cis-Jasmone indirect action on egg parasitoids (Hymenoptera: Scelionidae) and its application in biological control of soybean stink bugs (Hemiptera: Pentatomidae)

In many plants, the secondary metabolite cis-jasmone activates the metabolic pathway that produces volatile organic compounds attractive to natural enemies and, sometimes, repellent to herbivores. Previous studies indicate that the feeding damage caused by the herbivore Euschistus heros or the exogenous application of cis-jasmone in soybean plants induces the release of herbivore-induced plant volatiles (HIPVs) with a similar chemical profile and these compounds can attract the stink bug egg parasitoid Telenomus podisi (Scelionidae). Herein we tested in field conditions the effect of exogenous application of cis-jasmone in soybean plants on the parasitoid and stink bug community and on stink bug egg parasitism. In two areas, one within a soybean and another within a Crotalaria matrix, we randomly distributed 2 m² plots, with soybean plants induced (treatment, n = 5) or not induced by cis-jasmone (control, n = 5) in the field. We sampled the parasitoid community weekly with yellow sticky traps (n = 3/plot) and monitored parasitism with sentinel eggs of E. heros (n = 150/plot). We also monitored the population of stink bugs weekly, by sampling each plot with shake-cloth technique. The abundance of Scelionidae was highest overall and also in treated plots during the first four weeks in the area with a soybean matrix, but decreased thereafter. The richness of parasitoid families was similar between treatment and control plots in the area with a soybean matrix, but higher in control plots in the area with a Crotalaria matrix. Evenness was higher in control plots in the area with soybean matrix, whereas the reverse occurred in the area with a Crotalaria matrix. Results suggest that treatment with cis-jasmone effectively attracted and enhanced the population of scelionid parasitoids, but had no effect on the occurrence and intensity of parasitism and in the number of stink bugs.     

Apparent digestibility of differently processed grain legumes,cow pea and mung bean in black tiger shrimp,Penaeus monodon Fabricius and associated histological anomalies in hepatopancreas and midgut

Experiments were conducted to test the effect different treatment process like dehulling, soaking, autoclaving, germination and germination in combination with autoclaving on proximate composition and antinutritional factors (ANFs) of legume seeds, cow pea and mung bean. An in vivo digestibility trial was conducted in black tiger shrimp Penaeus monodon to determine the coefficient of total tract apparent digestibility (CTTAD) of differently processed legume seeds. The CTTADs were determined by comparing the concentrations of digestibility marker (Cr₂O₃) in the feed and faeces of the juvenile shrimp (4 ± 0.5 g). Seeds processed by germination in combination with autoclaving were low in ANFs and higher in proximate composition with increased protein contents of 18.3 and 15.6% in cow pea and mung bean, respectively. Though trypsin inhibitor activity was significantly (P<0.05) high in germinated seeds, there was a significant reduction by 83.3 and 81.21% on germination followed by autoclaving. Due to unexpected mortality of shrimp, dietary treatments containing raw, soaked, and germinated cow pea and mung bean were removed from the trial. There was a significant difference (P<0.05) in the CTTAD values between the feedstuffs and various treatment processes made. Higher CTTAD dry matter (DM), crude protein (CP) and nitrogen free extract (NFE) were obtained with seeds processed with germination in combination with autoclaving and the trend is similar in both the seeds tested. CTTAD for DM, CP and crude lipid of the grain legumes ranged between 0.683–0.885, 0.684–0.834 and 0.704–1.302, respectively. Histological examinations on hepatopancreas and midgut of shrimp sampled at slaughter revealed some common anomalies. With the exception of the shrimp fed dehulled cowpea, histology was normal in all the shrimps sampled at the end of the digestibility trial.     

New soybean variety,Agakong, as a host of Riptortus pedestris (Fabricius): Study on field occurrence and biological attributes in the laboratory

