Antagonistic yeasts with potential to control Colletotrichum gloeosporioides (Penz.) Penz. & Sacc. and Colletotrichum acutatum J.H. Simmonds on avocado fruits

Avocado is an economically important fruit that is severely affected by anthracnose disease due to the infection with Colletotrichum spp. In this study, avocado fruits with anthracnose symptoms were collected in Morelos, Mexico. Two phytopathogenic fungi were isolated from these fruits and identified as Colletotrichum gloeosporioides and Colletotrichum acutatum using ITS sequences. Further, eleven yeasts from avocado (three from fruits, four from leaves and four from rhizospheric soil) were isolated; of which three showed in vitro antagonistic activity against C. gloeosporioides and C. acutatum. ITS sequence analysis of the isolated yeasts revealed that the strains obtained from fruits belonged to Candida intermedia while those isolated from leaves belonged to Wickerhamomyces anomalus. C. intermedia reduced disease incidence caused only by C. gloeosporioides, whereas, W. anomalus caused a significant reduction in the incidence and severity of disease caused by both C. gloeosporioides and C. acutatum. To the best of our knowledge, this is the first report on the antagonistic activity of W. anomalus or C. intermedia against Colletotrichum acutatum. Thus, W. anomalus is a potential natural alternative for controlling anthracnose infection and associated loss in avocado crops.     

In vitro antifungal activity of extracts of Mexican Chihuahuan Desert plants against postharvest fruit fungi

Chemical fungicides have been intensively used in the control of diseases in fruits in postharvest conditions; nevertheless these actions have developed resistance in the phytopathogens, have contaminated the atmosphere, and have affected people's health through residual toxic compounds present in the food for human consumption. The objective of this study was to evaluate the in vitro inhibiting activity of extracts of Lippia graveolens Kunth, Agave lechuguilla Torr. Yucca carnerosana (Trel.) Mc Kelvey and Yucca filifera Chaub., against Rhizopus stolonifer, Colletotricum gloesporoides and Penicillium digitatum the postharvest fungi that causes diseases in fruits of commercial interest. The plants were collected in the neighborhood of the cities of Saltillo and Torreon in the Southern Region of the State of Coahuila in the semi-arid zones of the North of Mexico. The extracts of the plants were obtained with ethanol and hexane as solvents, and the resin was separated of solvent in a rotary evaporator. The fungi were isolated of apple, mango and orange fruits and were then seeded in Potato-Dextrose-Agar medium; the bioassays were inoculated with fungi and developed in Petri dishes. The evaluated variables were: Inhibition of mycelial growth, and Inhibition of the number of spores. For the analysis of the information a completely randomized experimental design in factorial arrangement was used. The results showed that the ethanolic extracts of L. graveolens at 500 μl L⁻¹ presented a fungicide effect of 100% against R. stolonifer, Y. filifera at 4000 μl L⁻¹ inhibited 100% the pathogen. The hexanic extracts of L. graveolens presented an inhibition of 100% at 500 μl L⁻¹. A. lechuguilla inhibited the pathogen in 100% at 3000 μl L⁻¹. The extract of L. graveolens, A. lechugilla, Y. carnerosana and Y. filifera showed its inhibiting activity in different percentages against the development of R. stolonifer, Colletotrichum gloeosporioides, and P. digitatum. This is the first scientific report that shows anti-fungal activity of ethanolic and hexanic extracts of L. graveolens, A. lechuguilla, Y. carnerosana, and Y. filifera against R. stolonifer, C. gloesporoides, and P. digitatum.     

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.     

