Characterisation and management of Phalaris paradoxa resistant to ACCase-inhibitors

Phalaris paradoxa is a competitive grass commonly found in durum wheat crops of central and southern Italy. Among the 85 populations screened from 1998 to 2008 for resistance to ACCase-inhibitors and graminicide sulfonylureas, 17 resulted as being resistant to at least one ACCase inhibitor while none of the populations showed resistance to sulfonylureas. ACCase resistance in hood canary-grass seems to be spreading rather slowly in Italy. Out of the 17 populations, seven were characterised through outdoor dose-response pot experiments to investigate resistance levels and cross-resistance patterns to ACCase-inhibitors and multiple resistance to other mode of action. Molecular bases of resistance to the recently introduced DEN herbicide pinoxaden were also investigated. Six populations were confirmed to be ACCase-resistant with various cross-resistance patterns. Two populations were resistant to all tested ACCase herbicides, with pinoxaden resistance indexes (RI) based on survival ranging from 22 to 50. The two populations have been molecularly characterised for resistance to pinoxaden. A single point-mutation in the ACCase gene was identified in each population, causing the amino-acid substitutions of Ile₁₇₈₁Val and Asp₂₀₇₈Gly in 0478L and 0025, respectively. The results suggest that resistance of P. paradoxa to pinoxaden is due to an altered target site and different mutations cause different resistance levels. The biological characteristics of the species, mainly self-pollinated, and the absence of multiple resistance allow herbicides with different modes of action to be used for controlling ACCase-resistant populations. Chemical tools should be carefully used within integrated weed management strategies.     

No fitness costs associated with resistance of Busseola fusca (Lepidoptera: Noctuidae) to genetically modified Bt maize

A concern regarding planting of Bt crops is that their widespread cultivation could lead to evolution of insect resistance to Bt toxins. In South Africa, the noctuid maize stem borer (Busseola fusca [Fuller]), is resistant to Bt maize (Zea mays L.; MON810) which produces Cry1Ab protein. The presence of fitness costs in resistant populations could be a valuable component of resistance management since the non-Bt maize refuge may select against resistance. The aim of the study was to determine if there are fitness costs associated with Bt resistance of B. fusca. Life history parameters were compared between individuals of a Bt maize resistant B. fusca population when feeding on Bt or non-Bt maize. Similar comparisons were done using a control population. Field collected larvae as well as their F₁-generation were used in the study. The following parameters were compared: pupal mass, moth longevity, fecundity, fertility, larval mass and survival, and sex ratio. Except for LT50-values, no fitness costs were associated with the resistance trait in the highly resistant B. fusca population. The absence of fitness costs and presence of resistant populations may promote the use of a multi-gene strategy which would be expected to impact negatively on fitness.     

Detecting ALS and ACCase herbicide tolerant accession of Echinochloa oryzoides (Ard.) Fritsch. in rice (Oryza sativa L.) fields

Inconsistent control of Echinochloa oryzoides has been reported repeatedly by farmers in the major rice growing area of Turkey. Greenhouse studies confirmed the existence of cross and multiple herbicide tolerance of E. oryzoides accessions including acetolactate synthase (penoxsulam, bispyribac-sodium) and acetyl CoA carboxylase (cyhalofob-butyl) inhibiting herbicides. Comparison of 95% lower confidence intervals of ED₉₀ derived from log-logistic dose–response curves, and twice the recommended field rates of the herbicides showed some, but not distinct separation of susceptible and tolerant accessions. We used a novel method to separate heterogeneous data without a priori knowledge of grouping into more than one group. On the basis of the distribution of ED₉₀ it was possible to identify two distinct groups of the 172 accessions tested, 78% were not controlled by ALS inhibitors (penoxsulam, and bispyribac-sodium) at recommended field rates; and 38% were not controlled by the ACCase Inhibitor (cyhalofob-butyl) at twice the field rates. The effective response level of ED₉₀ resulted in 64 and 14 tolerant accessions to ALS and ACCase, respectively. Fourteen accessions showed multiple resistances to ALS and ACCase Inhibitors.Some of the accessions were strongly tolerant to both herbicide modes of action and had 100% survival even at 6 times the recommended rates. Most of these tolerant accessions were from Marmara region, predominantly in Edirne and Balıkesir, which are the regions without any crop rotation.     