A new variety of soybean, Agakong, has good nutritious values, thus is expected to be grown widely in the near future. To evaluate Agakong as a new soybean host of Riptortus pedestris (Fabricius) (Hemiptera: Alydidae), we assessed the biological attributes of the stink bug fed on Agakong and its field (Fabricius) occurrence in comparison with other varieties, Cheongjakong and Daewonkong. In laboratory studies, the nymphal development time and fecundity of R. pedestris was unaffected by the soybean varieties. However, nymphal mortality of R. pedestris fed on Agakong was significantly lower than those fed on Daewonkong. Furthermore, adult females become significantly larger when they fed on Agakong. R. pedestris preferred Cheongjakong seeds to Daewonkong or Agakong seeds in Petri dish choice experiments. The population dynamics of eggs, nymphs, and adults on the three soybean varieties planted in a 3 × 3 Latin square design were assessed by direct counting from 13 July to 22 September, 2007 at 10 days intervals. R. pedestris was the most abundant stink bug species on all the tested soybean varieties. The occurrence of R. pedestris eggs and nymphs was not significantly different among the three varieties. However, the seasonal density of R. pedestris adults was lower on Agakong than on Cheongjakong. Although higher R. pedestris populations were not observed in the field, the possibility of R. pedestris becoming a pest on this newly developed soybean variety can't be ruled out since some of its biological attributes were positively affected by feeding on Agakong seeds.     

Lethal and sublethal effects of synthetic insecticides on the locomotory and feeding behavior of Riptortus pedestris (Hemiptera: Alydidae) under laboratory conditions

The bean bug, Riptortus pedestris (Hemiptera: Alydidae) is a polyphagous insect pest and has a wide range of hosts including leguminous plants and tree fruits. Currently, the management of R. pedestris mainly relies on the use of insecticides, and most studies have focused on the lethal effects of insecticides. However, insecticides can not only kill insects directly, but can also affect behavioral changes of survivors when exposed to sub-lethal doses. In this study, we investigated locomotory behaviors (vertical movement, horizontal movement, and flight ability) and feeding behaviors (frequency of insects approaching dried soybean seeds and number of stylet sheaths left on the dried soybean seeds by insects) of surviving R. pedestris pre-exposed to five insecticide residues for 4 h. None of the three insecticides (bifenthrin, etofenprox, and acetamiprid) tested had significant effects on the locomotory behaviors of R. pedestris adults compared to the water-treated control group. Fenitrothion- and dinotefuran-treated groups showed a significant decrease in the vertical movement compared to the water-treated control, but the insects recovered mobility 24 h after the initial exposure. The frequency of R. pedestris approaching to dried soybean seeds was affected by four insecticides (fenitrothion, etofenprox, bifenthrin, and dinotefuran), but the actual feeding activity of R. pedestris determined by the stylet sheaths remaining on the dried soybean seed was only affected by fenitrothion treatment. Given the relatively low toxic effects of five insecticides tested, a better understanding of the impact of insecticides on the behavior of target species is needed for a more robust pest control strategy and a more effective use of insecticides in IPM programs.     

Effects of salinity levels and seed mass on germination in Australian species of Frankenia L. (Frankeniaceae)

Halophyte species demonstrate differing levels of salt tolerance. Understanding interspecific variation to salinity levels is of value from both the scientific perspective, which includes the identification of traits associated with salinity tolerance, as well as from an applied perspective, which includes identifying plant species for specific salinity restoration and remediation projects. This paper investigates the effects of salinity on germination of 12 Australian species of the plant genus Frankenia L. (Frankeniaceae). We use saline solutions that corresponded to the average soil–water salinity concentrations in the arid zones of inland Australia. These solutions consisted of 10 mM calcium chloride, 30 mM magnesium sulphate, and 450 mM sodium chloride. The aims of our study were: (1) to investigate the germination (germination rates, germination success) of Frankenia seeds to four salinity levels (0%, 10%, 20%, 30%), (2) to test for possible interaction effects between seed mass, germination, and salinity, and (3) to examine the effect of salinity levels on the inhibition of germination and/or seed damage. Species varied in their salt tolerance for germination rates and success. Species with larger seeds had higher germination rates and germination success for high salinity levels. Several species did not germinate well at any salinity level. Finally, no seeds were adversely affected by exposure to high salinity levels pre-germination. There is potential for including some Frankenia species in remediation and revegetation projects in areas affected by salinity, and also as garden plants in saline regions.     