Activities of essential oils from Asarum heterotropoides var. mandshuricum against five phytopathogens

Some secondary metabolites of plants function as antimicrobial products against phytopathogens and constitute an increasingly important class of pesticides. In the present study, the essential oil of Asarum heterotropoides var. mandshuricum was analyzed by GC/MS and its antimicrobial activity was evaluated against five phytopathogenic fungi. Major components of the oil were methyleugenol (59.42%), eucarvone (24.10%), 5-allyl-1,2,3-trimethoxybenzene (5.72%), and 3,7,7-trimethylbicyclo(4.1.0)hept-3-ene (4.93%). The essential oil and the most abundant component, methyleugenol, were separately assayed for inhibition of 5 pathogens: Alternaria humicola, Colletotrichum gloeosporioides, Rhizoctonia solani, Phytophthora cactorum and Fusarium solani. Both the oil and methyleugenol strongly inhibited the growth of the test pathogens (IC₅₀ values <0.42 μg ml⁻¹) except F. solani, with the best activity against P. cactorum (IC₅₀ values = 0.073 and 0.052 μg ml⁻¹, respectively). It is concluded that the essential oil of A. heterotropoides var. mandshuricum has a broad antiphytopathogenic spectrum, and that methyleugenol is largely responsible for the bioactivity of the oil. The mode of action of methyleugenol against P. cactorum is discussed based on changes in the mycelial ultrastructure.     

Identification and antimicrobial activity of two alkaloids from traditional Chinese medicinal plant Tinospora capillipes

Two antimicrobial alkaloids, palmatine and jatrorrhizine, were isolated from tubers of traditional Chinese medicinal plant Tinospora capillipes using activity-guided isolation method and chromatography. Their antimicrobial activity was determined in vitro. The results showed that palmatine and jatrorrhizine had inhibitory activity against plant pathogens Colletotrichum gloeosporioides, Fusarium oxysporum f. sp. niveum, Mycosphaerella sentina, Pestalotia mangiferae, Cercospora kaki, Gymnosporangium haraeanum, Rhizoctonia solani and Colletotrichum graminicola, with the EC₅₀ values of 0.0348-0.8356 g L⁻¹ and 0.0240-0.8649 g L⁻¹, respectively. Palmatine and jatrorrhizine also exhibited inhibition against animal pathogens Bacillus cereus, Bacillus megaterium, Bacillus subtilis, Staphyloccocus aureus, Staphylococcus epidermidi, Micrococcus lysodeikticus, Proteus vulgaris, Salmonella typhi and Escherichia coli, with the MIC values of 0.1-0.8 g L⁻¹ and 0.1-0.6 g L⁻¹, respectively. These results suggested that palmatine and jatrorrhizine showed relatively broad spectrum antimicrobial activity against plant and animal pathogens.     

Nematicidal efficacy of isothiocyanates against root-knot nematode Meloidogyne javanica in cucumber

Isothiocyanates (ITCs), a series of new nematicides of the -NCS group, were evaluated for their efficacy against root-knot nematode Meloidogyne javanica. Of the compounds tested, AllylITC, AcITC, EtITC, BzTC, BzITC, 1-PEITC and 2-PEITC showed in vitro irreversible nematicidal activity against second-stage juveniles of M. javanica, following exposure for 72 h at concentrations as low as 5 μg mL⁻¹. When exposed to AllylITC, AcITC and EtITC at lower concentrations, motile juveniles also became irreversibly immobile in 3 days, with a LC₅₀ value at 2.76, 2.53 and 3.05 μg mL⁻¹, respectively. In the pot experiments, 1.0 ml AllylITC and 1.1 ml AcITC per kg of soil controlled M. javanica, similarly to or better than metam sodium at its recommended dose. Similar results were obtained in the field experiments using 1.0 kg AllylITC or 1.0 kg AcITC ha⁻¹. Based on the results of this study, AllylITC and AcITC have potential to be used as new bio-fumigant nematicides.     