Relative Fitness of Helicoverpa armigera (Lepidoptera: Noctuidae) on Seven Host Plants: A Perspective for IPM in Brazil

The cotton bollworm Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) is a widespread pest of many cultivated and wild plants in Europe, Africa, Asia, and Australia. In 2013, this species was reported in Brazil, attacking various host crops in the midwestern and northeastern regions of the country and is now found countrywide. Aiming to understand the effects of different host plants on the life cycle of H. armigera, we selected seven species of host plants that mature in different seasons and are commonly grown in these regions: cotton (Gossypium hirsutum, “FM993”), corn (Zea mays, “2B587”), soybean (Glycine max, “99R01”), rattlepods (Crotalaria spectabilis), millet (Pennisetum glaucum, “ADR300”), sorghum (Sorghum bicolor, “AGROMEN70G35”), and cowpea (Vigna unguiculata, “SEMPRE VERDE”). The development time of immatures, body weight, survivorship, and fecundity of H. armigera were evaluated on each host plant under laboratory conditions. The bollworms did not survive on corn, millet, or sorghum and showed very low survival rates on rattlepods. Survival rates were highest on soybean, followed by cotton and cowpea. The values for relative fitness found on soybean, cotton, cowpea, and rattlepods were 1, 0.5, 0.43, and 0.03, respectively. Survivorship, faster development time, and fecundity on soybean, cotton, and cowpea were positively correlated. Larger pupae and greater fecundity were found on soybean and cotton. The results indicated that soybean, cotton, and cowpea are the most suitable plants to support the reproduction of H. armigera in the field.     

Resistance of Spodoptera litura (Lepidoptera: Noctuidae) to profenofos: Relative fitness and cross resistance

Profenofos, an acetylcholine esterase inhibitor insecticide, has been used for the management of various lepidopteron pests of many crops in Pakistan. In the present study, we investigated the impact of insecticide resistance on fitness cost in Spodoptera litura, and evaluated cross resistance to other insecticides. The effect of profenofos on different life history parameters including survival rate, female ratio, fecundity and hatchability, intrinsic rate of population increase and biotic potential was determined. Significant differences associated with fitness costs were revealed. A field collected S. litura strain was selected by exposure to profenofos in the laboratory (Profen-SEL) and after 14 generations of selection it developed a 52-fold resistance to this insecticide. The Profen-SEL strain showed high cross-resistance to chlorpyrifos (62-fold), but very low to no cross resistance to lambda-cyhalothrin (2.34-fold) or methomyl (0.80-fold), respectively. The resistant strain had a relative fitness of 0.38 with a low larval survival rate, longer larval duration, longer male pupal duration, longer development time, low emergence rate of healthy adults, fecundity and hatchability compared with an unselected strain. The intrinsic rate of natural population increase, mean relative growth rate and biotic potential were lower for the selected strain compared with an unselected strain. Development of resistance may cause fitness costs for the resistant strain. This study provided important information for understanding profenofos resistance and facilitating a better strategy for the management of resistance.     

Interplay Between Oxytetracycline and the Homozygote kdr (L1014F) Resistance Genotype on Fecundity in Anopheles gambiae (Diptera: Culicidae) Mosquitoes

