Young Pods Research Articles

Identification and characterization of a LEA family gene CarLEA4 from chickpea (Cicer arietinum L.)

Late-embryogenesis abundant (LEA) proteins have been reported to be closely correlated with the acquisition of desiccation tolerance during seed development and response of plant to drought, salinity, and freezing, etc. In this study, a LEA gene, CarLEA4 (GenBank accession no. GU247511), was isolated from chickpea based on a cDNA library constructed with chickpea seedling leaves treated by polyethylene glycol (PEG). CarLEA4 contained two exons and one intron within genomic DNA sequence and encoded a putative polypeptide of 152 amino acids. CarLEA4 had a conserved pfam domain, and showed high similarity to the group 4 LEA proteins in secondary structure. It was localized in the nucleus. The transcripts of CarLEA4 were detected in many chickpea organs including seedling leaves, stems, roots, flowers, young pods, and young seeds. CarLEA4 was inhibited by leaf age and showed expression changes in expression during seed development, pod development and germination. Furthermore, the expression of CarLEA4 was strongly induced by drought, salt, heat, cold, ABA, IAA, GA(3) and MeJA. Our results suggest that CarLEA4 encodes a protein of LEA group 4 and may be involved in various plant developmental processes and abiotic stress responses.

Effect of flush existence, NAA and GA application on cocoa pod development

This experiment was carried out to study the photosynthate allocation between flush and young pods, and the effect of (naphthalene acetic acid) and (gibberellic acid) application to sink strength. Two cocoa clones KW 163 and KW 165 located in Kaliwining Experimental Station of Indonesian Coffea and Cocoa Research Institut were used on this experiment. Each clone was treated with flushes and without flush. Beside that, the young pods sprayed with NAA 250 mg L-1, GA 250 mg L-1, NAA 250 mg L-1 dan GA 250 mg L-1 and control (K = without NAA and GA). There were 2 x 4 treatment combinations for each clone, and replicated three trees for each combination. The parameter were cherelle wilt percentage, sucrose content, fresh and dry weight, long and diameter of healthy and wilting pods.The result showed that sink strength of young pods was lower than that of flushes, which caused application photosynthate translocation to the young pods was lower. NAA and GA application to the pods could improve sucrose allocation, increased pod weight and cherelle wilt was suppressed. The lack of photosynthate on young pod cause metabolism change, so pod became cherelle wilt. But, there was still not known the optimum concentration and method of application of those growth regulators to obtained minimum cherelle wilt.Key words: Cocoa, flush, pod, naphthylacatic acid, gibberellic acid, cherelle wilt.

An investigation on Different Harvesting Methods on Young Pods of KKU # 922 Maize (Zea mays L.) Cultivar for Baby Corn Production

This study aimed to search for the best indicator to be used for the harvest of maize pods for baby corn production. A Randomized Complete Block Design (RCBD) with four replications was used. The treatments are: T1 (Control) Taking sample when silks of female flower had extended from tip of pod up to 3 cm long T2, silks had extended 1 cm long T3, silks had extended 2 cm long T4, blooming of female flower for 2 days T5, blooming of female flowers for 4 days T6, blooming of female flower for 6 days T7, one third blooming of male flower T8, two third blooming of male flower and T9, full bloom of male flower. Five baby corn Characteristics were used i.e., (1) fresh weight of whole ears, (2) fresh weight of ears without husk, (3) commercial standard ears, (4) off standard ears and (5) disordered kernel-rows of ears. A range of scores from 1 to 9 was applied to judge quality and yield in each item of the five baby corn characteristics. A score of 1 = the best whilst further increases in scores indicated the decline in quality of baby corn. The results showed that an indicator for use in harvesting pods of maize for baby corn production was found with T6, i.e. the best time for the harvest of pods is when the female flowers had bloomed for 6 days after the appearance of silks.

A PCR-based marker for a locus conferring aroma in vegetable soybean (Glycine max L.)