Effect of yak rumen content treatments on seed germination of 11 alpine meadow species on the Qinghai-Tibetan Plateau

The Qinghai-Tibetan Plateau is located in the ‘Third Pole’ of the world, characterized by a harsh environment. Despite this, the alpine meadow ecosystem have developed over a wide area but serious grassland degradation is threatening the ecological environment on the Plateau. Recruitment of new plants to the population, via germination and establishment, is vital to plant community survival. Previous work on the seeds in this area has mainly focused on community-wide germination strategies, seed germination characteristics and their correlations with seed size and seed mass. However, there have been no studies on the effects of soaking in rumen contents on the plant seed germination characteristics of alpine meadow species. The present study had two main objectives: (i) to determine the effect of fresh rumen content from yaks on seed germination characteristics and seedling growth of species common to the eastern Tibetan Plateau alpine meadow, and (ii) to develop an effective method to enhance seed germination. Seeds of 11 common species were collected together with fresh rumen content from three yaks that grazed there. Seed germination tests were conducted after they had been soaked in rumen content for one of six soaking periods (12, 24, 36, 48, 60 or 72 h). The seeds were incubated under natural light conditions of 8 h light at 25 °C and 16 h darkness at 15 °C, for the germination period of 34 days. The results showed that seed germination and seedling growth were affected by soaking time, seed coat completeness and seed type. After soaking in rumen content, the germination percentages of scarified (peeled or with the seed coat cut through) seeds of some species (true seeds Oxytropis ochrocephala and Medicago ruthenia var inschanica, nutlet Carex enervis, achenes Anemone rivularis and Polygonum sibiricum) and complete seeds of C. enervis, and A. rivularis were improved but the duration of soaking was also important. Seed germination of caryopsis Achnatherum inebrians (a toxic grass) was significantly inhibited by any exposure to rumen fluids. Scarified seeds generally had higher germination percentages than complete ones after treatment, but with the increase in soaking time, germination percentages declined and scarified seeds were more sensitive to the treatment than the complete seeds. After soaking in yak rumen content, the germination indices of scarified M. ruthenia at 12 h treatment, O. ochrocephala and achene Rumex acetosa at 12–24 h treatment, nutlet Kobresia humilis at 24 h treatment, P. sibiricum at 24–48 h treatment, C. enervis at 12–48 h treatment and A. rivularis at 12–60 h treatment were significantly higher than the control (P < 0.05), while the germination indices of complete C. enervis seeds at 12 h and 36 h treatment, and A. rivularis at 12–60 h treatment were significantly higher compared with the control. The germination indices of other species gradually decreased with the increase in soaking time. We concluded that yak rumen digestion could enhance, inhibit or not affect seed germination and seedling growth of the alpine meadow species, which might influence seedling recruitment, interspecific competition, and the plant community structure of the eastern Tibetan Plateau alpine meadow. Overall, yak digestion has a positive effect on alpine meadow seed germination and seed dispersal.     

Evaluation of different leguminous seeds as food sources for the bean bug Riptortus pedestris

This study was conducted to determine the effects of six different leguminous seeds (cowpea, white kidney bean, soybean cultivars Cheongja and Daepung, mung bean, and azuki bean) on the life history traits of the bean bug Riptortus pedestris (F.) (Hemiptera: Alydidae). The total developmental time from the first instar nymph to adult ranged from 18 to 25 d; R. pedestris fed with white kidney beans were the slowest to develop. In addition, bugs fed with white kidney beans had the highest mortality (93%) and the shortest longevity (18 d). R. pedestris fed with cowpeas, soybeans, or azuki beans had high reproductive success, with the highest egg hatching success recorded in bugs fed cowpeas. The results suggest that cowpea may be a beneficial food source for the development and reproduction of bean bugs.     

Effects of rabbit gut passage on seed retrieval and germination of three shrub species

It has been known for a few decades that European rabbits consume seeds and fleshy fruits of native woody plants, but relevant factors in the endozoochory processes such as seed predation (chewing and digestion), sexual differentiation, or the temporal pattern of seed recovery have been little evaluated until now. In this study, we examined seed dispersal of three Mediterranean shrub species by wild rabbits through monitoring of seed retrieval and germination after gut passage. Twelve adult wild rabbits (Oryctolagus cuniculus; six males and six females) of similar size and age were fed seeds of three shrub species with fleshy fruits (Crataegus monogyna, Myrtus communis and Pistacia lentiscus). After ingestion of fruits, seeds were retrieved from dung every 12 h for a day and a half. The viability and germination of retrieved seeds were tested along with that of uneaten seeds. Between 5% and 76% of ingested seeds were retrieved from dung, with significant differences between species and sex. Most M. communis seeds were retrieved with 12–24 h after ingestion; almost all C. monogyna seeds were recovered with 0–12 h after ingestion; no seeds of P. lentiscus were recovered. Only in the case of M. communis seed was the recovery rate greater in female than in male. Passage through the rabbit gut significantly increased seed germination in M. communis, and decreased it in C. monogyna. In conclusion, wild rabbits acted in this study as predators of C. monogyna and P. lentiscus seeds and potential dispersers of M. communis seeds.     