The insecticide resistance in Anopheles gambiae mosquitoes has remained the major threat for vector control programs but the fitness effects conferred by these mechanisms are poorly understood. To fill this knowledge gap, the present study aimed at testing the hypothesis that antibiotic oxytetracycline could have an interaction with insecticide resistance genotypes and consequently inhibit the fecundity in An. gambiae. Four strains of An. gambiae: Kisumu (susceptible), KisKdr (kdr (L1014F) resistant), AcerKis (ace-1 (G119S) resistant) and AcerKdrKis (both kdr (L1014F) and ace-1 (G119S) resistant) were used in this study. The different strains were allowed to bloodfeed on a rabbit previously treated with antibiotic oxytetracycline at a concentration of 39·10^–5 M. Three days later, ovarian follicles were dissected from individual mosquito ovaries into physiological saline solution (0.9% NaCl) under a stereomicroscope and the eggs were counted. Fecundity was substantially lower in oxytetracycline-exposed KisKdr females when compared to that of the untreated individuals and oxytetracycline-exposed Kisumu females. The exposed AcerKis females displayed an increased fecundity compared to their nontreated counterparts whereas they had reduced fecundity compared to that of oxytetracycline-exposed Kisumu females. There was no substantial difference between the fecundity in the treated and untreated AcerKdrKis females. The oxytetracycline-exposed AcerKdrKis mosquitoes had an increased fecundity compared to that of the exposed Kisumu females. Our data indicate an indirect effect of oxytetracycline in reducing fecundity of An. gambiae mosquitoes carrying kdr^R (L1014F) genotype. These findings could be useful for designing new integrated approaches for malaria vector control in endemic countries.     

Artificial Diets With Different Protein Levels for Rearing Spodoptera frugiperda (Lepidoptera: Noctuidae)

Spodoptera frugiperda (J.E. Smith, 1797) (Lepidoptera: Noctuidae) is a pest of great economic importance which can feed on more than 300 plant species. As it is polyphagous, its host plants may have variable physical and chemical constitutions. This may influence larval development, as protein and carbohydrate levels are important factors for adequate biological development. The aim of this study was to evaluate insect developmental parameters as well as to compare the food consumption of S. frugiperda larvae reared using diets with different protein levels under laboratory conditions. Three artificial diet formulations were used: one typically used for routine laboratory rearing, based on bean, wheat germ and brewer’s yeast (D₁); one containing half the original amount of protein (D₂), and the other with twice the original amount of protein (D₃). The relative consumption rate (RCR), relative growth rate (RGR), and efficiency of conversion of ingested food (ECI) for S. frugiperda fourth instar larvae varied among diets. The protein present in the diet influenced the duration of larval and pupal periods and pupal weight, but did not affect larval survival, fecundity and longevity of adults. The different protein levels in the diets did not negatively influence population growth, so these three diet variations can be used for mass rearing in the laboratory. However, the influence of these diets on successive generations of the insect remains untested.     

The Influence of Gut Microbiota on the Fecundity of Henosepilachna vigintioctopunctata (Coleoptera: Coccinellidae)

The gut microbiota of insects usually plays an important role in the development and reproduction of their hosts. The fecundity of Henosepilachna vigintioctopunctata (Fabricius) varies greatly when they develop on different host plants. Whether and how the gut microbiota regulates the fecundity of H. vigintioctopunctata was unknown. To address this question, we used 16S rRNA sequencing to analyze the gut microbiomes of H. vigintioctopunctata adults fed on two host plant species (Solanum nigrum and Solanum melongena) and one artificial diet. The development of the ovaries and testes was also examined. Our results revealed that the diversity and abundance of gut microorganisms varied significantly in insects reared on different diets. The gut microbiota of H. vigintioctopunctata raised on the two host plants was similar, with Proteobacteria being the dominant phylum in both groups, whereas Firmicutes was the dominant phylum in the group reared on the artificial diet. The predominant microbiota in the S. nigrum group were Acinetobacter soli and Acinetobacter ursingii (Acinetobacter, Moraxellaceae); Moraxella osloensis (Enhydrobacter, Moraxellaceae); and Empedobacter brevis (Empedobacter, Weeksellaceae). The microbiota in this group are associated with high lipid metabolism. In addition, the beetles’ ovaries and testes were more highly developed in the S. nigrum group than in the other two groups. These findings provide valuable information for elucidating the complex roles the gut microbiota play in the fecundity of H. vigintioctopunctata, and may also contribute to developing future novel control strategies involving this economically important pest.     