Vegetable soybean (Glycine max L.) is an important economic and nutritious crop in South and Southeast Asian countries and is increasingly grown in the Western Hemisphere. Aromatic vegetable soybean is a special group of soybean varieties that produce young pods containing a sweet aroma, which is produced mainly by the volatile compound 2-acetyl-1-pyrroline (2AP). Due to the aroma, the aromatic vegetable soybean commands higher market prices and gains wider acceptance from unfamiliar consumers. We have previously reported that the GmAMADH2 gene encodes an AMADH that regulates aroma (2AP) biosynthesis in soybeans (Arikit et al. 2010). A sequence variation involving a 2-bp deletion in exon 10 was found in this gene in all investigated aromatic varieties. In this study, a codominant PCR-based marker for the aroma trait in soybeans was designed based on the 2-bp deletion in GmAMADH2. The marker was verified in five aromatic and five non-aromatic varieties as well as in F(2) soybean population segregating for aroma. The aromatic genotype with the 2-bp deletion was completely associated with the five aromatic soybean varieties as well as the aromatic progeny of the F(2) population with seeds containing 2AP. Similarly, the non-aromatic genotype was associated with the five non-aromatic varieties and non-aromatic progeny. The perfect co-segregation of the marker genotypes and aroma phenotypes confirmed that the marker could be efficiently used for molecular breeding of soybeans for aroma.

Investigating the Effect of Heavy Metals on Developmental Stages of Anther and Pollen in Chenopodium botrys L. (Chenopodiaceae)

Excessive amounts of heavy metals adversely affect plant growth and development. Whereas some regions naturally contain high levels of heavy metals, anthropogenic release of heavy metals into the environment continuously increases soil contamination. Preliminary studies have shown that Chenopodium botrys can grow in some heavy metal contaminated soils and is a high accumulator plant species for Cu and moderately accumulator plant species for Fe, Mn, and Zn, thus, was considered as an important species in this study. Based on that, in this species, we studied the individual effects of heavy metals on the formation, development, and structure of anther and pollen. To achieve this purpose, surrounding area of Hame-Kasi iron and copper mine (Hamedan, Iran) was chosen as a polluted area where the amount of some heavy metals was several times higher than the natural soils. Flowers and young pods were removed from non-polluted and polluted plants, fixed in FAA 70, and subjected to developmental studies. Analysis of anther development in plants from contaminated sites showed general similarities in the pattern of pollen formation with those from non-polluted ones, but also deviation from typical form of major stages of anther and pollen development was seen in plants from polluted ones. Stabilizing of tapetum layer, increasing in tapetum layer numbers, thickening callose wall in the microspore mother cell stage, changing the anther shape, and decreasing the size of anther were the effects of heavy metals. Reduction of pollen number was also seen in the plants collected from polluted area.

Pollen source and resource limitation to fruit production in the rare species Eremosparton songoricum (Fabaceae)

Eremosparton songoricum (Litv.) Vass. is a rare, central Asian desert species which shows lower fruit set and seed set (<16%) than most hermaphroditic species. We hypothesized that fruit production was limited by pollen and resources. To evaluate potential fruit abortion due to pollen limitation, supplemental hand-pollination was undertaken, the mating system was investigated and the foraging behavior of pollinators was recorded. To investigate possibile resource limitation, flowers and young pods were artificially removed and fertilization were manipulated. The results showed that under natural pollination, the number of pollen deposited on the stigma greatly exceed the number of ovules per ovary. Mating system experiments showed that the species is self-compatible, but depended on pollinators to set seeds. Supplemental outcross pollination increased fruit set significantly. The most frequent effective pollinator Megachile terminate Morawitz, was observed pollinating many flowers of the same individual plant (74.5±1.3%). These results suggested that fruit production is affected by insufficient outcross pollen rather than by pollen quantity. Removal of 2/3 of the flowers and young pods led to significantly higher fruit set, as did addition of fertilizers (N–P–K: 0.025–0.05–0.013 g, N–P–K: 0.05–0.1–0.025 g) showing that reducing resource acceptors and increasing inorganic resources both helps to improve fruit set. We therefore conclude that reproductive success of E. songoricum is limited by both outcross pollen and available nutrients.