Antifungal activity of polyacetylenes isolated from Cirsium japonicum roots against various phytopathogenic fungi

Antifungal substances from a methanol extract of Cirsium japonicum roots were purified and characterized, and their antifungal activities against various plant pathogens were evaluated. Three polyacetylene substances were isolated from roots of C. japonicum using repeated column chromatography; these were identified as ciryneol A, ciryneol C and 1-heptadecene-11,13-diyne-8,9,10-triol by mass and nuclear magnetic resonance spectral analyses. In vitro antifungal activity of the three substances varied according to compound and target species. Magnaporthe oryzae, Colletotrichum coccodes, Colletotrichum acutatum, Pythium ultimum and Botrytis cinerea were relatively sensitive to the three polyacetylenes, with IC₅₀ values below 50 μg mL⁻¹. In vivo, they all showed similar and broad antifungal spectra against the seven plant diseases tested. At 500 μg mL⁻¹, all three compounds effectively suppressed the development of rice blast, rice sheath blight, tomato late blight, wheat leaf rust and red pepper anthracnose, with control values over 90%. They were highly active especially against wheat leaf rust; they controlled the development of this disease more than 88% even at a concentration of 125 μg mL⁻¹. In addition, ciryneol C effectively suppressed barley powdery mildew. This is the first report on the antifungal activities of the three polyacetylenes from roots of C. japonicum against plant pathogenic fungi. Polyacetylenes from roots of C. japonicum may contribute to the development of environmentally safer alternatives to protect crops from various phytopathogenic fungi.     

Induced Marine Fungus Chondrostereum sp. as a Means of Producing New Sesquiterpenoids Chondrosterins I and J by Using Glycerol as the Carbon Source

Chondrostereum sp., a marine fungus isolated from a soft coral Sarcophyton tortuosum, can yield hirsutane framework sesquiterpenoids. However, the metabolites profiles vary dramatically with the composition change of the culture media. This fungus was cultured in a liquid medium containing glycerol as the carbon source, and two new metabolites, chondrosterins I and J (1 and 2), were obtained. Their structures were elucidated primarily based on MS, NMR and X-ray single-crystal diffraction data. By comparison with the known hirsutane sesquiterpenoids, chondrosterins I and J have unique structural features, including a methyl was migrated from C-2 to C-6, and the methyl at C-3 was carboxylated. Compound 2 exhibited potent cytotoxic activities against the cancer cell lines CNE-1 and CNE-2 with the IC₅₀ values of 1.32 and 0.56 μM.     

Evaluation of fungal epiphytes isolated from banana fruit surfaces for biocontrol of banana crown rot disease

Fungi isolated from the surface of banana fruits were evaluated for in vitro antagonism towards Lasiodiplodia theobromae. Thirteen fungi exhibiting pronounced growth inhibition of test pathogens were further tested for antibiosis against Thielaviopsis paradoxa, Colletotrichum musae, and Fusarium verticillioides. Clonostachys byssicola, Curvularia pallescens, Penicillium oxalicum, and Trichoderma harzianum were antagonistic to all test pathogens. Inhibition by C. pallescens and P. oxalicum to pathogens was at a distance, while C. byssicola and T. harzianum directly parasitized and killed the pathogens. The metabolites of C. byssicola, C. pallescens, and T. harzianum significantly affected the mycelial growth and conidial germination of the pathogens. In the artificial inoculation study, the antagonists survived and colonized banana fruits after 3 d. Interfungal parasitic relationship was observed between the antagonist and pathogen on artificial media and natural substrate. Postharvest application in the packing house showed that the incidence of crown rot in antagonist-treated banana was significantly lower when compared to fungicide and untreated control fruits.     

Antifungal activity of leaf extracts from South African trees against plant pathogens