Effect of nitrogen fertilizer on the growth and survival of Rhopalosiphum padi (L.) and Sitobion avenae (F.) (Homoptera: Aphididae) on different wheat cultivars

Increased nitrogen applications to crops influence plant-insect interactions and potentially increase herbivore population growth. The effect of nitrogen applications on the interactions between a wheat host plant, Triticum aestivum, and its herbivores, Sitobion avenae (Fabricius, 1775) and Rhopalosiphum padi (Linnaeus, 1758) was investigated. Adult body weight, fecundity, maturity rate and longevity of the aphids were measured under different nitrogen application on four wheat varieties, Solstice, Einstein, Deben and Alchemy. Adult body weight of R. padi on Alchemy and of S. avenae on Deben was lowest. Fecundity of R. padi was lesser on Deben and Alchemy while fecundity of S. avenae was least on Alchemy. Days to reach maturity were same on all varieties in S. avenae but in R. padi, Deben positively affected the days to reach maturity. Longevity of S. avenae and R. padi was the same on all varieties. N-fertilizer had a positive effect on the adult weight achieved by S. avenae and R. padi. Fecundity and longevity of both species were also positively correlated with N-fertilizer application. In R. padi, N-fertilizer reduced the time to reach maturity but not in S. avenae.     

Allocation of photoassimilates to biomass,resin and carbohydrates in Grindelia chiloensis as affected by light intensity

Grindelia chiloensis (Asteraceae) is a shrub native to Patagonia, Argentina, and can accumulate as much as 25% resin (on a dry weight basis) in leaves. The resin can be used in applications similar to those of pine resins. Reductions in available radiation are thought to decrease both the plant C:N ratio and resin production. The objective of this study was to assess the effect of light availability on the allocation of photoassimilates to biomass, resin (terpenes) and carbohydrates in G. chiloensis. To examine this, three radiation treatments were applied to field grown plants: (i) 100% radiation (full-sun), (ii) 50% radiation and (iii) 25% photon flux density radiation. Changes in available radiation resulted in significant changes in above ground biomass accumulation, carbon based secondary metabolites (resin), non-structural carbohydrate (TNC) content, and relative growth rate (RGR). At low radiation levels, above ground biomass accumulation, RGR, resin, TNC content and CO₂ assimilation rate were highly reduced (from 150 to 80 g per plant, from 16 to 7%, and from 30.2 to 8.6 g per plant, for biomass, resin content, and resin production, respectively). The responses to low radiation found in G. chiloensis would limit productivity and the distribution of this species when grown under cultivation.     

ARTP Mutagenesis of Schizochytrium sp. PKU#Mn4 and Clethodim-Based Mutant Screening for Enhanced Docosahexaenoic Acid Accumulation

Schizochytrium species are one of the best oleaginous thraustochytrids for high-yield production of docosahexaenoic acid (DHA, 22:6). However, the DHA yields from most wild-type (WT) strains of Schizochytrium are unsatisfactory for large-scale production. In this study, we applied the atmospheric and room-temperature plasma (ARTP) tool to obtain the mutant library of a previously isolated strain of Schizochytrium (i.e., PKU#Mn4). Two rounds of ARTP mutagenesis coupled with the acetyl-CoA carboxylase (ACCase) inhibitor (clethodim)-based screening yielded the mutant A78 that not only displayed better growth, glucose uptake and ACCase activity, but also increased (54.1%) DHA content than that of the WT strain. Subsequent optimization of medium components and supplementation improved the DHA content by 75.5 and 37.2%, respectively, compared with that of mutant A78 cultivated in the unoptimized medium. Interestingly, the ACCase activity of mutant A78 in a medium supplemented with biotin, citric acid or sodium citrate was significantly greater than that in a medium without supplementation. This study provides an effective bioengineering approach for improving the DHA accumulation in oleaginous microbes.     

Solanum berthaultii Hawkes affects the digestive system,fat body and ovaries of the Colorado potato beetle

Ovarian development and fecundity of Colorado potato beetles reared on the resistant potato species,Solanum berthaultii were reduced compared to females reared on the susceptible potato,S. tuberosum. Striking changes in the appearance of the digestive tract and large quantities of undigested plant material in the midgut of females reared onS. berthaultii suggest that ovarian development might be impaired by poor nutritional quality ofS. berthaultii foliage. Alternatively, enlargement of the midgut by undigested plant material might physically limit ovarian development and subsequent fecundity. These results suggest that a major impact ofS. berthaultii on CPB performance occurs in the physiology of digestion and reproduction.     

