect pest management such as baited traps.     

Biochemical basis of insect resistance in inged bean (Psophocarpus tetragonolobus) seeds

Mature seeds of the inged bean (Psophocarpus tetragonolobus) are toxic to developing larvae of a range of cosmopolitan storage Bruchidae of economic importance, including the copea seed eevil, Callosobruchus maculatus. Insect feeding trials ere carried out in hich protein fractions from seeds of inged bean ere incorporated at a range of concentrations into artificial seeds, and their effects upon development of C maculatus determined. Both albumin and globulin fractions ere toxic to the developing larvae and their toxicity correlated ith their haemagglutinating activity. Assay of Psophocarpin A, B and C fractions demonstrated Psophocarpin B to be the most insecticidal and to contain the highest haemagglutinating activity. Purified basic seed lectin as highly insecticidal to C maculatus larvae, ith an LC₅₀ value of c. 3·5 g kg^?1. The physiological level of this protein in inged bean seeds is sufficient to account for their resistance to attack by C maculatus. inged bean trypsin inhibitor as also purified and tested in artificial seeds against C maculatus. Hoever, even at concentrations in excess of tice the physiological concentration it had no deleterious effects upon development.     

Possible effects of Ultraviolet ray (UV-C) on biological traits of Callosobruchus maculatus (Col.: Chrysomelidae)

Cowpea seed beetle, Callosobruchus maculatus (F.) (Col.: Chrysomelidae), is one the most important pests of stored products worldwide, which specially distributed in the tropical and subtropical regions. In the present study, effects of different irradiation times of Ultraviolet ray (0, 10, 20, 30, 40 and 50 min) on the most important biological traits of this pest were evaluated under laboratory conditions. Our findings revealed that different irradiation times significantly affect mortality of immature stages of C. maculatus. The UV-C irradiation had no significant effects on duration of different life stages of this pest. Population growth parameters of C. maculatus were significantly affected by different treatments. The highest and lowest recorded values for net reproductive rate (R₀) were calculated at Control (38.70 offspring) and 50 min of irradiation (10.36 offspring), respectively. The calculated values for intrinsic rate of increase (r) at different treatments were significantly decreased with increasing irradiation time. The lowest value of this parameter was obtained at 40 min of irradiation (0.058 day⁻¹) and followed by 50 min (0.061 day⁻¹), while the highest value was recorded at Control (0.096 day⁻¹). Sex ratio of C. maculatus was not significantly affected at different treatments. The results of the present study can be used for further assessment of irradiation as a means to control C. maculatus.     

Cowpea resistance and bioactivity of two diatomaceous earths against Callosobruchus maculatus (F.) (Coleoptera: Chrysomelidae) on three cowpea varieties

The bruchid, Callosobruchus maculatus (F.) is the most important pest of stored cowpea in tropical climates. Experiments were conducted to evaluate the susceptibility of three cowpea varieties and the bioactivity of SilicoSec® and FossilShield® against this insect pest under ambient laboratory conditions at the contents 0, 0.5, 1, 1.5 and 2 g/kg of cowpea. The Dobie susceptibility index for cowpea genotypes was estimated to compare their relative tolerance to this insect pest. Adult mortality was assessed after 1, 2, 4 and 6 days of exposure followed by the evaluation of the F₁ progeny. Population increase, percentage seed damage and weight loss were assessed after three months of storage. The results showed that the CRPS and TN5-78 varieties were highly susceptible to C. maculatus, while Lori variety was moderately susceptible to the weevil. SilicoSec® and FossilShield® caused a significant and increasing bruchid mortality according to the dose rates and periods of exposure. Malathion 5% caused complete mortality after one day exposure time. SilicoSec® was more effective than FossilShield® on the three varieties of cowpea. The greatest dose of SilicoSec® and FossilShield® (2 g/kg) caused 100% mortality on all three varieties; 4 days of exposure in the Lori variety was the shortest exposure time leading to complete mortality. Regarding LD₅₀ and LD₉₅ values, it was observed that C. maculatus adults are more susceptible to SilicoSec® than to FossilShield®.The two formulations of diatomaceous earth (1.5 g/kg) reduced the F₁ progeny by more than 70%, and produced less than 10% of seed damage and weight loss for the three varieties of cowpea. The varietal resistance and the use of diatomaceous earth against C. maculatus in storage could represent an alternative to Malagrain® for the protection of the cowpea.     