Seed storage and germination in Kumara plicatilis,a tree aloe endemic to mountain fynbos in the Boland,south-western Cape,South Africa

Seed storage under appropriate conditions is a relatively inexpensive means of safeguarding plant genetic material for ex situ conservation. Post-storage germination trials are used to determine the viability of stored seeds, and hence the efficacy of the particular storage treatment. Kumara plicatilis (= Aloe plicatilis) is a tree aloe endemic to mountain fynbos in the Boland, south-western Cape. The viability and germination behaviour of K. plicatilis seeds were assessed for seeds stored for four and nine months at − 80 °C, 4 °C, 25 °C and under ambient conditions in a laboratory. Seeds were germinated under controlled conditions and germination rates and percentages determined. Ungerminated seeds were tested for viability using tetrazolium salt. Seed viability was not significantly reduced during storage. Seeds stored at − 80 °C for four and nine months exhibited the fastest germination rate overall (both 5.9 ± 0.3 weeks, mean ± S.E.), and slowest was for seeds stored under ambient conditions for four and nine months (both 7.8 ± 0.4 weeks). All seed lots showed similar percentage germination after four months of storage (78.0–90.4%). The highest percentage germination overall was for seeds stored at − 80 °C for four months (90.4%) and the lowest was for seeds kept at 4 °C and − 80 °C for nine months (39.2 and 39.6%, respectively). Respective percentage viability for ungerminated seeds in these two treatments was 82% and 87%, respectively, indicating the induction of secondary dormancy. Induced dormancy triggered by protracted cold temperatures may be an adaptation that enables seeds to survive prolonged extreme conditions that are unfavourable for germination. Further research on the long-term storage of aloe seeds would be beneficial for developing long-term seed storage and germination testing protocols for ex situ conservation.     

Rapid adaptation of seed germination requirements of the threatened Mediterranean species Malcolmia littorea (Brassicaceae) and implications for its reintroduction

Malcolmia littorea (Brassicaceae) is a threatened species growing in the coastal sandy dunes of the west-Mediterranean basin. In this study, the seed germination and seedling emergence requirements of this species were investigated in the only remaining native population in Italy. The highest germination percentage was achieved in darkness with scoring under safe green light at 5–10 °C. Seedling emergence was highest when seeds were buried between 1 and 10 mm in depth. The results suggest that germination and seedling emergence are adapted to Mediterranean coastal habitats by employing a common mechanism of light-inhibited germination and by germinating at cooler temperatures before the onset of the summer drought. Seeds were also collected from plants cultivated at a botanical garden and from plants reintroduced by sowing or by transplanting. For those populations, germination was maximal between 10–25 °C, suggesting that the thermal germination behaviour may be affected by the maternal environment of seed production within one generation. It is suggested to use seeds produced in the same environment to which they will be used for the reintroduction of this species.     

Lantana camara and the fruit- and seed-damaging fly,Ophiomyia lantanae (Agromyzidae): Seed predator,recruitment promoter or dispersal disrupter?

The seed damaging fly, Ophiomyia lantanae is a widespread agent that infests the fruits and seeds of Lantana camara. Its effectiveness in reducing seed dispersal or seedling recruitment has not been comprehensively tested. We determined the effects of O. lantanae damage on fruit removal rates of L. camara in a field study. We also investigated recruitment responses (seed germination in growth cabinets and seedling emergence in pot trials) of two common L. camara biotypes, pink and pink-edged red (PER) to O. lantanae damage. We found that fewer damaged fruits were removed than undamaged fruits, suggesting that frugivores select against damaged fruit. In all recruitment experiments, the responses to damage were biotype dependent. In germination experiments, these differential responses were primarily due to significantly reduced germination of damaged PER seeds. Seedling emergence from pots of the PER biotype was also lower in damaged seeds (27.5%) than undamaged seeds (56.1%). In contrast, emergence increased with seed damage in the pink biotype, from 28.2 to 41.1%. O. lantanae damage significantly reduced seed mass only in the smaller seeded PER biotype. In the larger seeded pink biotype, it may have promoted seedling emergence by interfering with dormancy mechanisms. We also examined in situ seed banks at L. camara populations prior to peak seed production. Mean viable seed densities ranged from 78.6 to 402.8 seeds m⁻². Of these, non-dormant seeds comprised 24.6 to 98.2 seeds m⁻², suggesting that recruitment is unlikely to be seed limited. We conclude that while O. lantanae influences recruitment and dispersal processes, the magnitude of the responses measured are unlikely to greatly influence plant densities in south-east Queensland infestations.     