In Silicon Cloning and Analysis of a LACS Gene from Glycine Max (L.)

Long chain acyl-coenzyme A synthetases (LACSs) activate free fatty acids to acyl-CoA thioesters, and play importantroles in the biosynthesis and degradation of lipids. In this study, a Glycine max(L.) LACS gene, designated as GmLACS,has been isolated through in silicon cloning. The gene is 2,219 bp with an open reading frame (ORF) of 1,989 bp, whichencodes a LACS with 662 amino acid residues, with the isoelectric point of 6.42 and the calculated molecular mass of65.6 kDa. Sequence analysis showed that GmLACS possessed typical domains of LACSs. Real-time quantitative PCRdata analysis suggested that GmLACS was hightly expressed in leaves and young pods.

Genetic compatibility among domesticated and wild accessions of the tropical tuberous legume Vigna vexillata (L.) A. Rich.

Phenotypic similarities and differences between a cultivated variety of the tuberous legume Vigna vexillata from Bali, Indonesia, the putative domesticated variety macrosperma and wild types from Africa, Australia and Indonesia, were reported previously. The present study was undertaken to establish the genetic compatibility of these three accession classes. Seventeen accessions, comprising eight cultivated Bali accessions, one var. macrosperma accession and eight wild accessions from Africa and Austronesia, were grown in large pots in shade house facilities in Townsville, Australia. Not all hybrid combinations were attempted because for some accession combinations, suitable matching flowers were not available at the same time. The main aim was to attempt enough crosses between accessions from the respective classes to establish whether the classes were genetically compatible. Hybridisation was conducted by hand pollination in the morning, using newly-open flowers that had been emasculated before sunset on the day before. Pods and viable hybrid seed were obtained from the Bali × Bali, var. macrosperma × wild and wild African × wild Austronesian combinations. However, difficulty was encountered in obtaining viable and/or self-fertile hybrids between the Bali accessions and the other two classes. Depending on the particular combination of parental accessions, different genetic breakdown mechanisms were observed with the Bali × var. macrosperma and Bali × wild combinations. In some instances, flowers failed to set pods and/or the young pods abscised before maturity; pods set but seed were shrivelled and/or non-viable; viable seeds were set but the hybrid seedling plants were short-lived; or, in a few instances (Jimbaran Bali × wild Austronesian), vigorous hybrid plants were obtained but were self-sterile. Mitotic chromosome counts showed there was no difference in chromosome number between the Bali accessions, the Austronesian accessions and those hybrids that were viable but infertile. All exhibited 2n = 22. Pollen viability analyses using Alexander’s stain indicated that the numbers of pollen grains per flower and the percentages of pollen grain that were viable were substantially lower in the hybrids than in both the cultivated Bali and wild parental accessions. Consistent with this observation, small numbers of viable seeds were obtained when viable pollen from the respective parents was backcrossed onto the self-sterile hybrids. The results suggested that the cultivated Bali accessions do not belong to the same primary gene pool as the other cultivated and wild V. vexillata accessions and that it would be difficult to use the Bali accessions and var. macrosperma concurrently to breed seed crop varieties. A taxonomic review of V. vexillata is also warranted.

Studies on reproductive abscission and seed yield of mungbean (&lt;i&gt;Vigna radiata&lt;/i&gt;) in sub-humid savanna of Nigeria.