Triple bag hermetic technology for post-harvest preservation of Bambara groundnut (Vigna subterranea (L.) Verdc.)

Experiments were conducted to evaluate the performance of hermetic triple bagging using Purdue Improved Crop Storage (PICS) bags for storage of Bambara groundnut (Vigna subterranea (L.) Verdc.). One set of experiments used grain heavily infested by Callosobruchus maculatus (F.) while a second set began with a low level infestation. Each experiment consisted of V. subterranea grain kept in four replicate 50 kg PICS bags or two replicate woven bags as controls. Two to five days after the beginning of the experiments, oxygen level inside the bags averaged about 21% (v/v) in the controls but decreased significantly in PICS bags, reaching 10% (v/v) with the heavily infested grain but falling only slightly in the lightly infested grain. After 7 months of storage, (i) the number of C. maculatus adults found between and within the grains, (ii) the 100 seed weight, (iii) the number of seed with holes, and (iv) the percentage germination of grain stored in PICS bags did not differ from what had been measured on the day that the experiment was set up. In woven bags, by contrast, there was a massive increase in C. maculatus numbers with means of 309 and 251 adults per 500 g in heavily and lightly infested grain, respectively. Grain weight losses in the woven bag controls ranged from 8 to 19% and the percentage of C. maculatus emergence holes per 100 seed increased from 51 to 135%.     

Storage of mung bean (Vigna radiata [L.] Wilczek) and pigeonpea grains (Cajanus cajan [L.] Millsp) in hermetic triple-layer bags stops losses caused by Callosobruchus maculatus (F.) (Coleoptera: Bruchidae)

Dry mung bean and pigeonpea grains that had sustained some insect damage but fumigated before the start of the experiment were stored in triple-layer hermetic bags (Purdue Improved Crop Storage (PICS™ bags) or woven polypropylene (PP) bags for 6 months. Some of the bags were artificially infested with cowpea bruchid Callosobruchus maculatus (F.) (PICS1, PP1) while others were not (PICS0, PP0). In an additional trial, PP bags containing the grains were treated with Actellic Super^® dust before being artificially infested (PP1Ac). Moisture content, live adult C. maculatus count, grain damage, weight loss, and seed germination were determined on a monthly basis. At six months, moisture contents of grain stored in PICS and PP bags remained below 12%. Storage in PICS bags halted multiplication of C. maculatus, and the initial damage level and weight of grains did not change. Conversely, in the PP bags, C. maculatus populations increased massively and seed damage reached 71.8 ± 1.9%, 76.9 ± 0.4%, and 60.3 ± 0.6% corresponding to weight losses of 14.5 ± 0.1%, 16.5 ± 0.2% and 12.5 ± 0.1% in PP0, PP1 and PP1Ac, respectively, in mung beans. With the pigeonpeas, seed damage reached 55.1 ± 0.6%, 95.7 ± 0.4% and 75.8 ± 0.9%, corresponding to weight losses of 13.0% ± 0.3%, 26.2 ± 0.2% and 13.5 ± 0.1%, in PP0, PP1 and PP1Ac, respectively. PICS bags are an effective tool for preserving mung beans and pigeonpeas against C. maculatus attack, and their performance is superior to that of Actellic Super^® dust.     

Resistance of landrace and commercial cowpea genotypes to Callosobruchus maculatus attack

In the northern and north-eastern regions of Brazil, the cultivation of cowpea (Vigna unguiculata L.) is socially and economically important. However, attack by weevils makes storage difficult. Landrace genotypes exhibit high genetic variability, which can confer resistance to pest attacks. In this study, the susceptibility of landrace genotypes of cowpea to the attack of the weevil (Callosobruchus maculatus (Fabr., 1775)) was assessed. A total of 13 genotypes were used (11 landraces and two commercial genotypes). Biological parameters (number of eggs; daily, accumulated, and final emergence; the instantaneous rate of population increase) of C. maculatus, and loss of cowpea seed mass were analysed. The treatments were composed of 30g of each genotype and 20 adult insects in an entirely randomised design with ten replicates. A principal component analysis and grouping analysis were performed due to the similarity between the genotypes, and three groups were described. Group 3 (‘BRS Pujante’, ‘Ligeiro’, and ‘Tardão’ genotypes) had the highest oviposition/number of eggs, daily emergence, number of emerging insects, and instantaneous rate of population increase. Group 2 (‘Azulão’, ‘Costela de Vaca’, and ‘Rabo de Tatu’ genotypes) showed intermediate values, and group 1 (‘Bala’, ‘Canapú’, ‘Corujinha’, ‘Manteiguinha’, ‘Moita’, ‘Seridó’, and ‘Sempre Verde’ genotypes) had the lowest values for all those variables. The commercial genotypes were grouped in groups 1 (‘Sempre Verde’) and 3 (‘BRS Pujante’) and showed similar behaviour to the landrace genotypes of those groups. This study demonstrated that the genotypes in group 3 are susceptible to the attack of C. maculatus, while those in group 1 showed antibiosis resistance. Utilization of insect-resistant genotypes can reduce cowpea infestation and synthetic insecticide application, leading to a positive economic impact.     