The antifungal activity of acetone, methanol, hexane and dichloromethane leaf extracts of six plant species (Bucida buceras, Breonadia salicina, Harpephyllum caffrum, Olinia ventosa, Vangueria infausta and Xylotheca kraussiana) were evaluated for antifungal activity against seven plant pathogenic fungal species (Aspergillus niger, Aspergillus parasiticus, Colletotricum gloeosporioides, Penicillium janthinellum, Penicillium expansum, Trichoderma harzianum and Fusarium oxysporum). These plant species were selected from 600 evaluated inter alia, against two animal fungal pathogens. All plant extracts were active against the selected plant pathogenic fungi. Of the six plant species, B. buceras had the best antifungal activity against four of the fungi, with minimum inhibitory concentration (MIC) values as low as 0.02 mg/ml and 0.08 mg/ml against P. expansum, P. janthinellum, T. harzianum and F. oxysporum. Some of the plant extracts had moderate to low activity against other fungi, indicating that the activity is not based on a general metabolic toxicity. P. janthinellum, T. harzianum and F. oxysporum were the most sensitive fungal species, with a mean MIC of 0.28 mg/ml, while the remaining four fungi were more resistant to the extracts tested, with mean MICs above 1 mg/ml. The number of active compounds in the plant extracts was determined using bioautography with the listed plant pathogens. No active compounds were observed in some plant extracts with good antifungal activity as a mixture against the fungal plant pathogens, indicating possible synergism between the separated metabolites, B. salicina and O. ventosa were the most promising plant species, with at least three antifungal compounds. Leaf extracts of different plant species using different methods (acetone, hexane, DCM and methanol) had antifungal compounds with the same R_f values. The same compounds may be responsible for activity in extracts of different plant species. Based on the antifungal activity, crude plant extracts may be a cost effective way of protecting crops against fungal pathogens. Because plant extracts contain several antifungal compounds, the development of resistant pathogens may be delayed.     

Changes in nutritional value of guava fruits infected by major post-harvest pathogens

Post-infection changes in ascorbic acid, sugars, proteins and phenols were studied in guava fruits infected by major post-harvest pathogens which in order of importance wereColletotrichum gloeosporioides, (Penz.),Botryodiplodia theobromae, Pat.,Rhizopus arrhizus Fischer.,Phomopsis psidii Nag Raj and Ponnappa apud Ponnappa and Nag Raj, andPestalotiopsis versicolor (Speg.) Steyaert. Contents of ascorbic acid, sugars and proteins declined in the fruits infected byBotryodiplodia theobromae, Colletotrichum gloeosporioides, Pestalotiopsis versicolor, Phomopsis psidii andRhizopus arrhizus. Total phenols increased in fruits infected byPestalotiopsis versicolor andRhizopus arrhizus while reverse was observed in fruits infected by other pathogens.Part of the Ph.D. thesis submitted by the senior author to the Rajasthan Agricultural University, Bikaner.     

A New Analogue of Echinomycin and a New Cyclic Dipeptide from a Marine-Derived Streptomyces sp. LS298

Quinomycin G (1), a new analogue of echinomycin, together with a new cyclic dipeptide, cyclo-(l-Pro-4-OH-l-Leu) (2), as well as three known antibiotic compounds tirandamycin A (3), tirandamycin B (4) and staurosporine (5), were isolated from Streptomyces sp. LS298 obtained from a marine sponge Gelliodes carnosa. The planar and absolute configurations of compounds 1 and 2 were established by MS, NMR spectral data analysis and Marfey’s method. Furthermore, the differences in NMR data of keto-enol tautomers in tirandamycins were discussed for the first time. Antibacterial and anti-tumor activities of compound 1 were measured against 15 drug-sensitive/resistant strains and 12 tumor cell lines. Compound 1 exhibited moderate antibacterial activities against Staphylococcuse pidermidis, S. aureus, Enterococcus faecium, and E. faecalis with the minimum inhibitory concentration (MIC) values ranged from 16 to 64 μg/mL. Moreover, it displayed remarkable anti-tumor activities; the highest activity was observed against the Jurkat cell line (human T-cell leukemia) with an IC₅₀ value of 0.414 μM.     