A field study was conducted on the Research and Experimental Farm of the University of Agriculture Makurdi (7o41’N, 08o37’N, and 400 m above mean sea level), Nigeria, in 2001 and 2002 to examine the abscission of reproductive structures in mungbean (Vigna radiata). Four exotic cultivars (VC 2768A, VC 1178A, VC 2778A and VC 1973A) and a local cultivar (Ex–Zaria) were used for the study, which was laid out in a randomized complete block design and was replicated four times. Grain legumes generally undergo considerable abscission of their reproductive structures during flowering and fruiting stages. In this study the abscissions of flowers and pods differed widely among the cultivars. The abscissions of flowers and young pods varied from 14.4 to 36.8% and 12.3 to 38.5%, respectively. The number of flowers and harvestable pods per plant also varied from a high of 77.2 and 48.8 in VC 2768A to a low of 49.1 and 24.0 in VC 2778A, respectively. Conversely, young pods varied in number from 56.0 in VC 1973A to 38.9 in VC 2778A. In all the cultivars, more flowers occurred at the bottom of the canopy where abscission was also highest. The cultivar VC 2778A had highest (50.8) percent total abscission compared to the lowest of 29.1percent in VC 1973A. Seed yield ranged from 541.67 kg/ha in VC 2778A to 2000.2 kg/ha in VC 2768A. Seed weight and the number of seeds per pod, however, did not vary significantly. There was a high positive correlation (r = 0.94) between flowers and harvestable pods. Seed yield also correlated positively with the number of flowers, harvestable pods, seed weight and the number of seeds per pod.This study has shown that reproductive abscission exists in mungbean but it is of less intensity when compared to other legumes. The lower rate of abscission coupled with low incidences of pests and diseases and high nutritive value make the crop a dependable source of protein for resource-poor rural farmers in the tropics.

Molecular analysis of an actin gene, CarACT1, from chickpea (Cicer arietinum L.)

Actins are ubiquitous and highly conserved proteins that play key roles in cell formation and cellular activities. In this study, an actin gene was isolated from chickpea for the first time and designated as CarACT1 (for Cicer arietinum L. actin gene 1; Genbank accession no. EU529707). It encoded a putative protein with 377 amino acids and contained five exons and four introns within genomic DNA sequence. CarACT1 was localized in cytoplasm and showed high similarity to other well known actins from various species. Reverse transcription-polymerase chain reaction (RT-PCR) assay proved that CarACT1 transcripts were ubiquitously accumulated in all major organs, such as seedling roots, stems, leaves, flowers, young pods, and seeds, as well as in diverse developmental stages, such as leaf senescence, seed development and germination. Our results suggested that CarACT1 is an actin gene with physiological functions and may be served as a potential reference gene for transcription level of interesting genes in chickpea.

Metabolic Changes in Different Developmental Stages of Vanilla planifolia Pods

The metabolomic analysis of developing Vanilla planifolia green pods (between 3 and 8 months after pollination) was carried out by nuclear magnetic resonance (NMR) spectroscopy and multivariate data analysis. Multivariate data analysis of the (1)H NMR spectra, such as principal component analysis (PCA) and partial least-squares-discriminant analysis (PLS-DA), showed a trend of separation of those samples based on the metabolites present in the methanol/water (1:1) extract. Older pods had a higher content of glucovanillin, vanillin, p-hydroxybenzaldehyde glucoside, p-hydroxybenzaldehyde, and sucrose, while younger pods had more bis[4-(beta-D-glucopyranosyloxy)-benzyl]-2-isopropyltartrate (glucoside A), bis[4-(beta-D-glucopyranosyloxy)-benzyl]-2-(2-butyl)tartrate (glucoside B), glucose, malic acid, and homocitric acid. A liquid chromatography-mass spectrometry (LC-MS) analysis targeted at phenolic compound content was also performed on the developing pods and confirmed the NMR results. Ratios of aglycones/glucosides were estimated and thus allowed for detection of more minor metabolites in the green vanilla pods. Quantification of compounds based on both LC-MS and NMR analyses showed that free vanillin can reach 24% of the total vanillin content after 8 months of development in the vanilla green pods.

Cloning and Characterization of a Novel NAC Family Gene CarNAC1 from Chickpea (Cicer arietinum L.)