Antibiosis levels of common bean genotypes toward Zabrotes subfasciatus (Boheman) (Coleoptera: Bruchidae) and its correlation with flavonoids

Expression of the antibiosis-resistance category to weevils has been evaluated in several bean genotypes with very promising results. Among the several causes responsible for this resistance category the arcelin protein and trypsin inhibitors stand out. Other mechanisms may be associated with plant resistance to the attack of weevils; however, few studies seek to discover these possible causes. Thus, our research aimed at identifying bean genotypes resistant to Zabrotes subfasciatus, classify them into resistance levels, quantify the content of flavonoids, and correlate it with data obtained from the genotypes. An antibiosis test was performed with beans of 43 genotypes and 40 replications (bean grains) under a completely randomized design. The biological parameters recorded from Z. subfasciatus were the periods from egg to larvae, larvae to adult, egg to adult, longevity and life cycle, in addition to egg viability, adults emerged, susceptibility relative index, adult weight, sex ratio, and the dry mass consumed by larvae. The chemical profile of flavonoids from each genotype was assessed by means of LC-MS. Based on the results of the weevil biological parameters and dry mass consumed provided by univariate and multivariate statistical analyses, the bean genotypes were classified into four levels of resistance (antibiosis): highly resistant, moderately resistant, susceptible and highly susceptible. Among the evaluated flavonoids, we could identify isoquercitrin; however, it has no correlation with the expression of resistance. From the results obtained in this work, more studies will be conducted with the genotypes that stood out as resistant, evaluating other resistance categories and defense mechanisms of these materials against the attack of Z. subfasciatus and other pests, as well as studies of other important agronomic characteristics aiming at future commercialization of the bean genotypes.     

Effect of bean water content on the production of the active form of Callosobruchus maculatus (F.) (Coleoptera: Bruchidae)

The effect of bean water content on production of the active form in Callosobruchus maculatus was investigated. High larval density caused an increase of water content of beans through larval metabolism. However, bean water content influenced the production of the active form only when combined with artificial temperature rise. The results showed (i) beans with high water contents (16.2 and 22.1%) create a favorable condition for the production of the active form, (ii) the active form does not emerge from dry beans (with water contents of 8.7 and 12.4%, (iii) the increased water content of beans during larval growth facilitates the production of the active form and (iv) decrease of bean water content prevents the production of the active form. It was also shown that bean water content and temperature are closely related and work, in one sense, in a complementary manner for the production of the active form.     

The influence of geographic origin and food type on the susceptibility of Callosobruchus maculatus (Fabricius) to Piper guineense (Schum and Thonn)

The tolerance of Callosobruchus maculatus from different geographical locations reared on two cowpea varieties, pale brown Ife Brown (IFBV) and dark brown IAR48 (IAR48V), to seed powder of Piper guineense (Schum and Thonn) was investigated. C. maculatus populations were collected from nine different locations across Osun state in the South Western part of Nigeria. The main and interactive effects of cowpea variety, population origin and dose on C. maculatus tolerance to P. guineense were explored. It was observed that bruchids that emerged from IAR48V had greater tolerance of P. guineense than bruchids reared on IFBV. There were significant effects (P < 0.001) of cowpea variety, population and dose, and significant interactions among these factors (except variety × dose, P > 0.05) on the response of bruchids to P. guineense. When reared on IAR48V, bruchid populations from the North-Eastern part of the state show greater tolerance to P. guineense than their counterparts from the South–West. This study underscores the importance of knowledge of the origin of the population and the cowpea variety on which C. maculatus developed when managing bruchids damage using P. guineense.     