Antioxidant and Antimicrobial Potential of the Bifurcaria bifurcata Epiphytic Bacteria

Surface-associated marine bacteria are an interesting source of new secondary metabolites. The aim of this study was the isolation and identification of epiphytic bacteria from the marine brown alga, Bifurcaria bifurcata, and the evaluation of the antioxidant and antimicrobial activity of bacteria extracts. The identification of epiphytic bacteria was determined by 16S rRNA gene sequencing. Bacteria extracts were obtained with methanol and dichloromethane (1:1) extraction. The antioxidant activity of extracts was performed by quantification of total phenolic content (TPC), 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity and oxygen radical absorbance capacity (ORAC). Antimicrobial activities were evaluated against Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis, Salmonella enteritidis, Staphylococcus aureus, Saccharomyces cerevisiae and Candida albicans. A total of 39 Bifurcaria bifurcata-associated bacteria were isolated and 33 were identified as Vibrio sp. (48.72%), Alteromonas sp. (12.82%), Shewanella sp. (12.26%), Serratia sp. (2.56%), Citricoccus sp. (2.56%), Cellulophaga sp. (2.56%), Ruegeria sp. (2.56%) and Staphylococcus sp. (2.56%). Six (15.38%) of the 39 bacteria Bifurcaria bifurcata-associated bacteria presented less than a 90% Basic Local Alignment Search Tool (BLAST) match, and some of those could be new. The highest antioxidant activity and antimicrobial activity (against B. subtilis) was exhibited by strain 16 (Shewanella sp.). Several strains also presented high antimicrobial activity against S. aureus, mainly belonging to Alteromonas sp. and Vibrio sp. There were no positive results against fungi and Gram-negative bacteria. Bifurcaria bifurcata epiphytic bacteria were revealed to be excellent sources of natural antioxidant and antimicrobial compounds.     

Isolation of entomopathogenic Bacillus from a biodynamic olive farm and their pathogenicity to lepidopteran and coleopteran insect pests

The occurrence of Bacillus entomopathogenic bacteria on a Tunisian biodynamic farm was determined by examining 75 samples from olive tree (Olea europaea L.) habitats. A total of 40 Bacillus isolates were characterized according to their phenotypic, physiological and biochemical parameters. Isolates of the species Bacillus subtilis, Bacillus mycoides, Brevibacillus brevis, Paenibacillus polymyxa, Bacillus licheniformis, Bacillus sp. (1), Bacillus sp. (2) and a standard strain Btk HD-1 were used separately in feeding bioassays on fresh artificial diet against larvae of lepidopterans Prays oleae (Bernard) and Palpita unionalis (Hübner) and coleopterans Hylesinus oleiperda (F.) and Phloeotribus scarabaeoides (Bernard), which are olive tree pests. Larvae were successfully reared on an artificial diet with 25 g powdered olive tree leaves. Compared to the control data, only Btk and the isolates of B. licheniformis, P. polymyxa and B. brevis were entomopathogenic. Larval mortality assessed 7 days post-treatment showed high mortality rates with Btk to lepidopteran larvae (86.6% for P. oleae and 80.9% for P. unionalis) and low mortality against coleopteran pests. B. brevis isolates showed high mortality rates against P. oleae (up to 67.9%). B. licheniformis isolates caused up to 59.2% larval mortality for P. oleae and 43.6% for P. unionalis. Highest coleopteran mortality was achieved by P. polymyxa isolates (up to 55%). According to the 16S rDNA results, isolates of each of the three entomopathogenic strains were similar. Proteins in the strain supernatants were toxic to P. oleae larvae with LC50 values of 10.0 (B. brevis), 12.5 (B. licheniformis) and 37.6 μg/ml (P. polymyxa). Also, P. polymyxa showed an LC50 of 12.4 mg/l against P. scarabaeoides. Our results suggest that entomopathogenic Bacillus present locally in the biodynamic farm could be used in biological control programmes of olive tree pests.     