The plant-specific NAC (for NAM, ATAF1,2 and CUC2) proteins have been found to play important roles in plant development and stress responses. In this study, a NAC gene CarNAC1 (for Cicer arietinum L. NAC gene 1) was isolated from a cDNA library constructed with chickpea seedling leaves treated by polyethylene glycol. CarNAC1 encoded a putative protein with 239 amino acids and contained 3 exons and 2 introns within genomic DNA sequence. CarNAC1 had a conserved NAC domain in the N-terminus and the CarNAC1:GFP (green fluorescent protein) fusion protein was localized in the nucleus of onion epidermal cells. Additionally, CarNAC1 exhibited the trans-activation activity which was mapped to the C-terminus. The CarNAC1 transcript was detected in many chickpea organs including seedling leaves, stems, roots, flowers, and young pods, but less accumulated in young seeds. CarNAC1 was induced by leaf age and showed changes in expression during seed development and germination. Furthermore, the expression of CarNAC1 was strongly induced by drought, salt, cold, wounding, H(2)O(2), ethephon, salicylic acid, indole-3-acetic acid, and gibberellin. Our results suggest that CarNAC1 encodes a novel NAC-domain protein and may be a transcriptional activator involved in plant development and various stress responses.

Effect of the Heavy Metals on the Developmental Stages of Ovule and Seed Proteins in Chenopodium botrys L. (Chenopodiaceae)

Excessive amounts of heavy metals adversely affect plant growth and development. Also, the presence of elevated levels of heavy metal ions triggers a wide range of cellular responses including changes in gene expression and synthesis of metal-detoxifying peptides. The overall objective of this research was to elucidate some microscopic effects of heavy metals on the formation, development, and structure of ovule and seed storage proteins in Chenopodium botrys L. To achieve this purpose, the surrounding area of Hame-Kasi iron and copper mine (Hamedan, Iran) was chosen as a polluted area where the amount of some heavy metals was several times higher than the natural soils. Flowers and young pods were removed from nonpolluted and polluted plants, fixed in FAA 70 and subjected to developmental studies. Our results showed that heavy metals can cause some abnormalities during the ovule developmental process. Decreasing the size of embryo sac, quick growth of inner integument, quick degradation of embryonic sac cells, accumulation of dark particles, irregularity, and even blockage of the nuclear envelope formation and increasing of embryonic sac cytoplasm concentration were the effects of heavy metals. Reduction of ovule number was also seen in the plants collected from polluted area. For protein studies, mature seeds were harvested from nonpolluted and polluted plants at the same time. Seed storage proteins (water soluble ones) were extracted and studied by sodium dodecyl sulfate-polyacrylamide gel electrophoresis after being prepared. The results revealed that there were no significant differences between seed protein bands of polluted and nonpolluted samples, but the quantity of protein bands was different, and there was a slight quantitative increase of bands with molecular mass of 35 and 15 kD and decrease of a band with molecular mass of 17 kD in the plants collected from the mine area.

Developmental Stages of Ovule and Megagametophyte in Chenopodium botrys L. (Chenopodiaceae)

The ovule ontogenesis and the megasporogenesis stages in Chenopodium botrys L. were studied with light microscopy. Flowers and young pods were removed from natural plants and fixed in FAA 70, stored in 70% ethanol, embedded in paraffin, and sectioned at 7 µm with a microtome. Staining was carried out with Hematoxylin and Eosin and developmental stages of ovule were studied. The results of this research showed that ovule development, including megasporogenesis and initial stages of megagametogenesis, occurred while flowers were still in bud. In C. botrys the female gametophyte has a monosporic origin and the developmental pattern exhibited by this species is referred to as the polygonum type. Development of ovule starts with the formation of a primordium. In this primordium, an archesporial cell produces a megaspore mother cell, which undergoes meiosis, forming a linear tetrad. The micropylar cell is a functional megaspore that survives and will function in megagametophyte development. The mature gametophyte is composed of 7 cells: 1 secondary nucleus, 2 synergids, 1 egg cell, and 3 antipodal cells.