Pretreating Callosobruchus maculatus (F.) eggs in mung bean with modified atmosphere conditions influence its adult emergence and survival

Cowpea bruchid (Callosobruchus maculatus Fab.) is a cosmopolitan pest that causes economic losses to legumes during storage. The present study determined the post-effects of exposing the C. maculatus eggs in mung bean to modified atmosphere (MA) conditions on the emergence and development of adults at ambient conditions (28 ± 3 °C and 65 ± 5% RH). The 24 h old C. maculatus eggs on mung bean kernel were packed with 500 g of mung bean in nylon/linear low-density polyethylene (nylon/LLDPE) bags (12.5 × 30 cm; 80 μm thick) and sealed with air (control), 100% CO₂, 100% N₂, and vacuum for 48 h. The very low O₂ conditions in the MA package had significantly caused longer onset and developmental duration of egg to adult emergence and significantly reduced the adult emergence percentage of C. maculatus, especially those in the vacuum treatment. This was due to low pressure that disrupted the structure of the eggs as indicated by the scanning electron microscopy (SEM). In addition, the MA conditions shortened the adult emergence duration, longevity, and mortality duration. The number of females was also reduced by the low O₂ conditions, particularly in those treated with vacuum. Eggs pretreated with the MA conditions probably affected the biomolecules of the eggs that in turn have affected the growth and development of the insect, with the order of effectivity highest in vacuum followed by 100% N₂ then 100% CO₂.     

Genetic analysis of seed resistance to Callosobruchus chinensis and Callosobruchus maculatus in cowpea

Callosobruchus chinensis (azuki bean weevil) and Callosobruchus maculatus (cowpea weevil) are the most destructive pests that cause significant losses to cowpea (Vigna unguiculata) seeds during storage. Development of cultivar(s) resistance to bruchids is a major goal in cowpea breeding program. Cowpea accession “TVu 2027” has been identified as moderately resistant to C. maculatus. Genetic studies of the seed resistance in this accession using strains of C. maculatus from Africa and America have demonstrated that the resistance is controlled by one or two recessive genes. However, there is no reports on genetics of the resistance to C. chinensis and to strain(s) of C. maculatus from Asia. Therefore, the objective of this study was to investigate genetics of the resistance to C. chinensis and C. maculatus in TVu 2027. TVu 2027 (P₂) and PK2015VTN001 (P₁; susceptible cowpea) were used to develop six basic generations (populations), viz. P₁, P₂, F₁ (P₁ × P₂), F₂ (P₁ × P₂), BC₁P₁ (P₁ × F₁) and BC₁P₂ (P₂ × F₁). The population were evaluated for percentage of damaged seeds (PDS) and area under the disease progress stairs (AUDPS; indicating infestation severity) by C. chinensis and C. maculatus. The results showed that TVu 2027 was moderately resistant to both bruchid species. Broad-sense heritability for PDS and AUDPS was moderate, being 70% and 73% for C. chinensis, respectively, and 64% and 61% for C. maculatus, respectively. Number of genes controlling C. chinensis resistance and C. maculatus resistance was two genes and one gene, respectively. Generation mean analysis revealed that genes with additive effect and additive × dominance gene interaction are involved in the resistance to both bruchid species. Correlation analysis suggested that the genes controlling resistance to C. chinensis and those conferring resistance to C. maculatus are unlinked.     

Hermetic storage as an alternative for controlling Callosobruchus maculatus (Coleoptera: Chrysomelidae) and preserving the quality of cowpeas

The aim of this study was to assess the use of modified atmosphere through hermetic storage in polyethylene silo bags and polyethylene terephthalate (PET) bottles as a technique to control Callosobruchus maculatus (F.) (Coleoptera: Chrysomelidae: Bruchinae) and to preserve the quality of cowpeas during storage. Cowpea grains were stored in polyethylene silo bags, polyethylene terephthalate (PET) bottles and glass recipients (control) for 30, 60, 90 and 120 days. Each treatment was replicated four times. After each storage period, we assessed the insect infestation percentage and measured the moisture content, the bulk density, the germination percentage and the electrical conductivity of the grains. The percentage of infestation by C. maculatus for cowpeas stored in silo bags and PET bottles was low and did not exceed 4% during the entire storage period. In contrast, the percentage of infestation by C. maculatus increased in untreated cowpeas over the storage period. The moisture content, bulk density, germination percentage and electrical conductivity of the cowpeas were preserved in both hermetic storage systems that were tested for 120 days. To conclude, the hermetic storage of cowpeas using silo bags and PET bottles can efficiently control C. maculatus and preserve the quality of cowpeas for at least 120 days of storage.