Competitiveness of rice (Oryza sativa L.) cultivars against Echinochloa crus-galli (L.) Beauv. in water-seeded production systems

Developing more competitive rice cultivars could help improve weed management and reduce dependency on herbicides. To achieve this goal, an understanding of key traits related to competitiveness is critical. Experiments were conducted at Gelemen and Bafra districts of Samsun province in Turkey between 2008 and 2009 to measure the competitiveness of rice cultivars against Echinochloa crus-galli, a problematic weed in rice fields. Five rice cultivars (Osmancık, Kızılırmak, Karadeniz, Koral and Neğiş) and five E. crus-galli densities (0, 5, 10, 20, and 30 plants m⁻²) were used. Koral produced significantly more tillers than the other cultivars irrespective of E. crus-galli densities and reduced E. crus-galli tiller production by about 29.5% at Gelemen and 15.8% at Bafra at the highest weed density. E. crus-galli interference reduced rice height and there was a density dependent relationship. Koral was the most competitive cultivar; it maintained high biomass accumulation in early growth stages and suffered smaller reductions in plant height in the presence of E. crus-galli, compared to the other cultivars. In the absence of weed competition, Koral and Neğiş produced the highest yields at both locations. Stepwise regression analyses of the combined data from both years showed tillering capacity, early growth crop biomass, and plant height were critical traits related to competitiveness. These traits should be considered by plant breeders in their efforts to develop rice cultivars with enhanced competitiveness against weeds. Development of such cultivars could substantially reduce herbicide and labor inputs for rice production.     

Effect of emergence time,inter- and intra-specific competition on growth and fecundity of Echinochloa crus-galli in dry-seeded rice

Since 2005, the evolution and spread of herbicide-resistant Echinochloa crus-galli biotypes have posed a serious threat to crop production in the Philippines. A comprehensive knowledge of E. crus-galli ecology and fecundity is fundamental in managing different biotypes of this weed. It was hypothesized that (a) high weed plant density produces more biomass and fertile seeds per unit area, (b) rice interference reduces the biomass and fecundity of the weed, and (c) a delay in weed emergence reduces the soil seed bank. In 2013, experiments were conducted in the wet season (WS) and dry season (DS), to understand the effect of E. crus-galli densities (40 and 80 plants m⁻²) on its growth, survival, and fecundity, with varying emergence times of 2, 15, 30, and 45 d after rice emergence (DARE). Relative to the weed plants grown without rice interference, E. crus-galli growth and seed production was lower in the presence of rice. Percent survival and plant height of E. crus-galli declined in a linear manner in the DS, and declined in a quadratic manner in the WS. Tiller number, inflorescence number, inflorescence biomass, and shoot biomass per plant declined in an exponential manner, with a delay in emergence of each cohort relative to rice. Across rice seeding rate, weed density, and emergence time, there was a linear relationship (y = 110x − 272 in the DS and y = 100x − 220 in the WS) between E. crus-galli shoot biomass and the number of seeds plant⁻¹. Relative to the late-emerging weed cohorts, E. crus-galli seed production (1320–1579 seeds plant⁻¹), 1000-seed weight (2.2–2.9 g), and seed yield (2808–2334 kg ha⁻¹) were higher when seedlings emerged with the crop (2 DARE). None of the seedlings that emerged 45 DARE produced viable seeds. Seed germination of the first two cohorts (2 and 15 DARE) ranged from 84 to 91%. The delay in emergence of E. crus-galli beyond 30 DARE reduced the percentage of germinable and viable seeds, and increased the percentage of non-viable seeds produced plant⁻¹. The results suggest that cultural weed management approaches that delay the emergence of E. crus-galli can reduce weed biomass and seed production, and is thus valuable for preventing seed rain to the seed bank by noxious weed biotypes in the field.     