Application of abscisic acid promotes yield in field-cultured soybean by enhancing production of carbohydrates and their allocation in seed

This study investigates the effect of abscisic acid (ABA) and gibberellin (GA3) applications on physiological and productive parameters in complementary experiments performed with soybean cultured in the field for 3 crop seasons and in the greenhouse for 1 crop season. ABA 300 mg/L was sprayed at the V7 and R2 phenological stages, while GA3 300 mg/L was sprayed at R2 and repeated 7 days later. GA3-treated plants had longer shoots and ABA-treated plants had greater dry weight of aerial parts. Nodule formation was not affected, but both shoot diameter and root density were greater in ABA-treated plants. ABA increased leaf area and chlorophyll content, while GA3 diminished them. In ABA-treated plants, there was a significant reduction in leaf conductance 24 h after the hormone had been applied, but then the conductance values started to rise and equalled those of the controls 11 days later. Although there were no differences in number of pods, in GA3-treated plants the number of seeds per pod was lower, and in ABA-treated plants, young pods were bigger. ABA application increased soybean yield by enhancing carbon allocation and partitioning to the seed. Exogenous ABA also improved the seed quality since it did not affect protein levels but enhanced oil concentration, while GA3 spraying increased oil concentration but diminished seed proteins.

Calcium Absorption from Commonly Consumed Vegetables in Healthy Thai Women

The absorbability of calcium from ivy gourd, a green leafy vegetable (Coccinia grandix Voigt.) and winged bean young pods (Psophocarpus tetragonolobus [L] DC) were measured in 19 healthy adult women aged 20 to 45 y, in a 3-way, randomized-order, crossover design with an average calcium load of 100 mg and milk as the referent. The test meals were extrinsically labeled with 44Ca and given with rice as breakfast after an overnight fast. Absorption of calcium was determined on a blood sample drawn 5 h after ingestion of the test meal. Fractional calcium absorption (X+/- SD) was 0.391 +/- 0.128 from winged beans, 0.476 +/- 0.109 from ivy gourd, and 0.552 +/- 0.119 from milk. The difference in fractional calcium absorption for these 2 vegetables was significant (P < 0.05) and the fractional calcium absorption from these 2 vegetables were both significantly lower than from milk. The difference was partly accounted for by the phytate, oxalate, and dietary fiber content of the vegetables. However, calcium bioavailability of these 2 vegetables, commonly consumed among Thais, was relatively good compared to milk (71% to 86% of milk) and could be generally recommended to the public as calcium sources other than milk and Brassica vegetables.

Seed banks of invasive Australian Acacia species in South Africa: Role in invasiveness and options for management

Despite impressive efforts at clearing stands of invasive Australian Acacia species in South Africa, insufficient attention has been given to understanding the role of seed banks in the invasiveness and long-term persistence of populations. We review information on seeds of these species, considering seed production, seed rain, and the dynamics of seeds in three layers: leaf litter, and upper and lower seed banks in the soil. Many factors affect the accumulation and susceptibility to destruction of seed banks and thus the opportunities for intervention to reduce seed numbers for each of these components. Reduction of seed banks is crucial for the overall success of the multi-million dollar management initiatives against these species. Classical biological control of buds, flower and young pods has reduced the seed production of many Australian acacias in South Africa. Fire can be applied to reduce seed numbers in the leaf litter and upper seed bank in some cases, although there are serious problems associated with high fire intensities in dense acacia stands. Other options, e.g. soil inversion and solarisation, exist to exercise limited reduction of seed numbers in some situations. There is little prospect of meaningful reduction of seed numbers in the lower seed bank. Preventing the accumulation of seed banks by limiting seed production through biological control is by far the most effective means, and in almost all cases the only practical means, of reducing seed numbers. This must be an integral part of management strategies. Several invasive Australian acacias are already under effective biological control, and further work to identify additional potential agents for all the currently invasive species and potentially invasive alien species is the top priority for improving the efficiency of management programmes.