Effects of seed storage on germination of two succulent desert halophytes with little dormancy and transient seed bank

Seeds of both Salsola imbricata and Haloxylon salicornicum have high germination level and germination speed, and form a transient seed bank in nature. The impacts of storage period and condition on germination level and speed were assessed in the two species. Storage for three months significantly increased both germination level and speed of seeds stored under the different conditions, compared to that of fresh seeds. In both species, nine months storage did not affect germination percentage in cold storage seeds, but completely inhibited it in field seeds. Storage for longer time in room and warm temperatures resulted in significant reduction or complete inhibition in the germination of the two species, so this was more pronounced in H. salicornicum. Storage significantly increased germinate rate index of seeds stored in all conditions till 17 months in S. imbricata and till 12 months in H. salicornicum. In both species, fridge storage had little effects on final germination and germination speed of seeds incubated at the different temperatures, compared to fresh seeds. However, room temperature and warm storages significantly reduced final germination and germination speed at the different temperatures, so the reduction was more pronounced at 35 °C, especially in H. salicornicum.     

Anthraquinone-based bird repellent for sunflower crops

Non-lethal alternatives are needed to manage bird damage to confectionery and oilseed sunflower crops (Helianthus annuus). Ring-necked pheasants (Phasianus colchicus) can cause localized damage to newly planted sunflower, and blackbirds (Icterids) damage ripening sunflower annually in the United States of America. We conducted seed germination experiments, a repellent efficacy study with ring-necked pheasants and Avipel^® repellent (a.i. 50% 9,10-anthraquinone), and laboratory and field efficacy studies with common grackles (Quiscalus quiscula) and Avipel^®-treated confectionery sunflower. Compared to the germination of seeds not treated with anthraquinone, we observed no negative effects of up to 12,223 ppm, 14,104 ppm, and 11,569 ppm anthraquinone seed treatments for germination of confectionery sunflower, oilseed sunflower, and canola seeds, respectively. Pheasants avoided emergent sunflower seedlings (12 days post-planting) from 15,800 ppm anthraquinone seed treatments during a caged preference test (P = 0.045). We observed a positive concentration–response relationship (P = 0.001) and predicted a threshold concentration (i.e., 80% repellency) of 9200 ppm anthraquinone for common grackles offered Avipel^®-treated confectionery sunflower seeds. Grackles also reliably discriminated between untreated sunflower and seeds treated with 1300 ppm anthraquinone in captivity (P < 0.001). During our field efficacy study for ripening confectionery sunflower, we observed 18% damage among anthraquinone-treated enclosures and 64% damage among untreated enclosures populated with common grackles (P < 0.001). Harvested seed mass averaged 2.54 kg (dry weight) among treated enclosures and 1.24 kg among untreated enclosures (P < 0.001). Our laboratory and field efficacy data provide a reliable basis for planning future field applications of anthraquinone-based repellents for protection of sunflower crops. Supplemental field efficacy studies are necessary for development of an effective avian repellent and management of avian depredation of ripening agricultural crops, including oilseed sunflower.     

Immunodetection and immunolocalization of tryptophanins in oat (Avena sativa L.) seeds