Diversity and Antimicrobial Activity of Vietnamese Sponge-Associated Bacteria

This study aimed to assess the diversity and antimicrobial activity of cultivable bacteria associated with Vietnamese sponges. In total, 460 bacterial isolates were obtained from 18 marine sponges. Of these, 58.3% belonged to Proteobacteria, 16.5% to Actinobacteria, 18.0% to Firmicutes, and 7.2% to Bacteroidetes. At the genus level, isolated strains belonged to 55 genera, of which several genera, such as Bacillus, Pseudovibrio, Ruegeria, Vibrio, and Streptomyces, were the most predominant. Culture media influenced the cultivable bacterial composition, whereas, from different sponge species, similar cultivable bacteria were recovered. Interestingly, there was little overlap of bacterial composition associated with sponges when the taxa isolated were compared to cultivation-independent data. Subsequent antimicrobial assays showed that 90 isolated strains exhibited antimicrobial activity against at least one of seven indicator microorganisms. From the culture broth of the isolated strain with the strongest activity (Bacillus sp. M1_CRV_171), four secondary metabolites were isolated and identified, including cyclo(L-Pro-L-Tyr) (1), macrolactin A (2), macrolactin H (3), and 15,17-epoxy-16-hydroxy macrolactin A (4). Of these, compounds 2-4 exhibited antimicrobial activity against a broad spectrum of reference microorganisms.     

First Total Syntheses and Antimicrobial Evaluation of Penicimonoterpene,a Marine-Derived Monoterpenoid,and Its Various Derivatives

The first total synthesis of marine-derived penicimonoterpene (±)-1 has been achieved in four steps from 6-methylhept-5-en-2-one using a Reformatsky reaction as the key step to construct the basic carbon skeleton. A total of 24 new derivatives of 1 have also been designed and synthesized. Their structures were characterized by analysis of their ¹H NMR, ¹³C NMR and HRESIMS data. Some of them showed significant antibacterial activity against Aeromonas hydrophila, Escherichia coli, Micrococcus luteus, Staphylococcus aureus, Vibrio anguillarum, V. harveyi and/or V. parahaemolyticus, and some showed activity against plant-pathogenic fungi (Alternaria brassicae, Colletotrichum gloeosporioides and/or Fusarium graminearum). Some of the derivatives exhibited antimicrobial MIC values ranging from 0.25 to 4 μg/mL, which were stronger than those of the positive control. Notably, Compounds 3b and 10 showed extremely high selectively against plant-pathogenic fungus F. graminearum (MIC 0.25 μg/mL) and pathogenic bacteria E. coli (MIC 1 μg/mL), implying their potential as antimicrobial agents. SAR analysis of 1 and its derivatives indicated that modification of the carbon-carbon double bond at C-6/7, of groups on the allylic methylene unit and of the carbonyl group at C-1, effectively enhanced the antimicrobial activity.     

Sensitivity of Botryosphaeria dothidea from apple to tebuconazole in China

The white rot disease caused by Botryosphaeria dothidea threatens apple production in Bohai bay area and along the Yellow River of China, where disease control is largely dependent on fungicides such as tebuconazole. A total of 146 isolates of B. dothidea obtained from different apple orchards in six provinces were tested for their sensitivity to tebuconazole, carbendazim and iprodione. The EC₅₀ values of all tested isolates for tebuconazole were from 0.035 to 1.415 μg/mL. The broad range of EC₅₀ values of tebuconazole suggests an obvious variation among the 146 isolates. Isolate HB13 (EC₅₀ = 1.415 μg/mL) showed reduced sensitivity to tebuconazole, with an EC₅₀ value significantly higher than those of the other 145 isolates tested. The low sensitivity of HB13 was stable after 15 generations, and this isolate showed similar pathogenicity as susceptible strains. EC₅₀ correlation analysis indicates no cross resistance between tebuconazole and carbendazim and iprodione. Field efficacy trials showed that tebuconazole remains very effective for apple white rot control in China.     