Effect of pre-emergence herbicides and timing of soil saturation on the control of six major rice weeds and their phytotoxic effects on rice seedlings

The study evaluated the effects of pre-emergence herbicides and their rates [oxadiazon (0.5 and 1 kg ai ha⁻¹), pendimethalin (1 and 2 kg ai ha⁻¹), and pretilachlor with safener (0.6 kg ai ha⁻¹)], and time of soil saturation establishment after herbicide application [1, 3, 5, and 7 days after spray (DAS)] in controlling the six major rice weeds, and their phytotoxic effects on rice seedling growth. All herbicides provided 100% control of Echinochloa colona, Echinochloa crus-galli, Leptochloa chinensis, Cyperus iria, and Amaranthus spinosus. Murdannia nudiflora was 100% controlled by oxadiazon and pretilachlor with safener, but poorly controlled (22–75%) by pendimethalin. Pendimethalin at 2 kg ai ha⁻¹ was more effective than at 1 kg ai ha⁻¹ in reducing the biomass of the stem, leaf, and root of M. nudiflora irrespective of timing of soil saturation. Rice plant height was reduced to a maximum (77–96%) by pendimethalin at 2.0 kg ai ha⁻¹ followed by oxadiazon at 1.0 kg ai ha⁻¹ (38–70%) compared to the non-treated control. In contrast, the tallest rice plants were observed in the non-treated control and those treated with pretilachlor with safener which had 80–100% rice plant survival. The lowest rice plant survival of 0, 6, 7, and 16% was found in the soil applied with pendimethalin at 2 kg ai ha⁻¹ and saturated at 1, 3, 5, and 7 DAS, respectively, which was followed by oxadiazon at 1 kg ai ha⁻¹. All herbicides except pretilachlor with safener reduced SPAD values with early soil saturation, which improved with delay in soil saturation timing. Pendimethalin at 2 kg ai ha⁻¹ reduced the SPAD values of rice plants by 100–164% relative to the non-treated control and produced the highest phytotoxicity symptoms. Pendimethalin also reduced rice shoot biomass more than oxadiazon, which was compounded by early soil saturation after herbicide application. Pretilachlor with safener was the only herbicide that exhibited low phytotoxic symptoms on rice plants and did not reduce leaf, stem, root, and shoot biomass of rice. Percent reduction in rice leaf, stem, root, and shoot biomass by the different herbicides was in the order of pendimethalin 2 > oxadiazon 1 > pendimethalin 1 > oxadiazon 0.5 > pretilachlor with safener 0.6 kg ai ha⁻¹. Each herbicide treatment reduced rice growth parameters as soil saturation was delayed in the order of 1 DAS > 3 DAS > 5 DAS > 7 DAS. The study suggests that soil water content and herbicide rates are important factors in influencing herbicide phytotoxicity in rice. The application of herbicides should be avoided when the soil is too wet, and irrigation should be delayed at least one week after herbicide application.     

Parthenium hysterophorus L. control in response to pyraflufen-ethyl application

Pyraflufen-ethyl is a phenylpyrazole herbicide for control of annual and perennial broadleaf weeds. Greenhouse and field studies were conducted to determine pyraflufen-ethyl efficacy for control of Parthenium hysterophorus at the rosette and flowering stages, respectively. Both growth stages were treated with pyraflufen-ethyl at six rates ranging from 0.46 to 14.60 g a.i. ha⁻¹. Aboveground dry weight of rosette P. hysterophorus was reduced 90% by pyraflufen-ethyl at 2.33–2.65 g a.i. ha⁻¹ 14 days after treatment (DAT). At the label use rate of 0.91–3.64 g a.i. ha⁻¹ for control of broadleaf weeds, pyraflufen-ethyl was estimated to provide 13–58% and 5–32% control of flowering P. hysterophorus 60 and 87 cm in height, respectively at 21 DAT. These results show that pyraflufen-ethyl can control rosette P. hysterophorus within the label use rate for broadleaf weeds. However, rates higher than the label use rate are required for control of flowering P. hysterophorus, showing that pyraflufen-ethyl must be applied at the early stages of P. hysterophorus growth for effective control.     