Tryptophanins (TRPs) are low molecular weight, tryptophan-rich, basic proteins found in oat (Avena sativa L.) seeds. Like their counterpart puroindolines (PINs) from wheat (Triticum aestivum L.), TRPs are thought to be involved in flour softness as well as disease resistance against phytopathogenic fungi. PINs are known to be the major components of ‘friabilin’ associated with the surface of water washed starch grains and possess lipid binding properties. Two polyclonal antisera against puroindoline-a (PIN-a), and puroindoline-b (PIN-b) respectively; and a monoclonal antiserum raised against ‘friabilin’ were used as primary antibodies in immunoblotting experiments. All antisera detected immunoreactive polypeptides, with approximate relative masses of 15–16 kDa, in oat, wheat, and barley (Hordeum vulgare L.) seed extracts but not in rice (Oryza sativa L.), maize (Zea mays L.), bean (Phaseolus vulgaris L.), pea (Pisum sativum L.) and lentil (Lens culinaris Medic.) seed extracts. Immunoreactive polypeptides were detected in aqueous ethanol [52% (v/v) ethanol] seed extracts. Both anti-‘friabilin’ monoclonal and anti-PIN-b polyclonal antisera recognized 15 as well as 16 kDa tryptophanins in oat seeds from different cultivars. On the other hand, anti-PIN-a polyclonal antiserum strongly cross-reacted with 16 kDa TRP and weakly with 15 kDa TRP. Tryptophanins were found to be associated with the surface of starch grains in oat endosperm tissue using both fluorescence and confocal laser scanning microscopies with anti-‘friabilin’ monoclonal antiserum. SDS-PAGE and immunoblotting assays revealed a gradual synthesis of TRPs as early as milk stage in developing oat seeds. On the other hand, TRPs tend to undergo degradation during seed germination.     

Effects of salt,alkali and salt–alkali mixed stresses on seed germination of the halophyte Salsola ferganica (Chenopodiaceae)

Salsola ferganica L. (Chenopodianceae) is an annual halophytic species. Experiments were carried out in laboratory to determine the effects of temperature, perianths and various types of salinity on seed germination and germination recovery. Seeds were germinated at 6 levels of temperature with perianths, plus perianths and removed perianths in complete darkness for 9 days. The germination responses of the seeds without perianths at 25 °C were determined over a wide range of NaCl, NaHCO₃ or NaCl–NaHCO₃ mixed stress for 13 days. Perianths seriously affected germination as a barrier for seed germination and the optimal temperature was at 25 °C. Highest germination percentage was obtained under control and seed germination was progressively inhibited with the increase of salinity concentration. The negative effect of NaHCO₃ at the same concentration on germination was stronger than that of NaCl and NaCl–NaHCO₃ mixed. When substrate salinity was removed, seeds exposed to a high NaCl concentration (400–800 mM), NaHCO₃ (50–200 mM) and NaCl–NaHCO₃ mixed (100–400 mM) germinated well. Final germination of Salsola ferganica seeds was significantly affected by types of salt at the low salinity (?200 mM) and with increased salinity it was influenced mainly by salinity concentration for various proportion of salt–alkali mixed stress.     

Germination response and viability of an endangered tropical conifer Widdringtonia whytei seeds to temperature and light

The tropical conifer Widdringtonia whytei Rendle is an endangered species endemic to Mulanje Mountain in Malawi. A study was conducted for the first time under controlled conditions in order to assess the effects of temperature and light on germination and viability of W. whytei seeds. Seeds incubated at a constant temperature of 20 °C attained the highest cumulative germination percentage (100%) followed by 87% germination under fluctuating temperatures of 15 °C night/25 °C day. No seed germination occurred at temperatures below 15 °C. Seeds that failed to germinate at temperatures below 15 °C showed the highest (> 90%) viability compared to the seeds incubated at 25 °C (60%). Across temperature regimes, germination was significantly higher under light (44.7%) than dark (35.6%) conditions. It is concluded that temperature is one of the critical factors for germination of W. whytei seed. The ability of W. whytei seeds to germinate both in light and darkness implies that the species would unlikely form a persistent soil seed bank, an attribute which is common in species that survive in habitats frequently disturbed by fires.     

Exposure of maize seeds to stationary magnetic fields: Effects on germination and early growth

The effect of the exposure of maize seeds to stationary magnetic fields on germination and early growth has been studied under laboratory conditions. Seeds were magnetically exposed to one of two magnetic field strengths, 125 or 250 mT for different periods of time. Mean germination time and the time required to obtain 10, 25, 50, 75 and 90% of seeds to germinate were calculated. The results showed a reduction of these parameters for most of magnetic treatments, therefore their rate of germination was increased.Growth data measured on the 7th and 10th day after seeding allowed us to corroborate the effect observed in germination tests. Treated plants grew higher and heavier than control; on the 10th day total length was greater than control plants exposed to stationary magnetic field, corresponding with increase of the total fresh weight. The greatest increases were obtained for plants continuously exposed to 125 or 250 mT.     