El Niño—Southern Oscillation influences on soybean yields in eastern Paraguay

AbstractSoybean (Glycine max. L. Merrill) production in Paraguay has increased dramatically during the last decade and the country is now the fourth largest soybean exporter in the world, producing about 3% of the world's soybean production. This paper explored associations between soybean yield in eastern Paraguay and the El Niño Southern Oscillation (ENSO) phases. Historical soybean yield data from official government sources were detrended to remove the effects of technological advances, and yield residuals were computed. In addition, differences in mean precipitation among ENSO phases were investigated under the context of crop development phases. The CSM‐CROPGRO soybean model was used to simulate soybean development for two locations representing the most important soybean producing areas in Paraguay. Influences of ENSO phases on mean precipitation during planting and blooming, blooming and seed podding, and from young pods to physiological maturity were explored through tests of differences in the central tendency. Relative yield residuals during El Niño years were positive six out of seven events and varied from − 9.4 to + 24.2% for the 1991/1992 and 2002/2003 cropping seasons, respectively. During La Niña years, calculated residuals were negative for three out of four events and varied from − 37.9 to + 1.5% for the 2005/2006 and 1988/1989 cropping seasons, respectively. Analysis of precipitation records showed significantly lower precipitation levels between planting and blooming during La Niña years than during El Niño years. Differences in mean precipitation during blooming and beginning of seed formation were found to be not significant. Mean precipitation between seed podding and crop maturity was found to be significantly lower during La Niña years than during El Niño years in one of the locations studied. Copyright © 2007 Royal Meteorological Society

Impact of mirid (Creontiades spp.) (Hemiptera: Miridae) pest management on Helicoverpa spp. (Lepidoptera: Noctuidae) outbreaks: the case for conserving natural enemies

Creontiades spp. (Hemiptera: Miridae) are sucking pests that attack buds, flowers and young pods in mungbeans, Vigna radiata (L.), causing these structures subsequently to abort. If left uncontrolled, mirids can cause 25-50% yield loss. Traditional industry practice has involved prophylactic applications of dimethoate to control mirids at budding and again a week later. The present trial was initiated to highlight the dangers of such a practice, in particular the risk of a subsequent Helicoverpa spp. lepidopteran pest outbreak. A single application of dimethoate halved the population of important natural enemies of Helicoverpa spp., and caused an above-threshold outbreak of Helicoverpa spp. within 11 days. This shows that even a moderate (e.g. 50%) reduction in natural enemies may be sufficient to increase Helicoverpa spp. populations in mungbeans. As a result, prophylactic sprays should not be used for the control of mirids in mungbeans, and dimethoate should be applied only when mirids are above the economic threshold. Indoxacarb was also tested to establish its effect on Helicoverpa spp., mirids and natural enemies. Indoxacarb showed potential for Helicoverpa spp. control and suppression of mirids and had little impact on natural enemies.

Comparative assessment of feeding damage by pod-sucking bugs (Heteroptera: Coreoidea) associated with cowpea, Vigna unguiculata ssp. unguiculata in Nigeria

Feeding trials were conducted on three (young, mid-fill and mature) developmental stages of cowpea Vigna unguiculata ssp. unguiculata pods in the screenhouse using fourth instar nymphs and adults of Anoplocnemis curvipes (Fabricius), Riptortus dentipes (Fabricius), Mirperus jaculus (Thunberg), Clavigralla tomentosicollis Stål and C. shadabi Dolling. Anoplocnemis curvipes was observed to be the most damaging coreoid species causing a yield reduction of 26.4-51.7% followed by R. dentipes (24.4-29.4%), M. jaculus (21.9-26.9%), C. tomentosicollis (17.9-22.4%) and C. shadabi (15.9-20.4%). The fourth instar nymphs of each pod-sucking bug species caused a significantly higher cowpea yield reduction than their respective adults. Similarly, infestation on young pods compared to mid-fill and mature stages resulted in significantly higher yield reduction. The results suggest that infestation levels of two fourth instar nymphs of A. curvipes or three fourth instar nymphs of the other four pod-sucking bug species per young pod should be adequate for screening of cowpea varieties for resistance to the coreoid bugs.