Resistance of Oryza spp. to thrips, Stenchaetothrips biformis (Bagnall) (Thysanoptera: Thripidae)

A method to evaluate rice cultivars for resistance to Stenchaetothrips biformis (Bagnall) in the greenhouse was developed. Eleven traditional cultivars of Oryza sativa and 12 wild rices were selected for resistance. Studies on the mechanisms of resistance indicated that resistant cultivars were non-preferred for feeding and oviposition. Larval survival was lower and adult life shorter on resistant compared with susceptible cultivars. Resistant cultivars had an adverse effect on fecundity and oviposition rate which resulted in a low population growth. Plant injury on susceptible cultivars reduced plant weight and height.     

Anti-fungal action of bioconverted eicosapentaenoic acid (bEPA) against plant pathogens

Bioconverted eicosapentaenoic acid (bEPA), obtained from Pseudomonas aeruginosa PR3, was assessed for its in vitro and in vivo anti-fungal potential. Mycelial growth inhibition of the tested plant pathogens (Rhizoctonia solani, Botrytis cinerea, Fusarium oxysporum, Fusarium solani, Phyptophthora capsici, Sclerotinia sclerotiorum and Colletotrichum capsici) was measured in vitro. bEPA at the concentration of 5 μl/ml inhibited 52–60% fungal mycelial growth for all of the plant pathogens in vitro except S. sclerotiorum. Minimum inhibitory concentrations (MICs) of bEPA were found in the range of 250–500 μg/ml. Also, bEPA had a detrimental effect on spore germination for all the tested plant pathogens. Three plant pathogenic fungi (F. oxysporum, P. capsici and C. capsici) were subjected to an in vivo anti-fungal screening. bEPA at the initial concentration of 3000 μg/ml had a 100% anti-fungal effect against all of the tested plant pathogens. Concentrations of bEPA corresponding to 1500, 500 and 300 μg/ml were applied to the plants and revealed promising anti-fungal effects, supporting bEPA as a potential anti-fungal agent.     

Biological control of Macrophomina phaseolina by chemotactic fluorescent Pseudomonas aeruginosa PN1 and its plant growth promotory activity in chir-pine

Ten strains of Pseudomonas aeruginosa (PN1 ˜ PN10) isolated from rhizosphere of chir-pine were tested for their plant growth promontory properties and antagonistic activities against Macrophomina phaseolina in vitro and in vivo. P. aeruginosa PN1 produced siderophore, IAA, cyanogen and solubilized phosphorus, besides producing chitinase and β-1,3-glucanase. In dual culture, P. aeruginosa PN1 caused 69% colony growth inhibition. However, cell free culture filtrate also posed inhibitory effect but to a lesser extent. After 90 days, P. aeruginosa PN1 increased plant growth and biomass in pots trial containing M. phaseolina-infested soil. PN1 showed the strong chemotaxis toward root exudates resulting in effective root colonization. Moreover, increased population in rhizosphere of these bacteria was also recorded after 90 days of treatment. Thus, chemotactic fluorescent P. aeruginosa PN1 exhibited strong antagonistic property against M. phaseolina, suppressed the disease and improved plant growth of the seedlings of chir-pine proving potential biocontrol agent.     

Effect of Cardinium Infection on the Probing Behavior of Bemisia tabaci (Hemiptera: Aleyrodidae) MED

Facultative endosymbionts can affect the growth, physiology, and behavior of their arthropod hosts. There are several endosymbionts in the invasive whitefly Bemisia tabaci Mediterranean (MED, Q biotype) that influence host fitness by altering stylet probing behavior. We investigated the probing behavior of B. tabaci MED infected with the facultative endosymbiont Candidatus Cardinium hertigii (Cardinium (Sphingobacteriales: Flexibacteraceae)). We generated genetically similar Cardinium-infected (C^*+) and uninfected (C^-) clonal sublines and analyzed the probing behavior of newly emerged adult on cotton (Malvales: Malvaceae), Gossypium hirsutum L., using electropenetrography (EPG). The C^- subline demonstrated a longer duration of E2 (2.81-fold) and more events of E2 (2.22-fold) than the C^*+ subline, indicating a greater level of sustained ingestion of plant phloem. These findings provide insight into the fitness costs (fitness of a particular genotype is lower than the average fitness of the population) of the Cardinium-infected B. tabaci.