Evaluation of three plant seeds as potential pre-season diets for Riptortus pedestris

Riptortus pedestris (Fabricius) (Hemiptera: Alydidae) is a polyphagous pest causing serious economic damage especially in soybean (Glycine max L.). R. pedestris start to emerge earlier in spring when reproduction is not possible due to scarcity of nutritious food sources, thus host exploitation pattern is not well known. In order to understand the patterns of seasonal occurrence and how it relates to suitability of host plants in the spring, we evaluated the seeds of barley (Hordeum vulgare L.), sesame (Sesamum indicum L.), and black locust (Robinia pseudoacacia L.) as pre-season food sources for R. pedestris. A diet of soybean seed was also compared as a control. When nymphs fed sesame seeds only, R. pedestris never became third instars. Only 2.5 and 5% of R. pedestris fed on barley and barley + sesame, respectively, successfully became adults. Only when supplemented with soybean seeds could barley and sesame seeds support nymphal development and reproduction of R. pedestris. This indicates that neither barley nor sesame is adequate food sources for the development and the reproduction of R. pedestris even though they occur in those crop fields in spring and summer. However, seeds of black locust supported the complete development and reproduction of R. pedestris. Thus, black locust can be an additional leguminous host plant for R. pedestris during the period when suitable food sources are limited.     

Effect of infection by Metarhizium anisopliae (Hypocreales: Clavicipitaceae) on the feeding and oviposition of the pea leafminer Liriomyza huidobrensis (Diptera: Agromyzidae) on different host plants

The effect of fungal infection by Metarhizium anisopliae on feeding and oviposition of adult Liriomyza huidobrensis was examined on three host plants, faba bean (Vicia faba), French bean (Phaseolus vuklgaris) and snow pea (Pisum sativum) in the laboratory. Flies were contaminated with dry conidia and allowed to feed and oviposit on the different host plants. Mortality in L. huidobrensis varied between 14% and 20% in the controls and between 77% and 100% in fungal treatments 120 h post-infection for the three host plants. L. huidobrensis made more punctures (47.3–52.6 cm^?2) in the control than in the fungal treatments (23.1–26.9 cm^?2) for the three host plants. The cumulative average number of punctures cm^?2/female by L. huidobrensis was higher in the controls than in fungal treatments from 72 h post-treatment in faba bean (12.2 vs. 8.2) and French bean (14.8 vs. 8.9), and from 48 h post-inoculation in snow pea (8.5 vs. 5.7). Female L. huidobrensis laid more eggs in the control (0.6–6.1) than in fungal treatments (0.2–1.5) across the host plants tested. The cumulative mean number of eggs cm^?2/female was significantly higher in the controls than in fungal treatments from 48 h post-treatment in faba bean (0.4 vs. 0.2) and French bean (0.1 vs. 0), and 96 h post-inoculation in snow pea (0.2 vs. 0.1). The host plant did not affect the average total number of punctures but had a significant effect on egg laying, with faba bean harboring greater number of eggs in both control and fungal treatments. A proper timeline application of the fungus before onset of feeding and oviposition peaks will be crucial in field suppression of the pest using M. anisopliae. In addition, a great consideration must be given to the target host plants prior to application of the fungus.     

Effect of gamma irradiation on OKRA (Abelmoschus esculentus L.)

The investigation was carried out to evaluate the effect of different doses of gamma rays (100, 200, 300, 400, 500 Gy and zero doses as control) on various morphological aspects of Abelmoschus esculentus. A comparison of the results of different doses with control showed that gamma irradiation significantly affected various parameters. Days to germination were almost the same as compared to control, but 400 Gy took minimum days to germination. Germination % was 100% both in control and the irradiated plants. 100 Gy took minimum days for flower initiation as compared to control and other doses. Fruit initiation early occurred in 100Gy as compared to other doses, and fruit maturation occurred early in 300 Gy as compared to control. Plant height was significantly increased at 500 Gy as compared to control. Number of fruits per plant was significantly decreased at 200 Gy as compared to control. Fruit length decreased in all doses but in control fruit length was maximum. Number of seeds per fruit was maximum at control, fresh and dry weights of seeds were increased in control as compared to other doses. The number of nodes decreased in all doses but in the control the numbers of nodes were maximum. Branches were increased in100Gy as compare to 200, 300,400,500 Gy as well in control. Numbers of leaves were increased in 300 Gy as compared to other doses.