Ribosome-inactivating proteins from apple have strong aphicidal activity in artificial diet and in planta

The apple (Malus domestica) genome contains gene sequences encoding type-1 and type-2 ribosome-inactivating proteins (RIPs). Both types of proteins contain a RIP domain with N-glycosidase activity, but the type-2 RIPs possess an additional domain with lectin activity. Here we investigated the activity of RIPs from apple against two sucking-piercing aphids that are important in agriculture, in particular pea aphids (Acyrthosiphon pisum) and green peach aphids (Myzus persicae).When the recombinant RIPs were dosed in an artificial liquid diet against pea aphids a strong aphicidal activity was observed. Based on LC₅₀s, the type-2 RIP (33 mg/L) was about 10 times more active than the type-1 RIP (341 mg/L), and the LC₅₀ of the recombinant protein corresponding to the type-2 RIP lectin domain alone was 106 mg/L. In in planta experiments with transgenic tobacco plants expressing the type-1 RIP or the type-2 RIP and infected with green peach aphids, mortalities of the nymphal stages amounted to approximately 50% for both types of transgenic lines when compared to wild type plants. In addition, significant sublethal effects were observed in the surviving aphids with a reduction in fecundity, intrinsic rate of increase, net reproductive rate and doubling time of the insect population. The insecticidal activity of the type-1 RIP and type-2 RIP from apple is discussed in relation to the domain structure of the RIPs and potential use in plant protection.     

Selection,mechanism, cross resistance and stability of spinosad resistance in Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae)

Spodoptera litura is one of the most destructive pests in Pakistan and in many other regions of the world. A field collected population of S. litura was selected with spinosad for eleven generations under controlled laboratory conditions to study the cross resistance, mechanism and stability of spinosad resistance in S. litura. The resistance to spinosad in S. litura increased 3921-fold (after eleven generations of selection with spinosad) as compared to a susceptible population of S. litura. No cross resistance between spinosad and emamectin benzoate, methoxyfenozide, fipronil, indoxacarb, profenofos, lufenuron or deltamethrin was found in the spinosad-selected population of S. litura. To find the possible mechanism of spinosad resistance in S. litura two synergists, Piperonyl butoxide (PBO), S, S, S-tributyl phosphorotrithioate (DEF) were tested on the susceptible and resistant strains and on the un-selected field population. The values of the synergism ratios of PBO and DEF were 2.33 and 1.06 for the spinosad-selected strain, 1.36 and 1.06 for the un-selected field population and 1.14 and 1.00 for the susceptible strain, respectively. As high PBO ratio indicates the role of microsomal O-demethylase in causing spinosad resistance in S. litura. The spinosad-resistant and field populations of S. litura were reared without any selection pressure from the 12th to the 16th generation (G₁₂–G₁₆). The spinosad resistance decreased from 3921 to 678-fold in the spinosad-resistant population and from 31.1 to 15.1-fold in the un-selected population of S. litura as compared to the susceptible strain. Spinosad resistance in S. litura has a high reversion rate (−0.15) which indicates that spinosad resistance in S. litura is unstable and can be easily managed by switching off the selection pressure for a few generations or alternating with insecticides having different modes of action.     

Investigation of the high-amylose maize starch gelatinization behaviours in glycerol-water systems

The effect of glycerol on gelatinization behaviours of high-amylose maize starch was evaluated by confocal laser scanning microscopy (CLSM), scanning electronic microscope (SEM), differential scanning calorimetry (DSC), texture analyzer (TPA) and rheometer. Gelatinization of the high-amylose maize starches with glycerol content of 10% (w/w) began at 95.4 °C (T_o), peaked at 110.3 °C (T_p), and completed at 118.9 °C (T_c). The birefringence began to disappear at around 100 °C and finished at 120 °C which corresponded well to the onset and conclusion temperatures obtained by DSC. The high-amylose maize starch granules maintained original morphological structure at 100 °C and swelled to a great degree at 110 °C. The high-amylose maize starch paste formed at 100 °C showed the lowest hardness (39.92 g), while at 120 and 130 °C, showed the highest hardness (610.89 g and 635.43 g, respectively). It should be noted that in going from 100 °C to 110 °C there is a significant increase in the viscosity of the slurry solution. The identical apparent viscosity was observed when the shear rate exceed 100 s⁻¹, resulting from the high-amylose maize starch granules were completely gelatinized at 120 °C, which was consistent with DSC analysis.